Experimental study on bipolar membrane electrodialysis of high-salt mine water concentrate

Based on the zero discharge and resource utilization of high-salt mine water, BP-A-C-BP three-chamber configuration bipolar membrane electrodialysis is used to treat high-salt mine water concentrate. Taking the high-salt mine water of a mine in Hebei as the raw water, after pretreatment + RO + decarburization + concentrated water RO + ED concentration, the final concentrate TDS reaches 93 040 mg/L, and the bipolar membrane electrodialysis test is carried out. The effects of current density, circulating flow rate and electrolyte concentration in the polar chamber on the acid and alkali production by bipolar membrane electrodialysis are investigated.The results show that in the current density range of 10-40 mA/cm², with the increase of current density, the operating voltage increases, the current efficiency and capacity decrease gradually, and the energy consumption increases gradually. The optimal current density is 30 mA/cm². When the circulating flow rate is in the range of 10-30 L/h, with the increase of the circulating flow rate, the current efficiency and production capacity increase, and the energy consumption decreases. Further increasing the circulating flow rate to 40 L/h will increase the energy consumption and reduce the production capacity. The optimal circulating flow rate is 30 L/h. The electrolyte concentration in the polar chamber should not be too low or too high, which is easy to increase energy consumption. The hydrolysis effect of bipolar membrane electrodialysis is the best when the concentration is moderate, and the optimal electrolyte concentration is 2%. The initial salt chamber concentrate of 4 L, the acid chamber and the alkali chamber are respectively 1.5 L deionized water and 2 L of 2% sodium sulfate in polar chamber. The current density is 30 mA/cm², the circulating flow rate in polar chamber is 60 L/h, and the circulating flow rate in other chambers is 30 L/h. After 120 min of operation, the acid and alkali concentrations are 6.91% and 5.38%, respectively, which reach the expected target of the experiment. The current efficiency, productivity and energy consumption are 74.21%, 1.49 kg/(m²·h) and 1.66 kWh/kg, respectively. The acid and alkali solution produced by bipolar membrane electrodialysis process can be used in the zero discharge process of high-salt mine water and the downstream industrial chain of coal to realize the non-phase change resource of concentrated liquid. It avoids the problem of miscellaneous salt difficult to deal with, and also improves the economic value of wastewater.