ARYL MONOSULFONATE COLLECTORS USEFUL IN THE FLOTATION OF MINERALS

Abstract: Dialkylated aryl monosulfonic acids or salts thereof or their mixture are useful as collectors in the flotation of minerals, particularly oxide minerals. Collector compositions comprising these salts and oleic acid are particularly useful in hard water. Collector compositions comprising these salts and sulfide collectors such as xanthates are useful in flotations conducted at natural pH of the slurry.

Description: ARYL MONOSULFONATE COLLECTORS USEFUL IN THE FLOTATION OF MINERALS This invention is related to the use of chemical collectors in the recovery of minerals by froth flotation. Froth flotation has been extensively practiced in the mining industry since at least the early twentieth century. A wide variety of compounds are taught to be useful as collectors, frothers and other reagents in froth flotation. For example, xanthates, simple alkylamines, alkyl sulfates, alkyl sulfonates, carboxylic acids and fatty acids are generally accepted as useful collectors. Reagents useful as frothers include lower molecular weight alcohols such as methyl isobutyl carbinol and glycol ethers. The specific additives used in a particular flotation operation are selected according to the nature of the ore, the conditions under which the flotation takes place, the mineral sought to be recovered and the other additives which are to be used in combination therewith. While a wide variety of chemical reagents are recognized by those skilled in the art as having utility in froth flotation, it is also recognized that the effectiveness of known reagents vary greatly depending on the particular ore or ores being subjected to flotation as well as the flotation conditions. It is further recognized that selectivity or the ability to selectively float the desired species to the exclusion of undesired species is a particular problem. Minerals and their associated ores are generally categorized as sulfides or oxides, with the latter group comprised of oxygen-containing species such as carbonates, hydroxides, sulfates and silicates. Thus, the group of minerals categorized as oxides generally includes any oxygen-containing mineral. While a large proportion of the minerals existing today are contained in oxide ores, the bulk of successful froth flotation systems is directed to sulfide ores. The flotation of oxide minerals is recognized as being substantially more difficult than the flotation of sulfide minerals and the effectiveness of most flotation processes in the recovery of oxide ores is limited. A major problem associated with the recovery of both oxide and sulfide minerals is selectivity. Some of the recognized collectors such as the carboxylic acids, alkyl sulfates and alkyl sulfonates discussed above are taught to be effective collectors for oxide mineral ores. However, while the use of these collectors can result in acceptable recoveries, it is recognized that the selectivity to the desired mineral value is typically quite poor. That is, the grade or the percentage of the desired component contained in the recovered mineral is unacceptably low. Due to the low grade of oxide mineral recovery obtained using conventional, direct flotation, the mining industry has generally turned to more complicated methods in an attempt to obtain acceptable recovery of acceptable grade minerals. Oxide ores are often subjected to a sulfidization step prior to conventional flotation in existing commercial processes. After the oxide minerals are sulfidized, they are then subjected to flotation using known sulfide collectors. Even with the sulfidization step, recoveries and grade are less than desirable. An alternate approach to the recovery of oxide ores is liquid/liquid extraction. A third approach used in the recovery of oxide ores, particularly iron oxides and phosphates, is reverse or indirect flotation. In reverse flotation, the flotation of the ore having the desired mineral values is depressed and the gangue or other contaminant is floated. In some cases, the contaminant is a mineral which may have value. A fourth approach to mineral recovery involves chemical disolution or leaching. None of these existing methods of flotation directed to oxide ores are without problems. Generally, known methods result in low recovery or low grade or both. The low grade of the minerals recovered is recognized as a particular problem in oxide mineral flotation. Known recovery methods have not been economically feasible and consequently, a large proportion of oxide ores are simply not processed. Thus, the need for improved selectivity in oxide mineral flotation is generally acknowledged by those skilled in the art of froth flotation. This invention is a process for the recovery of minerals by froth flotation characterized by the use of a collector comprising: (a) at least one aryl monosulfonic acid or salt thereof having at least two alkyl substituents or mixtures of such salts or acids, or (b) a sulfonic component comprising at least one alkylated aryl monosulfonic acid or salt thereof and a carboxylic component comprising at least one C* | _24 carboxylic acid or salt thereof. The recovered minerals may be the mineral that is desired or may be undesired contaminants. Additionally, the froth flotation process of this invention may utilize frothers and other flotation reagents known in the art. The practice of the flotation process of this invention results in improvements in selectivity and thus the grade of minerals recovered from oxide and/or sulfide ores while generally maintaining or increasing overall recovery levels of the mineral desired to be recovered. The use of the aryl monosulfonic acid or salt thereof having at least two alkyl substituents results in improvements in selectivity or recovery of mineral values when compwered to the use of similar acids or salts having comparable numbers of carbon atoms but only a single substituent. The use of a collector containing the sulfonic component and the carboxylic component results in highly effecient flotation of minerals, particularly in those instances where hard water exists in the flotation environment. The flotation process of this invention is useful in the recovery of mineral values from a variety of ores, including oxide ores as well as sulfide ores and mixed ores. The oxide or oxygen-containing minerals which may be treated by the practice of this invention include carbonates, sulfates, hydroxides and silicates as well as oxides. Non-limiting examples of oxide ores which may be floated using the practice of this invention preferably include iron oxides, nickel oxides, copper oxides, phosphorus oxides, aluminum oxides and titanium oxides. Other types of oxygen-containing minerals which may be floated using the practice of this invention include carbonates such as calcite or dolomite and hydroxides such as bauxite. Non-limiting examples of specific oxide ores which may be collected by froth flotation using the process of this invention include those containing cassiterite, hematite, cuprite, vallerite, calcite, talc, kaolin, apatite, dolomite, bauxite, spinel, corundum, laterite, azurite, rutile, magnetite, columbite, ilmenite, smithsonite, anglesite, scheelite, chromite, cerussite, pyrolusite, malachite, chrysocolla, zincite, massicot, bixbyite, anatase, brookite, tungstite, uraninite, gummite, brucite, manganite, psilomelane, goethite, limonite, chrysoberyl, microlite, tantalite, topaz