Techno-Chemical Evaluation of Palm Kernel Shell Waste Utilization as Activated Carbon for Heavy Metal Adsorption: Characterization and Adsorption Isotherm Study

Abstract

The abundant palm kernel shell waste has not been optimally utilized, while heavy metal pollution in water bodies requires low-cost adsorbents. This study evaluated the technical and economic feasibility of converting palm kernel shells into activated carbon for adsorbing Pb²⁺, Cd²⁺, Cr⁶⁺, Fe³⁺, Cu²⁺, and Zn²⁺. Activated carbon was synthesized through carbonization at 500 °C followed by KOH activation at 800 °C, characterized using BET, FTIR, and pHpzc analyses, and tested in batch experiments under varying pH, dosage, and contact time. Adsorption data were analyzed using Langmuir and Freundlich isotherms and pseudo-first- and pseudo-second-order kinetic models. Continuous adsorption and regeneration tests were also conducted. The activated carbon exhibited a surface area of 425 ± 12 m²/g and the highest adsorption capacity for Cr⁶⁺ (49.65 ± 1.02 mg/g), with removal efficiencies above 90% for all tested metals. Adsorption behavior followed the Langmuir isotherm (R² = 0.992) and pseudo-second-order kinetics (R² = 0.997). Economically, a 15,000 ton/year plant showed an ROI of 47.13% and remained feasible under raw material price increases, indicating strong potential for heavy metal wastewater treatment.