Derivation of pure fine particle silica and pure aluminium hydroxide from clay minerals

摘要

A process which allows the conversion of clay minerals of the kaolinite group, to a relatively pure form of alumina and silica respectively includes: (a) heating the kaolinite group minerals to greater than 500 °C, which causes dehydroxylation of the crystallographic lattice and formation of an intermediate meta-kaolin; (b) reacting the intermediate with only one of a selection of reagents including acids, alkalines or metalliferous compounds followed by heating of the mixture to form an aluminium salt in solution and residue of silica; (c) separation of the aluminium salt solution from the residue of silica by filtration and further treatment of the silica residue to produce a relatively pure form of fine particled silica; and (d) formation of an alum by addition of ammonium sulphate in solution to the aluminium salt solution and further treatment of the alum to produce a relatively pure form of aluminium hydroxide.