Synthesis,characterization and application of ZnO-Ag as a nanophotocatalyst for organic compounds degradation,mechanism and economic study

The current work deals with ZnO-Ag nanocomposites（in the wide range of x in the Zn1-x O-Ag x chemical composition） synthesized using microwave assisted solution combustion method.The structural, morphological and optical properties of the samples were characterized by XRD（X-ray diffraction）, FTIR（Fourier transform infrared spectrometry）, SEM（scanning electron microscopy technique）, EDX（energy dispersive X-ray spectrum）, ICP（inductively coupled plasma technique）, TEM（transmission electron microscopy）, BET（Brunauer–Emmett–Teller method）, UV–Vis（ultraviolet–visible spectrophotometer） and photoluminescence spectrophotometer. The photocatalytic activity of the ZnO-Ag was investigated by photo-degradation of Acid Blue 113（AB 113） under UV illumination in a semi-batch reactor. This experiment showed that ZnO-Ag has much more excellent photocatalytic properties than ZnO synthesized by the same method. The enhanced photocatalytic activity was due to the decrease in recombination of photogenerated electron-holes. The results showed the improvement of ZnO photocatalytic activity and there is an optimum amount of Ag（3.5 mol%） that needs to be doped with ZnO.The effect of operating parameters such as p H, catalyst dose and dye concentration were investigated. The reaction byproducts were identified by LC/MS（liquid chromatography/mass spectrometry） analysis and a pathway was proposed as well. Kinetic studies indicated that the decolorization process follows the first order kinetics. Also, the degradation percentage of AB113 was determined using a total organic carbon（TOC） analyzer. Additionally, cost analysis of the process, the mechanism and the role of Ag were discussed.

Combined effects of adsorption and photocatalysis by hybrid TiO_2/ZnO-calcium alginate beads for the removal of copper

The use of nanosized titanium dioxide（TiO2） and zinc oxide（ZnO） in the suspension form during treatment makes the recovering and recycling of photocatalysts difficult.Hence,supported photocatalysts are preferred for practical water treatment applications.This study was conducted to investigate the efficiency of calcium alginate（CaAlg） beads that were immobilized with hybrid photocatalysts,TiO2/ZnO to form TiO2/ZnO-CaAlg.These immobilized beads,with three different mass ratios of TiO2：ZnO（1：1,1：2,and 2：1） were used to remove Cu（Ⅱ） in aqueous solutions in the presence of ultraviolet light.These beads were subjected to three cycles of photocatalytic treatment with different initial Cu（Ⅱ） concentrations（10-80 ppm）.EDX spectra have confirmed the inclusion of Ti and Zn on the surface of the CaAlg beads.Meanwhile,the surface morphology of the beads as determined using SEM,has indicated differences of before and after the photocatalytic treatment of Cu（Ⅱ）.Among all three,the equivalent mass ratio TiO2/ZnO-CaAlg beads have shown the best performance in removing Cu（Ⅱ） during all three recycling experiments.Those TiO2/ZnO-CaAlg beads have also shown consistent removal of Cu,ranging from 7.14-52.0 ppm（first cycle） for initial concentrations of10-80 ppm.In comparison,bare CaAlg was only able to remove 6.9-48 ppm of similar initial Cu concentrations.Thus,the potential use of TiO2/ZnO-CaAlg beads as environmentally friendly composite material can be further extended for heavy metal removal from contaminated water.