and samarskite. One skilled in the art will recognize that the froth flotation process of this invention will be useful for the processing of additional ores including oxide ores, wherein oxide was defined to include carbonates, hydroxides, sulfates and silicates as well as oxides. The process of this invention is also useful in the flotation of sulfide ores. Non-limiting examples of sulfide ores which may be floated by the process of this inven ion include those containing chalcopyrite, chalcocite, galena, pyrite, sphalerite, molybdenite and pentlandite. Noble metals such as gold and silver and the platinum group metals wherein platinum group metals comprise platinum, ruthenium, rhodium, palladium, osmium, and iridium, may also be recovered by the practice of this invention. For example, such metals are sometimes found associated with oxide and/or sulfide ores. Platinum, for example, may be found associated with troilite. By the practice of the present invention, such metals may be recovered in good yield. Ores do not always exist purely as oxide ores or as sulfide ores. Ores occurring in nature may comprise both sulfur-containing and oxygen-containing minerals as well as small amounts of noble metals as discussed above. Minerals may be recovered from these mixed ores by the practice of this invention. This may be done in a two-stage flotation where one stage comprises conventional sulfide flotation to recover primarily sulfide minerals and the other stage of the flotation utilizes the process and collector composition of the present invention to recover primarily oxide minerals and any noble metals that may be present. Alternatively, both the sulfur-containing and oxygen-containing minerals may be recovered simultaneously by the practice of this invention. A particular feature of the process of this invention is the ability to differentially float various minerals. The susceptibility of various minerals to flotation in the process of this invention is thought to be related to the crystal structure of the minerals. More specifically, a correlation appears to exist between the ratio of crystal edge lengths to crystal surface area on a unit area basis. Minerals with higher ratios appear to float preferentially when compared to minerals with lower ratios. Thus, minerals whose crystal structure have 24 or more faces (Group I) are generally more likely to float than minerals with 16 to 24 faces (Group II). Group III minerals comprising minerals with 12 to 16 faces are next in order of preferentially floating followed by Group IV minerals with 8 to 12 faces. In the process of this invention, generally Group I minerals float before Group II minerals which would float before Group III minerals which float before Group IV minerals. By floating before or preferentially floating, it is meant that the preferred species float at lower collector dosages. That is, a Group I mineral may be collected at a very low dosage. Upon increasing the dosage and/or the removal of most of the Group I mineral, a Group II mineral is collected and so on. One skilled in the art recognizes that these groupings are not absolute. Various minerals may have different possible crystal structures. Further, the size of crystals existing in nature also varies which influences the ease with which different minerals are floated. An additional factor affecting flotation preference is the degree of liberation. Further, within a group, that is, among minerals whose crystals have similar edge length to surface area ratios, these factors and others influence which member of the group floated first. One skilled in the art can readily determine which group a mineral belongs to by examining standard mineralogy characterization of different minerals. These are available, for example, in Manual of Mineralogy, 19th Edition, Cornelius S. Hurlbut, Jr. and Cornells Klein (John Wiley and Sons, New York 1977). Non-limiting examples of minerals in Group I include graphite, niccolite, covellite, molybdenite and beryl. Non-limiting examples of minerals in Group II include rutile, pyrolusite, cassiterite, anatase, calomel, torbernite, autunite, marialite, meionite, apophyllite, zircon and xenotime. Non-limiting examples of minerals in Group III include arsenic, greenockite, millerite, zincite, corundum, hematite, brucite, calcite, magnesite, siderite, rhodochrosite, smithsonite, soda niter, apatite, pyromorphite, mimetite and vanadinite. Non-limiting examples of minerals in Group IV include sulfur, chalcocite, chalcopyrite, stibnite, bismuthinite, loellingite, marcasite, massicot, brookite, boehmite, diaspore, goethite, samarskite, atacamite, aragonite, witherite, strontianite, cerussite, phosgenite, niter, thenardite, barite, celestite, anglesite, anhydrite, epsomite, antlerite, caledonite, triphylite, lithiophilite, heterosite, purpurite, variscite, strengite, chrysoberyl, scorodite, descloizite, mottramite, brazilianite, olivenite, libethenite, adamite, phosphuranylite, childrenite, eosphorite, scheelite, powellite, wulfenite, topaz, columbite and tantalite. As discussed above, these groupings are theorized to be useful in identifying which minerals float preferentially. However, as discussed above, the collector and process of this invention are useful in the flotation of various minerals which did not fit into the above categories. These groupings are useful in predicting which minerals float at the lowest relative collector dosage, not in determining which minerals may be collected by flotation in the process of this invention. The selectivity demonstrated by the collectors of this invention permits the separation of small amounts of undesired minerals from the desired minerals. For example, the presence of apatite is frequently a problem in the flotation of iron as is the presence of topaz or tourmaline in the flotation of cassiterite. Thus, the collectors of the present invention are, in some cases, useful in reverse flotation where the undesired mineral is floated such as floating topaz or tourmaline away from cassiterite or apatite from iron. In addition to the flotation of ores found in nature, the flotation process and collector composition of this invention are useful in the flotation of minerals from other sources. One such example is the waste materials from various processes such as heavy media separation, magnetic separation, metal working and petroleum processing. These waste materials often contain minerals that may be recovered using the flotation process of the present invention. Another example is the recovery of a mixture of carbon based inks such as graphite ink and other inks in the recycling of paper. Typically such recycled papers are de-inked to separate the inks from the paper fibers by a flotation process. The flotation process of the present invention is particularly effective in such de-inking flotation processes. The aryl monosulfonic acid or monosulfonate collector of this invention comprise an aromatic core having from two to about five alkyl substituents and a sulfonic acid or sulfonate moiety. For purposes of this invention, the term sulfonate include both the sulfonic acid moiety and the sulfonate moiety. It is preferred that the collector has two to three substituents and more preferred that it has two. The aromatic core preferably comprises