Adsorption Performance and Modelling of Cd2+ Ions Removal Using Pyrolysed Palm Kernel Shell

Abstract

Valorisation of agricultural waste into sustainable high-performance adsorbents offers a cost-effective pathway for heavy metal removal. This study reports the adsorption performance and mechanistic behaviour of cadmium(II) remediation employing raw and pyrolysed palm kernel shell (PPKS). Characterisation data of PPKS indicated substantiate functional groups at the surface, enhanced mesopore structure up to 112.91 m²/g, and produced higher thermal stability, all of which were demonstrated by FTIR, BET, SEM–EDX, XRD, TGA, and zeta potential data. Batch adsorption experiments showed substantial pH-dependent adsorption, with higher removal efficiency of about 92% – 96% at pH 5 – pH 6. The maximum adsorption capacity increased from 72.1 mg/g (raw PKS) to 107.4 mg/g after pyrolysis. Adsorption kinetic data highlighted that the process occurs via multiple steps, which are best interpreted through the model by Avrami fractional order, while the Liu isotherm provided an excellent fit for the equilibrium data. Thermodynamic parameters emphasized spontaneous and endothermic adsorption with negative ∆G° and positive ∆H° values. These data present pyrolysed palm kernel shell (PPKS) as an efficient, low-cost, and circular-economy-compatible adsorbent for remediation of cadmium-contaminated water, offering practical insights for sustainable wastewater management. The Liu isotherm provided a better equilibrium fitting, while the adsorption kinetic study showed multiple steps that were best controlled by the model from Avrami fractional order. Based on the data obtained in this present study, pyrolysed palm kernel shell (PPKS) is an alternative and effective adsorbent for removal of cadmium from contaminated aquatic systems, and this offers important understanding for eco-friendly wastewater treatment methods.