Sustainable treatment of hazardous Spent Pot Lining waste from aluminum manufacturing through optimized alkali and acid leaching

Abstract

Aluminium manufacturing industries generate substantial quantities of hazardous solid waste known as Spent Pot Lining (SPL), posing significant environmental risks such as groundwater and soil contamination. This study stands out as one of the pioneering investigations into the chemical leaching of Spent Pot Lining (SPL) using a combination of alkali and acids, including chloric acid (HClO 3 ), hydrochloric acid (HCl), and nitric acid (HNO 3 ), under varying experimental conditions. The novelty lies in the systematic optimization of critical process parameters such as temperature (ranging from 30°C to 120°C), liquid-to-solid ratio (varying from 2 cm³/g to 5 cm³/g), alkali concentration (ranging from 0.8 M to 3.2 M), and acid concentration (ranging from 3 M to 12 M) using a Taguchi L16 orthogonal array. Additionally, the study identifies HClO 3 as the most effective leaching agent, achieving the highest efficiency of 59.59 %. This research also provides detailed insights into the dominant influence of acid concentration across different leaching processes, presenting a unique approach to SPL treatment and offering a sustainable pathway for managing hazardous industrial waste. Through the systematic optimization of chemical leaching parameters and the identification of the most effective leaching agents, this study offers a fundamental framework for furthering research in SPL treatment. Important insights that can direct future research into more effective and sustainable SPL management techniques are provided by the thorough examination of parameter influence, especially acid concentration. Additionally, the results help create environmentally friendly and scalable methods for treating hazardous waste, opening the door for additional innovations like combining leaching with recovery procedures or investigating different reagents and approaches. • Chloric acid achieved the highest leaching efficiency at 59.59 % among tested acids. • Systematic parameter optimization using the Taguchi L16 orthogonal array approach. • Explored the effects of acid concentration, temperature, L/S ratio, and alkali levels. • Identified acid concentration as the dominant factor influencing leaching efficiency. • Highlighted Chloric acid's superior performance over Hydrochloric and Nitric acids.