phenol, benzene, napthalene, anthracene and compounds corresponding to the formula: wherein X represents a covalent bond; —(CO)—; or R wherein R is a linear or branched alkyl divalent moiety having one to three carbon atoms. It is preferred that the aromatic core is benzene, napthalene or biphenyl and more preferred that it is benzene or napthalene and most preferred that it is benzene. The two or more alkyl substituents may be the same or may be different and may be ortho, para or meta to each other with para and meta being preferred and para being more preferred. The alkyl groups may be the same or different and may be substituted or unsubstituted and preferably contain from 3 to 24 carbon atoms. More preferably each of the alkyl groups contains from 6 to 18 carbon atoms and most preferably 8 to 12 carbon atoms. The alkyl groups contain a total of at least 10, more preferably at least 12 and most preferably at least 16 carbon atoms. The maximum total number of carbon atoms in the alkyl groups is preferably no greater than 32 and more preferably no greater than 24. The alkyl groups can be linear, cyclic or branched with linear or branched being preferred. The alkyl substituted aryl sulfonates are available commercially or may be prepared by methods known in the art. For example, the alkyl substituted aryl sulfonate collectors may be prepared by alkylation of aryl centers by nucleophilic aromatic alkylation using alkyl halides, alcohols or alkenes as the alkylation agent with appropriate catalysts. It is a critical feature of the present invention that the aryl sulfonate collectors contain at least two alkyl substituents. It will be recognized by one skilled in the art that methods of production of substituted aryl sulfonates sometimes result in mixtures of non-substituted, mono-substituted, di-substituted and higher substituted aryl sulfonates. Such mixtures are operable in the practice of this invention. It is preferred that at least 15 percent of the alkylated aryl sulfonates contain two or more alkyl substituents. More preferably at least 35 percent of the alkylated aryl sulfonates contain at least two alkyl substituents and even more preferably at least 50 percent of the alkylated aryl sulfonates contain at least two alkyl substituents. In a particularly preferred embodiment, the two or more alkyl groups are different. In this embodiment, it is preferred that one alkyl group is a C- | _g alkyl group and the second alkyl group is a C- |Q _2i | alkyl group. In the preparation of these unsymmetrical sulfonates, alpha-olefins, alkyl halides and alcohols having sufficient carbon atoms to provide the desired hydrophobicity are used as alkylating agents. Typically, groups having from 10 to 24, preferably from 16 to 24 carbon atoms are used. The species which is alklyated is typically toluene, cumene, ethyl benzene or xylene. The alklyated species is sulfonated by methods known in the art. Other sulfonates useful in the collector composition include a central aromatic group having one alkyl substituent and one non-alkyl substituent. Examples of such sulfonates include monoalkylated diphenyloxide sulfonate. Particular examples of unsymmetrically substituted monosulfonates include hexadecyl cumene sulfonic acid, octadecyl cumene sulfonic acid, octadecyl ethylbenzene sulfonic acid, octadecyl p-xylene sulfonic acid, octadecyl o-xylene sulfonic acid, and hexadecyl m-xylene sulfonic acid. The aryl sulfonate collector of this invention is preferably a dialkylated or higher alkylated benzene sulfonate collector and corresponds to the following formula or to a mixture of compounds corresponding to the formula: wherein each R is independently in each occurrence a saturated alkyl or substituted saturated alkyl radical or an unsaturated alkyl or substituted unsaturated alkyl radical; m is at least two and no greater than five; each M is independently hydrogen, an alkali metal, alkaline earth metal, or ammonium or substituted ammonium. Preferably, the R group(s) are independently in each occurrence an alkyl group which has from three to 24, more preferably from 6 to 18 carbon atoms and most preferably 8 to 12 carbon atoms with the proviso that the total number of carbon atoms in the alkyl groups is at least 10, more preferably at least 12 and most preferably at least 16 and no greater than 32, preferably no greater than 24. The alkyl groups can be linear, branched or cyclic with linear or branched radicals being preferred. In one preferred embodiment, the R groups are different with one having from 1 to 3 carbon atoms and the other from 10 to 24 carbon atoms. The M + ammonium ion radicals were of the formula (R'HHN* wherein each R' is independently hydrogen, a C- j -Ci j alkyl or a C 1 -C hydroxyalkyl radical. Illustrative C-J-CIJ alkyl and hydroxyalkyl radicals include methyl, ethyl, propyl, isopropyl, butyl, hydroxymethyl and hydroxyethyl. Typical ammonium ion radicals include ammonium (N + Hi), methylammonium (CH N + H ), ethylammonium (C 2 H5N + H ), dimethylammonium ((CH 3 ) 2 N + H 2 ), methylethylammonium (CH3N + H 2 C 2 H 5 ), trimethyla monium ((CH^J^N + H), dimethylbutylammonium ((CH3) 2 N + HCi j H g ), hydroxyethylammonium (H0CH 2 CH 2 N + H 3 ) and methylhydroxyethylammonium (CH N + H 2 CH 2 CH 2 0H). Preferably, each M was hydrogen, sodium, calcium, potassium or ammonium. The dialkylated sulfonic acid or salt is useful as a collector either alone or in conjunction with the carboxylic component. Another sulfonic compound useful in conjunction with the carboxylic component is an alkylated diaryl oxide sulfonic acid collector known in the art and described in U. S. Patent 5,015,367. In a preferred embodiment, this collector is a diphenyl oxide collector and corresponds to the following formula or to a mixture of compounds corresponding to the formula: wherein each R is independently a saturated alkyl or substituted saturated alkyl radical or an unsaturated alkyl or substituted unsaturated alkyl radical; each m and n is independently 0, 1 or 2; each M is independently hydrogen, an alkali metal, alkaline earth metal, or ammonium or substituted ammonium and each x and y is individually 0 or 1 with the proviso that the sum of x and y is one. Preferably, the R group(s) is independently an alkyl group having from about 1 to about 24, more preferably from about 6 to about 24 carbon atoms, even more preferably about 6 to about 16 carbon atoms and most preferably about 10 to about 16 carbon atoms. The alkyl groups can be linear, branched or cyclic with linear or branched radicals being preferred. It is also preferred that m and n are each one. The M + ammonium ion radicals are of the formula (R') HN + wherein each R' is independently hydrogen, a C* ] -Ci j alkyl or a C- | -Ci j hydroxyalkyl radical. Illustrative C* | -C| | alkyl and hydroxyalkyl radicals include methyl, ethyl, propyl, isopropyl, butyl, hydroxymethyl and hydroxyethyl. Typical ammonium ion radicals include ammonium (N + Hχ j ), me hylammonium (CH N + H ), ethylammonium (C 2 H5N + H 3 ), dimethylammonium ((CH 3 ) 2 N + H 2 ), methylethylammonium (CH 3 N + H 2 C 2 H 5 ) , trimethylammonium ((CH ) N + H), dimethylbutylammonium ((CH 3 ) 2 N + HCi j H g ), hydroxyethylammonium (H0CH 2 CH N + H 3 ) and methylhydroxyethylammonium (CH 3 N + H 2 CH 2 CH 2 OH) . Preferably, each M is hydrogen, sodium, calcium, potassium or ammonium. The carboxylic component is a Cι_24 carboxylic