Photocatalytic Degradation of Synthetic Dyes Using Cyanobacteria-Derived Zinc Oxide Nanoparticles

In the current era of globalization, synthetic dyes are one of the key factors of water pollution. These were recalcitrant, carcinogenic, teratogenic, and mutagenic pollutants of textile, leather, and paper printing industries. Textile industries use a wide range of dyes and chemicals that generate a significant amount of wastewater containing a number of hazardous components. To mitigate environmental damage, it is difficult to treat this wastewater in an efficient and economical way. But apart from traditional treatment strategies, nanophotocatalysis appears as a promising technology for wastewater treatment, particularly dye degradation. In the present study, photocatalytic potential of biogenic zinc oxide nanoparticles (ZnO NPs) derived from Oscillatoria sp. NCCU-369 cell extract was evaluated for degradation of synthetic dyes (methylene blue and methyl orange). Biogenic ZnO NPs (10 mg/L) exhibited 91% of methylene blue degradation in 80 min in comparison to 86% of methyl orange degradation in 150 min. The free radical scavenging analysis suggested that ZnO NP-assisted degradation of dyes was mainly induced by superoxide ions. Degradation of dyes agreed with the Langmuire Hinshelwood model exhibiting pseudo-first-order kinetics and corresponded to the rate constants of 0.026 and 0.012 min(-1) for methylene blue and methyl orange, respectively. Furthermore, ZnO NPs demonstrated high reusability for up to five cycles in a row, indicating their potential use as an efficient, cost-effective, and environmentally friendly photocatalyst. The convincing results show that the biogenic ZnO NPs could play a significant role in the development of innovative biosorbents for removal of dyes from industrial effluents and wastewater.