The Influence of pH on Cd (II) Adsorption onto NaOH-Treated Oil Palm Empty Fruit Bunch (OPEFB)

Abstract

This study aims to investigate how pH affects the removal of Cd (II) ions using both raw and NaOH-treated oil palm empty fruit bunch (OPEFB). As the NaOH concentration increases from 0.1 M to 1.0 M, the removal percentage increases from 58.58% to 61.20% after a 12-hour immersion duration and 62.27% to 64.54% as the immersion duration was raised to 24 hours. Stronger interactions with Cd (II) ions are made possible by the increased number of active sites on the OPEFB surface caused by higher NaOH concentrations. Extending treatment duration allows NaOH to penetrate OPEFB structure, enhancing its cadmium binding ability. The best NaOH treatment was 1.0 M of NaOH concentration with 24 hours of immersion time (64.54% Cd (II) removal with q_e= 32.3 mg/g). Energy-dispersive X-ray (EDX) analysis showed that the O/C ratio increased by 44.77% after alkaline treatment indicating the partial removal of the OPEFBs’ lignin and hemicellulose primarily made up of C which enhances adsorption capabilities. The optimal starting solution pH for raw and treated OPEFB was pH 6, with maximal adsorption being 65.2% (q_e= 32.6 mg/g) and 70.8% (q_e= 35.4 mg/g), respectively. The results demonstrated that the NaOH-treated OPEFB can be used as an alternative for Cd (II) removal in wastewater treatment.