Liquid phase synthesis of flower cluster-like ZnO via lignosite template and its photocatalytic property

Abstract

In recent years, increasing interest has been concentrated in the treatment of organic pollutants in wastewater or sewage by means of photocatalysis based on semiconductor nano-catalysts. Photocatalysis is a very potential method for the complete destruction of contaminants and wide selection of target polluted compounds. ZnO as a very efficient metal oxide semiconductor photocatalyst has been studied extensively since found. Owing to its abundant availability, cost effectiveness, nontoxicity, reusability, high photo-sensitivity and excellent chemical stability, wide band gap and large excitation binding energy at room temperature, ZnO displays a promising application. Organic pollution in water can be significantly reduced when ZnO is used as photocatalyst and secondary pollution could be avoided by the mineralization of inorganic ions, which is quite attractive in the field of environmental protection technology. In this work, the purpose was to use inexpensive lignosite from low-priced resources of lignin as surfactant, template and nucleating promoter to prepare nanocrystalline ZnO to cut down the synthesis cost. Flower cluster-like nanometer ZnO photocatalysts doped with different amounts of lignosite were prepared by liquid-phase precipitation. The prepared pure ZnO and lignosite-doped ZnO(ZnO-LS) samples were characterized by FT-IR, UV-Vis diffusion refraction spectroscopy (UV-DRS), XRD, SEM/EDS and BET. The photocatalytic activity of the samples was evaluated by the photodegradation of methyl orange under UV light irradiation. The results showed that lignosite doping significantly altered the morphology of ZnO, improved zinc oxide surface state, increased the specific surface area, made ZnO produce more hydroxyl on the surface, and was helpful to obtain petal-like ZnO. On the other hand, the calcination temperatures influenced the crystallinity and crystal size of the photocatalysts. The tests indicated that the sample calcined at 300°C had good crystallinity and a small crystal size. At the optimal calcination temperature of 300°C and when LS-doping quality is 2 g, the petal ZnO composite photocatalysts had smaller band gap width and much higher photocatalytic activity than the pure ZnO and those ZnO-LS (LS was other quality). The high photocatalytic performance of ZnO doped with the lignosite could be attributed to an increase in surface hydroxyl groups and high crystallinity. The obtained results show that the photocatalytic efficiency of the optimal ZnO-LS was superior to commercially available TiO2 Degussa P-25 for the photodegradation of methyl orange. © Copyright.