Patent Application: US-17785905-A

Abstract:
adsorbents and methods used for effective removal or concentration or retention and recovery of harmful or valuable dissolved ions and compounds from aqueous systems using quantum size effect on large band gap semiconductors are provided . this invention provides methods for creating surface hydroxyl groups on surfaces of anatase , brookite and rutile large band gap semiconductors which comprise methods of reducing dimensions of individual crystals to the sizes where surface hydroxyl groups are self generated via quantum size effects when they contacted with electrolytes . this invention also provides methods of reproducible preparation of quantum sized effected anatase , brookite and rutile , which comprise in non - batch and continues process in which growth of said crystals is aborted . the invention also provides methods using quantum size effected anatase , brookite and rutile products for treatment of water , comprising rapid and high capacity adsorption of dissolved molecules and ions to the surface of said crystals via surface reaction process between said effect created hydroxyl groups with molecules and ions . invention in general provides an effective means for treatment of water from harmful contaminants , especially as , p , u , transuranic elements , w , mo , cu , pb , cd , co , ni , cr and others

Description:
the present invention now will be described more fully hereinafter with reference to the accompanying drawings , in which illustrative embodiments of the invention are shown . this invention may , however , be embodied in many different forms and should not be construed as limited to the embodiments set forth herein ; rather , these embodiments are provided so that this disclosure will be thorough and complete , and will fully convey the scope of the invention to those skilled in the art . foregoing detailed description has been given for clearness of understanding and no undue limitation should be deduced therefrom , but the appended claims should be construed as broadly as permissible in view of the prior art . present invention is describing the chemical compounds , their structural aspects , processes , methods , properties , testing of said compounds , more particularly solid state compounds of titanium dioxides : anatase , brookite and rutile . first we would like to define anatase , brookite and rutile in terms of composition and structure . anatase , brookite and rutile compositions , structures and materials as they are described here should be understood by skilled in art as if they correspond to descriptions given below . anatase titanium dioxide of present invention is defined to be a structural analog of a compound as it is described in icsd ( inorganic crystal structure database , fachinformationszentrum karlsruhe , germany ( fiz ) and the national institute of standards and technology , gaithersburg , md . usa ( nist ), version 1 . 3 . 1 , 2003 ) icsd no 63711 , based on work of howard , c . j . ; sabine , t . m . ; dickson , f . structural and thermal parameters for rutile and anatase acta crystallographica b 47 , 462 - 468 ( 1991 ). it crystallizes in tetragonal space group 14 1 / amd ( no 141 ) with unit cell parameters a = 3 . 7845 å , b = 3 . 7845 å , c = 9 . 5143 å and alpha = 90 , beta = 90 , gamma = 90 degrees . anatase titanium dioxide samples of present invention show a x - ray powder diffraction pattern obtained employing a well aligned powder bragg - brentano geometry diffractometer , with calibrated zero shift and other standards , such as internal standard and when it is free from preferred orientation , that agrees with that of given in pdf no 21 - 1272 in pdf - 2 database published by icdd ( the international centre for diffraction data ) newtown square , pa ., usa . the structural arrangement of titanium and oxygen atoms , partial isomorphic substitution of titanium and / or oxygen atoms , vacancies , sample synthesis methods , preferred orientation , crystallinity , crystal size and others for the particular sample could affect the diffraction pattern , such as unit cell parameters , diffraction peak positions and intensities . importantly , these minor but common effects are easily detectable by qualified crystallographer . all such changes may affect certain physical and chemical properties of samples , for example band gap energy and band gap energy for valence and conductivity levels for anatase semiconductor . however , such property modifications are also an object of present invention as far as structure is considered to be isostructural to anatase as it is defined above . physical evidence for anatase titanium dioxide of present invention could be an x - ray powder diffraction method that will show a powder diffraction pattern , when applied correctly , with bragg diffraction peaks as those described in pdf no 21 - 1272 and simultaneously , the chemical analysis that will show presence of titanium and oxygen in molar ratio essentially not deviating from ti : o = 1 : 2 . however , some titanium atoms could be substituted with other atoms , such as zr , nb , sn , ge , si , al and others . brookite titanium dioxide of present invention is defined to be a structural analog of a compound as it is described in icsd ( inorganic crystal structure database , fachinformationszentrum karlsruhe , germany ( fiz ) and the national institute of standards and technology , gaithersburg , md . usa ( nist ), version 1 . 3 . 1 , 2003 ) icsd no 63710 , based on work of meagher , e . p . ; lager , g . a polyhedral thermal expansion in the ti o2 polymorphs . canadian mineralogist 17 , 77 - 85 ( 1979 ). it crystallizes in orthorhombic space group pbca ( no 61 ) with unit cell parameters a = 9 . 174 å , b = 5 . 449 å , c = 5 . 138 å and alpha = 90 , beta = 90 , gamma = 90 degrees . brookite titanium dioxide samples of present invention show a x - ray powder diffraction pattern obtained employing a well aligned powder bragg - brentano geometry diffractometer , with calibrated zero shift and other standards , such as internal standard and when it is free from preferred orientation , that agrees with that of given in pdf no 29 - 1360 in pdf2 database published by icdd ( the international centre for diffraction data ) newtown square , pa ., usa . the structural arrangement of titanium and oxygen atoms , partial isomorphic substitution of titanium and / or oxygen atoms , vacancies , sample synthesis methods , preferred orientation , crystallinity , crystal size and others for the particular sample could affect the diffraction pattern , such as unit cell parameters , diffraction peak positions and intensities . importantly , these minor but common are effects easily detectable by qualified crystallographer . all such changes may affect certain physical and chemical properties of samples , for example band gap energy and band gap energy for valence and conductivity levels for brookite semiconductor . however , such property modifications are also an object of present invention as far as structure is considered to be isostructural to brookite as it is defined above . physical evidence for brookite titanium dioxide of present invention could be an x - ray powder diffraction method that will show a powder diffraction pattern , when applied correctly , with bragg diffraction peaks as those described in pdf no 29 - 1360 and simultaneously , the chemical analysis that will show presence of titanium and oxygen in molar ratio essentially not deviating from ti : o = 1 : 2 . however , some titanium atoms could be substituted with other atoms , such as zr , nb , sn , ge , si , al and others . rutile titanium dioxide of present invention is defined to be a structural analog of a compound as it is described in icsd ( inorganic crystal structure database , fachinformationszentrum karlsruhe , germany ( fiz ) and the national institute of standards and technology , gaithersburg , md . usa ( nist ), version 1 . 3 . 1 , 2003 ) icsd no 63710 , based on work of howard , c . j . ; sabine , t . m . ; dickson , f . structural and thermal parameters for rutile and rutile acta crystallographica b 47 , 462 - 468 ( 1991 ). it crystallizes in tetragonal space group p4 2 / mnm ( no 136 ) with unit cell parameters a = 4 . 5937 å , b = 4 . 5937 å , c = 2 . 