Photocatalytic degradation of organic waste derived from textile dye by ZnO-Ag nanocomposite synthesized by spray pyrolysis

Organic waste derived from the textile dye of textile industry in Gresik is toxic and dangerous to humans and the ecosystem. The waste from textile dye must be handled properly before its disposal to the river. Photodegradation of the organic pollutant by catalyst derived from semiconductor materials is one of the promising methods. ZnO is widely used as photocatalyst because of its wide bandgap energy (3.4 eV) and large free excitation binding energy. Furthermore, the addition of ZnO with noble metals can enhance the photocatalytic performance. In this study, ZnO-Ag nanocomposites have been successfully synthesized via a one-step process using spray pyrolysis method. Pure oxygen was used as the carrier gas. The effect of Ag content ranging from 0 to 10 %wt on the photocatalytic performance was studied. Zinc acetate dihydrate 0.1 M and silver nitrate were used as precursors to produce ZnO-Ag nanocomposite inside the tubular reactor. The produced nanocomposites were analyzed by Scanning Electron Microscopy (SEM) and X-ray Diffractometry (XRD). SEM observation showed that the morphology of the produced nanocomposite was sphere-like structures with interwoven nanoplate particles with some aggregation. The different crystallite size was also observed by XRD analyses. Based on the XRD patterns, the existence of Ag in the nanocomposite was detected when the Ag concentration was greater or equal to 5 %wt. Brunauer-Emmett-Teller (BET) was also performed to estimate the specific surface area of the nanocomposites, where the increase of Ag content is proportional to the specific surface area. Fourier Transform Infrared Spectroscopy (FTIR) was conducted to better understand the functional groups in the nanocomposites and dye pollutants. Finally, the photocatalytic activity of ZnO-Ag was evaluated by the degradation of the dye pollutants from textile home industry at Kabupaten Gresik under UV light irradiation. The photocatalytic activity of the ZnO-Ag was higher than that of pristine ZnO, where the maximum photodegradation was obtained at Ag content as much as 5 %wt with the degradation efficiency that reached 23%.