The purpose of this research was to investigate the adsorption of arsenic (As) from aqueous solutions using MPAC-500 and MPAC-600 (magnetic-activated carbons synthesized from the peel of Pisum sativum (pea) pyrolyzed at 500 °C and 600 °C temperatures, respectively). The potential of both biosorbents for As adsorption was determined in batch and column mode. The characterization of both biosorbents was performed by energy dispersive spectroscopy, scanning electron microscope, pHZPC, particle size distribution, X-ray diffraction, zeta potential and Fourier-transform infrared spectroscopy. It was found that the efficiency of MPAC-600 was better than MPAC-500 for the adsorption of As(III) and As(V) ions. The adsorption capacities of MPAC-500 and MPAC-600 in removing As(III) were 0.7297 mg/g and 1.3335 mg/g, respectively, while the values of Qmax for As(V) on MPAC-500 and MPAC-600 were 0.4930 mg/g and 0.9451 mg/g, respectively. The Langmuir isotherm model was found to be the best fit for adsorption of As(III) by MPAC-500 and MPAC-600, as well as adsorption of As(V) by MPAC-500. The Freundlich isotherm model, on the other hand, was optimal for As(V) removal with MPAC-600. With R2 values close to unity, the pseudo-second-order kinetics were best fitted to the adsorption process of both As species. The Thomas model was used to estimate the breakthrough curves. The effects of coexisting oxyanions and regeneration studies were also carried out to examine the influence of oxyanions on As adsorption and reusability of biosorbents.
Keywords: Adsorption; As(III) and As(V) remediation; Fixed-bed column; Isotherm and kinetic modeling; Magnetic activated carbon; Pea (Pisum sativum) peel waste.
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