9587 å and alpha = 90 , beta = 90 , gamma = 90 degrees . rutile titanium dioxide samples of present invention show a x - ray powder diffraction pattern obtained employing a well aligned powder bragg - brentano geometry diffractometer , with calibrated zero shift and other standards , such as internal standard and when it is free from preferred orientation , that agrees with that of given in pdf no 21 - 1276 in pdf2 database published by icdd ( the international centre for diffraction data ) newtown square , pa ., usa . the structural arrangement of titanium and oxygen atoms , partial isomorphic substitution of titanium and / or oxygen atoms , vacancies , sample synthesis methods , preferred orientation , crystallinity , crystal size and others for the particular sample could affect the diffraction pattern , such as unit cell parameters , diffraction peak positions and intensities . importantly , these minor but common effects are easily detectable by qualified crystallographer . all such changes may affect certain physical and chemical properties of samples , for example band gap energy and band gap energy for valence and conductivity levels for rutile semiconductor . however , such property modifications are also an object of present invention as far as structure is considered to be isostructural to rutile as it is defined above . physical evidence for rutile titanium dioxide of present invention could be an x - ray powder diffraction method that will show a powder diffraction pattern , when applied correctly , with bragg diffraction peaks as those described in pdf no 21 - 1276 and simultaneously , the chemical analysis that will show presence of titanium and oxygen in molar ratio essentially not deviating from ti : o = 1 : 2 . however , some titanium atoms could be substituted with other atoms , such as zr , nb , sn , ge , si , al and others . the present invention comprises methods for producing surface hydroxyl groups on surfaces of crystalline titanium dioxides by production of the crystallites with sizes when the crystallite sizes and size distribution are essentially below 100 å , so that the obtained titanium dioxide surfaces are affected by quantum size effects and able to self - generate plethora of surface hydroxyl groups . the quantum size effect should be understood as a physical and chemical phenomenon when the size of ionic and / or covalently bonded group of atoms in a certain way show non - classical behavior of individual atoms , molecules or bulk solids . the chemical formula of titanium dioxide is composed from titanium atom and two oxygen atoms . bulk crystals of titanium dioxide of anatase , brookite and rutile structures contain large number of atoms , with the quantity of internal atoms being very large in comparison with quantity of surface atoms . when the sizes of titanium dioxide crystal become smaller , for example , few nanometers , the physical and chemical behavior of surface atoms change dramatically , because of the change in the ratio of surface atoms to the internal atoms . for example , anatase crystals having size of one unit cell ( 1 × 1 × 1 ) contain 31 atoms , 2 × 2 × 2 cells ( 8 cells ) contain 159 atoms , 3 × 3 × 3 cells ( 27 cells ) contain 457 atoms , 4 × 4 × 4 cells ( 64 cells ) contain 997 atoms , 5 × 5 × 5 cells ( 8 cells ) contain 1851 atoms and 10 × 10 × 10 cells ( 1000 cells ) contain 13351 atoms . the ratio of surface atoms to the internal atoms in these very small crystals is much larger than that of micron sized crystal . importantly , physical and chemical properties of surface atoms in these small crystals are dramatically different from those of large crystals . the oxygen atoms bound to the surface titanium atoms in these small crystals are being transformed into highly reactive hydroxyl groups when in contact with electrolytes . in fact , as it will be seen further the adsorption properties of these small crystals are dramatically better than those of large crystals . it is also important to say that these high adsorption capacity and rates mostly do not result from the higher surface area . we will also demonstrate that for example the adsorption properties of one large crystal versus adsorption of several small crystals of same surface area are different . in fact , the large crystal of certain size basically adsorbs very small amounts , if any , of contaminants dissolved in water . it may be further speculated that generation of surface hydroxyl groups is a result of photosplitting of water molecules by nanosized semiconductors . it may be also difficult to measure and quantify surface hydroxyl groups directly in water by fourier transform infrared spectroscopy ( ftir ) because of interference of water molecules . to resolve vibration of hydroxyl groups a sample should be vacuumed to remove water , but this is not relevant and not adequate because it cannot provide an ‘ in situ ’ conditions . various embodiments of the present invention will now be described with reference to the figures in which like numbers correspond to like references throughout . this major embodiment of present invention is illustrated in fig1 , fig2 and fig3 . while the explanation and theory given appear reasonable , any and all theory and explanations of the method are disclaimed . it is needed to be said that this embodiment and related claims appended are not claiming the theoretical speculation and explanation given here , but rather a method of generation surface hydroxyl groups by reducing the size of crystals to values when properties of surface atoms dramatically change leading to the self - generation of plethora of highly reactive hydroxyl groups . as it will be shown in further description and examples , these hydroxyl groups are highly reactive towards molecules and ions of water contaminants . it is important to state that this is not obvious , moreover has never been previously attended . furthermore , this method of creation of surface hydroxyl groups and use of this method for the removal of dissolved in water ions and compounds has very important economic and health related consequence as it is able to produce adsorbents in cost effective and predictable manner and clean up water of natural and industrial origins . adsorbents , as it also will be shown below are very effective for the removal of many poisonous and radioactive substances such as arsenate , arsenite , chromates , uranium and transuranic elements , tungsten , molybdenum , copper , nickel , mercury , cadmium , lead , selenium and others . referring to fig1 diagram showing large and small anatase crystals . the large crystal is comprised of 106 × 39 × 39 ≈ 160 , 000 unit cells and has approximately ( 150 × 150 × 1000 ) å dimensions . small anatase crystal is composed of 7 × 7 × 7 = 343 unit cells and has approximately ( 26 × 26 × 67 ) å dimensions . the black and white squares and rectangles are two dimensional unit cells . according to the embodiments and claims of present invention the small crystals when put in contact with electrolyte solutions or vapors , water for example , will generate plethora of surface hydroxyl groups due to the quantum size effects in semiconductors , which adsorb to very high extent the molecules and ions of contaminant . the sizes of small crystals cannot be expressed using exact numbers ; however these quantum size effects leading for self - generation of reactive surface hydroxyl groups in ample quantities are particularly enhanced when sizes of crystals are approximately below 100 å or approximately below 10 - 20 unit cell sizes . the large crystals do not generate surface hydroxyl groups or the surface groups or generate them in very small quantities . the drawings ( fig1 , fig2 and fig3 ) are made for anatase crystals but they are also applicable to brookite and rutile provided the cell sizes of brookite and rutile are taken into account . referring to fig2 a schematic drawing of anatase crystals structure cross - section , where vertical direction is [ 001 ], horizontal direction is [ 010 ] and [ 100 ] direction is perpendicular to the plane of the paper . positive [ 001 ] direction represents the surface of crystal . according to present invention most of oxygen atoms coordinating surface titanium atoms will be hydroxylated upon contact with electrolytes . the drawing is made for anatase crystals but is also applicable to brookite and rutile provided the cell sizes of brookite and rutile are taken into account . referring to fig3 a cross - sectional drawing of anatase structure with terminal direction . the shortest terminal oxygen - oxygen distances are 3 . 78 å . defect - free surface of xy plane will have approximately one hydroxyl group for every 14 . 2 å 2 . however , the surface hydroxyl will be formed only on the surfaces of small crystals , as the large micron sized crystals do not have such hydroxyl groups on defect - free surfaces . theoretical density of the hydroxyl groups is about seven oh groups per nm 2 . for example a hypothetical anatase crystal has 6 . 6 nm side length cubes . volume of such crystal is 287 . 5 nm 2 , surface area is 261 . 36 nm 2 , mass is 1 . 12 × 10 − 18 grams . the total surface area of one gram of such crystals will have 2 . 33 × 10 20 nm 2 . for monodentate adsorption of arsenate groups on the surface of titanium dioxide case one gram adsorbent should theoretically adsorb 0 . 2 ( 20 wt %) grams of as , and for bidentate case 0 . 1 ( 10 wt %)— grams of arsenic . even in the case of five percent adsorption the bonding of arsenic to the surface of titanium dioxide should be regarded as chemosorption , because of the formation of the covalent bonds as — o — ti . the drawing is made for anatase crystals but is also applicable to brookite and rutile provided the cell sizes of brookite and rutile are taken into account . present invention further comprises methods of producing quantum size effect enabled anatase , brookite and rutile . as we have described above in prior art and will describe in foregoing description and examples there are no suitable methods for large scale and reproducible production of anatase , brookite and rutile with crystallites sizes favorably distributed preferably below 100 å . the size and size distribution of individual crystals have a critical importance for practical benefits of the present invention . as it was stated earlier currently only titanium dioxide of anatase type is available in approximately required size ranges , obtained by so called sulfate process during production of titanium dioxide pigments . however , only products from some batches are obtained in sizes suitable to practice present invention . with present invention we are introducing a new method and continuous process for production of all three types , namely anatase , brookite and rutile , with excellent control over crystallite size and crystallite size distribution . this