Assessment of activated carbon derived from municipal solid waste char as a precursor for mitigation of heavy metals

Abstract

The study explored the potential of activated carbon from mixed municipal solid waste (MSW) char produced at 250 and 350 °C. The resulting char was activated using NaCl, KOH, and ZnCl₂, serving as a novel precursor to optimizing the synthesis conditions for cost-effective activated carbon aimed at removing Pb(II) from water. Characterization techniques, including proximate analysis, iodine number, pH, BET surface area, XRD, FTIR, FESEM, and atomic adsorption spectroscopy, were employed to identify the most effective activated carbon for Pb(II) removal. The findings revealed that KOH-activated carbon produced from char at 250 °C exhibited the most potential adsorbent and fell within the range of commercial activated carbon. Batch adsorption experiments using KOH-activated carbon demonstrated the highest Pb(II) removal of more than 90 % under optimized conditions of pH 6, 1 g activated carbon, zero contact time, and 1000 mg/L metal concentration. The adsorption kinetics followed Lagergren's second-order model, and the isotherm suggested the Langmuir model with an R² value of 0.99. Additionally, the cycle study revealed that the activated carbon could be reused for up to two cycles with 90 % adsorption efficiency. Desorption experiments showed that HNO₃ was the most effective eluent, achieving 80 % removal efficiency at pH 1. The recovery rate of MSW char-activated carbon (MSW-AC) after desorption was approximately 64.89 %. Thus, the performance of MSW-AC in adsorption, desorption, and cycle studies is recommended as an effective adsorbent for heavy metal mitigation. Furthermore, its utilization represents a valuable strategy for waste management, contributing to waste minimization efforts.