acid or salt thereof. Examples of useful materials include acetic acid, citric acid, tartaric acid, maleic acid, oxalic acid, ethylenediamine dicarboxylic acid, ethyleneamine tetracarboxylic acid and fatty acids. Fatty acids or their salts were particularly preferred. Illustrative examples of such acids include oleic acid, linoleic acid, linolenic acid, myristic acid, palmitic acid, strearic acid, palmitoleic acid, caprylic acid, capric acid, lauric acid and mixtures thereof. One example of a mixture of fatty acids was tall oil. Preferred fatty acids include oleic acid, linoleic acid, linolenic acid and mixtures thereof. The fatty acids may be used in the acid form or may be used in salt form. As used herein, the terms "acid" and"carboxylate" include both the acid and salt form. The collector comprising the sulfonic component and the carboxylic component is particularly useful when hard water is used in the flotation process. In the context of this invention, hard water is water having an equivalent conductivity of ionic strength equal to or greater than that of 50 ppm Na + equivalents. An effective amount of carboxylic component is that amount which, when replacing an equal amount of sulfonate, results in improved recovery of the desired mineral. The amount of carboxylic component used is preferably at least 1 weight percent, more preferably at least 2 weight percent and most preferably at least 5 weight percent, based on the combined weight of the sulfonic and carboxylic components. The maximum amount of carboxylic component used is preferably no greater than 50 weight percent, more preferably no greater than 40 weight percent, and most preferably no greater than 30 weight percent. As will be recognized by one skilled in the art, the optimum amount of carboxylic component used depends on the degree of hardness of the water used in flotation, the minerals to be recovered and other variables in the flotation process. The carboxylic component may be added to the flotation system prior to the addition of the sulfonate or they may be added simultaneously. It is preferred, however, that the sulfonic and carboxylic components be formulated and then added to the flotation system. The collector composition may be formulated in a water based mixture or a hydrocarbon based mixture which depends on the particular application. When a water formulation is used, the sulfonic and/or the carboxylic component are in the salt form. When a hydrocarbon based formulation is used, one or both of the components are in the acid form. Typical hydrocarbon formulations include any saturated hydrocarbon, kerosene, fuel oil, alcohol, alkylene oxide compound, or organic solvents such as dodecene, dimethylsulfoxide, limonene and dicyclo- pentadiene. The type of collector formulation and whether the acid or salt form is used also impacts the preferred ratio of sulfonate to carboxylate. When the salt form is used, the amount of carboxylate used was preferably at least 1 weight percent, more preferably at least 2 weight percent and most preferably at least 5 weight percent, based on the combined weight of the sulfonate and carboxylate component. The maximum amount of carboxylate used is preferably no greater than 60 weight percent, more preferably no greater than 40 weight percent, and most preferably no greater than 25 weight percent. When the acid form is used, the amount of carboxylic component used is preferably at least 1 weight percent, more preferably at least 5 weight percent and most preferably at least 10 weight percent, based on the combined weight of the sulfonic and carboxylic component. The maximum amount of carboxylic component used is preferably no greater than 70 weight percent, more preferably no greater than 50 weight percent, and most preferably no greater than 30 weight percent. In preferred embodiments, both the sulfonic and carboxylic components are in either the salt form or the acid form. Mixed formulations where one is a salt and the other an acid are possible, but are generally not preferred. The acid form, or hydrocarbon based ormulations, are generally preferred in those situations where pH regulators are used to raise the pH above 7. In those instances where the flotation was conducted at a natural pH, it is typically preferred to use the salt form or water based formulations. The collector can be used in any concentration which gives the desired selectivity and recovery of the desired mineral values. In particular, the concen¬ tration used is dependent upon the particular mineral to be recovered, the grade of the ore to be subjected to the froth flotation process and the desired quality of the mineral to be recovered. Additional factors to be considered in determining dosage levels include the amount of surface area of the ore to be treated. As will be recognized by one skilled in the art, the smaller the particle size, the greater the surface area of the ore and the greater the amount of collector reagents needed to obtain adequate recoveries and grades. Typically, oxide mineral ores must be ground finer than sulfide ores and thus require very high collector dosages or the removal of the finest particles by desliming. Conventional processes for the flotation of oxide minerals typically require a desliming step to remove the fines present and thus permit the process to function with acceptable collector dosage levels. The collector of the present invention functions at acceptable dosage levels with or without desliming. Preferably, the concentration of the collector was at least 0.001 kg/metric ton, more preferably at least 0.05 kg/metric ton. It is also preferred that the total concentration of the collector is no greater than 5.0 kg/metric ton and more preferred that it is no greater than 2.5 kg/metric ton. In general, to obtain optimum performance from the collector, it is most advantageous to begin at low dosage levels and increase the dosage level until the desired effect is achieved. While the increases in recovery and grade obtained by the practice of this invention increase with increasing dosage, it will be recognized by those skilled in the art that at some point the increase in recovery and grade obtained by higher dosage is offset by the increased cost of the flotation chemicals. It will also be recognized by those skilled in the art that varying collector dosages are required depending on the type of ore and other conditions of flotation. Additionally, the collector dosage required has been found to be related to the amount of mineral to be collected. In those situations where a small amount of a mineral susceptible to flotation using the process of this invention is present, a very low collector dosage is needed due to the selectivity of the collector. It has been found advantageous in the recovery of certain minerals to add the collector to the flotation system in stages. By staged addition, it is meant that a part of the collector dose is added; froth concentrate is collected; an additional portion of the collector is added; and froth concentrate is again collected. The total amount of collector used is preferably not changed when it is added in stages. This staged addition can be repeated several times to obtain optimum recovery and grade. The number of stages in which the collector is added is limited only by practical and economic constraints. Preferably, no more than about six stages