CA1264919A - Inorganic anion exchangers and preparation thereof - Google Patents
Inorganic anion exchangers and preparation thereofInfo
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- CA1264919A CA1264919A CA000512034A CA512034A CA1264919A CA 1264919 A CA1264919 A CA 1264919A CA 000512034 A CA000512034 A CA 000512034A CA 512034 A CA512034 A CA 512034A CA 1264919 A CA1264919 A CA 1264919A
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- exchanger
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Abstract
ABSTRACT
A novel composition including an inorganic mixed metal oxides and partially hydrated oxides exhi-biting anion exchange properties is disclosed. Also a process of preparing the exchanger composition is dis-closed which involves (a) coprecipitating hydroxides or hydrated oxides of a pair of metal elements such, as aluminum and titanium, (b) drying the mixed metal hydroxides or hydrated oxides, (c) exchanging the anion of the mixed metal hydroxide or hydrated oxide for a nonvolatile anion, such as a sulfate anion, and (d) calcining the mixed metal hydroxide or hydrated oxide to form a mixed metal oxide or partially hydrated oxide exhibiting anion exchange properties.
A novel composition including an inorganic mixed metal oxides and partially hydrated oxides exhi-biting anion exchange properties is disclosed. Also a process of preparing the exchanger composition is dis-closed which involves (a) coprecipitating hydroxides or hydrated oxides of a pair of metal elements such, as aluminum and titanium, (b) drying the mixed metal hydroxides or hydrated oxides, (c) exchanging the anion of the mixed metal hydroxide or hydrated oxide for a nonvolatile anion, such as a sulfate anion, and (d) calcining the mixed metal hydroxide or hydrated oxide to form a mixed metal oxide or partially hydrated oxide exhibiting anion exchange properties.
Description
1264c919 INORGANIC ANION EXCHANGERS
AND PREPARATION THEREOF
This invention concerns ion exchangers and, more particularly, inorganic anion exchangers.
U.S. Patent 3,002,932 describes several noncrystalline inorganic anion exchangers consisting essentially of hydrated oxides of pairs of elements selected from the group consisting of aluminum, silicon, titanium, zinc, and zirconium. The compositions above are prepared by coprecipitating the hydrates of the combination of the oxides of the elements referred to above in an aqueous medium. The coprecipitation is carried out by gradually adding a base to an acid below a pH of 5 to bring the aqueous solution to a pH of about 5 to 7. The agueous mixture is dried below about 150C, followed by washing the dried mixed hydrated oxide with water, and again finally drying the mixture below about 150C.
31,630-F -1-.,~,. ..
126~9~9 In a paper by E. J. Duwell and J. W. Shepard, "The Preparation and Properties of Some Synthetic Inorganic Anion Exchangers", Journal of PhYsical Chemistry, Volume 63, December, pages 2044-47, (1959), various amorphous inorganic anion exchangers are described. The paper describes a method for preparing an amorphous Zn(OH)2 exchanger and ~l(OH)3 exchanger.
The amorphous exchangers are prepared by coprecip-itating cations of higher valence with aluminum and zinc hydroxide in slightly acidic solutions to form a gel. The gels are then dried to form whi~e, ~inely divided amorphous powders of Al(OH)3 and Zn(OH)2.
The prior art above states that dehydration of the exchangers at 150C results in the loss of anion exchanger capacity. Thus, the compositions prepared by the methods disclosed in the above art are unsatis-factory as anion exchangers at temperatures above 150C .
It is desired, therefore, to provide novel inorganic anion exchangers with increased thermal and chemical stability at elevated temperatures and with greater exchange capacity at elevated temperatures than previously known inorganic exchange materials. It is also desired to provide a process by which these anion exchangers may be prepared.
One aspect of the present invention is an anion exchanger material comprising a material exhi-biting anion exchange properties at temperatures of above 160C, said material represented by the formula:
31,630-F -2-~2649'19 ( I ) [Mla x Qx 1 oy (OH) ~ (A l)d(A 2)e(A 3)f(A 4)g nH20 wherein M is a metal element or elements each with a positive valence of a; Q is a metal element or elements each with a positive valence of a+1; a is 2, 3, 4, or 5, A 1, A 2, A 3, and A 4 are each one or more exchange-able anions each having a negative valence of 1, 2, 3, and 4, respectively; x is O < x < 0.5; and n, y, z, d, e, f, and g are real numbers greater than or equal to zero and satisfy the following:
< z/y C 1.0 2y ~ z = a O < d + 2e + 3f + 4g < x O < n < 10 is provided that when y = O, a is not e~ual to 2.
Another aspect of the present invention is a process of preparing the compositions of formula (I) which comprises providing an inorganic mixed metal hydroxide or hydrated oxide having anion exchange propertie~, exchanging the anion of the mixed metal hydroxide or hydrated oxide for a non-volatile anion, and heating the exchanged mixed metal hydroxide or hydrated oxide to form a mixed metal oxide exhibiting anion exchange properties at above 160C.
The novel compositions of the formula (I) include mixed metal oxides and partially hydrated mixed 31,630-F -3-~26491g metal oxides exhibiting anion exchange properties. The compositions consist essentially of a combination of oxides and hydrated oxides of pairs of metal cations or elements. A first metal element of the pair of metal elements has a lower valence than that of a second metal element of the pair of metal elements. The first lower valent member has a positive valence lower by one integer than that of the second higher valent member of the pair. For example, if the first metal element has a ~alence of +2, the second metal element has a valence of +3, and i~ the first metal element has a valence of +3 then the second metal element has a valence of +4, and so on.
The first lower valent metal element of the compositions of formula (I) is present in a major molar amount and the second higher valent metal element is present in a minor molar amount. It is theorized that the minor constituent is substituted in the lattice structure of the major constituent. The combination of the oxides and hydrated oxides of the pair of metal elements has a positive excess charge and this charge is balanced by an exchangeable anion or a mixture of two or more exchangeable anions.
The mixed metal oxides and partially hydrated mixed metal oxides of the present invention may also be represented by the general formula (I) above. A
"hydroxide" is represented by the formula when y=0; an "oxide" is represented by the formula when z=0; and a "partially hydrated oxide" is represented by the formula when y and z are both positive real numbers. Prefer-ably, y is 1 and z is 0 or 1. The range for x is preferably from about 0.01 to about 0.4.