process is new , has not been described in scientific and patent literature and provides a crucial improvement over existing methods and technologies . processes and methods of controlled crystallites size anatase preparation . the batch processes and methods to prepare titanium dioxide of anatase structure are known in prior art . it is also well known how to produce anatase titanium dioxide in form of fine crystals . as we have described in background of invention section , production of pigmentary titanium dioxide is very voluminous industry , which produces fine crystallites of anatase by a batch process through thermal hydrolysis of titanium sulfate solutions obtained from digestion of titanium rich ore , such as ilmenite . many modifications and improvements have been developed during almost 100 years of existence of sulfate process . currently , the titanium dioxide industry produces anatase titanium dioxide in large quantities . the quality of anatase titanium dioxide is satisfying the needs of various applications , such as food , polymer , paper , cosmetic and others . however , to achieve the goals of present invention , as it was described above we need to develop process , which has an accurate and predictable control over crystallite sizes and their favorable distribution properties . as even very small crystallites anatase about 20 nm and bigger sizes are mostly not suitable to practice our invention we need to develop a process , which in controllable and reproducible manner produces anatase in sizes up 100 å , with crystallite size distribution that provides most if not all crystallites below 100 å . our studies of current anatase products samples from various suppliers showed that the anatase crystals from many producers are larger than it is needed for purposes to reduce to practice the advantages of present invention . some samples of anatase from several producers had nearly suitable properties ; however they changed unpredictably from batch to batch . anatase can be produced using various titanium sources . practically all hydrolysable inorganic titanium compounds such as titanium trichloride , titanium tetrachloride , titanium sulfate , titanium iron sulfate solution , and titanium oxychloride as well as titanium alkoxides , such as titanium ethoxide , titanium butoxide , titanium isopropoxide could be used for production of anatase under certain conditions . the inorganic titanium compounds are , however , preferred as precursor compounds for large - scale production of the titanium dioxide because of cost considerations . from economic point of view titanium sulfate solution obtained from ilmenite ore and used to for production of anatase by so - called sulfate process is probably most suitable . the process of synthesis of anatase in present invention follows previously known methods and is identical to described in prior art patent and scientific literature . however , in order to control sizes of crystals we introduce new steps and modifications . first , our process is not a batch process , but instead it is a continuous process , in which titanium sulfate solution is heated in a flow reactor . since titanium sulfate solutions in water , sulfuric acid , iron salts may start hydrolyzing at various times depending on concentration of components , it is necessary to control and abort the hydrolysis process upon reaching crystals certain sizes . further hydrolysis and growth of crystals is affected by relatively rapid cooling . abortive cooling to stop crystal growth above certain sizes is a second important difference between our new method and prior art methods . yield of titanium dioxide in this process is not as high as in processes , which seek a full hydrolysis ; however the sizes of crystals are very uniform and easily could be kept below 10 å . for titanium sulfate solutions of various compositions and hydrolysis properties the time during which the solutions is in heating zone is different and is determined experimentally . third , important difference of present invention method is an introduction of real time control step . suspension of samples is constantly withdrawn from heated flow reactor zone and analyzed using powder diffractometer . first few reflections of solid are scanned , and then are analyzed using warren - averbach method . limited duration of heating is achieved by flow rate adjustment . referring to fig4 — titanium containing solution 1 is fed into the heating zone of the flow reactor 2 and is heated continuously . depending on the concentration of components titanium - containing solution hydrolyzes to form titanium dioxide of certain structure . at the end of heating zone the sample is constantly taken for rapid crystallite size analysis 7 . to obtain the crystallites of desired structure , crystal sizes and yields , the flow rate is adjusted 8 . upon reaching certain crystallite sizes the suspension of titanium dioxide crystallites and mother liquid is rapidly cooled in cooling zone 3 to prevent further crystallization and crystal growth above certain sizes . then obtained titanium dioxide products are separated from mother liquid 4 and collected in 5 . titanium rich solution is collected in 6 for concentration and other parameters adjustment and transferred into the fed solution container 1 . this continuous process provides means for production of anatase with desired properties . processes and methods of controlled crystallites size brookite preparation . a continuous process of the present invention for production titanium dioxide of brookite structure is based on previously disclosed batch method of ohmori , however an important modifications and improvements have been introduced . first , our process is not a batch process , but instead a continuous process , in which yellowish and free from precipitates titanium oxychloride solution with 0 . 25 mol / l concentration is fed by peristaltic pump into a flow reactor which is constantly heated to 105 degrees celsius . the tube reactor diameter and length is chosen to achieve and almost immediate heating of solution to 105 ° c . the pumping rate is adjusted in such a way that the time of hot solution being in a flow reactor ranges from 10 to 60 minutes . the turbid suspension containing titanium dioxide crystals at the end of heated hydrolysis reaction zone are constantly withdrawn for analysis . further hydrolysis and growth of the crystal is affected by relatively rapid cooling . abortive cooling to stop crystal growth above certain sizes is a second important difference between our new method and prior art methods . yield of titanium dioxide in this process is not as high as in processes which lead to full hydrolysis , however the sizes of crystals are very uniform and could be easily kept below 100 å . for titanium oxychloride solutions of various compositions and hydrolysis properties the times during which the solutions are in heating zone is different and determined experimentally . third , important difference of present invention method is an introduction of a real time control step . suspension of samples is constantly withdrawn from heated flow and analyzed using powder diffractometer . first few reflections of solid are scanned , and then are analyzed using warren - averbach method . limited duration of heating is achieved by flow rate adjustment . referring to fig4 titanium oxychloride solution 1 is fed into the ‘ heating zone of flow reactor 2 and heated continuously . depending on concentration of components titanium containing solution hydrolyzes to form titanium dioxide of certain structure . at the end of heating zone the sample is constantly taken for rapid crystallite size analysis 7 . to obtain the crystallites of desired structure , crystal sizes and yields the flow rate are adjusted 8 . upon reaching certain crystallite sizes the suspension of titanium dioxide crystallites and mother liquid is rapidly cooled in cooling zone 3 to prevent further crystallization and crystal growth above certain sizes . then obtained titanium dioxide products are separated from mother liquid 4 and collected in 5 . titanium rich solution is collected in 6 for concentration and other parameters adjustment and transferred into fed solution container 1 . this continuous process provides means for production of brookite with desired properties . processes and methods of controlled crystallites size rutile preparation . a continuous process of the present invention for production titanium dioxide of rutile structure is based on previously disclosed batch method of m gopal and others ( journal of materials science , 1997 , 32 , 6001 - 6008 , however , important modifications and improvements have been introduced . first , our process is not a batch process , but instead is a continuous process , in which freshly prepared and not dried ( wet ) amorphous titanium dioxide is dissolved in nitric acid to form a transparent and free from precipitates solution . the molar ratio of components in the solution is ti : hno 3 : h 2 o = 0 . 02 : 0 . 