Abstract: A process for the wet processing of kaolin clay which includes a step for physically removing discrete particles of colored impurities by high gradient magnetic separation (HGMS) in which all processing steps including HGMS are carried out with the feed clay slurry at high solids, above 50%, and the magnetically purified clay slurry is also recovered at high solids, above 50%. A feature of the invention is that the HGMS unit is operated in a novel manner such as to avoid the dilution of the magnetically purified clay slurry with water during all stages of HGMS treatment without adverse effect on the yield of magnetically purified clay.

Abstract: Materials containing vanadium values which are leachable by water are treated to reduce the leachability of vanadium to minimum practical values, thereby rendering the material suitable for disposal as landfill. Vanadium is insolubilized by adding a polyvalent metal salt which is capable of dissolving in water to form an acidic solution from which polyvalent metal cations are precipitated at a pH of 5, the polyvalent cations having a valence of +3 or higher or being a divalent metal that is oxidizable to a valence of +3 or higher. The salt-treated mixture is then neutralized by a base. The vanadium may be contained in a solid such as, for example, a spent cracking catalyst or a spent sorbent used in the upgrading of petroleum feedstock by selective vaporization or it may be contained in liquid material.