Removal efficiency optimization of organic pollutant (methylene blue) with modified multi-walled carbon nanotubes using design of experiments (DOE)

Photo degradation of the organic pollutants using photocatalysts is affected by several factors. The main goal of the current study is investigation the effect of UV irradiation time (ranging from 5 to 25 min), pH of suspension (4, 7 and 10) and weight fraction (0.125, 0.25 and 0.5wt%) of decorated MWCNTs with ZnO nanoparticles (MWCNTs-ZnO) as photocatalyst on the removal efficiency of methylene blue using design of experiments. The results demonstrate that the photocatalytic performance increase by increasing the UV irradiation time and weight fraction. The statistical results show that all of the main factors, interaction between two and three factors have remarkable effect (at alpha = 0.05) on the photocatalytic performance of three synthesized MWCNTs-ZnO. The adequacy study of the proposed models reveals that all of the proposed models can predict the photocatalytic performance of MWCNTs-ZnO. The optimazation of the process show that the optimal level of the main factors such as UV irradiation time, pH and weight fraction, for maximizing the photo degradation of methylene blue as organic pollutant, are 25 min, 4 and 0.5wt%, respectively.