Effective Treatment of Acidic Effluent Generated from Li-ion Battery Recycling

The present study investigates a comprehensive treatment strategy for managing acidic effluent generated during the hydrometallurgical processing of discarded lithium-ion batteries (LIBs), specifically following cobalt oxalate precipitation. The effluent, characterized by extremely low pH (0.1), high total dissolved solids (TDS = 50,000 mg/L), and elevated chemical oxygen demand (COD = 1640 mg/L), was treated through a sequential combination of coagulation, adsorption, and distillation. Coagulation using ferric sulfate achieved 34% TDS reduction through precipitation of dissolved metal ions and oxalates. Subsequent adsorption employing thermally activated carbon derived from waste RO filters further reduced TDS by ~55% due to enhanced surface area and porous structure. Final distillation at 150°C yielded a >99% decrease in TDS and COD, producing condensate meeting CPCB discharge standards (TDS = 79 mg/L, COD = 32 mg/L). The integrated approach effectively transformed a high-strength acidic effluent into reusable water while concentrating recoverable metal residues. A preliminary techno-economic assessment indicated that the process is technically viable and scalable, with energy consumption during distillation being the major cost factor. The study demonstrates a sustainable and resource-efficient treatment pathway for LIB recycling effluents, contributing toward circular economy and zero-liquid discharge objectives.