Preparation of Orange-Peel-Derived Biochar for the Removal of Pb(II) and Methylene Blue from Aqueous Solution: Equilibrium, Kinetic and Thermodynamic Studies

Abstract

Agricultural waste-based biochar offers an opportunity to integrate the simultaneous treatment of drinking water with pesticides and other pollutants with the management of agricultural waste. This manuscript develops a framework to analyze the potential of orange peel biochar (OPB) to adsorb Pb (II) as well as methylene blue (MB). The source manuscript contained a proposed methodology, but lacked experimental data, which means that all the values reported in this manuscript are estimations and will be represented as such. Several batch adsorption conditions including solution pH, OPB dosage, adsorption time, initial concentration, and temperature were evaluated. The dataset was subjected to one-way ANOVA, nonlinear Langmuir and Freundlich adsorption isotherms, pseudo-first-order and pseudo-second-order (PSO) kinetics, van't Hoff thermodynamics, and five-cycle regeneration. Illustrative adsorption of either pollutant exceeded 90%. For Pb(II) adsorption, Langmuir fitting produced qmax values of 74.82 mg g-1, with R2 of 0.998, but for MB adsorption, qmax values were higher at 112.83 mg g-1 and R2 of 0.999. Pseudo-second order kinetic model produced better fit for both pollutants compared to pseudo-first order, despite the fact that this does not confirm chemisorption. Thermodynamic analysis of the adsorption of either pollutant calculated endothermic and spontaneous adsorption for the Pb(II) and MB adsorption, respectively. After five regeneration cycles, the adsorbents retained 82% and 86% of Pb(II) and MB adsorption, respectively, and the entire manuscript illuminates a cohesive and concise description of orange peel biochar (OPB) and its adsorption capacity.