Efficient photocatalytic degradation of organic dyes with Ag doped ZnO nanoparticles under UV light irradiation

Abstract

Semiconductor based photocatalyst for degradation of cationic and anionic dye pollutants under UV light was demonstrated for wastewater treatment. In the present work, un-doped and Ag (mol% = 0, 0.05, 0.075 and 0.1)-doped ZnO nanoparticles were synthesized by co-precipitation method. X-ray diffraction (XRD) pattern confirms that the samples are found to be of highly crystalline hexagonal wurtzite structure. Scanning electron microscopy (SEM) image reveals that the morphology of the doped ZnO nanoparticles are highly affected by the addition of silver (Ag). Fourier transform infra-red (FTIR) and energy-dispersive spectra (EDS) demonstrates the presence of Ag in the ZnO lattice. UV–Vis absorption spectra shows that the Ag-doped ZnO nanoparticles exhibit a red-shift with reduced bandgap energy compared with un-doped ZnO nanoparticles. Hence, our aim is to find the effect of Ag- doping in ZnO nanoparticles for the improvement of photocatalytic degradation. The photocatalytic activities of these Ag-doped nanoparticles were evaluated by measuring the rate of photo-degradation reaction of hazardous methylene blue (MB) and methyl orange (MO) dye under UV-light irradiation. Photocatalytic efficiency in the degradation of MB and MO dyes was compared with the efficiency of un-doped ZnO. The effects of various factors like solution pH, photocatalytic dosage and UV irradiation time with concentration of MB and MO on photocatalytic degradation were studied. It was found that cationic dyes shows better photo-degradation than the anionic dyes. The main objective of the present work was optimizing the various factor for better photocatalytic activity, complete mineralization and evaluating the photocatalytic-degradation mechanism.