Combined UV catalytic ozonation process on iron loaded peanut shell ash for the removal of methylene blue from aqueous solution

This study explores the effectiveness of peanut shell ash (PSA) as a catalyst for the removal of methylene blue (MB) using a synergistic photocatalytic process (UV/Fe-PSA/O3). The color and chemical oxygen demand (COD) removals were studied for ozonation and synergistic process, and the mechanism of the catalytic ozonation synergistic process was explained by studying the production of reactive oxygen species, such as hydroxyl radicals (HR), superoxide ion radicals (SOR), and hydrogen peroxide. The process comparison, scavenger effect, catalyst-dose effect, and pH effect were studied, and a mechanism was proposed. The synergistic process effectively performed 94% decolorization and 72.7% COD removal at pH 6 and 0.1 g Fe-PSA dose at room temperature. The pH studies showed effective performance of synergistic photocatalytic process at pH 4, 6, and 9, respectively, with the maximum efficiency at alkaline pH near the pHPZC of the catalyst. The process efficiency reduction by the addition of scavenger confirms that the UV-irradiated Fe-PSA based ozonation process follows a radical mechanism provoking the production of SORs and HRs. Therefore, it has been found that Fe-PSA/O3 irradiated with UV radiation can act as a cheap alternative process for treating dye composed wastewater.