Biochar of Orange Peel as an Adsorbent for the Uptake of Lead (II) Ions

Abstract

Prepared orange peel biochar (OPB) was evaluated as a low-cost adsorbent for removing Pb(II) ions from aqueous solutions. The OPB was examined using scanning electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, and Brunauer-Emmett-Teller analysis to identify surface morphology, functional groups, thermal stability, and surface porosity responsible for adsorption, respectively. The biochar showed typical lignocellulosic decomposition behavior and exhibited a microporous surface whose hydroxyl, carbonyl, carboxylate, and phenolic groups allowed effective Pb²⁺ uptake. Batch studies revealed maximum Pb²⁺ at a pH 5, adsorbent dosage of 0.7 g, contact time of 80 min, adsorbate concentration of 150 mg/L, and temperature of 50 °C. The Langmuir isotherm revealed adsorption maximum capacity of the adsorbent to be 73.5 mg/g, while thermodynamics analysis showed that Pb(II) uptake was endothermic. These results demonstrate that orange-peel biochar can be an effective, environmentally friendly, and renewable adsorbent for lead ions in wastewater treatment.