Mineral extraction from seawater reverse osmosis brine of gulf seawater

The brine disposal from desalination plants and its environmental impact are the major challenges faced by the desalination industry all over the world. The desalination brine contains higher concentration of inorganic compounds than that in seawater in addition to the chemical additives used by the pre-treatment units. The precipitation of minerals from brine reduces the fresh water production cost as well as minimizes the brine disposal problem. This article explores a systematic approach for the brine treatment problem by assessing the performance of mineral precipitation using chemical precipitation technique for precipitating valuable minerals, including magnesium, calcium, boron, sulfate, and strontium, from the rejected brine of two seawater reverse osmosis (SWRO) desalination plants in Kuwait. The preliminary mineral precipitation results showed that sodium hydroxide is the best suitable base for precipitation of all minerals compared with calcium hydroxide and ammonium hydroxide. Further, the mineral precipitation experiments were performed by using sodium hydroxide as base at different processing temperature and pH. The results showed that more than 78% of magnesium (Mg) was precipitated from RO brine at pH 10 and temperature of 90°C. The preliminary economic evaluation of magnesium oxide production using RO brine of desalination plants at Doha Desalination Research Plant and Shuwaikh sites of Kuwait are 228 and 97,909 tons per year, respectively. Overall, this study established optimum operating condition for effective precipitation of minerals from high saline Arabian Gulf SWRO brine with high efficiency and showed promising results for large-scale mining.