Purification of quartz contaminated clay by selective flocculation

Claim 1

A METHOD FOR PURIFYING KAOLIN CLAY CONTAINING FROM 2 TO 50 PERCENT BY WEIGHT OF A FINELY DIVIDED QUARTZ IMPURITY WHICH COMPRISES DISPERSING SAID IMPURE CLAY IN WATER TO FORM A DISPERSED CLAY SLIP HAVING A PH IN THE RANGE OF 8.0 TO 9.5, SEPARATELY INCORPORATING THEREIN A SOLUBLE COMPOUND CONTAINING POLYVALENT METAL CATIONS IN AMOUNT TO PROVIDE A CONCENTRATION OF POLYVALENT METAL CATIONS IN THE RANGE OF 10 P.P.M TO 200 P.P.M. AND INSUFFICIENT TO FLOCCULATE THE SLIP AND FORM 1/4 TO 5 P.P.M. OF A WATER-SOLUBLE SYNTHETIC ORGANIC WEAKLY ANIONIC POLYACRYYLAMIDE FLOCCULANT, SAID AMOUNT OF POLYACRYLMIDE FLOCCULANT BEING SUFFICIENT, IN COMBINATION WIITH SAID SOURCE OF POLYVALENT CATIONS, TO FLOCCULATE SELECTIVELY A SUBSTANTIAL AMOUNT OF THE FINELY DIVIDED QUARTZ IMPURITY, AGITATING THE SLIP MILDLY UNTIL FLOCS OF QUARTZ FORM AND SETTLE TO THE BOTTOM OF THE SLIP AND SEPARATING THE FLOCS FROM THE SLIP OF PURIFIED CLAY.

Claim 2

A METHOD FOR PURIFYING KAOLIN CLAY CONTAINING FROM 2 TO 50 PERCENT BY WEIGHT OF A FINELY DIVIDED QUARTZ IMPURITY WHICH COMPRISES DISPERSING SAID IMPURE CLAY IN WATER TO FORM A DISPERSED CLAY SLIP HAVING A PH IN THE RANGE OF 8.0 TO 9.5, SEPARATELY INCORPORATING THEREIN A SOLUBLE COMPOUND CONTAINING POLYVALENT METAL CATIONS IN AMOUNT TO PROVIDE A CONCENTRATION OF POLYVALENT METAL CATIONS IN THE RANGE OF 10 P.P.M TO 200 P.P.M. AND INSUFFICIENT TO FLOCCULATE THE SLIP AND FORM 1/4 TO 5 P.P.M. OF A WATER-SOLUBLE SYNTHETIC ORGANIC WEAKLY ANIONIC POLYACRYYLAMIDE FLOCCULANT, SAID AMOUNT OF POLYACRYLMIDE FLOCCULANT BEING SUFFICIENT, IN COMBINATION WIITH SAID SOURCE OF POLYVALENT CATIONS, TO FLOCCULATE SELECTIVELY A SUBSTANTIAL AMOUNT OF THE FINELY DIVIDED QUARTZ IMPURITY, AGITATING THE SLIP MILDLY UNTIL FLOCS OF QUARTZ FORM AND SETTLE TO THE BOTTOM OF THE SLIP AND SEPARATING THE FLOCS FROM THE SLIP OF PURIFIED CLAY.

Claim 3

A method for purifying kaolin clay containing from 2 to 50 percent by weight of a finely divided quartz impurity which comprises dispersing said impure clay in water to form a dispersed clay slip having a pH in the range of 8.0 to 9.5, separately incorporating therein a soluble compound containing polyvalent metal cations in amount to provide a concentration of polyvalent metal cations in the range of 10 p.p.m. to 200 p.p.m. and insufficient to flocculate the slip and from 1/4 to 5 p.p.m. of a water-soluble synthetic organic weakly anionic polyacrylamide flocculant, said amount of polyacrylamIde flocculant being sufficient, in combination with said source of polyvalent cations, to flocculate selectively a substantial amount of the finely divided quartz impurity, agitating the slip mildly until flocs of quartz form and settle to the bottom of the slip and separating the flocs from the slip of purified clay.

Claim 4

A method for purifying kaolin clay containing from 2 to 50 percent by weight of a finely divided quartz impurity which comprises dispersing said impure clay in water to form a dispersed clay slip having a pH in the range of 8.0 to 9.5, separately incorporating therein a soluble compound containing polyvalent metal cations in amount to provide a concentration of polyvalent metal cations in the range of 10 p.p.m. to 200 p.p.m. and insufficient to flocculate the slip and from 1/4 to 5 p.p.m. of a water-soluble synthetic organic weakly anionic polyacrylamide flocculant, said amount of polyacrylamIde flocculant being sufficient, in combination with said source of polyvalent cations, to flocculate selectively a substantial amount of the finely divided quartz impurity, agitating the slip mildly until flocs of quartz form and settle to the bottom of the slip and separating the flocs from the slip of purified clay.