Patent Application: US-201213977445-A

Abstract:
a method includes combining an aqueous solution of sodium fumarate with an aqueous solution of iron chloride to form a mixture , and obtaining an iron coordination polymer as an amorphous compound formed as a precipitate from the mixture . the iron coordination polymer may be used to bind contaminants , such as arsenate and phosphate from water .

Description:
iron - containing coordination polymers were developed to address the removal of arsenic from water . in recognition that the most important component of many of the reagents for arsenate absorption are iron ions , and that most of these materials are restricted to only binding iron on their surfaces , it was decided that a better approach would be to use an insoluble iron - containing coordination polymer that was capable of using all of its iron content to bind arsenate . in the present disclosure , the term insoluble refers to the property that a substance does not separate or dissolve on a molecular level in water . in this way , an insoluble substance remains intact in an aqueous environment , and able to adsorb the target contaminant . several different reagents were prepared by precipitation reactions between aqueous salts iron and either organic dicarboxylates or carboxylate - containing polymers . examples include precipitates formed by reaction of solutions of sodium polyacrylate , sodium carboxymethylcellulose , ammonium terephthalate , or sodium maleate with an aqueous solution of a ferric salt . many of these precipitates can adsorb arsenate but the most effective sorbent was prepared by reaction of sodium fumarate with aqueous ferric chloride . in one embodiment , the arsenate adsorbing precipitate has the formula of fe ( o 2 cch ═ chco 2 ) oh . 1 . 5h 2 o and an approximation of its structure is shown in fig1 . this material can adsorb up to 150 mg arsenate per gram of iron fumarate . the possible binding of arsenate to an iron center by the displacement with water is shown in fig2 . in one example , iron fumarate ( product 1 ) was prepared by adding 300 ml of de - ionized water to 30 . 02 mmol of fumaric acid and 57 . 98 mmol of sodium hydroxide . another aqueous solution was prepared using 300 ml of de - ionized water and 14 . 93 mmol of iron ( iii ) chloride hexahydrate ( a molar ratio of 1 : 2 : 4 iron ( iii ) chloride : fumaric acid : sodium hydroxide ). the first solution was added to the second , resulting in immediate precipitate formation . the resulting mixture was stirred for 30 hours using a magnetic stirrer . the product was obtained by vacuum filtration and washed with copious amounts of de - ionized water . it was then allowed to dry under vacuum , yielding 3 . 156 g ( 9 . 93 mmol , 66 . 5 %) of amorphous iron basic carboxylate powder . within the present disclosure , the term amorphous refers to a substance that does not have any appreciable repeating crystalline structure . thermogravimetric analysis was carried out on product 1 , which indicated a molecular formula of fe 2 ( c 4 h 2 o 4 ) 4 ( oh 2 ) 2 , and a formula weight of 638 g / mol . phosphate adsorption experiments were performed for product 1 . phosphate solutions of increasing concentrations were prepared and added to 0 . 05 grams of iron fumarate prepared as stated . the volume of phosphate solution added was kept constant at 15 ml . after two days , the phosphate concentration was measured using a colorimeter . a langmuir isotherm curve was then prepared from this data as shown in fig3 . in another example , iron fumarate ( product 2 ) was prepared by adding 300 ml de - ionized water to 30 . 03 mmol of fumaric acid and 90 . 46 mmol of sodium hydroxide . another aqueous solution was prepared by adding 300 ml de - ionized water to 30 . 03 mmol of iron ( iii ) chloride hexahydrate ( a molar ratio of 1 : 1 : 3 iron ( iii ) chloride : fumaric acid : sodium hydroxide ). the first solution was added to the second , resulting in immediate precipitate formation . the resulting mixture was stirred for about 7 days using a magnetic stirrer . the product was obtained by vacuum filtration and washed with de - ionized water . it was then allowed to dry under vacuum , yielding 5 . 776 g of product . phosphate adsorption experiments were again performed for product 2 . phosphate solutions of increasing concentrations were prepared and added to 0 . 05 grams of iron fumarate prepared as stated . the volume of phosphate solution added was kept constant at 15 ml . after two days , the phosphate concentration was measured using a colorimeter . a langmuir isotherm curves was then prepared from this data as shown in fig4 . in another example , iron fumarate ( product 3 ) was prepared by adding 0 . 09 mmol ( 3 . 6 g ) sodium hydroxide to 300 ml de - ionized water in a 500 ml erlenmeyer flask . to this solution was added 0 . 03 mmol ( 3 . 482 g ) fumaric acid , which was stirred to dissolution . in a 1 l erlenmeyer flask 0 . 03 mmol ( 8 . 