A systematic comparison of inorganic and organic acids under constant-pH conditions identifies acetic acid as a green, selective, and low-temperature leaching system for lithium recovery from LiFePO 4 black mass. • Constant-pH leaching enables precise control of Li extraction and selectivity. • Acetic acid achieves 96% Li recovery with 95%) under optimized conditions, but selectivity depended on acid chemistry and oxidation potential. Sulfuric and hydrochloric acids enabled near-complete Li recovery, with HCl showing superior selectivity (Li:Fe > 100) at 38 °C. Nitric acid alone exhibited limited oxidative strength, but addition of H 2 O 2 significantly improved efficiency. Oxalic acid dissolved Li completely but lacked selectivity due to ferrioxalate complexation. Acetic acid delivered the best overall performance, achieving 96% Li recovery with negligible Fe (<0.1%) and minimal P (3%) dissolution at pH 4.3 and 25 °C. Cost analysis showed that while sulfuric acid is least expensive, acetic and hydrochloric acids offer the best balance of selectivity, efficiency, and safety. This study provides a unified framework for evaluating leaching systems and demonstrates that selective lithium recovery from LFP can be achieved under mild, low-acid conditions with minimal environmental impact.
Zadeh et al. (Mon,) studied this question.