Effects of reaction parameters on photodegradation of caffeine over hierarchical flower-like ZnO nanostructure

Abstract

In this paper, the flower-like ZnO nanostructure was prepared by hydrothermal method. As-synthesized sample was characterized by XRD, SEM, and N2 adsorption/desorption isotherm. The photocatalytic performance of ZnO was evaluated by degradation of caffeine under UV irradiation. The effects of various reaction parameters such as catalyst dosage, pH of solution, and caffeine concentration on degradation of caffeine were investigated. The results showed that 3 g/L of ZnO could completely degrade 5 mg/L of caffeine under neutral or desired alkaline medium within 120 min. In addition, the impacts of inorganic ions (cation and anion) on degradation process were also studied. Flower-like ZnO also exhibited the good degradation efficiency of some popular organic dyes in wastewater such as methyl orange, congo red, tartrazine, nile blue and janus green B. The reaction kinetic of photodegradation of caffeine was studied by first kinetic model.