Adsorption of Cd(II) and Cr(III) Ions using Magnetic Activated Carbon Derived from Plajau Wood (Pentaspadon motleyi)

This study investigates the adsorption behaviour of Cd2+ and Cr3+ ions from aqueous solutions using magnetic activated carbon (MAC) synthesized from Plajau wood (P. motleyi). Magnetic activated carbon was synthesized by compositing activated carbon with magnetite (Fe3O4), using a Fe3+/Fe2+ mixture in a 2:1 molar ratio. The formation of Fe3O4 on the carbon surface introduced new active sites and modified the pore structure of the activated carbon. Infrared spectra show the presence of magnetite in infrared absorption at 570 cm–1, SEM-EDX analysis shows magnetite on the surface with oxide compound 6.8% and the XRD diffractogram confirms the suitability of magnetite. The optimum adsorption of Cd2+ and Cr3+ was achieved at pH 6 and 7, adsorbent doses of 0.04 g and 0.06 g, stirring speed of 150 rpm, contact times of 3 and 4 h and an initial concentration of 50 ppm, yielding maximum adsorption capacities of 48.36 mg/g and 39.27 mg/g, respectively. Adsorption of Cd2+ ion follows the Langmuir isotherm model (R2 = 0.9123) and pseudo-second order kinetic model (R2 = 0.9110). Meanwhile, the Cr3+ ion follows the Redlich-Peterson isotherm model (R2 = 0.9475) and pseudo-second order kinetic model (R2 = 0.9983). The efficiency of magnetic activated carbon recovery after adsorption was 81.18% indicating good magnetic responsiveness and potential for reuse with minimal material loss.