Technology of the comprehensive desalination of wastewater from mines

The issue of desalination is relevant for many countries of the world; the most promising technology for demineralization appears to be membrane technology. The stabilizing treatment of water before feeding it to the membrane filters involved the ion exchange softening of the solution based on the weakly acidic cation exchanger DOWEX MAC-3 in the H+ and Na+ forms. This makes it possible to improve the efficiency of baromembrane desalination and the service time of membranes. The nanofiltration membrane OPMN-P ensures the purification of low mineralized waters from sulfates (by 74–93 %) and hardness ions (67–90 %); at the same time, the membrane has low selectivity in terms of bicarbonate anions and does not retain chlorides. This avoids the accumulation of these in the concentrates at the nanofiltration purification of low mineralized waters. The inverse osmotic membrane Filmtec TW30-1812-50 shows selectivity for sulfates and hardness ions of over 99 %. The selectivity for chlorides is 83–94 % for low mineralized water, and 90–95 % for highly mineralized water. The concentrates contain hardness ions, sulfates, chlorides, and bicarbonate anions in significant concentrations. We have defined conditions for the effective softening of the formed concentrates at the comprehensive treatment by lime and aluminum coagulants. When desalinizing the concentrate of low- and highly mineralized waters, the sulfate concentration decreased to 2.55–6.53 mg-equiv./dm3 and 3.31–9.02 mg-equiv./dm3, respectively. At the same time, the concentration of hardness ions was 3.31–9.02 mg-equiv./dm3 and 4.20–10.65 mg-equiv./dm3. Creating comprehensive technologies for the purification of mineralized waters makes it possible to ensure the proper efficiency of water desalination and to utilize the waste formed with obtaining useful products. That could reduce anthropogenic pressure on the environment and solve the problem of freshwater shortage for people and industry