04 : 60 . the transparent and free from precipitates titanium nitrate solution is fed by peristaltic pump into a flow reactor which is constantly heated to 50 ° c . the tube reactor diameter and length is chosen to achieve almost immediate heating of solution to 50 ° c . the pumping rate is adjusted in such a way that the time of hot solution being in a flow reactor is from 10 to 60 minutes . the turbid suspension containing titanium dioxide crystals at the end of heated hydrolysis reaction zone is constantly withdrawn for analysis . further hydrolysis and growth of the crystals is affected by relatively rapid cooling . abortive cooling to stop crystal growth above certain sizes is a second important difference between our new method and prior art methods . yield of titanium dioxide in this process is not as high as in processes which seek a full hydrolysis , however , the sizes of crystals are very uniform and could be easily kept below 100 å . for titanium oxychloride solutions of various compositions and hydrolysis properties the time during which the solutions are present in heating zone is different and determined experimentally . third , important difference of present invention method is an introduction of real time control step . suspension of samples is constantly withdrawn from heated flow and is analyzed using powder diffractometer . first few reflections of solid are scanned , and then analyzed using warren - averbach method . limited duration of heating is achieved by flow rate adjustment . referring to fig4 titanium oxychloride solution 1 is fed into the heating zone of flow reactor 2 and heated continuously . depending on concentration of components titanium containing solution hydrolyzes to form titanium dioxide of certain structure . at the end of heating zone the sample is constantly taken for rapid crystallite size analysis 7 . to obtain the crystallites of desired structure , crystal sizes and yields the flow rate are adjusted 8 . upon reaching certain crystallite sizes the suspension of titanium dioxide crystallites and mother liquid is rapidly cooled in cooling zone 3 to prevent further crystallization and crystal growth above certain sizes . then obtained titanium dioxide products are separated from mother liquid 4 and collected in 5 . titanium rich solution is collected in 6 for concentration and other parameters adjustment and transferred into fed solution container 1 . this continuous process provides means for production of rutile with desired properties . the preferred methods of making crystalline titanium dioxides that are described above consistently produce a product that consists predominantly , if not entirely , of anatase , brookite or rutile crystals having crystallite diameters below 100 å . however , they could be also produced by other modified methods . the methods and adsorbents consisting of mixture of anatase , brookite and rutile crystals having essentially crystallite diameters below 100 å in any combination are also disclosed by present invention . other materials containing titanium oxide products also may be produced in accordance with this process . for example , a particulate substrate , such as granular activated carbon , alumina , silica , clays may be added to the solution and coated with titanium in similar conditions to precipitate the titanium oxide onto the surface or into the pores of the particulate substrate . present invention further comprises methods of using quantum size effect enabled titanium dioxides in water treatment processes . we have performed many batch and column tests for removal of dissolved contaminants from water using anatase , brookite and rutile as well as from samples containing the mixtures of thereof . we have found that all these three crystalline compounds are highly efficient adsorbents of ions and molecules provided their crystal sizes are in disclosed in present invention range . they have a high adsorptive capacity and favorable adsorption kinetics for removing oxyanions , such as arsenate and arsenite , phosphates , dissolved metals and some low - molecular weight organic compounds at low concentrations in water — properties which lead to high rates of removal for those substances . the crystalline titanium dioxides of present invention may be used to substantially reduce the concentrations of such substances to concentrations below a few micrograms - per - liter ( μg / l ). substances which may be effectively adsorbed by the crystalline titanium dioxides of present invention include but not limited to aluminum , antimony , arsenic ( iii ), arsenic ( v ), barium , cadmium , cesium , chromium , cobalt , copper , gallium , gold , iron , lead , manganese , mercury , molybdenum , nickel , platinum , radium , selenium , silver , strontium , tellurium , tin , tungsten , uranium , vanadium , zinc , nitrite , phosphate , sulfite , sulfide , and low - molecular weight organic arsenic compounds , such as monomethylarsonic acid , dimethylarsinic acid and phenylarsonic acid . in particular , the crystalline titanium dioxides of present invention are effective in adsorbing arsenite ( as ( iii )), arsenate ( as ( v )) and the dissolved metals : cadmium , chromium , copper , lead , mercury , tungsten , uranium , zinc and others . dissolved inorganic substances may be removed from a dilute aqueous stream by contacting the dilute aqueous stream with the crystalline titanium oxides of present invention for a period of time . preferably , the crystalline titanium dioxides comprises anatase , brookite and rutile , all these materials being particularly effective in removing arsenic and dissolved metals from water , as disclosed herebelow in the examples . for convenience , the following methods of removing dissolved inorganic substances from water are discussed with respect to the use of anatase , brookite and rutile . however , many other contaminants may also be removed from water according to the methods hereinafter disclosed . a dilute aqueous stream may be contacted with titanium dioxide of disclosed characteristics by known water treatment processes , e . g ., suspending a powdered titanium dioxide in a batch or a stream of contaminated water for a period of time , then separating the titanium dioxide solids from the water , or by filtering the dilute aqueous stream through a bed or column of the titanium dioxide product . the titanium dioxides of present invention could be used in water treatment processes in a powdered or granular form ; it may be dispersed in a bed of a particulate substrate ; or it may adhere to the surface or be within the pores of a particulate substrate such as granular activated carbon , porous alumina , porous silica or any other support material . referring to fig5 the powder diffraction patterns of samples consisting of anatase titanium dioxide , essentially free from other crystalline and amorphous phases are shown . these samples were prepared to test their properties as adsorbents . these kinds of samples normally would be described in scientific and patent literature as an ultrafine , nanocrystalline and other terms to signify the fact that they contain very small crystallites . however , as present invention discloses here , they are significantly different from each other : some of them are practically not useful to practice the advantages of present invention . crystallite sizes shown have been determined by spherical crystal approximation using scherrer equation . it is obvious that the shapes of crystal are not spherical and scherrer approximation has little use to prove the main embodiment of present invention . what is needed is to determine the crystallite sizes in more accurate manner and also determine the crystallite size distribution . there are many , in fact , too many , publications using so called “ naked - eye ”, scanning electron microscopy ( sem ), scherrer equation or simple believe for estimation of the crystal sizes . for example , u . s . pat . no . 6 , 001 , 326 to kim and others and u . s . patent application publication no . 6 , 516 , 804 b1 to kim and others estimate the crystal sizes by scanning electron microscopy . however , it is not described which sem instrument was used , what was the resolution of sem instrument . it is well known that currently available sem instruments are neither able of resolving in 10 nm range nor that these resolutions are reliable . for example , fig3 - fig6 of patent ( u . s . pat . no . 6 , 001 , 326 ) show that the sizes of particles are absolutely not uniform ; in fact the difference in sizes was more than 100 times . to eliminate such uncertainties we have undertaken more rigorous determination of crystallites sizes and dependency of adsorption properties from crystallite size . fig8 is warren - averbach crystallite size distribution for anatase sample of present invention . spherical approximation of crystallite diameter estimated by scherrer equation shows d ( scherrer )= 73 å . in reality , volume weighted crystal size is d ( vol )= 38 å and surface weighted crystal size d ( sur )= 19 å integration of lognormal distribution function shows that 96 . 