31,630-F -4-~2649~
As an example of the composition of the present invention, the metal element or elements M each may have a valence of +2 and the metal element or elements Q each may have a valence of +3. The metal element M with a +2 valence may be selected from ele-ments such as magnesium, calcium, strontium, barium, iron, cobalt, mang~nese, nickel, copper, zinc and mixtures thereof, and the metal element Q with a valence of +3 may be selected from elements such as aluminum, iron, chromium, gallium, cobalt, rhenium, indium and mixtures thereof.
Another example of a combination of metal elements illustrating the present invention is the metal element or elements M each having a valence of +3 such as those listed above and the metal element or elements Q each having a +4 valence including, for example, titanium, germanium, tin, lead, zirconium, hafnium, vanadium ana mixtures thereof. Still another example of a combination of metal elements illustrating the present invention is the metal element or elements M each having a valence of +4 such as those listed above and the metal element or elements Q each having a +5 valence including, for example, antimony, vanadium, niobium, tantalum and mixtures thereof. Yet another example of a combination of metal elements illustrating the present invention is the metal element or elements M each having a +5 valence such as those listed above and the metal element or elements Q each having a +6 valence including, for example, chromium, molybdenum, tungsten and mixtures thereof.
Preferably, a pair of metal elements M and Q
selected from the group magnesium, aluminum and titanium 31,630-F -5-~Z649~9 are used in the present invention. More preferably, mixed metal oxides or partially hydrated mixed metal oxides of aluminum and titanium, and mixed metal oxides or partially hydrated mixed metal oxides of magnesium and aluminum are used as the anion exchange material as herein described.
The preferred compositlons of the present invention having a pair of elements of aluminum and titanium may be represented by the following general formula:
(II) ~All X TiX Oy (0~)~ (A l)d(A 2)e(A 3~f(A 4)g- nH2O
where A 1, A 2, A 3, and A are each one or more exchangeable anions each having a negative valence of 1, 2, 3, and 4, respectively; x is 0 < x < 0.5, and n, y, z, d, e, f, and g are real numbers greater than or egual to zero and satisfy the following:
O < z/y < 1.0 ~ 2y + z = a 20 0 c d + 2e + 3f + 4g < x 0 < n < 10 Thus, formula II above is equivalent to formula I where M is Al and Q is Ti.
31,630-F -6-lZ6~
The preferred compositions of the present invention having a pair of elements of magnesium and aluminum may be represented by the following general formula:
(III) Egl-x Alx y (oH)3 (A )d(A )e(A 3)f(A 4) nH O
where A 1, A 2, A 3, and A 4 are each one or more exchangeable anions each having a negative valence of 1, 2, 3, and 4, respectively; x is 0 c x < 0.5, and n, y, z, d, e, f, and g are real numbers greater than or equal to zero and satisfy the following:
O < z/y < 1.0 2y + z = a 0 < d-+ 2e + 3f + 4g < x 0 < n < 10 Thus, formula III above is equivalent to formula I
where M is Mg and Q is Al.
The "exchangeable anions" of the aforemen-tioned compositions may be selected from any inorganic or organic exchangeable anions commonly known in the art of anion exchangers. The exchangeable anions may be selected from monovalent, bivalent, trivalent, tetravalent anions, or mixtures of two or more of these exchangeable anions. In the above formulas, the anion A 1, for example, may be an inorganic anion selected from halides such as fluorides (F 1), chlorides (Cl l);
31,630-F -7-~64~1g bromides (Br 1); and iodides (I l); sulfates such as HSO4 ; phosphates such as H2PO4 ; permanganates (MnO41); nitrates (NO31); carbonates such as HCC31;
hydroxides (OH 1); and mixtures thereof. For example, th~ anion A 1 may be a combination of two or more exchangeable anions described above such as a mixture of Cl 1 and HCO 1 anions. In the above formulas, the anion A 2, for example, may be an inorganic anion selected from carbonates such as C032; sulfates such as S042; phosphates such as HPO4 2; and mixtures thereof. For example, the anion A , may be a com-bination of two or more exchangeable anions described above such as a mixture of S042 and C032. In the above formulas, the anion A 3, for example, may be a phos-` 15 phate such as PO43. An example of the anion A 4 used in the above formulas may include organic anions such as ethylenediaminetetraacetic acid (EDTA3 and diphos-phates such as (OH)2 (~)2 o=P-CH2-P=O -Other organic exchangeable anions used in the above formulas may include, for example, stearates, formates, benzoates and mixtures thereof.
,.~
In addition to the above anions used in the present invention, the compositions of the present invention may include a combination of two or more exchangeable anions selected from the group A 1, A 2, A 3 and A 4 as described above. For example, the compositions may include a mixture of exchangeable anions such as Cl 1 and C032 anions or Cl 1 and S042 anions. Preferably, the exchangeable anion in the 31,630-F -8-~6~9 g above compositions of the present invention is a sulfate anion. The total negative charge of the exchangeable anion or mixture of exchange~ble anions should be sufficient to balance the excess positive charge of the combination of pairs of metal oxides and hydrated oxides of the composition. The exchangeable anions of the composition is present and bound, i.e., firmly incorporated, in the lattice structure of the composition. Generally, the exchangeable anion cannot be washed free of the composition and remains in the composition until the exchangeable anion is exchanged for or replaced by another anion.
The compositions of formula (I) are charac-terized as exhibiting anion exchange properties, i.e., anion exchange capacity, and, thus, are useful as anion exchangers. Generally, the anion exchangers exhibit anion exchange capacity at elevated temperatures, for example, above 160C~and up to 800C. Typically, anion exchangers in the prior art have been thermally unstable and lose anion exchange capacity at temperatures of above 150C. The anion exchangers of the present invention are particularly useful at temperatures of from 160C to 800C. Preferably, the exchangers of the present invention are used in the temperature range from 160C to 500C.
The anion exchangers of formu~la (I) also exhibit high anion exchange capacities in the tem-perature range described above. Generally, the anion exchange capacity of the exchanger may range from 0.5 milliequivalent per gram (meq/g) to 2.0 meg/g and preferably from 0.5 meq/g to 1.0 meq/g.
