Abstract
The photocatalytic oxidation of methylene blue (MB) in aqueous media is explored using nanoscale ZnO nanoparticles (ZnO NPs) for maximal dye removal within the high-surface-area nanoparticle photocatalyst. The operating parameters such as illumination time, initial MB load, ZnO NP dose, solution flow rate and pH were examined. The experimental results revealed the alkaline pH (12.0) corresponding to the higher oxidation rate within only 20 min of reaction time; however, increasing the initial MB load decreased the reaction rate at the optimum circulation flow rate of 460 mL/min and ZnO NP dose of 0.4 g. Additionally, for providing maximum performance, the interaction between the most effective independent parameters (ZnO NP dose, flow rate, and initial pH) were explored using Box–Behnken experimental design based on the response surface methodology. The results showed a good fitness of the model (R2 = 96.86%) with the experimental data. The optimum values were recorded after 20 min of reaction time with the values: 0.45 g/L for ZnO NP dose, 370 mL/min for flow rate and pH 11, showing a 94% maximum dye removal compared to 92% using manual optimization. Finally, the kinetic models were applied and the data were described by second-order kinetic model.
Highlights
As a result of industrialization, water recourses are polluted from several industrial streams
Two sets of experiments were done: The first experiment is conducted in the presence of 0.4 g/L of ZnO nanoparticles (ZnO NPs) under UV irradiation, while the other one is conducted with the exposure to UV irradiation only
After an irradiation time of 90 min, the results revealed that the degradation reached to 97% in the presence of ZnO NPs
Summary
As a result of industrialization, water recourses are polluted from several industrial streams. Among several other industries, is considered a major source of dye-polluted wastewater, producing a huge amount of dyecontaining wastewater Discharging such dyes to the environment causes a massive deterioration to human and aquatic system. A promising treatment technique is required to overcome such challenge for a safe disposal Oxidation of such dyes from aqueous industrial discharges is considered a difficult technique since dyes show resistance to various oxidants, chemicals, UV light and heat besides being non-biodegradable (Kargi and Ozmıhc 2004; Akar et al 2006; Gupta et al 2011; Saleh and Gupta 2012; Sareen et al 2014; Tony and Bedri 2014; Saravanan et al 2015a)
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