5 % percent of crystals are smaller than 100 å . the ratio of volume weighted crystallite size ( vwcs ) to surface weighted crystallite size ( swcs ) is equal to 2 . fig9 shows the results of analysis of another sample by above method and crystallite sizes are shown in d ( scherrer )= 67 å , d ( vol )= 54 å and d ( sur )= 27 å . this sample consisted of pure anatase and had about 90 % crystals smaller than 100 å with vwcs / swcs = 2 . following discussion is important for understanding of present invention and particularly for understanding of novelty of adsorbents prepared using these crystals and directly related to their performance as adsorbents . it is an important and determinative feature of present invention which states that the sample of fig8 will have more adsorption capacity , and faster adsorption rates than the sample of fig9 , since the former has smaller crystallite size and more crystals below 100 å , which would be opposite if we had used spherical crystal approximation . we have prepared and investigated numerous samples prepared via continuous process offered by present invention . for example , sample analyzed in fig1 , fig1 , fig1 ( p - 25 ™ sample from degussa ). the adsorbents of present invention are self - limited to those containing titanium dioxide crystals below 100 å , they should be present at least in quantities 15 %. it is a scientific result of present invention that above 100 å the crystals rapidly loose their adsorptive properties proportionally to their crystal size . for example sample of fig1 . d ( scherrer )= 158 å , d ( vol )= 85 å and d ( sur )= 42 å contains only 66 % percent of crystals below 100 å . even though the scherrer size is 158 å , this sample according to present invention will have a certain adsorption properties and these adsorption properties are due to present small crystals . the sample shown in fig1 has very limited amount of crystals smaller than 100 å ( 26 %). the d ( vol )= 158 å . p - 25 ™ from degussa is currently one of commonly investigated commercial titanium dioxides and is widely used as a photocatalyst for degradation of contaminants . rietveld quantification analysis of p - 25 ™ shows that it is a mixture of anatase ( 75 . 7 %) and rutile ( 24 . 5 %). crystallite size and crystallite size distribution of p - 25 ™ shows d ( scherrer )= 336 å , d ( vol )= 210 å and d ( sur )= 128 å for anatase and d ( scherrer )= 540 å , d ( vol )= 329 å and d ( sur )= 210 å for rutile crystals . this sample contains only 12 . 8 % percent of crystals below 100 å due to anatase and 1 . 58 % due to rutile . again , this is important for understanding and appreciating of present invention over prior art . according to embodiments and claims of present invention , in spite of p - 25 ™ having more than 75 % anatase with volume weighted crystallite size of 210 å , it will have very insignificant to none useful properties which could be used to practice the advantages offered by present invention . even though p - 25 ™ has useful properties as a photocatalyst , it cannot be successfully used for adsorption of contaminants from aqueous systems contrary to the adsorbents of present invention . thus , this example shows that there is no direct dependence between the photocatalytic properties of titanium dioxides and their ability to function as adsorbents . now , referring to fig2 , which is a graphical representation of adsorption properties obtained under the same experimental conditions . briefly , 0 . 1 gram of each sample just described above were contacted with 100 ml of as ( v ) in first series of experiments and 100 ml of as ( iii ) in a second series of experiments . the concentration of as ( v ) and as ( iii ) was 50 ppm ( mg / l ). as evidenced by obtained results and plotted in this fig2 , the amount of adsorbed as ( v ) as well as of adsorbed as ( iii ) is directly related to the amount of present small crystals . oxidation of as ( iii ) to as ( v ) was also directly influenced by the quantity of small crystals . use of titanium dioxide of brookite structure , as an adsorbent of water contaminants is not suggested by the references . in fact , the synthesis brookite has been described only very recently . in ‘ background of the invention ’ section we gave detailed account of prior art of brookite - related scientific and patent publications . we have prepared by methods of present invention numerous pure single - phase brookite samples . representative samples of brookite titanium dioxide with different crystallite sizes are shown in fig6 . the crystallite sizes and crystallite size distribution are determined in similar fashion as for anatase samples , just described above . the fig1 , fig1 and fig1 are examples of crystallite size distribution for some brookite samples . now , referring to fig2 , which is a graphical representation of adsorption properties obtained under the same experimental conditions . briefly , 0 . 1 gram of each brookite sample just described above were contacted with 100 ml of as ( v ) in first series of experiments and 100 ml of as ( iii ) in a second series of experiments . the concentration of as ( v ) and as ( iii ) was 50 ppm ( mg / l ). as it evidenced by obtained results and plotted in this fig2 , the amount of adsorbed as ( v ) as well as of adsorbed as ( iii ) is directly related to the amount of present small crystals . oxidation of as ( iii ) to as ( v ) was also directly influenced by the quantity of small crystals . it should be noted that , adsorption of arsenic on brookite - based adsorbents as effective as on anatase - based adsorbents . in fact , the brookite - based adsorbents are on average 2 - 5 % better performing than similar samples of anatase - based adsorbents . use of titanium dioxide of rutile structure , as an adsorbent of water contaminants is not suggested by the references . in fact , the synthesis of rutile in low nanosized range has been described only very recently . in background of invention we gave the detailed account of prior art of rutile - related scientific and patent publications . we have prepared by methods of present invention numerous pure single - phase rutile samples . representative samples of rutile titanium dioxide with different crystallite sizes are shown in fig7 . the crystallite sizes and crystallite size distribution are determined in similar fashion as for anatase and brookite samples , just described above . the fig1 , fig1 , fig1 and fig1 are illustrations of crystallite size distribution for some rutile samples . now , referring to fig2 , which is a graphical representation of adsorption properties obtained under the same experimental conditions . briefly , 0 . 1 gram of each rutile sample just described above were contacted with 100 ml of as ( v ) in first series of experiments and 100 ml of as ( iii ) in a second series of experiments . the concentration of as ( v ) and as ( iii ) was 50 ppm ( mg / l ). as evidenced by obtained results and plotted in this fig2 , the amount of adsorbed as ( v ) as well as of adsorbed as ( iii ) is directly related to the amount of present small crystals . oxidation of as ( iii ) to as ( v ) was also directly influenced by the quantity of small crystals . it should be noted that , adsorption of arsenic on rutile - based adsorbents was also very effective . preceding description of adsorption of arsenic on anatase , brookite and rutile , when they have a suitable crystallite size and crystallite size distribution , suggested that the mixtures and intergrowth of the same crystals most probably would also have favorable adsorption properties . fig2 and fig2 depict the x - ray powder diffraction pattern of such binary and ternary mixture , with quantified amounts of each phase . quantification of phases is performed by rietveld quantification method and crystallite sizes are determined by warren - averbach method . we have been able to prepare many such samples during pure rutile synthesis . the process was found to be very sensitive in regard to composition of initial solution and duration of crystallization . however the crystal sizes in each phase were usually within desired range . now , referring to fig2 , which is a graphical representation of adsorption properties obtained under the same experimental conditions . briefly , 0 . 1 gram of each binary and ternary mixture samples just described above were contacted with 100 ml of as ( v ). the concentration of as ( v ) was 50 ppm ( mg / l ). as it evidenced by obtained results and plotted in this fig2 , the amount of adsorbed as ( v ) was again directly related to the amount of present small crystals . it should be noted that , adsorption of arsenic on binary and ternary mixtures of titanium oxide adsorbents was also very effective . referring to fig2 showing the dynamic adsorption characteristics of titanium dioxide of present invention . the experimental details are described in example 16 . it shows that 20 cm . sup . 3 adsorbent was capable of treating more than 1 , 000 gallons of water to reduce the concentration of dissolved as from 30 ppb to 10 ppb which is us epa starting 2006 mandated drinking water standard . the effectiveness of crystalline titanium dioxides of present invention , specifically , anatase , brookite and rutile structures in removing arsenate , arsenite and other dissolved inorganic substances from water is an unexpected result in view of the conventional understanding that the adsorption capacity of a metal oxide is controlled by the availability of hydroxyl groups on the surface of the metal oxide product ( see , e . g ., u . s . pat . no . 5 , 618 , 437 , col . 4 , lines 26 - 30 , and u . s . pat . no . 6 , 383 , 395 , col . 