31,630-F -9-~2649~9 In its broadest scope, the compositions of the present invention are synthesized via controlled techniques of precipitation, drying, washing, ion exchange and calcination. More particularly, the compositions of the present invention are prepared by coprecipitating mixed metal hydroxides or hydrated mixed metal oxides followed by drying by evaporation, washing with a solvent such as water, exchanging the anion of the coprecipitated mixed metal hydroxides or hydrated mixed metal oxides for another anion, described hereinafter as a ~nonvolatile anion~, and then calcining the mixed metal hydroxides or hydrated mixed metal oxides to form mixed metal oxides or partially hydrated mixed metal oxides.
In carrying out the method of the present invention, a precursor mixed metal hydroxide or hydrated mixed metal oxide anion exchanger (precursor material) i.e., having an anion exchange capacity, is first provided as a starting material. The precursor material may be an amorphous or crystalline material prepared by known methods in the art. For example, the coprecipi-tation method described in U.S. Patent 3,002,932 may be used to prepare an amorphous or noncrystalline mixed metal hydrated oxide which is useful as the precursor material in the present invention. Preferably, a precursor material determined by X-ray diffraction, electron diffraction, electron microscopy or micro area X-ray fluorescence analysis to be crystalline is used in the present invention.
Generally, the precursor material is prefer-ably prepared by precipitating mixed metal hydroxides 31,630-F -10-~26~9~C~
--ll--and hydrated mixed metal oxides, drying the precipitate, and then exchanging the anion of the mixed metal hydroxide or hydrated oxide anion exchanger with a nonvolatile anion.
A "nonvolatile anion" is an exchangeable anion bound to the lattice st~ucture of the precursor material which (a) does not react with some other component of the precursor resulting in loss of the precursor material's anion exchange capacity and/or (b) does not volatilize to form a gaseous product resulting in a loss of the precursor material's anion exchange capacity when the precursor material is sub-jected to heating or to calcination temperatures described hereinafter. For example, a Cl anion may evolve a HCl gas upon calcining the precursor material and, therefore, considered a volatile anion. Nonvolatile anions used in the present invention include, for example, sulfates, phosphates, chromates, molybdates, tungstates, niobates, and nitrates, with sulfates being the most preferred.
Any salt of the above nonvolatile anion materials may be used to exchange the anion of the precursor material.
,~ Preferably, potassium sulfate or sodium sulfate is used rr because it is readily available, relatively inexpensive and easily handled in the present process.
As an illustration of one embodiment of preparing the precursor material of the present invention, salts or other derivatives of metals M and Q of the composition of the present invention, are dissolved in a solvent such as water. Preferably, the stoichiometric ratio of Q/M should be above zero to 0.5. The total concentration of M and Q used in the solution may .
31,630-F
~26491C~
be above 0.1 molar and preferably, above 0.5 molar.
The salts used may be acidic, and which on neutral-ization with a base p;ecipitate the hydroxides or hydrated oxides of metals M and Q. Water-soluble salts or water-insoluble salts may be used. The water-soluble salts may include, for example, salts of chloride (Cl 1); sulfates (S042); nitrates (N031);
carbonates ~C032); and mixtures thereof of the metals M
and Q. Water insoluble salts used may include salts of hydroxides. Preferably, the water-soluble salts of elements M and Q are used.
The preferred base used for neutralization and consequent coprecipitation of the hydroxide or hydrated oxides are the alkali metal bases such as sodium hydroxide or potassium hydroxide. Other bases may include, for example, ammonium hydroxide.
Coprecipltation of the mixed metal hydroxides or hydrated mixed oxides is preferably carried out in an aqueous media at a p~ suitable to produce anion exchange capacity in the hydroxides or hydrated oxides.
The preferred pH is a function of the metal cations or elements used to form the composition of the present invention. For example, an aluminum and titanium oxide material may be formed by coprecipitating an aluminum and titanium hydroxide or hydrated oxide at a pH of 3 to 7, preferably at a pH of 4 to 6, and more preferably at a pH of 6 ~ 1. The coprecipitation is carried out at a temperature of from room temperature (~20C) to 150C, preferably from 50C to 100C, and more pre-ferably from 70C to 90C. As another example ofpreparing a precursor material, a magnesium and 31,630-F -12-~L26~9 aluminum oxide material may be formed by copre-cipitating a magnesium and aluminum hydroxide or hydrated oxide ct a pH of 8 to 13, and preferably at a pH of 9 to 11. The coprecipitation is carried out at a S temperature of from about room temperature to 150C, prefexably from 30C to 90C, and more preferably from 40~C to 60C.
During the coprecipitation above, a precip-itate material containing a substantial quantity of 10 water is formed when the combination of hydroxides or hydrated oxides are precipitated. The major portion of the water may be removed or separated from the precip-itate, for example, by filtration techniques known in the art. After separating the precipitate material - 15 from the aqueous media, the material is then dried by heating in air at relatively low temperatures to remove ~ the water in the material. Preferably, a temperature ti~ below 150C and more~preferably a temperature being in the range of 100C to below 150C is used to dry the ; 20 material. This dried product may then be washed free `~ of impurities such as sodium chloride, with water such o as distilled or deionized water. Removal of such ` impurities is carried out with water at a pH of from 4 to 7. The washed material may be used as the precursor 25 material which is then exchanged with a nonvolatile anion described above.
:
After the anion of the precursor mixed metal ~ hydroxide or hydrated oxide anion exchanger has been - exchanged for a nonvolatile anion, the resulti~g 30 exchanged material is heated or calcined at a tempera-ture sufficient to form a mixed metal oxide or par-tially hydrated mixed metal oxide exhibiting anion :'~
;~ 31,630-F -13-12649~9 exchange properties. Calcination temperatures may rangé from 160C to 800C. Preferably, a temperature range of ~00C to ~00C is used. The length of time of calcination may vary, but calcination should be carried out for a length of time sufficient to remove substan-tially all of the water present in the material.
Generally, 10 minutes to 3 hours may be used. A white, free-flowing powdery material results after calcination and is characterized as being a mixed metal oxide or partially hydrated mixed metal oxide having anion exchange capacities at above 160C.
Optionally, the exchanged material may be washed with water and separated from the aqueous media by well known means, such as vacuum filtration and then dried at a relatively low temperature, such as below 150C prior to the calcination step described above.
The dried material calcined at the afore-mentioned calcination temperature is a white, free-flowing, fine, powdery product, typically containing solids having a particle size of 10 microns or less and preferably a particle size of 5.0 microns or less. The powder particles may easily be broken up into indi-vidual particles having a size of from 0.1 to 0.4 micron by techniques known in the art such as grinding.
