Removal of lead in water by potassium hydroxide-activated biochar developed from Syzygium cumini stem

Abstract Lead (Pb) contamination in water poses a significant threat to public health across the globe which requires effective remediation strategies. The main objective of this study is to achieve a removal efficiency of Pb(II) ions from aqueous media using activated Syzygium cumini (java plum) stem biochar. It was prepared by slow pyrolysis at 400 °C after treating the biomass with potassium hydroxide for activation. These biochars were characterized thoroughly (SEM, SEM–EDX, TEM, FTIR, XRD, elemental analyses, and SBET) to conduct a set of batch experiments. The effect of several parameters such as pH, temperature, contact time, adsorbent dosage, initial lead concentrations, and co-existing ions were explored. The decrease in starting lead concentrations from 50 to 10 mg L−1 resulted in improved removal efficiency. The removal effectiveness of activated biochar was 97%, but non-activated biochar was just 19%. Lead adsorption increased considerably as pH increased from 3 to 5. Further, the activated biochar was optimized through various isotherms models, kinetic equations, and thermodynamic analysis. It was observed that the pseudo-second-order kinetic model and Temkin isotherms were the best-fitted models that identify the mechanism of chemisorption and monolayer sorption. According to this study, activated biochar is a promising biosorbent for removing lead from an aqueous solution. Graphical Abstract