An over review on recently developed techniques, mechanisms and intermediate involved in the advanced azo dye degradation for industrial applications

Abstract The continuous growth of population and increasing industrial activities in the different sectors, viz., textiles, leather, plastics, cosmetics and food processing industries require the development of varying nature of novel dyes. Among the dyes used in different industries, azo dyes are considered to be the most widely consumed and play an important role in the dyeing of textiles, leather, and plastics, etc. Azo dyes and their degradation products are toxic toward aquatic life and mutagenic for humans. The textile industry is one of the major contributors of azo dye pollutants and discharges the large quantity of azo dye effluents, which causes an acute hazardous effect on environment and human health. The conventional physical and chemical methods adopted to degrade azo dye effluents are not always efficient, due to the factors such as pH, temperature, and concentration of dyes. The existence of drawbacks on physico-chemical methods on the degradation of azo-dyes has triggered an interest for the researchers around the world to develop cost effective, alternative and eco-friendly techniques. Even though, the recent available reports indicate that the nanoparticles based microbial enzyme conjugates is considered to be an efficient technique to remove the azo dye from textile effluents within a few minutes, however, they are very high cost and possess difficulties in scale-up. In the present work, an attempt has been made to bring the relevant detailed literature available with regard to effective and efficient method and mechanism of degradation of azo-dyes in order to benefit the researchers of both from academia and industry. Furthermore, the present article also provides degradation based on their chemical structure and the conditions, in addition to mechanism involved for the bio-degradation and photo-catalytic degradation of azo dyes including merits and demerits of the each method.