Electrochemically assisted membrane distillation crystallization for efficient resource reclamation from ammonia-rich battery leachates

The sustainable management of ammonia-rich leachates containing valuable metals is imperative for closing the loop in the hydrometallurgical recycling of spent lithium-ion batteries. This study introduced an electrochemically enhanced membrane distillation crystallization recovery (EEMDCR) system for concurrent ammonia recovery and selective separation of lithium and cobalt from simulated battery leachates. A baseline membrane distillation crystallization recovery (MDCR) process achieved 85.25% ammonia recovery and 56.75% lithium crystallization at 60 °C and 0.2 M NH₄HCO₃, but was critically limited by both severe membrane scaling and compromised Li₂CO₃ product purity at [Co(NH₃)₆]³⁺ concentrations ≥0.03 M. The integrated electric field in EEMDCR demonstrated dual functions by simultaneously mitigating scaling through electrokinetic repulsion and enabling cobalt recovery via electrochemical reduction. Over the tested current range of 40-80 mA, the system achieved >95% ammonia recovery and >93% cobalt recovery, ultimately yielding CoCO₃/Co₂(OH)₂CO₃/Co and Li₂CO₃ products. Notably, the intermittent application of the electric field, particularly at optimized duty cycles, effectively mitigated electrode scaling and further enhanced system robustness and cobalt recovery (∼100%). Comprehensive material characterizations confirmed minimal membrane scaling and the relatively high purity of the recovered crystalline products. This work established EEMDCR as a synergistic strategy that effectively addressed scaling and recovery challenges, demonstrating significant potential for sustainable resource recovery in battery recycling.