The anion exchanger material produced by the present invention may be used as an exchanger, alone, or in combination with other additives which are not detrimental to the anion exchange capacity of the exchanger. Other materials or phases which may be mixed with the exchanger may include, for example, fillers such as clays; binders such as cellulosic 31,630-F -14-~6~gl9 polymers, in particular, carboxymethylcellulose; and extenders such as Tio2, A1203, and Al(0~)3 which will not substantially adversely affect the anion exchange capacity of the exchanger. Other additives may be used, for example, to pelletize, agglomerate or coat the exchanger, provided the anion exchange capacity of the exchanger is not substantially reduced. The various additives used with the anion exchanger will depend on the application in which the exchanger is used.
The anion exchange material of the present invention may be used in any application wherein an anion exchange mechanism is desired. Applications in which the exchanger is particularly useful include, for example, removing unwanted anions from agueous systems such as removing chromates and dichromates from water waste streams or removing silicates and colloidal silica from industrial boiler systems.
Another application the anion exchanger of the present invention finds use in is in laundry deter-gents as an additive for removing undesirable dye migration from one article of clothing to another.
Still another application for using the anion exchanger involves removing sulfonated polystyrene from corn syrup by passing the syrup over an ion exchange column containing the anion exchanger of the present invention.
Yet another application in which the anion exchanger may be used is in forming pigments by mixing the anion exchanger with a dye.
The present invention, described broadly above, is now illustrated more specifically by the 31,630-F -15-12649~9 following examples which are not to be construed as limiting the scope of the invention.
Example 1 An acidic solution was made by diluting 25 liters of a 28 weight percent AlC13 solution to 60 liters total volume with water. In addition, a TiCl4 solution was made by adding 800 ml of TiCl4, slowly, to 2000 ml of water to obtain a clear solution. The TiCl4 solution was then added to the AlCl3 solution. A base solution was made by dissolving 9000 g of NaOH in 60 liters of water. The AlC13-TiCl4 solution and the base solution were fed simultaneously into a 10 liter glass reactor in which the pH, temperature, stirring rate and reactant feed rates were controlled. The AlCl3-TiC14 solution was introduced at lO0 ml/min and the base feed rate was controlled to maintain the solution at a pH of about 6Ø The temperature was kept at 9OC and the stirring rate at 750~rpm. The first three reactor volumes of the reaction material were discarded and the remainder of the material was collected, filtered, dried at 120C in an oven overnight, washed with water and redried at 120C for three hours.
A white, free-flowing powdery precursor material was obtained having a substantially crystal-line structure, a uniform particle size of approxi-mately 0.2 micron and an exchange capacity of 1.5 meq/g. The approximate composition of the precursor material was [Alo gTio lO(OH)]Clo l nH2O By X ray diffraction analysis, the precursor showed the fol-lowing peaks in the diffraction pattern:
31,630-F -16-~264919 dA
6.35 3.08
AND PREPARATION THEREOF
This invention concerns ion exchangers and, more particularly, inorganic anion exchangers.
U.S. Patent 3,002,932 describes several noncrystalline inorganic anion exchangers consisting essentially of hydrated oxides of pairs of elements selected from the group consisting of aluminum, silicon, titanium, zinc, and zirconium. The compositions above are prepared by coprecipitating the hydrates of the combination of the oxides of the elements referred to above in an aqueous medium. The coprecipitation is carried out by gradually adding a base to an acid below a pH of 5 to bring the aqueous solution to a pH of about 5 to 7. The agueous mixture is dried below about 150C, followed by washing the dried mixed hydrated oxide with water, and again finally drying the mixture below about 150C.
31,630-F -1-.,~,. ..
126~9~9 In a paper by E. J. Duwell and J. W. Shepard, "The Preparation and Properties of Some Synthetic Inorganic Anion Exchangers", Journal of PhYsical Chemistry, Volume 63, December, pages 2044-47, (1959), various amorphous inorganic anion exchangers are described. The paper describes a method for preparing an amorphous Zn(OH)2 exchanger and ~l(OH)3 exchanger.
The amorphous exchangers are prepared by coprecip-itating cations of higher valence with aluminum and zinc hydroxide in slightly acidic solutions to form a gel. The gels are then dried to form whi~e, ~inely divided amorphous powders of Al(OH)3 and Zn(OH)2.
The prior art above states that dehydration of the exchangers at 150C results in the loss of anion exchanger capacity. Thus, the compositions prepared by the methods disclosed in the above art are unsatis-factory as anion exchangers at temperatures above 150C .
It is desired, therefore, to provide novel inorganic anion exchangers with increased thermal and chemical stability at elevated temperatures and with greater exchange capacity at elevated temperatures than previously known inorganic exchange materials. It is also desired to provide a process by which these anion exchangers may be prepared.
One aspect of the present invention is an anion exchanger material comprising a material exhi-biting anion exchange properties at temperatures of above 160C, said material represented by the formula:
31,630-F -2-~2649'19 ( I ) [Mla x Qx 1 oy (OH) ~ (A l)d(A 2)e(A 3)f(A 4)g nH20 wherein M is a metal element or elements each with a positive valence of a; Q is a metal element or elements each with a positive valence of a+1; a is 2, 3, 4, or 5, A 1, A 2, A 3, and A 4 are each one or more exchange-able anions each having a negative valence of 1, 2, 3, and 4, respectively; x is O < x < 0.5; and n, y, z, d, e, f, and g are real numbers greater than or equal to zero and satisfy the following:
< z/y C 1.0 2y ~ z = a O < d + 2e + 3f + 4g < x O < n < 10 is provided that when y = O, a is not e~ual to 2.
Another aspect of the present invention is a process of preparing the compositions of formula (I) which comprises providing an inorganic mixed metal hydroxide or hydrated oxide having anion exchange propertie~, exchanging the anion of the mixed metal hydroxide or hydrated oxide for a non-volatile anion, and heating the exchanged mixed metal hydroxide or hydrated oxide to form a mixed metal oxide exhibiting anion exchange properties at above 160C.
The novel compositions of the formula (I) include mixed metal oxides and partially hydrated mixed 31,630-F -3-~26491g metal oxides exhibiting anion exchange properties. The compositions consist essentially of a combination of oxides and hydrated oxides of pairs of metal cations or elements. A first metal element of the pair of metal elements has a lower valence than that of a second metal element of the pair of metal elements. The first lower valent member has a positive valence lower by one integer than that of the second higher valent member of the pair. For example, if the first metal element has a ~alence of +2, the second metal element has a valence of +3, and i~ the first metal element has a valence of +3 then the second metal element has a valence of +4, and so on.
