Synthesis, Characterization and Application of Nanostructured ZnO for the Photocatalytic Degradation of Malachite Green, Methylene Green, Direct blue-1, Orange-II, Acridine Orange and Neutral Red Dyes in the presence of Visible Light

Abstract

Nowadays the environment is severely affected by hazardous water-soluble organic dyes present in water effluents from textile and dyeing industries. Stability of these dyes causes severe environmental problems such as depleting of the dissolved oxygen content of water and releasing toxic compounds in water bodies endangered the aquatic life. Several physicals, chemical and biological methods have been used to remove dyes from contaminated water. Among them, physical adsorption and degradation are considered as a competitive method because of high efficiency, economic suitability and easy to design and for operation. Photo-catalytic degradation is one of the best methods used for removal of toxic chemicals produced by dyes and degraded via redox reactions in the presence of photo-catalyst. Dyes are widely used in cellulosic fabrics, including textiles, paper making, wool, silk and tannin-mordant cotton and sprit ink manufacture and other colouring agents in many industries. Dyes are carcinogenic and potential pollutants and hence attention has been paid toward the removal of harmful and hazardous contaminants from wastewater. Industrialization is vital to a nation's economy because it assists as a vehicle for development. Speedy industrialization has provided much comfort to human beings; however, it also has some adverse effects on environments. During the last fifty years, the number of industries especially textile in India has grown rapidly and this is a serious threat to human health and economy as well. Photo-catalytic degradation for organic dyes is quite popular due to high efficiency, low-cost method, less hazardous intermediate products, low reaction time and mild reaction conditions. The present work deals with the synthesis of ZnO nanoparticles and it's used in the photocatalytic degradation of dyes taken for present study using visible light irradiation. Advanced oxidation processes (AOPs) are highly efficient in wastewater treatment especially containing hazardous organic pollutants such as dyes. In the present study, we have carried out photo-catalytic degradation of Acridine Orange (AO) dye using ZnO NPs in the presence of visible light. An effective and green reaction procedure has been established. ZnO as nanocatalyst is highly efficient for dye degradation particularly Acridine Orange. Several reaction parameters such as the amount of catalyst, reaction pH, the addition of H2O2 and K2S2O8 and addition of Na2CO3, and NaCl have been studied. Advanced oxidation processes rely on the efficient generation of reactive radical species and are gradually attractive choices for water remediation from a wide range of organic pollutants of human health and environmental concern. AOPs are defined as a set of chemical treatment processes which are specially designed to remove organic compounds from wastewater. With a large number of active sites, ZnO NPs exhibit very high surface reactivity, rendering it an efficient visible light photo-catalyst as compared to other photo-catalysts. Semiconductor ZnO NPs is a powerful photo-catalyst in the presence of visible light and used effectively in various photo-catalytic reactions. It is well known that semiconductor having a large bandgap acts as a good photo-catalyst. The main advantage of using ZnO NPs photo-catalyst is its photo-activity in the visible region. Studies also reveal that photo-reactivity of ZnO NPs is independent of the particle size which is a huge advantage for practical application of the ZnO NPs system in large-scale decontamination of polluted water. The primary objective of the present study was aimed to optimize the photo-degradation of some dyes using different experimental conditions.