Production of high capacity inorganic crystalline base exchange materials

A method for producing crystalline base exchange alumino silicate materials having high total ion exchange capacities, specific initial exchange rates which yield well-defined residual concentrations for the elements of Group II of the Periodic Table and trace metals, and a crystal size in the range of from 0.25 to 8.0 microns, said method comprising the steps of:

• a. preparing an aqueous solution of an alkali metal silicate, said silicate having an SiO.sub.2 /X.sub.2 O mole ratio of from 1 to 4, wherein X is an alkali metal selected from the group consisting of sodium, potassium and lithium;
• b. introducing said alkali metal silicate solution into a precipitation-digestion vessel and subjecting to vigorous agitation;
• c. preparing an aqueous solution of an alkali metal aluminate, separating organic complexes and ferruginous sludges from said aluminate solution to form a clarified aluminate solution;
• d. introducing said aluminate solution into the alkali metal silicate solution at a controlled rate while subjecting the resulting aqueous mixture to vigorous agitation at a temperature of between about 70.degree. and 180.degree. F.;
• e. continuing the vigorous agitation of said aqueous mixture, said resulting aqueous mixture comprising an alkali metal alumino silicate/water mixture whose composition, expressed in terms of oxide-mole ratios, is as follows:
• X.sub.2 o/siO.sub.2 ratio from 1.0 to 3.0 and an
• H.sub.2 o/x.sub.2 o ratio from 35 to 200 when the
• SiO.sub.2 /Al.sub.2 O.sub.3 ratio is from 0.5 to 1.3;
• X.sub.2 o/siO.sub.2 ratio from 0.8 to 3.0 and an
• H.sub.2 o/x.sub.2 o ratio from 35 to 200 when the
• SiO.sub.2 /Al.sub.2 O.sub.3 ratio is from 1.3 to 2.5;
• f. maintaining the pH of the said aqueous mixture at a level of at least 10.0 and a temperature between about 70.degree. and 180.degree. C. to thereby precipitate a finely divided pigmentary amorphous alumino silicate intermediate in the substantial absence of gel formation;
• g. crystallizing said precipitated intermediate by heating the aqueous mixture containing said precipitate to a temperature in the range of from 170.degree. to 230.degree. F.;
• h. withdrawing the supernatant mother liquor formed on the top portion of said aqueous mass containing the crystallized product from the precipitation-digestion vessel;
• i. passing said supernatant mother liquor through cooling means and thereafter returning the thus-cooled mother liquor to the aqueous mass containing the crystallized product to thereby quench and cool the same to arrest further crystal growth, and produce said crystalline base exchange alumino silicate material having a predetermined crystalline structure;
• j. recovering the crystallized product from the aqueous mass by passing said mass onto the front end of a continuous, porous, rotating belt to thereby form, on said rotating belt, a wet cake of the crystalline product;
• k. contacting the wet cake of the crystallized product on said belt with a wash liquid, at least a portion of said wash liquid comprising recycled liquors collected from filtrate liquids recovered near the intermediate and second end portion of said continuous belt;
• l. recovering and drying the wet cake comprising the crystalline alumino silicate from the said end portion of said continuous belt;
• m. collecting and combining the process liquors from said belt;
• removing ferruginous sludges and negative organic complexes from said process liquors;
• n. concentrating said process liquors to remove water therefrom;
• passing said concentrated liquors into a purification zone to remove alkali metal chlorides therefrom;
• and
• o. recycling the concentrated process liquors to the vessel in which the alkali metal aluminate solution is prepared, said recycle process liquors providing a source of clarified alkali metal aluminate employed in the precipitation of the said alumino silicate intermediate.

A method for producing crystalline base exchange alumino silicate materials having high total ion exchange capacities, including a total exchange capacity of at least 250 mg. CaCO.sub.3 per gram of crystalline inorganic base exchange material;

• specific initial exchange rates which yield well-defined residual concentrations for the elements of Group II of the Periodic Table and for trace metals, including an initial exchange rate of at least 2 grains per gram per minute, being capable of reducing a normal hardness water to a level of less than 0.3 grain/gallon and being capable of producing residual concentration of trace metals on the order of parts per billion, and having a crystal size in the range of from 0.25 to 8.0 microns, said method comprising the steps of:
• a. preparing an aqueous solution of an alkali metal silicate, said silicate having an SiO.sub.2 /X.sub.2 O mole ratio of from 1.0 to 4.0, wherein X is an alkali metal selected from the group consisting of sodium, potassium and lithium;
• b. introducing said alkali metal silicate solution into a precipitation-digestion vessel;
• c. preparing an aqueous solution of an alkali metal aluminate, said aluminate having an X.sub.2 O/Al.sub.2 O.sub.3 mole ratio of from 1.0 to 6.0 wherein X is an alkali metal selected from the group consisting of sodium, potassium, and lithium;
• d. separating ferruginous sludges and vegetative organic complexes from said aluminate solution to form a clarified aluminate solution;
• e. introducing said aluminate solution into the alkali metal silicate solution at a controlled rate while subjecting the resulting aqueous mixture to vigorous agitation at a temperature of between about 70.degree. and 180.degree. F.;
• f. continuing the vigorous agitation of the mixture formed by the addition of said aluminate solution to said silicate solution, said mixture comprising an alkali metal alumino silicate/water mixture whose reaction composition, expressed in terms of oxide-mole ratios, is as follows:
• ##EQU2## g. maintaining the pH of the said aqueous mixture at a level of at least 10.0 and the temperature between about 70.degree. and 180.degree. C. to thereby precipitate a finely divided pigmentary amorphous alumino silicate intermediate in the substantial absence of gel formation;
• h. crystallizing said precipitated intermediate by heating the aqueous mixture containing said precipitate to a temperature in the range of from 170.degree. to 230.degree. F. over a period of 1 to 8 hours;
• i. withdrawing the supernatant mother liquor formed on the top portion of said aqueous mass containing the crystallized product from the precipitation-digestion vessel;
• j. passing said supernatant through cooling means and thereafter returning the thus-cooled mother liquor to the aqueous mass containing the crystallized product to thereby quench and cool the same to arrest further crystal growth, and to produce said crystalline base exchange alumino silicate material having high total ion exchange capacities and crystal size in the range of from 0.25 to 8.0 microns;
• k. recovering the crystallized product from the aqueous mass by passing said mass onto the front end of a continuous, porous, rotating belt to thereby form, on said rotating belt, a wet cake of the crystalline product;
• l. contacting the wet cake of the crystallized product on said belt with a wash liquid, at least a portion of said wash liquid comprising recycled liquors collected from filtrate liquids recovered near the intermediate and second end portion of said continuous belt;
• m. recovering and drying the wet cake comprising the crystalline alumino silicate from the said second end portion of said continuous belt;
• n. collecting and combining the process liquors from said belt;
• o. removing ferruginous sludges and vegetative organic complexes from said process liquors;
• p. concentrating said process liquors to remove water therefrom;
• q. passing said concentrated liquors into a purification zone to remove impurities including alkali metal chlorides and halide salts therefrom;
• and
• r. recycling the concentrated process liquors to the vessel in which the alkali metal aluminate solution is prepared, said recycle process liquors providing a source of alkali metal aluminate employed in the precipitation of the said alumino silicate intermediate.