are used. An additional advantage of staged addition is related to the ability of the collector of the present invention to differentially float different minerals at different dosage levels. As discussed above, at low dosage levels, one mineral particularly susceptible to flotation by the collector of this invention is floated while other minerals remain in the slurry. At an increased dosage, a different mineral is floated thus permitting the separation of different minerals contained in a given ore. In addition to the collector of this invention, other conventional reagents or additives may be used in the flotation process. Examples of such additives include various depressants and dispersants well-known to those skilled in the art. Additionally, the use of hydroxy-containing compounds such as alkanol amines or alkylene glycols is useful in improving the selectivity to the desired mineral values in systems containing silica or siliceous gangue. In addition, frothers may be and typically are used. Frothers are well known in the art and reference is made thereto for the purposes of this invention. Examples of useful frothers include polyglycol ethers and lower molecular weight frothing alcohols. Additionally, the collectors of this invention may be used with hydrocarbon as an extender. Examples of hydrocarbons useful in this context include those hydrocarbons typically used in flotation. Examples of such hydrocarbons include fuel oil, kerosene and motor oil. The collectors of this invention may also be used in conjunction with other collectors. For example, it has been found that in the flotation of sulfide mineral containing ores, the use of the collector of this invention with sulfide thiol collectors such as xanthates, dithiol phosphates and trithiol carbonates is advantageous. The use of a collector composition comprising both sulfide collectors and dialkyl aromatic sulfonate collectors is particularly advantageous when it is desired to conduct the flotation at natural or non-elevated slurry pH. The collectors of this invention may also be used in conjunction with other conventional collectors in other ways. For example, the aryl sulfonate collectors of this invention may be used in a two-stage flotation in which the sulfonate flotation recovers primarily oxide minerals while a second stage flotation using conventional collectors recovers primarily sulfide minerals or additional oxide minerals. When used in conjunction with conventional collectors, a two-stage flotation may be used wherein the first stage comprises the process of this invention and is done at the natural pH of the slurry. The second stage involves conventional collectors and is conducted at an elevated pH. It should be noted that in some circumstances, it may be desirable to reverse the stages. Such a two- -stage process has the advantages of using less additives to adjust pH and also permits a more complete recovery of the desired minerals by conducting flotation under different conditions. A particular advantage of the collector of the present invention is that additional additives are not required to adjust the pH of the flotation slurry. The flotation process utilizing the collector of the present invention operate effectively at typical natural ore pH's ranging from 5 or lower to 9. This is particularly important when considering the cost of reagents needed to adjust slurry pH from a natural pH of around 7.0 or lower to 9.0 or 10.0 or above which is typically necessary using conventional carboxylic xanthic collectors. As noted above, a collector composition comprising the collector of the present invention and a xanthate collector is effective at a lower pH than a xanthate collector used alone. The ability of the collector of the present invention to function at relatively low pH means that it may also be used in those instances where it is desired to lower the slurry pH. The lower limit on the slurry pH at which the present invention is operable was that pH at which the surface charge on the mineral species is suitable for attachment by the collector. Since the collector of the present invention functions at different pH levels, it is possible to take advantage of the tendency of different minerals to float at different pH levels. This makes it possible to do one flotation run at one pH to optimize flotation of a particular species. The pH can then be adjusted for a subsequent run to optimize flotation of a different species thus facilitating separation of various minerals found together. The following examples are provided to illus¬ trate the invention and should not be interpreted as limiting it in any way. Unless stated otherwise, all parts and percentages are by weight. The following examples include work involving Hallimond tube flotation and flotation done in laboratory scale flotation cells. It should be noted that Hallimond tube flotation is a simple way to screen collectors, but does not necessarily predict the success of collectors in actual flotation. Hallimond tube flotation does not involve the shear or agitation present in actual flotation and does not measure the effect of frothers. Thus, while a collector generally must be effective in a Hallimond tube flotation if it is to be effective in actual flotation, a collector effective in Hallimond tube flotation is not necessarily effective in actual flotation. It should also be noted that experience has shown that collector dosages required to obtain satisfactory recoveries in a Hallimond tube are often substantially higher than those required in a flotation cell test. Thus, the Hallimond tube work cannot precisely predict dosages required in an actual flotation cell. Example 1 - Hallimond Tube Flotation of Rutile, Apatite, Hematite and Silica 1.1 g sample either the specified mineral or silica sized to about -60 to +120 U.S. mesh was placed in a small bottle with 20 ml of deionized water. The mixture was shaken 30 seconds and then the water phase containing some suspended fine solids or slimes was decanted. This desliming step was repeated several times. A 150-ml portion of deionized water was placed in a 250-ml glass beaker. Next, 2.0 ml of a 0.10 molar solution of potassium nitrate was added as a buffer electrolyte. The pH was adjusted to the specified level with the addition of 0.10 N HCl and/or 0.10 N NaOH. Next, a 1.0-g portion of the deslimed mineral was added along with deionized water to bring the total volume to about 180 ml. The specified collector was added and allowed to condition with stirring for 15 minutes. The pH was monitored and adjusted as necessary using HCl and NaOH. All collectors indicated were converted to the Na + salt form before addition. The slurry was transferred into a Hallimond tube designed to allow a hollow needle to be fitted at the base of the 180-ml tube. After the addition of the slurry to the Hallimond tube, a vacuum of 5 inches of mercury was applied to the opening of the tube for a period of 10 minutes. This vacuum allowed air bubbles to enter the tube through the hollow needle inserted at the base of the tube. During flotation, the slurry was agitated with a magnetic stirrer set at 200 revolutions per minute (RPM). The floated and unfloated material was filtered out of the slurry and oven dried at 100°C. Each portion was weighed and the fractional recoveries of each mineral and silica were reported in Table I below. After each test, all equipment was washed with concentrated HCl and rinsed with 0.10 N NaOH and deionized water before the next run. The recovery of each mineral and silica, respectively, reported was that fractional portion of the original mineral placed in the Hallimond tube that was recovered. Thus, a recovery of 1.00 indicated that all of the material was recovered. It should be noted that although the recovery of each mineral and silica, respectively, was reported together, the data was actually collected in four experiments done under identical conditions. It should further be noted that low silica recovery indicated a selectivity to the the desired minerals. The values given for the various mineral recoveries generally were correct to +0.05 and those for silica recovery were generally correct to +0.03. TABLE I TABLE I (Cont.) TABLE I (Cont.) TABLE I (cont.) TABLE I (cont.) TABLE I (cont.) TABLE I (cont.) TABLE I (cont.) 