Method for improving the brightness of clay

Claim 1

IN A METHOD FOR IMPROVING THE BRIGHTNESS OF GRAY KAOLIN CLAY WHICH COMPRISES THE STEPS OF PROVIDING AN AQUEOUS SLIP OF SAID CLAY, INCORPORATING A DISPERSING AGENT THEREIN, CONDITIONING SAID DISPERSED AQUEOUS SLIP OF THE CLAY FOR FROTH FLOTATION WITH A COLLECTOR REAGENT SELECTIVE TO COLORED IMPURITIES IN SAID CLAY, SUBJECTING THE CONDITIONED SLIP TO FROTH FLOTATION THEREBY PRODUCING A FROTH PRODUCT WHICH IS A CONCENTRATE OF COLORED IMPURITIES ORIGINALLY IN SAID CLAY AND A MACHINE DISCHARGE PRODUCT WHICH IS A CONCENTRATE OF CLAY OF ENHANCED BRIGHTNESS, AND FURTHER INCREASING THE BRIGHTNESS OF CLAY IN SAID MACHINE DISCHARGE PRODUCT BY BLEACHING IT WITH A REDUCING AGENT, THE IMPROVEMENT WHICH COMPRISES ACTIVATING SAID AQUEOUS SLIP OF GRAY KAOLIN CLAY FOR FLOTATION AND BLEACHING BY FORMING AN AQUEOUS SLIP CONSISTNG ESSENTIALLY OF WATER, SAID CLAY AND A WATERSOLUBLE INORGANIC COMPOUND CONTAINING MOLECULARLY AVAILABLE OXYGEN, BEFORE SAID SLIP IS CONDITIONED FOR FROTH FLOTATION, AND AGITATING SAID SLIP UNTIL CLAY IN SAID SLIP DARKENS SUBSTANTIALLY, WHEREBY THE SLIP THUS DARKENED WILL BRIGHTEN TO A GREATER EXTENT BY COMBINED FLOTATION AND TREATMENT WITH REDUCING AGENT THAN IT WOULD IN THE ABSENCE OF SAID ACTIVATING TREATMENT.