Characterization and Optimization of Photocatalytic Activity of Sol Gel-Synthesized TiO2 and Ag-doped TiO2 through Degradation of Synthetic Textile Effluent by UV Lamp-Assisted Experimental Setup
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College of Earth and Environmental Sciences, University of the Punjab, Lahore, Pakistan
Department of Science Education (IER), University of the Punjab, Lahore, Pakistan
Institute of Geology, University of the Punjab, Lahore, Pakistan
Tayyaba Muhammad Akram   

University of the Punjab, University of the Punjab, Phone: + (92) 4299231251, Lahore (54590), Pakistan., 54590 LAHORE, Pakistan
Submission date: 2017-03-07
Final revision date: 2017-11-12
Acceptance date: 2018-03-04
Online publication date: 2019-03-05
Publication date: 2019-04-09
Pol. J. Environ. Stud. 2019;28(4):2571–2583
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 0ºC 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 350ºC, and peaks kept growing until 550ºC. Furthermore, at 650-750ºC anatase and rutile co-exist, while in Ag-doped TiO2, anatase appeared at 350-450ºC and at 550ºC anatase phase/silver co-existed, whereas at 650-750ºC 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 350ºC and peaks of anatase phase of TiO2 appeared at 450ºC and kept growing sharper as temperature increased from 450-750ºC, whereas anatase peaks detected at 350ºC in Ag-TiO2, and anatase-silver co-existed at 450ºC and 550ºC. Hence, anatase disappeared and only silver metal peaks remained at 650-750°C. Degradation and decolorization results revealed that optimum photocatalytic activity was achieved by catalysts calcinated at 550ºC 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 550ºC that favored degradation and decolourization. The order of catalyst calcination at 550°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).