'Not an embodiment of the invention 2 In these runs, the collector is a mixture of the components listed The data in Table I above demonstrated various aspects of the invention. A comparison of Run 8 with Run 9 or of Run 10 with Run 11 demonstrated that the arrangement of carbon atoms present in the alkyl groups was important. Each pair of runs had the same total number of carbon atoms present, but the dialkylated version shows significantly improved results when compared to monoalkylated version. A comparison of Runs 1-7» 9. 11 and 17-19 > which were not embodiments of the present invention, with the remaining runs, which were embodiments of the present invention, clearly show the importance of total carbon content of the substituents being greater than 12 as well as showing the importance of a degree of alkylation greater than one. Runs 28-30 and 33 show that mixtures of the collectors were effective. Run 34 demonstrates the effectiveness of a compound where one substituent was an ethyl group while the other was a dodecyl and Run 35 similarly demonstrates the effectiveness of compounds where one substituent was an hexyl group while the other was a dodecyl. In each case, the collector was more effective than a collector having more carbon atoms, but in a single substituent rather than split between two substituents. Additionally, comparing those runs where the alkyl groups were asymmetrical with those having similar numbers of carbon atoms in symmetrical alkyl groups, it was shown that asymmetrical alkyl groups provide improved performance. Example 2 - Flotation of Various Oxide Minerals The general procedure of Example 1 was followed with the exception that both the sulfonate and carboxylate components were pre-blended and then added to the slurry. Additionally, the ion concentrations are indicated for those runs where metal ions were deliberately added to the processing water for flotation. The ratio of metal ions added is five parts Na + , two parts Mg ++ , and one part Fe +++ with the total amount of these ions added being determined by measuring the ionic strength of the water in equivalent Na + concentration as measured by a conductivity cell. The data in Table II demonstrate the broad range of minerals which may have been floated using the collector and process of this invention. Table II (Continued) Not an embodiment of the invention -38- The above information demonstrated the effect of ratio of sulfonate to carboxylate and also shows that the combination of sulfonate and carboxylate functions better 5 than either alone. Example 3 - Flotation of Various Oxide Minerals The general procedure of Example 1 was followed with the exception that various oxide minerals were used 10 in place of the ores specified in Example 1. All runs were conducted at a pH of 8.0. The collectors used were a C12 dialkylated benzene sulfonate and a C20-22 toluene sulfonate, each at a dosage of 0.024 kg of collector per _.,- kilogram of mineral. The results are shown in Table III below. 0 5 0 TABLE III © Sample includes some pyrrhotite. ® Sample comprises powdered elemental metal of similar size to other mineral samples. The data in Table III demonstrated the broad range of minerals which may have been floated using the collector and process of this invention. The asymmetrical collector generally outperformed the symmetrical collector at constant dosage. Only in the flotation of silica, dolomite and pyrite (typically viewed as gangue consituents) does the symmetrical collector perform better. Example 4 - Flotation of minerals The procedure of Example 3 was followed with the exception that the collector used was 0.018 of C 12 alkylated benzene sulfonic acid and 0.006 kg of oleic acid per kg of mineral. The sulfonic and oleic components were pre-blended prior to addition to the cell. In all runs, the ratio of metal ions added was five parts Na + , two parts Mg ++ , and one part Fe +++ with the total amount of these ions added being sufficient to result in measured ionic strength of the water being equivalent to Na + of 1000 ppm as measured by a conductivity cell. The results obtained are shown in Table IV below. TABLE IV TABLE IV (Continued) © Sample includes some pyrrhotite. © Sample comprises powdered elemental metal of similar size to other mineral samples. The data in Table IV demonstrated the broad range of minerals which may have been floated using the collector composition and process of this invention. Example 5 - Sequential Flotation This example used the Hallimond tube flotation procedure outlined in Example 1. In each case, the feed material was a 50/50 weight percent blend of the components listed in Table V. The specific collectors used (in the sodium salt form) and the mineral recoveries obtained are also listed in Table V below. All runs were performed at a pH of 7.0. TABLE V 1 Inks are carbon based materials of graphite form. Printed newsprint was soaked in water and caustic with a pH of 9.5 in a hallimond tube and then standard experiment is followed. TABLE V (Cont.) 1 Inks are carbon based materials of graphite form. Printed newsprint was soaked in water and caustic with a pH of 9.5 in a hallimond tube and then standard experiment is followed. TABLE V (Cont.) 1 Inks are carbon based materials of graphite form. Printed newsprint was soaked in water and caustic with a pH of 9.5 in a hallimond tube and then standard experiment is followed. The above data demonstrated that various minerals subject to flotation in the process of the present invention may be effectively separated by the control of collector dosage. For example, while apatite and hematite can both be floated by the process of this invention, it is clear that apatite floats more readily at lower dosages than does hematite. Thus, the apatite can be floated at a first stage, low dosage float. This can be followed by flotation at higher collector dosages to float the hematite. An examination of the other runs in this example demonstrates that similar separations are possible using other minerals. It should also be noted that the asymmetrical collector consistently outperforms the symmetrical collector. Example 6 - Separation of Apatite and Silica A series of 30-g samples of a -10 mesh (U.S.) mixture of 10 percent apatite (Ca5(Cl,F)[P04] 3 ) and 90 percent silica (Siθ2) was prepared. Each sample of ore was ground with 15 g of deionized water in a rod mill (2.5 inch diameter with 0.5 inch rods) for 240 revolutions. The resulting pulp was transferred to a 300 ml flotation cell. The pH of the slurry was left at natural ore pH of 6.7. After addition of the collector (in the sodium salt form) as shown in Table VI, the slurry was allowed to condition for one minute. Next, the frother, a polyglycol ether available commercially from The Dow Chemical Co. as Dowfroth ® 420 brand frother, was added in an amount equivalent to 0.050 kg per ton of dry ore and the slurry was allowed to condition an additional minute. The float cell was agitated at 1800 RPM and air is introduced at a rate of 2.7 liters per minute. The froth concentrate was collected by standard hand paddling for four minutes after the start of the introduction of air into the cell. Samples of the concentrate and the tailings were dried and analyzed as described in the previous examples. The results obtained are presented in Table VI below. Table VI Table VI (Cont.) Table VI (Cont.) Table VI (Cont.) Table VI (Cont . ) x Not an embodiment of the invention. 