Preparation of Nanoscale Zinc Oxide-Laponite Composites by Polyvinyl Alcohol Polymerization and Usability for Removal of Trichloroethylene in Water

Innovative nanoscale ZnO-laponite-polyvinyl alcohol composites (NZLPc) were developed as a valid alternative to nanoscale photocatalysts for mineralization of chlorinated hydrocarbons without difficulties in recovery of nanoscale photocatalyst particles. NZLPc were synthesized by mixing nanoscale ZnO particles with laponite in PVA solution, and by crosslinking PVA solution in the presence of boric acid (≥1.6 M). Different mixing ratios of the raw materials were investigated to develop the stable NZLPc, and X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy characterizations were performed. From the results, a 3:1:1:10 ratio of ZnO, laponite, PVA, and deionized water by weight was appropriate to form spherical NZLPc with high porosities and enhanced mechanical strengths. Also, the degradation efficiencies of trichloroethylene were significantly improved with both NZLPc and UV irradiation, indicating that ZnO-mediated heterogeneous photocatalytic degradation occurred. Thus, the proposed synthesis of NZLPc paves a way for the economical and effective photocatalytic approach to remove the recalcitrant organic compounds in water through the multiple reaction processes (i.e., sorption, photolysis, and photocatalysis).