Bipolar membrane electrodialysis for sustainable utilization of inorganic salts from the reverse osmosis concentration of real landfill leachate

Developing an effective resource utilization method for landfill leachate reverse osmosis concentrate (LLRC) remains a challenge because of the high concentrations of inorganic salts and refractory organic compounds. This study applied a bipolar membrane electrodialysis (BMED) to separate inorganic salts from real LLRC while simultaneously reclaiming inorganic acids and bases. The performance of BMED was affected by operating parameters, such as operating voltage, membrane surface flow velocity, and initial acid-base concentration. With optimized operating parameters, the reclaimed acid-base concentrations, desalination rate, and current efficiency were higher with less energy consumption. Ultimately, 0.41 mol/L acids and 0.40 mol/L bases were reclaimed from LLRC. The reclaimed acids contained 88 wt% HCl and 12 wt% HNO3. The reclaimed bases were 52 wt% NaOH and 45 wt% KOH. Furthermore, the concentrations of arsenic and heavy metals were low enough to safely utilize reclaimed products. The electromigration of organic compounds was controlled by protonation. After excluding the fixed costs, the net profit of 1 m3 LLRC treatment by BMED was $27.630, which showed remarkable economic feasibility. Our research offers a new strategy to realize sustainable utilization of inorganic salts from LLRC.