Leaching of toxic elements from secondary alkaline lead slag and stabilized/solidified products

Secondary alkaline lead slag (SALS), generated during lead–acid batteries recycling, is a hazardous waste due to its high reactivity, solubility, and migration of toxic elements. After pulverization caused by storage under atmospheric condition for 30 days, the SALS was sieved and coarse fraction (+ 1 mm) was returned to the recycling process. Finer fraction (− 1 mm) was treated by water leaching to remove soluble compounds. SALS compositions prior and after the pre-treatment and effects of liquid-to-solid ratio, stirring rate, and temperature on Na, S, Fe, As, and Pb leaching from SALS were analyzed. The results show that maximal leaching degrees were 95.78%, 75.32%, and 79.89% for Na, S, and As, respectively (20 l kg−1, 600 min−1, 333 K, 120 min). Leachability of Na and S from SALS was controlled by dissolution of Na2SO4 that could be recovered from leaching solution. Isothermal As leaching is described by diffusion mechanism with activation energy of 15.5 kJ mol−1. Insoluble Pb and Fe sulfates, sulfides, and oxides remained in the SALS. Pre-treated SALS, with reduced mass up to 32%, was solidified in cement matrix. The results of toxicity characteristic leaching procedure and unconfined compressive strength confirmed effectiveness of As removal from SALS by water leaching and Pb immobilization in cement matrix containing 20% of SALS.