The first lower valent metal element of the compositions of formula (I) is present in a major molar amount and the second higher valent metal element is present in a minor molar amount. It is theorized that the minor constituent is substituted in the lattice structure of the major constituent. The combination of the oxides and hydrated oxides of the pair of metal elements has a positive excess charge and this charge is balanced by an exchangeable anion or a mixture of two or more exchangeable anions.
The mixed metal oxides and partially hydrated mixed metal oxides of the present invention may also be represented by the general formula (I) above. A
"hydroxide" is represented by the formula when y=0; an "oxide" is represented by the formula when z=0; and a "partially hydrated oxide" is represented by the formula when y and z are both positive real numbers. Prefer-ably, y is 1 and z is 0 or 1. The range for x is preferably from about 0.01 to about 0.4.
31,630-F -4-~2649~
As an example of the composition of the present invention, the metal element or elements M each may have a valence of +2 and the metal element or elements Q each may have a valence of +3. The metal element M with a +2 valence may be selected from ele-ments such as magnesium, calcium, strontium, barium, iron, cobalt, mang~nese, nickel, copper, zinc and mixtures thereof, and the metal element Q with a valence of +3 may be selected from elements such as aluminum, iron, chromium, gallium, cobalt, rhenium, indium and mixtures thereof.
Another example of a combination of metal elements illustrating the present invention is the metal element or elements M each having a valence of +3 such as those listed above and the metal element or elements Q each having a +4 valence including, for example, titanium, germanium, tin, lead, zirconium, hafnium, vanadium ana mixtures thereof. Still another example of a combination of metal elements illustrating the present invention is the metal element or elements M each having a valence of +4 such as those listed above and the metal element or elements Q each having a +5 valence including, for example, antimony, vanadium, niobium, tantalum and mixtures thereof. Yet another example of a combination of metal elements illustrating the present invention is the metal element or elements M each having a +5 valence such as those listed above and the metal element or elements Q each having a +6 valence including, for example, chromium, molybdenum, tungsten and mixtures thereof.
Preferably, a pair of metal elements M and Q
selected from the group magnesium, aluminum and titanium 31,630-F -5-~Z649~9 are used in the present invention. More preferably, mixed metal oxides or partially hydrated mixed metal oxides of aluminum and titanium, and mixed metal oxides or partially hydrated mixed metal oxides of magnesium and aluminum are used as the anion exchange material as herein described.
The preferred compositlons of the present invention having a pair of elements of aluminum and titanium may be represented by the following general formula:
(II) ~All X TiX Oy (0~)~ (A l)d(A 2)e(A 3~f(A 4)g- nH2O
where A 1, A 2, A 3, and A are each one or more exchangeable anions each having a negative valence of 1, 2, 3, and 4, respectively; x is 0 < x < 0.5, and n, y, z, d, e, f, and g are real numbers greater than or egual to zero and satisfy the following:
O < z/y < 1.0 ~ 2y + z = a 20 0 c d + 2e + 3f + 4g < x 0 < n < 10 Thus, formula II above is equivalent to formula I where M is Al and Q is Ti.
31,630-F -6-lZ6~
The preferred compositions of the present invention having a pair of elements of magnesium and aluminum may be represented by the following general formula:
(III) Egl-x Alx y (oH)3 (A )d(A )e(A 3)f(A 4) nH O
where A 1, A 2, A 3, and A 4 are each one or more exchangeable anions each having a negative valence of 1, 2, 3, and 4, respectively; x is 0 c x < 0.5, and n, y, z, d, e, f, and g are real numbers greater than or equal to zero and satisfy the following:
O < z/y < 1.0 2y + z = a 0 < d-+ 2e + 3f + 4g < x 0 < n < 10 Thus, formula III above is equivalent to formula I
where M is Mg and Q is Al.
The "exchangeable anions" of the aforemen-tioned compositions may be selected from any inorganic or organic exchangeable anions commonly known in the art of anion exchangers. The exchangeable anions may be selected from monovalent, bivalent, trivalent, tetravalent anions, or mixtures of two or more of these exchangeable anions. In the above formulas, the anion A 1, for example, may be an inorganic anion selected from halides such as fluorides (F 1), chlorides (Cl l);
31,630-F -7-~64~1g bromides (Br 1); and iodides (I l); sulfates such as HSO4 ; phosphates such as H2PO4 ; permanganates (MnO41); nitrates (NO31); carbonates such as HCC31;
hydroxides (OH 1); and mixtures thereof. For example, th~ anion A 1 may be a combination of two or more exchangeable anions described above such as a mixture of Cl 1 and HCO 1 anions. In the above formulas, the anion A 2, for example, may be an inorganic anion selected from carbonates such as C032; sulfates such as S042; phosphates such as HPO4 2; and mixtures thereof. For example, the anion A , may be a com-bination of two or more exchangeable anions described above such as a mixture of S042 and C032. In the above formulas, the anion A 3, for example, may be a phos-` 15 phate such as PO43. An example of the anion A 4 used in the above formulas may include organic anions such as ethylenediaminetetraacetic acid (EDTA3 and diphos-phates such as (OH)2 (~)2 o=P-CH2-P=O -Other organic exchangeable anions used in the above formulas may include, for example, stearates, formates, benzoates and mixtures thereof.
,.~
In addition to the above anions used in the present invention, the compositions of the present invention may include a combination of two or more exchangeable anions selected from the group A 1, A 2, A 3 and A 4 as described above. For example, the compositions may include a mixture of exchangeable anions such as Cl 1 and C032 anions or Cl 1 and S042 anions. Preferably, the exchangeable anion in the 31,630-F -8-~6~9 g above compositions of the present invention is a sulfate anion. The total negative charge of the exchangeable anion or mixture of exchange~ble anions should be sufficient to balance the excess positive charge of the combination of pairs of metal oxides and hydrated oxides of the composition. The exchangeable anions of the composition is present and bound, i.e., firmly incorporated, in the lattice structure of the composition. Generally, the exchangeable anion cannot be washed free of the composition and remains in the composition until the exchangeable anion is exchanged for or replaced by another anion.
