Photocatalytic degradation of toxic dyes by Ni-doped ZnO in the presence of reactive oxidative species under UV and sunlight irradiation

The removal of toxic pollutants from industrial wastewater would reduce their environmental impact and health effect. Very few azo-dyes have been oxidized aerobically, because their solubility in water is low, being usually inversely proportional to the molecular complexity of their structure. Among the various techniques, heterogeneous photo- catalysis is a popularly employed process to eliminate hazardous waste materials especially organic pollutants, which are degraded to less toxic or less harmful materials. ZnO semiconductors with direct wide band gap (Eg3.37 eV) are highly explored n-type semiconductors owing to their high electron–hole binding energy (60meV), high thermo-mechanical stability, and good piezoelectric and optoelectronic properties. Moreover, ZnO semiconductors are known to be an excellent material for the fabrication of various efficient electronic, optoelectronic devices, photovoltaic devices and photocatalysts. In the present study, photocatalytic degradation of acid orange has been investigated in aqueous solution over ZnO nanoparticles doped with Ni. Experimental condition including pH, dye concentration, photocatalyst concentration and temperature were optimized. XRD, SEM, TEM and DRS were used to characterize the prepared photocatalyst. The decomposition experiments of acid orange against UV and sun light has been studied in the presence and absence of reactive oxidative species. Consequently, our results show Ni-ZnO nanoparticles has an extraordinary photocatalytic activity to degradation of acid orange under both UV and sunlight irradiation.