Catalytic Optimization of Lignin-Cr/Zn Binary Oxide Nano-composite for Dye Removal from Industrial Waste Water using Box-Behnken Design

Abstract

measuring the zone of inhibition, i.e., 5.5±0.3 against S. aureus and 5.8±0.1 for E. coli, the highest zone of inhibition than lignin, ZnO, and Cr@ZnO. Among all the synthesized composites, L@CrZnO showed the best antibacterial activity. Additionally, a potential mechanism for the MB and bactericidal breakdown using L@CrZnO NPs has been proposed. Furthermore, tests were conducted on the effectiveness of degradation of methylene blue (MB) concerning changes in several experimental parameters, such as dose of L@CrZnO nanoparticles (0.005–0.025 g/mL), reaction time (30–75 min) and temperature (25-40 oC). Using the Box-Behnken design expert, the aforementioned factors were enhanced and their impact on the degrading process efficiency was assessed. Moreover, the application of RSM to enhance photocatalytic removal of MB from the wastewater through the utilization of L@CrZnO as nano-catalyst is examined. Initially, the RSM method will be discussed along with the second-order design experiments that are more commonly used with it. After that, a description of the nano-photocatalyst's removal mechanisms will be followed. Lastly, a representation of the use of RSM experimental designs in modeling and photocatalytic removal optimization procedures will be given. The ANOVA results showed a significant regression between experimental and predicted values of MB degradation, validating the developed quadratic model, with a 94% confidence level. Thus, L@CrZnO nanoparticles possess great practical usefulness and work well as effective photocatalyst for MB removal. The significant increase in antibacterial and photocatalytic activity of produced L@CrZnO NPs may be related to a reduction in their energy bandgap and the inhibition of electron-hole (e-h) pair recombination brought on by the introduction of extra energy levels that are below ZnO and Cr@ZnO NP's conduction band. Good photocatalytic persistence was demonstrated by the L@CrZnO NPs even after five consecutive cycles.