The compositions of formula (I) are charac-terized as exhibiting anion exchange properties, i.e., anion exchange capacity, and, thus, are useful as anion exchangers. Generally, the anion exchangers exhibit anion exchange capacity at elevated temperatures, for example, above 160C~and up to 800C. Typically, anion exchangers in the prior art have been thermally unstable and lose anion exchange capacity at temperatures of above 150C. The anion exchangers of the present invention are particularly useful at temperatures of from 160C to 800C. Preferably, the exchangers of the present invention are used in the temperature range from 160C to 500C.
The anion exchangers of formu~la (I) also exhibit high anion exchange capacities in the tem-perature range described above. Generally, the anion exchange capacity of the exchanger may range from 0.5 milliequivalent per gram (meq/g) to 2.0 meg/g and preferably from 0.5 meq/g to 1.0 meq/g.
31,630-F -9-~2649~9 In its broadest scope, the compositions of the present invention are synthesized via controlled techniques of precipitation, drying, washing, ion exchange and calcination. More particularly, the compositions of the present invention are prepared by coprecipitating mixed metal hydroxides or hydrated mixed metal oxides followed by drying by evaporation, washing with a solvent such as water, exchanging the anion of the coprecipitated mixed metal hydroxides or hydrated mixed metal oxides for another anion, described hereinafter as a ~nonvolatile anion~, and then calcining the mixed metal hydroxides or hydrated mixed metal oxides to form mixed metal oxides or partially hydrated mixed metal oxides.
In carrying out the method of the present invention, a precursor mixed metal hydroxide or hydrated mixed metal oxide anion exchanger (precursor material) i.e., having an anion exchange capacity, is first provided as a starting material. The precursor material may be an amorphous or crystalline material prepared by known methods in the art. For example, the coprecipi-tation method described in U.S. Patent 3,002,932 may be used to prepare an amorphous or noncrystalline mixed metal hydrated oxide which is useful as the precursor material in the present invention. Preferably, a precursor material determined by X-ray diffraction, electron diffraction, electron microscopy or micro area X-ray fluorescence analysis to be crystalline is used in the present invention.
Generally, the precursor material is prefer-ably prepared by precipitating mixed metal hydroxides 31,630-F -10-~26~9~C~
--ll--and hydrated mixed metal oxides, drying the precipitate, and then exchanging the anion of the mixed metal hydroxide or hydrated oxide anion exchanger with a nonvolatile anion.
A "nonvolatile anion" is an exchangeable anion bound to the lattice st~ucture of the precursor material which (a) does not react with some other component of the precursor resulting in loss of the precursor material's anion exchange capacity and/or (b) does not volatilize to form a gaseous product resulting in a loss of the precursor material's anion exchange capacity when the precursor material is sub-jected to heating or to calcination temperatures described hereinafter. For example, a Cl anion may evolve a HCl gas upon calcining the precursor material and, therefore, considered a volatile anion. Nonvolatile anions used in the present invention include, for example, sulfates, phosphates, chromates, molybdates, tungstates, niobates, and nitrates, with sulfates being the most preferred.
Any salt of the above nonvolatile anion materials may be used to exchange the anion of the precursor material.
,~ Preferably, potassium sulfate or sodium sulfate is used rr because it is readily available, relatively inexpensive and easily handled in the present process.
As an illustration of one embodiment of preparing the precursor material of the present invention, salts or other derivatives of metals M and Q of the composition of the present invention, are dissolved in a solvent such as water. Preferably, the stoichiometric ratio of Q/M should be above zero to 0.5. The total concentration of M and Q used in the solution may .
31,630-F
~26491C~
be above 0.1 molar and preferably, above 0.5 molar.
The salts used may be acidic, and which on neutral-ization with a base p;ecipitate the hydroxides or hydrated oxides of metals M and Q. Water-soluble salts or water-insoluble salts may be used. The water-soluble salts may include, for example, salts of chloride (Cl 1); sulfates (S042); nitrates (N031);
carbonates ~C032); and mixtures thereof of the metals M
and Q. Water insoluble salts used may include salts of hydroxides. Preferably, the water-soluble salts of elements M and Q are used.
The preferred base used for neutralization and consequent coprecipitation of the hydroxide or hydrated oxides are the alkali metal bases such as sodium hydroxide or potassium hydroxide. Other bases may include, for example, ammonium hydroxide.
Coprecipltation of the mixed metal hydroxides or hydrated mixed oxides is preferably carried out in an aqueous media at a p~ suitable to produce anion exchange capacity in the hydroxides or hydrated oxides.
The preferred pH is a function of the metal cations or elements used to form the composition of the present invention. For example, an aluminum and titanium oxide material may be formed by coprecipitating an aluminum and titanium hydroxide or hydrated oxide at a pH of 3 to 7, preferably at a pH of 4 to 6, and more preferably at a pH of 6 ~ 1. The coprecipitation is carried out at a temperature of from room temperature (~20C) to 150C, preferably from 50C to 100C, and more pre-ferably from 70C to 90C. As another example ofpreparing a precursor material, a magnesium and 31,630-F -12-~L26~9 aluminum oxide material may be formed by copre-cipitating a magnesium and aluminum hydroxide or hydrated oxide ct a pH of 8 to 13, and preferably at a pH of 9 to 11. The coprecipitation is carried out at a S temperature of from about room temperature to 150C, prefexably from 30C to 90C, and more preferably from 40~C to 60C.
During the coprecipitation above, a precip-itate material containing a substantial quantity of 10 water is formed when the combination of hydroxides or hydrated oxides are precipitated. The major portion of the water may be removed or separated from the precip-itate, for example, by filtration techniques known in the art. After separating the precipitate material - 15 from the aqueous media, the material is then dried by heating in air at relatively low temperatures to remove ~ the water in the material. Preferably, a temperature ti~ below 150C and more~preferably a temperature being in the range of 100C to below 150C is used to dry the ; 20 material. This dried product may then be washed free `~ of impurities such as sodium chloride, with water such o as distilled or deionized water. Removal of such ` impurities is carried out with water at a pH of from 4 to 7. The washed material may be used as the precursor 25 material which is then exchanged with a nonvolatile anion described above.