2 In these runs, the collector is a mixture of the components listed. 3 Mixture added together and then added to cell. Collector mixed with 0.150 kg/metric ton fuel oil #2 and both added to cell. 5 Ionic strength of water used equivalent to 100ppm Na+ impounded by conductivity cell. 6 Ionic strength of water used equivalent to 250ppm Na+ impounded by conductivity cell. 7 Ionic strength of water used equivalent to 500ppm Na+ impounded by conductivity cell. 8 Ionic strength of water used equivalent to lOOOppm Na+ impounded by conductivity cell. The data in Table VI demonstrate the effectiveness of the present invention. Runs 13-20 show the effect of mixing collectors of the present invention with similar monoalkylated species. Clearly the monoalkylated species is significantly less effective than the dialkylated species as shown by the steadily decreasing recoveries obtained when the monoalkylated species are added. For example, a comparison of Run 3 with Run 20 showed that replacing 0.050 kg/metric ton of di-dodecyl benzene sulfonic acid with a similar amount of dodecyl benzene sulfonic acid results in lower recovery. As more monoalkylated species is added, recoveries consistently decline. Runs 9 and 10 again demonstrated that mixtures of the collectors of this invention are effective. Additionally, Runs 21-23 show that the collector of the present invention may be used with hydrocarbons. The replacement of a portion of the collector with a hydrocarbon gives comparable results which is of economic benefit assuming the hydrocarbon is less expensive than the collector. Runs 3 and 24-32 demonstrate the effect of hard water on the present invention and how the use of an oleic acid in conjunction with the dialkylated aromatic sulfonate collector counteracts this effect. The use of oleic acid and di-dodecylbenzene sulfonate together result in recoveries in hard water significantly improved over what either can obtain in hard water. Example 7 - Separation of Apatite and Silica The procedure of Example 6 was followed with the exception that the water used to prepare each sample contained 5 parts Na+, 4 parts Ca++, 2 parts Mg++, and 1 part Fe+++ in the appropriate amounts to produce the ionic strengths indicated in the Table VII. The ionic strengths were measured in Na+ equivalents using a conductivity cell. The results obtained are shown in Table VII below. TABLE VII (Cont.) TABLE VII (Cont.) TABLE VII (Cont.) TABLE VII (Cont.) I 2 Components added to cell separately and sumultaneously. I 3 Carboxylate added to cell first, conditioned for one minute followed by addition of sulfonate. Sulfonate added to cell first, conditioned for one minute followed by carboxylic addition. 5 Not an embodiment of the invention. The data in Table VII demonstrate the effectiveness of the present invention. It is of particular interest to note that the collector composition resulted in efficient recovery of the desired minerals in water containing high amounts of salts. When compared with either the sulfonate or carboxylate component alone, the combination results in enhanced recoveries. The importance of preferred ratios of sulfonate to carboxylate is demonstrated in, for example, Runs 15-17 and Runs 2-4. Example 8 - Flotation of Mixed Copper Sulfide Ore Containing Molybdenum A series of 30-gram samples of a -10 mesh (U.S.) ore from Arizona containing a mixture of various copper oxide minerals and copper sulfide minerals plus minor amounts of molybdenum minerals was prepared. The grade of copper in the ore was 0.013 and the grade of the molybdenum was 0.00016. Each sample of ore was ground in a laboratory swing mill for 10 seconds and the resulting fines were transferred to a 300 ml flotation cell. Each run was conducted at a natural ore slurry pH of 6.5. The collector (in the sodium salt form) was added at a dosage of 0.150 kg/ton of dry ore and the slurry was allowed to condition for one minute. Ore concentrate was collected by standard hand paddling between zero and four minutes. Just before flotation was initiated, a frother, a polyglycol ether available commercially from The Dow Chemical Company as Dowfroth ® 250 brand frother, was added in an amount equivalent to 0.030 kg/ton of dry ore. The float cell in all runs was agitated at 1800 RPM and air was introduced at a rate of 2.7 liters per minute. Samples of the concentrates and the tailings were then dried and analyzed as described in the previous examples. The results obtained are presented in Table VIII below. ©Not an embodiment of the invention ©The collector is a mixture of the components listed. ©Collectors are added to the cell at the same time. ©Run conducted at a pH of 9.5. The data in the above table demonstrate the effectiveness of the present invention in the recovery of copper and molybdenum. Runs 10-12 demonstrate the effectiveness of collector compositions containing the dialkylated aromatic sulfonate and a xanthate collector are in recovering copper and molybdenum at lower pH. It should be noted that Run 12, not an embodiment of the invention, was conducted at a pH of 9.5 after attempts to conduct flotations at a pH of 6.5 resulted in essentially no recovery. However, when the xanthate replaces comparable amounts of di-dodecylbenzene sulfonate, good recoveries are obtained at the lower pH. Example 9 - Flotation of Mixed Copper Sulfide Ore Containing Molybdenum The procedure in Example 9 was followed with the exception that the water used contained 600 ppm Ca ++ , 20 ppm Fe +++ , 140 ppm S04 = and 50 ppm Mg ++ . Each run was conducted at a natural ore slurry pH of 6.5. The collector composition (in the sodium salt form) was added at a total dosage of 0.150 kg/ton of dry ore and the slurry was allowed to condition for one minute. Ore concentrate was collected by standard hand paddling between zero and four minutes. Just before flotation was initiated, a frother, a polyglycol ether available commercially from The Dow Chemical Company as Dowfroth ® 250 brand frother, was added in an amount equivalent to 0.030 kg/ton of dry ore. Samples of the concentrates and the tailings were then dried and analyzed as described in the previous examples. The results obtained are presented in Table IX below. TABLE IX The data in the above table demonstrate the effectiveness of the present invention in the recovery of copper and molybdenum. In particular, it shows that, in this system, the ratio of sulfonate to