7 , lines 49 - 53 ). a hydrous and amorphous titanium hydroxide should have a greater number of available hydroxyl groups than a crystalline titanium oxide and , therefore , would be expected to exhibit a greater adsorptive capacity according to the conventional understanding . contrary to this expectation , the titanium dioxides of the present invention have higher adsorptive capacity than the amorphous titanium oxides , hydrous titanium dioxides and any other known titanium oxygen compounds . moreover , the favorable adsorption kinetics of the titanium oxides of the present invention are observed in the absence of acidic anions , such as chloride or sulfide , in contrast to expectations based on the disclosure of the japanese patent application publication 58 - 045705 . present inventions provide a broad base and open possibilities for application of these highly effective adsorbents in various areas . the adsorbents replace currently used materials in existing adsorption based water treatment processes , including industrial , municipal , regional water treatment facilities . the small units could be used in point of entry ( poe ) and point of use ( pou ) systems . the columns filled with these adsorbents have no limitations in size , shape etc . the solid adsorbent could be used in powdered , granulated , and coated on substrate forms . particularly important area of application for adsorbents of the present invention is application of them as sols . crystallites of such small sizes are easily stabilized in weak basic , neutral and acidic solutions to form stable sols . these sols contain the materials without degradation of adsorption properties of titanium dioxides of the present invention . thus they could be injected into aquifer , ground water systems , soils contaminated with undesired molecules and ions where they will adsorb the contaminants and adhere to the soil particles , thus providing the barrier for migrating contaminants . the sols and fine powder could be used to treat the contaminated lakes , liquid waste basins , just by spreading them over water to bind the contaminants and precipitate . adsorbents of the present invention could be used to coat paper and plastic drinking cups or any other drinking water devices , storage units and others . adsorbents of the present invention could be used to separate , isolate , and concentrate radionuclides . without further elaboration , it is believed that one skilled in the art , using the preceding description , can utilize the present invention to its fullest extend . the following preferred specific embodiments are therefore to be construed as merely illustrative of the remainder of the disclosure in any way whatsoever . prior to the description of specific examples for carrying out the best modes of present invention with characteristic variables , we would like to describe the methods which were applied throughout all experiments . it will be appreciated the foregoing is merely illustrative of art - recognized methods and instruments for investigation of composition , structure , properties of solid materials , however , if it is in question the methods described are preferred . x - ray powder diffraction instrumentation and data collection . step - scanned x - ray powder diffraction data for the powdered samples were collected using well aligned with less than 0 . 01 zero shift and instrumental line broadening of about 0 . 07 degrees of two theta x - ray powder diffractometer ( trademark : rigaku dxr - 3000 , rigaku / msc corporation , the woodlands , tex .) using bragg - brentano geometry , an copper ( cu ) anode operating at 40 kv and 30 ma , and equipped with a diffracted beam graphite - monochromator . measurements were taken using a 1 degree divergence and 1 degree scatterer slits and a 0 . 15 mm receiving slit . cuka radiation from the cu anode , i . e ., radiation having a wavelength of 1 . 54183å , was used as the x - ray source . data were collected between 20 degree - 60 degree of two theta , which represents two times the bragg angle of diffraction with a step size of 0 . 05 degree and a count time of 5 seconds per step . highly crystalline and well characterized standard silicon powder ( nbs 640 , a = 5 . 43088 å ) were used to correct the two theta values and also evaluate instrumental broadening . crystalline phase identification . the interplanar distances ( d ) were calculated using bragg &# 39 ; s law : where θ is the bragg angle of diffraction ; λ is an integer value ; and x is the wavelength of the x - ray source , in this case , λ = 1 . 54183 å . obtained interplanar distances with their corresponding intensities were compared against pdf2 database manually and using automatic search - match procedures . in present invention the samples showing a diffraction pattern matched with that of given for anatase ( for example , pdf no 21 - 1272 ), brookite ( for example , pdf no 29 - 1360 ) and rutile ( for example , pdf no 21 - 1276 ) pdf - 2 database published by icdd ( the international centre for diffraction data ). the phase identification of samples comprising single phases and also mixtures were determined in similar fashion . crystalline phase quantification . crystalline samples were quantified by rietveld quantification method ( the reitveld method editor r . a . young , oxford university press , 1993 ). briefly , using the structural data given in icsd for anatase , brookite and rutile and csas ( generalized structure analysis system , by a . c . larson and r . v . dreele , lansce , ms - h805 , los alamos national laboratory , los alamos , nmn 87545 usa ) rietveld refinement software the observed diffraction pattern were fitted to obtain best fit between observed and calculated patterns and then the scale factor was normalized to obtain final concentration of present phases . the quantification analyses of samples were confirmed also by commercial analysis performed for us by xrd . us ( http :// www . xrd . us ). crystallite size and crystallite size distribution determination . the sizes of individual crystals and crystals in crystalline agglomerates were determined to evaluate the relationship between crystallite size and crystallite size distribution and adsorption properties . primary crystallite diameters ( d . sub . 0 ) were calculated by the scherrer equation : where k have value of 0 . 89 ; λ is the wavelength of the x - ray source , in this case , λ = 1 . 54183 å ; β is the fwhm ( full width of half maximum ), free from instrumental line broadening , expressed in radians , and θ is the bragg angle of diffraction . the calculated primary crystallite diameters for the titanium oxide product obtained by the scherrer equation were consistently higher than those estimated by fourier methods , even though this method is most commonly used among non - specialists . unfortunately , using the above techniques we repeatedly obtained different adsorption results for samples of the same structure and surface area and the same scherrer crystallite diameter . however , to test the main hypothesis and major embodiments of present invention we had to employ more vigorous methods of crystallite size determination . because of crucial importance of crystallites sizes and even more importantly of crystal size distribution it was treated by warren - averbach method . ( b . e . warren , x - ray diffraction , addison wesley , reading , mass ., 1969 ; h . p . klug and l . e . alexander , x - ray diffraction procedures , 2nd edition , john wiley , new york , 1974 ). for the details of calculations of the root - mean - square strain ( rmss ) and both surface - and volume - weighted domain sizes according to the double - voigt method see , for example , d . balzar and h . ledbetter , j . appl . cryst . 26 ( 1993 ) 97 - 103 and 3 . d . balzar , j . res . natl . inst . stand . technol . 98 ( 1993 ) 321 - 353 . briefly , if the distortion coefficient is approximated by a harmonic term , the size and distortion integral breadths of caucy ( β sc and β dc ) and gauss ( β sg and β dg ) parts conform certain relations . to determine the unknowns β sc , β dc , β sg and β dg data for at least two reflections must be available . if data for more than two peaks are present , unknowns are calculated by means of the linear least squares fit . in our analysis we have used all reflections for brookite , anatase and rutile located between 20 and 60 degrees of two theta . surface and volume weighted domain sizes are derived directly from calculation along with their distributions . surface area and porosity determination . the samples of titanium dioxide powders were dried at a temperature of 110 . degree . c . for one hour . the bet specific surface area and the porosity of the samples were determined by a static volumetric gas adsorption technique . measurements were taken using a gas - absorption / desorption analyzer ( trademark : asap 2010 , micromeritics , norcross , ga .). a sample tube containing the sample of titanium dioxide was cooled in liquid nitrogen and evacuated to de - gas the sample . measured amounts of nitrogen gas were then introduced and the amount of nitrogen adsorbed by the nano - crystalline anatase was determined under different pressures . the resulting data , i . e ., curves of the volume of nitrogen adsorbed vs . the relative nitrogen pressure , were reduced using the bet equation to determine the bet specific surface area of the sample and using the bjh method to determine pore size distribution . surface hydroxyl group determination . an acid - base titration method was used to determine the number of the surface sites . anatase titanium dioxide powder was added to pure millipore deionized water to make 100 ml of 10 g / l tio 2 suspension . the ph of the suspension was lowered to ph 3 . 0 using hcl , then the mixture was purged for 2 hrs with nitrogen gas to remove dissolved carbon dioxide . after purging , the ph of suspension was raised to the point of zero charge ( pzc )= 5 . 8 determined by zeta potential measurements , and allowed to rest for 24 hours . the suspension was assumed to be in complete equilibrium , and excess amount of hcl was added and allowed to saturate the suspension for another 24 hours . when completely saturated , the solids in suspension were separated with a 0 . 2 - micron membrane filter , and the supernatant was back - titrated to ph 5 . 