Efficient adsorption of heavy metals using Friedel's salt synthesized from municipal solid waste incineration fly ash leachate.

Municipal solid waste incineration fly ash (MSWIFA) is a hazardous waste with high content of complex pollutants and soluble chlorides, generally requiring water-washing dechlorination for resource utilization. However, the abundant leachate with environmental risks requires energy-intensive purification treatment. Herein, we employed a novel and scalable coprecipitation strategy for in-situ synthesis of Friedel's salt directly from chlorine-rich MSWIFA washing leachate, transforming waste into a valuable adsorbent. Experimental results showed that the products reached 95 % purity with high crystallinity under optimal synthesis conditions of pH 12.5, Ca/Al ratio 1:1 and 40 °C. Friedel's salt possessed satisfactory adsorption of Cr(VI) and Cd(II) with maximum capacities achieving 132.5 mg/g and 680.1 mg/g, outperforming many hydrotalcite-based materials. The main adsorption mechanisms of isomorphic substitution and interlayer exchange were revealed by various techniques such as X-ray photoelectron spectrometer. This work explores the potential value of MSWIFA washing leachate as an adsorbent, offering new perspectives for promoting the sustainable development of solid waste.