oleate collector that is most effective is ranges from 30:1 to 2:1. Example 10 - Flotation of Iron Oxide Ore A series of 600-g samples of iron oxide ore from Michigan was prepared. The ore contained a mixture of hematite, martite, goethite and magnetite mineral species. Each 600-g sample was ground along with 400 g of deionized water (Runs 1-10) in a rod mill at about 60 RPM for 10 minutes. In Runs 11-40, water containing 300 ppm Ca + , 10 ppm Fe +++ , 80 ppm S04 = , 20 ppm Cl " and 40 ppm Mg ++ was used. The resulting pulp was transferred to an Agitair 3000 ml flotation cell outfitted with an automated paddle removal system. The collector was added and the slurry was allowed to condition for one minute. Next, an amount of a polyglycol ether frother equivalent to 40 g per ton of dry ore was added followed by another minute of conditioning. The float cell was agitated at 900 RPM and air was introduced at a rate of 9.0 liters per minute. Samples of the froth concentrate were collected at four minutes after the start of the air flow. Samples of the froth concentrate and the tailings were dried, weighed and pulverized for analysis. They were then dissolved in acid, and the iron content determined by the use of a D.C. Plasma Spectrometer. Using the assay data, the fractional recoveries and grades were calculated using standard mass balance formulas. The results are shown in Table X below. TABLE X TABLE X (Cont.) TABLE X (Cont.) TABLE X (Cont. ) ©Not an embodiment of the invention ®The collector is a mixture of the components listed. ®The two components are mixed together before addition to cell. A comparison of Runs 4 and 11 and of Runs 3 and 12 show the effect of hard water on the collectors of the present invention. An examination of Runs 11-40 show the effect of mixtures of collectors of the present invention with oleic acid to overcome the detrimental effects of hard water. When oleic acid or oleate was mixed with the collectors of the present invention, results comparable to those obtained in deionized water are obtained even when using the very hard water used in those runs. Oleate itself used in hard water also results in poor recovery as shown in Runs 13 and 14. It is the mixtures shown in Runs 15 and 17 that demonstrate surprising results. Example 11 — Separation of Apatite and Silica The procedure outlined in Example 6 was used with the exception that deionized water was replaced with water having 600 ppm Ca ++ , 20 ppm Fe +++ , 140 ppm and 50 ppm Mg ++ . The results obtained are shown in Table VII below: TABLE XI lNot an embodiment of the invention. 2Two components mixed together before addition to cell. 3First component added to cell, conditioned for one minute followed by second component added to cell conditioned for one minute. 4 Second component added to cell, conditioned for one minute followed by addition of first component added to cell conditioned for one minute. δMixture of oleic, linoleic and linoleic acids. S Mixture added to grinding step. The data in Table XI above shows that higher collector dosages are required in the presence of the hard water used in this example. The examples also demonstrate the benefits obtained when the collectors of the present invention are used with fatty acids. The benefits are most noticeable when the two types of acids are mixed together prior to being added to the float cell as in Runs 9-12 and 15 or are mixed and added to the grinding step as shown in Runs 18-19. Example 12 - Flotation of Ink from Printed Paper A special column flotation cell with a one inch diameter glass tube 16 inches tall with a porous frit at the bottom thorugh which air can be introduced was used. Air was introduced through the porous frit at the rate of 3 liters/minute. One gram samples of printed material (70 percent newsprint and 30 percent magazine) were soaked in 50 cm 3 of water containing sufficient sodium silicate to raise the slurry pulp pH to 9.5. The collector was added to the mixture and then it was mixed in a blender for 10 minutes. The collector concentration was 0.5 kg/metric ton of dried printed material. The contents were transferred to the column cell and sufficient water is added to bring the slurry level to the top of the cell. Air was then introuduced causing the liberated ink to rise to the top of the column where it is collected, weighed and anlayzed. Dried mats of the remaining de-inked fiber in the cell were made and a brightness meaurement was conducted on a light meter using white light as a basis. TABLE XII t an embodiment of the invention

Claims: CLAIMS: 1. A process for the recovery of minerals by froth flotation wherein an aqueous slurry of particulate minerals is subjected to froth flotation characterized by the use of a collector comprising (a) at least one aryl monosulfonic acid or salt thereof having at least two alkyl substituents or mixtures of such salts or acids, or (b) a sulfonic component comprising at least one alkylated aryl monosulfonic acid or salt 10 thereof and a carboxylic component comprising at least one C- |-2 4 carboxylic acid or salt thereof. 2. The process of Claim 1 wherein the • j c collector comprises aryl monosulfonic acids or salts thereof wherein at least about 15 percent of such acids or salts have at least two alkyl substituents. 3. The process of Claim 1 or 2 wherein the 0 aryl monosulfonic acid or salt thereof corresponds to the formula 5 wherein each R is independently in each occurrence a saturated alkyl or substituted saturated alkyl radical or an unsaturated alkyl or substituted unsaturated alkyl radical, with the proviso that the total number of carbon atoms in the alkyl groups is at least 12 and no greater than about 32; m is at least two and no greater than five; each M is independently hydrogen, an alkali metal, alkaline earth metal, or ammonium or substituted ammonium. 4. The process of Claim 3 wherein R 1 is independently in each occurrence an alkyl group having from about 8 to about 12 carbon atoms. 5. The process of Claim 1 wherein the process is conducted at the natural pH of the slurry. 6. The process of Claim 1 wherein the collector further comprises a sulfide collector. 7. The process of Claim 6 wherein the sulfide collector is selected from the group consisting of xanthates, dithiol phosphates and trithiol carbonates. 8. The process of Claim 1 wherein the C _24 carboxylic acid comprises a fatty acid or salt thereof. 9. The process of Claim 8 wherein the fatty acid or salt is selected from the group consisting of oleic acid or salt, linoleic acid or salt, linolenic acid or salt and mixtures thereof. 10. A collector composition comprising (1 ) at least one aryl monosulfonic acid or salt thereof having at least two alkyl substituents or mixtures of such salts or acids and (2) a fatty acid or salt thereof. 11. The composition of Claim 10 wherein the fatty acid or salt thereof is selected from the group consisting of oleic acid or salt thereof, linoleic acid or salt thereof, linolenic acid or salt thereof and mixtures thereof. 12. The process of Claim 1 wherein the recovered mineral comprises ink and the aqueous slurry comprises pulped paper.

Inventors: FRAZIER KEVIN A, KLIMPEL RICHARD R, LEONARD DONALD E, MCCANN GORDON D, FRAZIER, KEVIN, A., KLIMPEL, RICHARD, R., LEONARD, DONALD, E., MCCANN, GORDON, D.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1991
Main classification: B03D1
IPC codes: B03D1