8 with naoh . the number of surface sites was calculated by subtracting the number of moles of the back titrant , naoh , from the initial number of moles of hcl added , and dividing the result by the weight of the titanium dioxide used preparation of crystalline titanium dioxide of brookite structure with d ( vol )( 54 å ). titanium sulfate solution with composition similar to that of used industrial titanium dioxide production by sulfate process was prepared having the composition of 250 gram per liter of tio 2 , weight ratio of free sulfuric acid to tio 2 of 1 . 90 : 1 and weight ratio of ferrous sulfate to tio 2 of 0 . 8 : 1 . this solution was fed using peristaltic pump into the glass tube with 10 mm internal diameter and length located inside the constantly heated silicon oil bath with temperature of 105 ° c . the feed rate was 2 ml per minute . the transparent solution became turbid while moving inside the glass tube . after 10 minute in the heating zone , the suspension was rapidly cooled by dividing it into smaller 0 . 3 mm diameter tubes cooled by ice filed water bath . solid titanium oxide suspension was separated by centrifuging of suspension . x - ray powder diffraction analysis showed that the solid consisted entirely of anatase , with broad diffraction lines . crystallite size determined by scherrer equation was 66 å . crystallite size distribution determined by warren - averbach method is shown in fig1 . volume - weighted crystallites size was 54 å and more than 90 percent of crystals were smaller than 100 å . the sample was determined to have a bet specific surface area of about 340 m 2 / gm and a total pore volume of 0 . 42 cm 3 / gm for pores with diameters of less than 0 . 63 μm . yield of titanium dioxide was 65 weight percent . preparation of crystalline titanium dioxide of anatase structure with different crystallite sizes . crystallite size distribution analysis . the same solution used in experiment of example 1 was treated in similar fashion by varying the time of heating , which was easily achieved by adjusting the pumping rate . the solid samples separated from suspensions were analyzed using powder diffraction . some samples were heated at various temperatures . powder diffraction patterns of these samples are presented in fig5 . crystallite size distributions of the samples obtained are shown in fig8 , fig9 , fig1 , and fig1 . comparative analysis of p - 25 ™ from degussa is shown in fig1 . surface hydroxyl group determination for anatase samples . the available surface hydroxyl content of the sample of fig9 was determined to be about 2 . 7 mmol / gm of nano - crystalline anatase . the available hydroxyl content of the sample of fig1 was determined to be about 0 . 6 mmol / gm . batch adsorption test using anatase samples of present invention . batch adsorption of as ( v ) and as ( iii ) from spiked tap water . anatase samples obtained in examples 1 - 14 were used to determination of adsorption properties . aqueous samples of the arsenate ( as ( v )) and arsenite ( as ( iii )), were prepared for testing by dissolving salts of the selected substances in tap water to the initial concentrations of 50 mg / l . batch experiments were conducted by adding the anatase samples to each aqueous sample , to obtain the titanium oxide concentration of 1 g / l and suspending the anatase powder in the aqueous sample by mixing for about three hours . the results ( fig2 ) show that anatase not only effectively removed as ( v ), but also as ( iii ) in a relatively short time , i . e ., three hours or less . the high degree of arsenite ( as ( iii )) removal is particularly noteworthy , since conventional adsorbents , such as alumina or ferric hydroxide , are known to have much lower capacities for removal of this oxyanion . it is also important to note that , the conversion of as ( iii ) to as ( v ) and its adsorption are achieved on samples containing the higher percentage of smaller crystals . these tests demonstrated that presence of chloride , or of other acidic anions , is not necessary for achieving high rates of removal with anatase of the present invention . one can appreciate the advantages of present invention by comparing the adsorption on commercial p - 25 ™ from degussa and on the samples provided by present invention . another important conclusion which can be drawn from the data shown in fig2 that not just crystallite is size important , but the crystallite size distribution as well . in other words , the spherical approximation of scherrer equation does not provide a reliable data that could be used for crystallite size distribution . arsenic removal from spiked tap water column test using anatase sample a glass column with internal diameter of 2 cm was filled with granulated anatase sample prepared as described in fig8 and having 96 . 5 % volume weighted crystallites smaller than 100 å . tap water containing about 20 μg / l spiked with arsenic was pumped through the column at an ebct of about 1 . 5 minute . as shown in fig2 , arsenic concentrations in the treated effluent were less than 10 μg / l , with breakthrough occurring after more than 200 , 000 bed volumes of water had been treated . there is no experimental or industrial adsorbent , which has comparable characteristics . the best adsorbents , known to date , show many times poorer adsorption during column tests than adsorbents of present invention . adsorption of as ( v ) using anatase from sigma aldrich . anatase titanium dioxide supplied by sigma aldrich corporation , st . louis , mo ., usa catalog number a248576 with particles size - 325 mesh was used to test the adsorption property of this material for removal of arsenic from water . 0 . 1 gram of material was contacted with 100 ml of artificially spiked with 50 mg / l as ( v ) water . after three hours the as ( v ) concentration was determined by atomic absorption spectroscopy ( aas ) and found to be 49 . 94 mg / l or about 0 . 1 %. thus , anatase titanium dioxide from sigma - aldrich was found to be highly inefficient adsorbent of as ( v ). this experiment shows that the exceptional adsorption properties of anatase samples of present invention for as ( v ) are achieved not because of the anatase structure or fine particle size , but because of certain crystallite size and their distributions . adsorption of u ( vi ) using anatase from sigma aldrich . anatase titanium dioxide supplied by sigma aldrich corporation , st . louis , mo ., usa catalog number a248576 with particles size - 325 mesh was used to test the adsorption property of this material for removal of uranium from water . 0 . 1 gram of material was contacted with 100 ml of artificially spiked with 1000 ( g / l u ( vi ) water . after three hours the u ( v ) concentration was determined by kinetic phosphorescence analyzer ( kpa ) ( chemchek instruments ) and was found to be 995 mg / l or about 0 . 5 %. thus , anatase titanium dioxide from sigma - aldrich was found to be highly inefficient adsorbent of u ( vi ). this experiment shows that the exceptional adsorption properties of anatase samples of present invention for u ( vi ) are achieved not because of that anatase structure or fine particle size , but because of certain crystallite size and their distributions . preparation of crystalline titanium dioxide of brookite structure with d ( vol )= 35 å yellowish and free from precipitates titanium oxychloride solution with 0 . 25 mol / l concentration is fed by peristaltic pump into a flow reactor which is constantly heated to 105 ° c . the tube reactor diameter and length were chosen to achieve almost immediate heating of solution to 105 ° c . this solution was fed using peristaltic pump into the glass tube with 10 mm internal diameter and length placed into constantly heated silicon oil bath with temperature of 105 ° c . the feed rate was 2 ml per minute . the transparent solution became turbid while moving inside of glass tube . after 30 minute in the heating zone , the suspension was rapidly cooled by dividing it into smaller 0 . 3 mm diameter tubes cooled by ice filed water bath . solid titanium oxide suspension was separated by centrifuging of suspension . x - ray powder diffraction analysis showed that the solid consisted entirely of brookite , with broad diffraction lines . crystallite size determined by scherrer equation was 37 å . crystallite size distribution determined by warren - averbach method is shown in fig1 . volume weighted crystallites size was 35 å and more than 96 . 4 percent of crystals were smaller than 100 å . the sample was determined to have a bet specific surface area of about 370 m 2 / gm and a total pore volume of 0 . 45 cm 3 / gm for pores with diameters less than 0 . 