109 g ) of iron chloride hexahydrate was stirred to dissolution in 300 ml of de - ionized water . while stirring slowly , the sodium hydroxide / fumaric acid solution was added to the iron chloride solution . the resulting precipitate was collected by vacuum filtration with a fine porosity glass frit . the collected precipitate was washed with de - ionized water until no chloride was detected ( via formation of silver chloride ). the precipitate was then dried at room temperature under vacuum producing the final product . the surface area of the iron fumarate of product 3 was measured using a quantachrome nova 1200 by the 6 point bet method . the specific surface area was determined to be 18 . 80 m 2 / g . the dry density of product 3 was measured using a graduated cylinder and balance and found to be 0 . 44 g / cm 3 . fig5 illustrates the infrared spectrum of product 3 , while fig6 illustrates the results of a thermogravimetric analysis of the same . the formula of the resultant product is indicated by thermogravimetric analysis as approximately fe ( c 4 h 2 o 4 )( oh ). 0 . 5h 2 o . for testing of product 3 , stock solutions of phosphate were prepared using sodium phosphate monobasic hydrate . 15 ml of each solution was added to a 20 ml scintillation vial and 50 mg of iron fumarate ( product 3 ) was added to each vial . the vials were shaken to ensure uniform distribution of iron fumarate and allowed to react while mixing for a period of two days . after 48 hours , samples were filtered using 10 ml disposable syringes and 0 . 45 micron syringe filters . the solutions were diluted with deionized water until phosphate concentrations were within 0 . 05 to 2 . 5 mg / l , as measured using a hach colorimeter . fig7 illustrates the phosphate update adsorbed with as a result of this experiment . fig8 illustrates the results of a thermogravimetric analysis of the resultant product , while fig9 illustrates the infrared spectrum . infrared spectroscopy suggests that fumaric acid has been replaced by phosphate in the test reactions described above . hence the reaction may be more characteristic of a chemical reaction than adsorption per se . from the foregoing , it was determined that the capacity for adsorption of phosphate of the various iron fumarate products exceeded 480 mg / g . the iron fumarate products of the present disclosure were also tested for absorbency of arsenate and found to have the capacity adsorb 150 mg / g of adsorbent ( 15 % by weight ). fig1 illustrates a langmuir isotherm of iron ( iii ) fumarate absorbency of arsenate ( as 5 + ). fig1 illustrates the kinetics of the adsorption . in another example of the effectiveness of the iron coordination polymer of the present disclosure , ground water contaminated with arsenic was collected from a well in central oklahoma . the sample was analyzed by graphite furnace atomic absorption spectroscopy and found to contain 54 ppm of arsenic . 4 . 9 g of this ground water was treated 58 mg of the iron fumarate coordination polymer of the present disclosure for 12 hours . analysis of the treated sample showed an arsenic concentration of 0 . 24 ppb , a 99 . 6 % reduction . in another test of efficacy , water was collected from an outdoor fountain on the campus of oklahoma christian university . the water was analyzed and found to contain 13 ppb of arsenic . treatment of 10 . 1 g of this water with 10 . 7 mg of the iron fumarate coordination polymer of the present disclosure for 12 hours reduced the arsenic concentration to 0 . 16 ppb . water was prepared that simulated the composition of oil sands tailings pond water . the composition of the water is given in table 1 . treatment of 10 . 0 g of this solution with 9 . 8 mg of the iron fumarate coordination polymer of the present disclosure for 12 hours reduced the arsenic concentration to 0 . 66 ppm . in another example , water was prepared that contained 1000 ppm of arsenic ( as potassium hydrogen arsenate ) as a simulant for waste water from polishing of gallium arsenide wafers . treatment of 10 . 0 g of this solution with 2 . 0 g of the iron fumarate coordination polymer of the present disclosure reduced the arsenic concentration to 5 . 5 ppb , a 99 . 99 % reduction . the above examples are only exemplary methods in which the iron fumarate products of the present disclosure may be formed . it is understood that one of skill in the art will readily adapt these methods to large scale production of the iron fumarate products if so desired . thus , the present invention is well adapted to carry out the objectives and attain the ends and advantages mentioned above as well as those inherent therein . while presently preferred embodiments have been described for purposes of this disclosure , numerous changes and modifications will be apparent to those of ordinary skill in the art . such changes and modifications are encompassed within the spirit of this invention as defined by the claims . masscheyleyn , p . h . ; delaune , r . d . ; patrick , w . h . jr . j . environ qual . 1991 , 20 , 522 - 527 . masscheyleyn , p . h . ; delaune , r . d . ; patrick , w . h . jr . environ sci . technol . 1991 , 25 , 1414 - 1419 . korte , n . e . ; fernando , q . crit . rev . environ . control 1991 , 21 , 1 - 39 . khaodhiar , s . ; azizian , m . f . ; osathaphan , k . ; nelson , p . o . water , air , 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