Valorization of waste potato peel as iron adsorbent and catalyst in photo-oxidation: a sustainable waste management strategy

Abstract

The study presents a unique approach for synergistic remediation of iron and methylene blue from aqueous media using waste potato peel. The waste potato peel was thermally modified at 550 oC to improve the properties desirable for adsorption (high-specific surface area and porosity). The thermally modified waste potato peel was employed in batch adsorption of iron from an aqueous medium at natural pH. Maximum iron adsorption of 202 mg g−1 was recorded for 7.5 mM iron concentration and 1 g L−1 of adsorbent dose. The iron adsorption on thermally modified waste potato peel followed pseudo-second-order kinetics and was best described by the Langmuir isotherm model. The iron adsorption was noted as endothermic, spontaneous, and thermodynamically feasible. The iron-adsorbed waste potato peel derived sorbent was used as a catalyst for photo-oxidative degradation of methylene blue in aqueous solution. The impacts of various process variables (initial dye concentration, catalyst dosage, and hydrogen peroxide concentration) on methylene blue degradation were analyzed. The highest methylene blue degradation of 91.76% was achieved using 1 mM of hydrogen peroxide and 3 g L−1 of iron-adsorbed catalyst in 15 min of exposure time to ultraviolet radiation. An apparent degradation rate of 0.116 min−1 was noted for the photo-degradation. The activation energy of the iron-adsorbed catalyst in the photo-oxidative of methylene blue was 12.97 kJ mol−1. The catalyst was noted to have good long-term stability. The low-cost catalyst obtained from waste peel was found to perform exceptionally well, relative to commercial activated carbon-based photo-catalysts.