7 μm . yield of titanium dioxide was 24 weight percent . preparation of crystalline titanium dioxide of brookite structure with different crystallite sizes . crystallite size distribution analysis . the same solution used in experiment of example 17 was treated in similar fashion by varying the time of heating , which was easily achieved by adjusting pumping rate . solid samples separated from suspensions were analyzed using powder diffraction . some samples were heated at various temperatures . powder diffraction patterns of these samples are illustrated in fig6 . crystallite size distributions of the obtained samples are shown in fig1 , fig1 , and fig1 . batch adsorption of as ( v ) and as ( iii ) from spiked tap water . brookite samples obtained in examples 17 - 23 were used to determine adsorption properties of various samples . aqueous samples of the arsenate ( as ( v )) and arsenite ( as ( iii )) were prepared for testing by dissolving salts of the selected substances in tap water to the initial concentrations of 50 mg / l . batch experiments were conducted by adding the brookite samples to each aqueous sample , to obtain the titanium oxide concentration of 1 g / l and suspending the brookite powder in the aqueous sample by mixing for about three hours . the results ( fig2 ) show that brookite not only effectively removes as ( v ), but also as ( iii ) in a relatively short time , i . e ., three hours or less . the high degree of arsenite ( as ( iii )) removal is particularly noteworthy , since conventional adsorbents , such as alumina or ferric hydroxide , are known to have much lower capacities for removal of this oxyanion . it is also important to note that , the conversion of as ( iii ) to as ( v ) and its adsorption are achieved on samples containing the higher percentage of smaller crystals . one can appreciate the advantages of present invention by comparing the adsorption on commercial p - 25 ™ from degussa and the samples provided by present invention . another important conclusion can be drawn from data shown in fig2 that the crystallite size distribution is more important than crystallite size . in other words , the spherical approximation of scherrer equation does not provide a reliable data that could be used for crystallite size distribution . freshly prepared and not dried ( wet ) amorphous titanium dioxide is dissolved in nitric acid to form a transparent and free from precipitates solution . the molar ratio of component in the solution is ti : hno 3 : h 2 o = 0 . 02 : 0 . 04 : 60 . the transparent and free from precipitates titanium nitrate solution is fed by peristaltic pump into a flow reactor which was constantly heated to 50 ° c . the tube reactor diameter and length were chosen to achieve almost immediate heating of solution to 50 ° c . the pumping rate was adjusted in such a way that the time of hot solution in a flow reactor varied from 10 to 60 minutes . this solution was fed using peristaltic pump into the glass tube with 10 mm internal diameter and length placed inside the constantly heated silicon oil bath with temperature of 50 ° c . the feed rate was 2 ml per minute . the transparent solution became turbid while moving inside the glass tube . after about 10 minute in the heating zone , the suspension was rapidly cooled by dividing it into smaller 0 . 3 mm diameter tubes cooled by ice filed water bath . solid titanium oxide was separated by centrifuging of suspension . x - ray powder diffraction analysis showed that the solid consisted entirely of anatase , with broad diffraction lines . crystallite size determined by scherrer equation was 66 å . crystallite size distribution determined by warren - averbach method is shown in fig1 . volume weighted crystallites size was 75 å and more than 73 . 1 percent of crystals were smaller than 100 å . the sample was determined to have a bet specific surface area of about 210 m 2 / gm and a total pore volume of 0 . 32 cm 3 / gm for pores with diameters of less than 0 . 45 μm . yield of titanium dioxide was 29 weight percent . the same solution used in experiment of example 25 was treated in similar fashion by varying the time of heating , which was easily achieved by adjusting pumping rate . the solid samples separated from suspensions were analyzed using powder diffraction . some samples were heated at various temperatures . powder diffraction patterns of these samples are illustrated in fig7 . crystallite size distributions of the obtained samples are shown in fig1 , fig1 , and fig1 . comparative analysis of p - 25 ™ from degussa is shown in fig1 . batch adsorption of as ( v ) and as ( iii ) from spiked tap water . rutile samples obtained in examples 25 - 31 were used to determine adsorption properties of various samples . aqueous samples of the arsenate ( as ( v )) and arsenite ( as ( iii )) were prepared for testing by dissolving salts of the selected substances in tap water to the initial concentrations of 50 mg / l . batch experiments were conducted by adding the rutile samples to each aqueous sample , to obtain the titanium oxide concentration of 1 g / l and suspending the rutile powder in the aqueous sample by mixing for about three hours . the results ( fig2 ) show that rutile not only effectively removes as ( v ), but also as ( iii ) in a relatively short time , i . e ., three hours or less . the high degree of arsenite ( as ( iii )) removal is particularly noteworthy , since conventional adsorbents , such as alumina or ferric hydroxide , are known to have much lower capacities for removal of this oxyanion . it is also important to note that the conversion of as ( iii ) to as ( v ) and its adsorption are achieved on samples containing the higher percentage of smaller crystals . these tests demonstrated that presence of chloride , or of other acidic anions , is not necessary for achieving high rates of removal with rutile of the present invention . one can appreciate the advantages of present invention by comparing the adsorption on commercial p - 25 ™ from degussa and the samples provided by present invention . another important conclusion can be drawn from data shown in fig2 that not only crystallite size is important , but the crystallite size distribution is even more important . in other words , the spherical approximation of scherrer equation does not provide a reliable data that could be used for crystallite size distribution . rutile titanium dioxide supplied by sigma aldrich corporation , st . louis , mo ., usa catalog number a224227 with particles size 5 micron was used to test the adsorption property of this material for removal of arsenic from water . 0 . 1 gram of material was contacted with 100 ml of water artificially spiked with 50 mg / l as ( v ). after three hours as ( v ) concentration was determined by atomic absorption spectroscopy ( aas ) and was found to be 49 . 99 mg / l or about 0 . 02 %. thus , rutile titanium dioxide from sigma - aldrich was found to be highly inefficient adsorbent of as ( v ), practically not capable of adsorbing any quantity of dissolved arsenic . this experiment shows that the exceptional adsorption properties of rutile samples of present invention for as ( v ) are achieved not because of the rutile structure or fine particle size , but because of certain crystallite size and their distributions . rutile titanium dioxide supplied by sigma aldrich corporation , st . louis , mo ., usa catalog number a224227 with particles size 5 micron was used to test the adsorption properties of this material for removal of arsenic from water . 0 . 1 gram of material was contacted with 100 ml of water artificially spiked with 1000 g / l u ( vi ). after three hours the u ( vi ) concentration was determined by kinetic phosphorescence analyzer ( kpa ) ( chemchek instruments ) and was found to be 998 g / l or about 0 . 2 %. thus , rutile titanium dioxide from sigma - aldrich was found to be highly inefficient adsorbent of u ( vi ), practically not capable of adsorbing any quantity of dissolved uranium . this experiment shows that the exceptional adsorption properties of rutile samples of present invention for u ( vi ) are achieved not because of the rutile structure or fine particle size , but because of certain crystallite size and their distributions . arsenate adsorption on mixtures . batch adsorption of as ( v ) from spiked tap water . various samples with known phase quantities determined by rietveld quantification method and crystallite size distribution method described earlier ( fig2 and fig2 ) and obtained mostly during rutile synthesis procedures were used for determination of adsorption properties of these mixtures . aqueous samples of arsenate ( as ( v )) were prepared for testing by dissolving salts of the selected substances in tap water to the initial concentrations of 50 mg / l . batch experiments were conducted by adding the mixture samples to each aqueous sample , to obtain the titanium oxide concentration of 1 g / l and suspending the rutile powder in the aqueous sample by mixing for about three hours . the results ( fig2 ) show that the mixtures of samples were as effective in absorption as pure - phase samples . all publications and patent applications mentioned in this specification are indicative of the level of skill of those in the art to which the invention pertains . all publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference in its entirety . although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding , it will be readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto to adapt it to various usages and conditions without departing from the spirit or scope of the invention , as defined by the appended claims . u . s . pat . no . 6 , 383 , 395 ; may 7 , 2002 . water treatment method and apparatus . s . r . clarke et al . u . s . pat . no . 5 , 618 , 437 ; apr . 8 , 1997 . process for removing sulphate from aqueous solution . j . g . ulan et al . u . s . pat . no . 5 , 227 , 053 ; jul . 13 , 1993 . water purification system . s . j . brym u . s . pat . no . 4 , 268 , 399 ; may 19 , 1981 . purification of polluted water . jr . box et al . u . s . pat . no . 4 , 304 , 687 dec . 8 , 1981 catalyst for the purification of polluted water , jr . box et al . u . s . pat . no . 4 , 892 , 712 ; jan . 9 , 1990 , fluid purification . m . k . robertson et al . u . s . pat . no . 3 , 332 , 737 ; jul . 25 , 1967 . process for separating inorganic anions with hydrous oxide anion exchangers . k . a . kraus u . s . patent application publication no . 20030155302 a1 ; aug . 21 , 2003 . methods of preparing a surface - 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