OVAT DEGRADATION ANALYSIS OF METHYLENE BLUE USING RICE HUSK ASH (AGRO-WASTE) BASED CATALYST IN SOLAR IRRADIATION

This study investigated the degradation of methylene blue dye with ZnO-CuO/RHA, a synthesised agro waste-based photocatalyst under solar irradiation at ambient temperature. Preliminary screening of the methylene blue degradation facilitated the selection of the best ZnO-CuO/RHA combination. The photocatalytic degradation was done by taking varying weights of catalyst in 100 mL of dissolved 10-30 ppm MB solutions. The sample was magnetically stirred at 500 rpm in darkness before being exposed to sunlight irradiation. The suspension was magnetically stirred continuously and 5 ml was withdrawn intermittently, centrifuged and analysed with UV-Vis spectrophotometer. The effect of catalyst dosage, initial concentration and irradiation time on the photodegradation were studied using the one-variable-at-a-time method. The result showed that the degradation percentages of the catalyst with 1, 2, 3, 4, and 5 wt. % of RHA were 80.31%, 88.23%, 99.94%, 91.06 % and 81.12% respectively after 180 minutes. These results showed that degradation percentage was directly proportional to the irradiation time up to 3 wt. % thereafter, there was a decline in the percentage degradation. Hence, as the irradiation time increases, there was a significant increase in the degradation of methylene blue dye. ZnO-CuO/RHA catalyst was found to possess a higher photocatalytic activity in the presence of sunlight in comparison to bare ZnO-CuO since using RHA as a base for ZnO-CuO increased the surface area resulting in more active sites under visible light irradiation. ZnO-CuO/RHA may serve as an efficient-photocatalyst for industrial applications with excellent prospects. Keywords: Photocatalytic degradation, Sunlight irradiation, One-variable-at-a-time