Utilisation of salts from inland saline water sources

Abstract

Processing of saline water to produce industrial minerals with large volume applications is considered one way to attack the salinity problem in the Murray-Darling Basin. We propose that saline water in the Basin be treated to produce industrial mineral salts such as sodium chloride, magnesium sulphate, and magnesium chloride. The magnesium-rich bittern fraction of the saline waters may be processed further to value-added products such as magnesium hydroxide, Sorel cement, or spinel refractories. Sorel cement could be consumed in large quantities in the Basin as construction material and may be used to seal new interception scheme lakes, although the stability of the Sorel cement in aqueous environment remains to be investigated. The processing of mineral sands can be linked with treatment of saline water in an integrated and cost-effective manner that aims to remove salt from the Basin. The sodium chloride fraction can be used to produce chemicals such as chlorine, hydrochloric acid and sodium hydroxide that can be used in the processing of zircon. Direct chlorination of ilmenite could consume the equivalent of about 1.4 tonnes of sodium chloride for each tonne of ilmenite treated if no chlorine was recycled. Chlorination of synthetic rutile (about 90% TiO2) could consume the equivalent of about 0.3 tonnes of sodium chloride for each tonne of titania pigment produced. Work in CSIRO Minerals has produced low radioactivity zirconia from a Murray Basin zircon by caustic soda decomposition followed by concentrated hydrochloric acid leaching. In addition, it is proposed that desalination plants be established across the Basin to recover fresh water, heat, and electricity from saline water. These plants will obtain heat and electricity from solar power generation schemes with storage of power in solar ponds and molten salts. Integrated saline water and mineral sands mining industry in the Basin may ultimately lead to new technology for Australia such as titanium metal production. Titanium metal produced from TiO2 pigment may be used in building desalination plants across the Basin to recover fresh water from saline waters.