:
After the anion of the precursor mixed metal ~ hydroxide or hydrated oxide anion exchanger has been - exchanged for a nonvolatile anion, the resulti~g 30 exchanged material is heated or calcined at a tempera-ture sufficient to form a mixed metal oxide or par-tially hydrated mixed metal oxide exhibiting anion :'~
;~ 31,630-F -13-12649~9 exchange properties. Calcination temperatures may rangé from 160C to 800C. Preferably, a temperature range of ~00C to ~00C is used. The length of time of calcination may vary, but calcination should be carried out for a length of time sufficient to remove substan-tially all of the water present in the material.
Generally, 10 minutes to 3 hours may be used. A white, free-flowing powdery material results after calcination and is characterized as being a mixed metal oxide or partially hydrated mixed metal oxide having anion exchange capacities at above 160C.
Optionally, the exchanged material may be washed with water and separated from the aqueous media by well known means, such as vacuum filtration and then dried at a relatively low temperature, such as below 150C prior to the calcination step described above.
The dried material calcined at the afore-mentioned calcination temperature is a white, free-flowing, fine, powdery product, typically containing solids having a particle size of 10 microns or less and preferably a particle size of 5.0 microns or less. The powder particles may easily be broken up into indi-vidual particles having a size of from 0.1 to 0.4 micron by techniques known in the art such as grinding.
The anion exchanger material produced by the present invention may be used as an exchanger, alone, or in combination with other additives which are not detrimental to the anion exchange capacity of the exchanger. Other materials or phases which may be mixed with the exchanger may include, for example, fillers such as clays; binders such as cellulosic 31,630-F -14-~6~gl9 polymers, in particular, carboxymethylcellulose; and extenders such as Tio2, A1203, and Al(0~)3 which will not substantially adversely affect the anion exchange capacity of the exchanger. Other additives may be used, for example, to pelletize, agglomerate or coat the exchanger, provided the anion exchange capacity of the exchanger is not substantially reduced. The various additives used with the anion exchanger will depend on the application in which the exchanger is used.
The anion exchange material of the present invention may be used in any application wherein an anion exchange mechanism is desired. Applications in which the exchanger is particularly useful include, for example, removing unwanted anions from agueous systems such as removing chromates and dichromates from water waste streams or removing silicates and colloidal silica from industrial boiler systems.
Another application the anion exchanger of the present invention finds use in is in laundry deter-gents as an additive for removing undesirable dye migration from one article of clothing to another.
Still another application for using the anion exchanger involves removing sulfonated polystyrene from corn syrup by passing the syrup over an ion exchange column containing the anion exchanger of the present invention.
Yet another application in which the anion exchanger may be used is in forming pigments by mixing the anion exchanger with a dye.
The present invention, described broadly above, is now illustrated more specifically by the 31,630-F -15-12649~9 following examples which are not to be construed as limiting the scope of the invention.
Example 1 An acidic solution was made by diluting 25 liters of a 28 weight percent AlC13 solution to 60 liters total volume with water. In addition, a TiCl4 solution was made by adding 800 ml of TiCl4, slowly, to 2000 ml of water to obtain a clear solution. The TiCl4 solution was then added to the AlCl3 solution. A base solution was made by dissolving 9000 g of NaOH in 60 liters of water. The AlC13-TiCl4 solution and the base solution were fed simultaneously into a 10 liter glass reactor in which the pH, temperature, stirring rate and reactant feed rates were controlled. The AlCl3-TiC14 solution was introduced at lO0 ml/min and the base feed rate was controlled to maintain the solution at a pH of about 6Ø The temperature was kept at 9OC and the stirring rate at 750~rpm. The first three reactor volumes of the reaction material were discarded and the remainder of the material was collected, filtered, dried at 120C in an oven overnight, washed with water and redried at 120C for three hours.
A white, free-flowing powdery precursor material was obtained having a substantially crystal-line structure, a uniform particle size of approxi-mately 0.2 micron and an exchange capacity of 1.5 meq/g. The approximate composition of the precursor material was [Alo gTio lO(OH)]Clo l nH2O By X ray diffraction analysis, the precursor showed the fol-lowing peaks in the diffraction pattern:
31,630-F -16-~264919 dA
6.35 3.08
2.35 1.86 1.44 Thereafter, 100 g of the white powdery precursor material was exchanged with 50 g of K2S04 in 500 ml of distilled water. The exchanged material was then filtered and washed with distilled water. The washed material was then dried at 110 to 120C. The dried material was then calcined at 600C for three hours.
The calcined material was allowed to cool to room temperature and then washed with distilled water and dried at 110C to 120C. The dried calcined material had the form [All 8Tio 23](S4 )0.1 nH2 capacity of the product was measured to be 1.0 meq/g.
Example 2 A 500 ml solution of AlC13 and TiC14 which was 28 percent AlC13 and 4 percent TiC14 was added dropwise to a stirred reactor containing 1000 ml of water maintained at a pH of 5 by the addition of NaOH.
The reactor was kept at room temperature. The precipi-tate formed was filtered and dried at 125C overnight.
X-ray diffraction showed the precipitate to be an amorphous hydrous mixed oxide. The precipitate was then exchanged with 75 g K2SO4 dissolved in 500 ml of distilled water. The exchanged material was then filtered, washed, and dried at 125C for five hours.
The dried material was then calcined at 500C for three 31,630-F -17-~LZ6491~9 hours. The calcined product was cooled to room tempera-ture and then washed, and dried at 125C overnight.
The anion exchange capacity of the calcined product which had the form [All 8Tio 2o3](S04 )o.l nH20 was analyzed and determined to be O.8 meq/g.
ExamPle 3 A 500 ml solution containing 200 g MgCl2 6H20 and 79.5 g AlCl3 6H20 was added dropwise to a reactor containing 500 ml of water maintained at a pH of 10.0 by the addition of NaOH at 50C. A precipitate formed in the reactor which was filtered and dried. The precipitate material which had the form [Mg3Al(OH)8]Cl-nH20 was then exchanged with 100 g ~2S04 in 500 ml of water for several minutes. The exchanged material was then filtered and dried at 125C. The dried material was calcined at 500C for 15 minutes, cooled, washed and dried at 125C overnight. The calcined product had the form tMg3 Al04](so4 ~o.5 n~2 i .~
31,630-F -18-
The calcined material was allowed to cool to room temperature and then washed with distilled water and dried at 110C to 120C. The dried calcined material had the form [All 8Tio 23](S4 )0.1 nH2 capacity of the product was measured to be 1.0 meq/g.
Example 2 A 500 ml solution of AlC13 and TiC14 which was 28 percent AlC13 and 4 percent TiC14 was added dropwise to a stirred reactor containing 1000 ml of water maintained at a pH of 5 by the addition of NaOH.
