Reuse of wastewater from dicamba production by bipolar membrane electrodialysis

Bipolar membrane electrodialysis (BMED) is used to convert NaCl in dicamba production wastewater into HCl and NaOH and reuse it in pesticide production to realize the resource utilization of pesticide wastewater. Firstly, batch experiments of BMED that last for 110 minutes were conducted to explore the best-operating conditions for treating sodium chloride solution. The results showed that when the initial concentration of the feed solution was 160 g/L, the current density was 70 mA/cm2 and the initial concentration of acid and base compartment was 0.075 mol/L, the concentration of the resultant HCl and NaOH solution could reach 1.98 mol/L and 2.06 mol/L, respectively. Meanwhile, the current efficiency was as high as 42.74%. Then, considering the COD index of the actual wastewater is because of methanol, sodium chloride solution with different concentrations of methanol was used to simulate the actual wastewater from the dicamba production. After the experiments, a small amount of methanol was detected in the acid and alkali compartments, indicating that there was a certain degree of permeation during the operation of the BMED, but it did not significantly affect the performance of the membrane stack. Based on the results, BMED was adopted to treat the actual wastewater obtained from the dicamba production after some pretreatment, and it was found that the performance of the membrane resembled the situation of treating NaCl solution with high concentration during the operation time. It was proved that the BMED is feasible to realize the reuse of dicamba production wastewater. © 2021, Editorial Board of CIESC Journal. All right reserved.