抄録
Efficient concentration of lithium–containing solutions is essential in direct lithium extraction (DLE) and lithium–ion battery recycling processes. Conventional reverse osmosis (RO) suffers from an inherent concentration limit imposed by osmotic pressure, while thermal evaporation requires large energy input due to phase change. Osmotically assisted reverse osmosis (OARO) has attracted attention as a membrane–based concentration process capable of achieving high concentration without phase change, enabling concentration beyond the practical limits of RO. In principle, OARO does not impose an intrinsic upper limit on achievable concentration and allows stepwise concentration without phase change. Concentration tests using lithium chloride (LiCl) and lithium sulfate (Li2SO4) solutions demonstrated stable performance under both short–term and long–term operation, even at high osmotic pressures. Initial membrane compaction was observed, followed by stable continuous operation. Furthermore, a commercial application for concentrating black mass–derived Li2SO4 solution is introduced. Operational data show stable concentration from approximately 2 ～ 3 g/L to 14 ～ 17 g/L over extended periods. These results indicate that BC membrane–based OARO is a practical and energy–efficient concentration technology for DLE and recycling processes.
