Characterization and Optimization of Photocatalytic Activity of Sol Gel-Synthesized TiO_2 and Ag-doped TiO_2 through Degradation of Synthetic Textile Effluent by UV Lamp-Assisted Experimental Setup

摘要

The textile industry is one of the largest producers of harmful effluent, and this has become a serious threat to the environment when disposed of into water bodies, which may lead to high pollution risk - especially in developing countries. There are several treatment methods ranging from conventional to advanced for treating textile effluent before disposal in the environment. Photocatalytic oxidation (AOPs) is the most sophisticated process among all other advanced oxidation processes. In this study, TiO2 and Ag-doped TiO2 were used for the photcatalytic degradation of synthetic textile effluent. TiO2 and Ag-doped TiO2 catalyst were synthesized through two routes of sol-gel method (M1 and M2 reported in our previous study) for mobilized and immobilized utilization purposes [ 1], and characterization of the catalysts was carried out through X-ray diffrectrometric analysis. XRD patterns showed that catalysts synthesized by both routs of sol-gel method were initially found in amorphous form as no peak appeared in an X-ray diffractrogram at 0 degrees C calcination (catalyst without calcinations), whereas with an increase of temperature the amorphous form of catalyst turned into crystalline. Results showed that TiO2 synthesized by the sol-gel route showed anatase phase at 350 degrees C, and peaks kept growing until 550 degrees C. Furthermore, at 650-750 degrees C anatase and rutile co-exist, while in Ag-doped TiO2, anatase appeared at 350-450 degrees C and at 550 degrees C anatase phase/silver co-existed, whereas at 650-750 degrees C anatse-silver-rutile co-existed. An X-ray diffractrogram showed that catalyst synthesized through the 2nd sol-gel route also possessed an amorphous nature at 350 degrees C and peaks of anatase phase of TiO2 appeared at 450 degrees C and kept growing sharper as temperature increased from 450-750 degrees C, whereas anatase peaks detected at 350 degrees C in Ag-TiO2, and anatase-silver co-existed at 450 degrees C and 550 degrees C. Hence, anatase disappeared and only silver metal peaks remained at 650-750 degrees C. Degradation and decolorization results revealed that optimum photocatalytic activity was achieved by catalysts calcinated at 550 degrees C as 91.96% degradation (COD removal %) with Ag-doped TiO2 immobilized catalyst, and 99.57% decolorization (colour removal percentage) was achieved with Ag-doped TiO2 mobilized catalyst on 60 min treatment of synthetic textile effluent (Remazol red RGB: 10 ppm concentration, pH3). Results showed that Ag-doped TiO2 developed anatase crystalline phase at 550 degrees C that favored degradation and decolourization. The order of catalyst calcination at 550 degrees C with respect to degradation was found as Ag-TiO2 (immobilized) Ag-TiO2 (mobilized) TiO2 (mobilized) TiO2 (immobilized) and decolourization found as Ag-TiO2 (mobilized) Ag-TiO2 (immobilised) TiO2 (immobilized) TiO2 (mobilized).