The Preliminary Studies on the Tremendous Degradation Rate of Methylene Blue with Cu-doped α-MnO2 Photocatalyst Under UV Light Irradation

Dye contaminations have severe impacts to environment (air, soils, plants, water) due to their adverse effects. Most dyes are toxic, carcinogenic, mutagenic and resistant to bio-degradation. Photocatalysis-based advanced oxidation process (AOP) has been considered as the most effective and efficient way to treat this recalcitrant compounds. Manganese oxides are ubiquitous and environmentally friendly in natural environments and can act as semiconducting materials. Tunnel structure of manganese oxide such as α-MnO 2 (cryptomelane) has been widely studied for broad applications as Fenton-based AOP. Catalytic efficiency of α-MnO 2 could be further increased by doping α-MnO 2 with a metal ion like the Cu ion. Although the synthesis and catalytic activity of Cu-α-MnO 2 have been reported by previous studies, its photocatalytic performance using this one-pot-sol-gel approach for MB degradation has never been reported previously. Herein, Cu-doped α-MnO 2 was synthesized by one-pot sol-gel method and characterized by X-ray diffraction (XRD), BET surface area and atomic absorption spectroscopy (AAS). The AAS results suggested the presence of Cu ions in α-MnO 2 since the increase in doping Cu resulted in the corresponding increase in Cu content in the α-MnO 2 . The BET surface area indicated that the doping 10% Cu in α-MnO 2 led to about two fold increase in suface area compared to undoped α-MnO 2 . The photo catalytic performance of Cu-α-MnO 2 via UV light irradiation for the degradation of methylene blue (MB) was significantly higher that that of undoped α-MnO 2 and was associated with the increased in surface area of Cu-α-MnO 2 over undoped α-MnO 2 . The maximum degradation of MB was 97.9, 98.3, 98.7 and 99.5% achieved using α-MnO 2 , 1% Cu-α-MnO 2 , 5% Cu-α-MnO 2 , and 10% Cu-α MnO 2 and 10% Cu-α-MnO 2 .