Arsenite and Arsenate Sorption Efficiency of Pomegranate Peel in Aqueous Solutions
Arsenic (As) contamination of groundwater is a serious health and environmental issue in the world. Hence, in this study, we evaluated the biosorption potential of pomegranate peel as a novel material for arsenite (As(III)) and arsenate (As(V)) removal from aqueous solutions as a function of pH, initial As concentration, biosorbent dose and contact time. The results showed that pomegranate peel removed more As(III) (77 %) compared to As(V) (52 %) at an optimum pH of 7.6 and 4.5 and at 1 g L–1 biosorbent dose. Sorption isotherm data showed greater sorption capacity for As(III) than As(V) (2.90 and 2.6 mg g–1, respectively). The pseudo-second order kinetic model and Langmuir model provided the best fits (R2 = 0.99) for As(III) and As(V) sorption, suggesting chemisorption as a dominant process for removal in aqueous solutions. Fourier transform infrared spectroscopy complemented our modeling data and indicated that mainly hydroxyl (–OH), carboxyl (–COOH), alkyl (–CH3) and amine (–NH2) surface functional groups were involved in As(III) and As(V) sorption. However, scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDX) was unable to detect sorbed As (wt. %). Arsenite (68 %) desorption was more compared to As(V) (66 %) from pomegranate peel in first cycle demonstrating its reusability and possibility of As recovery. Overall, this pilot scale study highlights the potential use of pomegranate peel as an efficient and cost-effective precursor biowaste for As removal, preferably As(III), in naturally occurring aqueous environments, such as As-contaminated drinking water or wastewater.
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