Abstract: Nanofiltration processes using one or more conventional nanofiltration membrane modules under a positive applied pressure is used to selectively change the concentration of one solute, such as sodium chloride or sodium chlorate providing monovalent ions, from another solute such as sodium sulfate or sodium dichromate to provide multivalent ions in high salt aqueous concentrations. The process is particularly useful in favourably lowering the concentration of undesirable ions, particularly, of silica and dichromate ions in chloralkali and chlorate brine containing solutions and favourably raising the sodium sulphate level relative to sodium chloride in chloralkali liquor.

Abstract: Process for the removal of heavy metal, metalloid and fluoride species present in trace mounts from aqueous brine of use in the production of chlorine and sodium hydroxide by electrolysis in membrane cells or in chlorate production; particularly to said removal by adsorption on hydroxyapatite; and more particularly to adsorption on bone charcoal.

Abstract: A method for removing sulphate ions from an aqueous solution of an alkali metal halide containing sulphate ions, which method comprises contacting said solution with a particulate, composite ion-exchange material comprising a hydrous oxide of a metal selected from the group consisting of titanium, zirconium and cerium, dispersed on a support comprising a brine solution compatible material. Preferably the compatible material is selected from hydrous oxides of titanium, cerium and zirconium. An improved cost-effective practical method of sulphate removal is provided.

Abstract: A process is described by which a chemical species is sorbed into the channels of a host phase which is then heated to affect an irreversible phase transformation of the host phase which seals the chemical species within its crystal structure. The host phase is an insoluble solid, non-toxic and stable both to the chemical species it encases and its environment.