Electrochemical precipitation to reduce waste brine salinity

Desalination of seawater is becoming the main process to produce fresh water in many countries. Waste brine or concentrate rejects are leftovers of the desalination process and can have an adverse impact on the environment due to its high salinity. In this study we show a facile process to reduce the salinity of concentrated brine and at the same time produce a value-added product, namely calcium and magnesium oxides. An electrochemical system is used to precipitates inorganic salts available in seawater brine. The system consists of two graphite electrodes, a DC power source and the waste-brine works as the electrolyte. The DC potential applied reduces water to hydroxyl ions which reduces the ionic species in the waste-brine. With an applied potential in the range of 2.5–4.0 V for 3 h time interval, the TDS of the brine solution reduces from 47,000 ppm to 42,000 ppm. Ion chromatography results indicate that there is a decrease in the Mg²⁺ and Ca²⁺ cations and chloride anion in the treated brine. X-ray diffraction data of the calcinated precipitates showed peaks for mainly magnesium oxide and calcium oxide.