The reactor was kept at room temperature. The precipi-tate formed was filtered and dried at 125C overnight.
X-ray diffraction showed the precipitate to be an amorphous hydrous mixed oxide. The precipitate was then exchanged with 75 g K2SO4 dissolved in 500 ml of distilled water. The exchanged material was then filtered, washed, and dried at 125C for five hours.
The dried material was then calcined at 500C for three 31,630-F -17-~LZ6491~9 hours. The calcined product was cooled to room tempera-ture and then washed, and dried at 125C overnight.
The anion exchange capacity of the calcined product which had the form [All 8Tio 2o3](S04 )o.l nH20 was analyzed and determined to be O.8 meq/g.
ExamPle 3 A 500 ml solution containing 200 g MgCl2 6H20 and 79.5 g AlCl3 6H20 was added dropwise to a reactor containing 500 ml of water maintained at a pH of 10.0 by the addition of NaOH at 50C. A precipitate formed in the reactor which was filtered and dried. The precipitate material which had the form [Mg3Al(OH)8]Cl-nH20 was then exchanged with 100 g ~2S04 in 500 ml of water for several minutes. The exchanged material was then filtered and dried at 125C. The dried material was calcined at 500C for 15 minutes, cooled, washed and dried at 125C overnight. The calcined product had the form tMg3 Al04](so4 ~o.5 n~2 i .~
31,630-F -18-
Claims (14)
1. An anion exchanger material comprising a material exhibiting anion exchange properties at tempera-tures above 160°C, said material represented by the formula:
wherein M is a metal element or elements each with a positive valence of a; Q is a metal element or elements each with a positive valence of a+1; a is 2, 3, 4, or 5;
A-1, A-2, A-3, and A-4 are each one or more exchangeable anions each having a negative valence of 1, 2, 3, and 4, respectively; x is 0 < x < 0.5; and n, y, z, d, e, f, and g are real numbers greater than or equal to zero and satisfy the following:
0 < z/y < 1.0 2y + z = a 0 < d + 2e + 3f + 4g < x 0 < n < 10 provided that when y = 0, a is not equal to 2.
31,630-F -19-
wherein M is a metal element or elements each with a positive valence of a; Q is a metal element or elements each with a positive valence of a+1; a is 2, 3, 4, or 5;
A-1, A-2, A-3, and A-4 are each one or more exchangeable anions each having a negative valence of 1, 2, 3, and 4, respectively; x is 0 < x < 0.5; and n, y, z, d, e, f, and g are real numbers greater than or equal to zero and satisfy the following:
0 < z/y < 1.0 2y + z = a 0 < d + 2e + 3f + 4g < x 0 < n < 10 provided that when y = 0, a is not equal to 2.
31,630-F -19-
2. The anion exchanger of Claim 1 wherein x is from about 0.01 to about 0.4.
3. The anion exchanger of Claim 1 wherein y is 1 and z is 1 or 0.
4. The anion exchanger of Claim 1 wherein M
and Q are selected from the group of magnesium, alu-minum and titanium.
and Q are selected from the group of magnesium, alu-minum and titanium.
5. The anion exchanger of Claim 4 wherein M
is magnesium and Q is aluminum.
is magnesium and Q is aluminum.
6. The anion exchanger of Claim 4 wherein M
is aluminum and Q is titanium.
is aluminum and Q is titanium.
7. The anion exchanger of Claim 4 which is [Al1.8Ti0.2O3](SO4-2)0.1?nH2O, or [Mg3AlO4](SO4-2)0.5?nH2O.
8. The anion exchanger of Claim 1 wherein A-1, A-2, A-3, and A-4 are each one or more anions of halides, hydroxides, nitrates, phosphates, carbonates, sulfates or mixtures thereof.
9. The anion exchanger of Claim 1 wherein A-1 is Cl-1, Br-1, F-1, I-1, H2PO? or mixtures thereof and e, f, and g are zero.
10. The anion exchanger of Claim 1 wherein A-2 is SO?, CO?, HP0? or mixtures thereof and d, f, and g are zero.
31,630-F -20-
31,630-F -20-
11. The anion exchanger of Claim 1 wherein A-1 is Cl-1, A-2, is So? and f and g are zero.
12. The anion exchanger of Claim 1 charac-terized as exhibiting anion exchange properties at temperatures from 160°C to 800°C.
13. A process of preparing an anion exchanger material of Claim 1 which comprises providing an inor-ganic mixed metal hydroxide or hydrated oxide having anion exchange properties, exchanging the anion of the mixed metal hydroxide or hydrated oxide for a nonvolatile anion, and heating the exchanged mixed metal hydroxide or hydrated oxide to form a mixed metal oxide exhibiting anion exchange properties at above 160°C.
14. A process of Claim 13 which comprises:
(a) coprecipitating in an aqueous medium at a constant pH an inorganic mixed metal hydroxide or hydrated oxide;
(b) drying the mixed metal hydroxide or hydrated oxide at a temperature of below 150°C, (c) exchanging the anion of the dried mixed metal hydroxide or hydrated oxide for a nonvolatile anion, and (d) heating the exchanged mixed metal hydroxide or hydrated oxide to form a mixed metal oxide exhibiting anion exchange properties at above 160°C.
(a) coprecipitating in an aqueous medium at a constant pH an inorganic mixed metal hydroxide or hydrated oxide;
(b) drying the mixed metal hydroxide or hydrated oxide at a temperature of below 150°C, (c) exchanging the anion of the dried mixed metal hydroxide or hydrated oxide for a nonvolatile anion, and (d) heating the exchanged mixed metal hydroxide or hydrated oxide to form a mixed metal oxide exhibiting anion exchange properties at above 160°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000512034A CA1264919A (en) | 1986-06-20 | 1986-06-20 | Inorganic anion exchangers and preparation thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000512034A CA1264919A (en) | 1986-06-20 | 1986-06-20 | Inorganic anion exchangers and preparation thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1264919A true CA1264919A (en) | 1990-01-30 |
Family
ID=4133391
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000512034A Expired - Fee Related CA1264919A (en) | 1986-06-20 | 1986-06-20 | Inorganic anion exchangers and preparation thereof |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1264919A (en) |
-
1986
- 1986-06-20 CA CA000512034A patent/CA1264919A/en not_active Expired - Fee Related
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