Screening and optimization of the most influencing factors during the photodegradation of Rhodamine B by zinc oxide photocatalyst: application of Plackett–Burman and central composite designs

Abstract

Zinc oxide (ZnO) powder synthesized by microwave irradiation method was used as photocatalyst for optimization of the photocatalytic degradation conditions of Rhodamine B dye under UV irradiation. The structural, morphological and optical characterizations of elaborated ZnO were performed by infrared spectroscopy, UV spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and Bruner-Emmett-Teller surface area analysis. Plackett–Burman design was first used to evaluate the effects of five parameters (initial dye concentration, contact time, lamp height, material dose and initial pH of the solution) on the photocatalytic degradation efficiency of the dye. The obtained results showed that contact time and initial dye concentration are the parameters that influence the photocatalytic degradation yield. The effects in decreasing order of the five factors were as follows: contact time (46.597) > initial dye concentration (− 29.149) > lamp height (− 8.419) > ZnO mass (7.263) > pH (1.0072). Subsequently, a central composite design for the two influencing parameters was performed to optimize the dye photodegradation process. It was found that the effect of contact time on the photodegradation efficiency was the highest, followed by the effect of initial dye concentration, and the interactions between initial dye concentration and contact time. The predicted and the experimental values were found to be in good agreement; the coefficient of determination value 0.996 and the adjusted coefficient of determination value 0.993 indicated that the model was significant. First‐order kinetic model successfully fitted the experimental data. The synthesized photocatalyst was found to be photostable during at least five regeneration cycles.