Photocatalytic degradation of methylene blue using TiO2 nanoparticles Nupur Mittal
Chemical Engineering, IIT (BHU) Varanasi.
Abstract: The aim of this research is to reduce the pollution caused by methylene blue dye in waste water coming from textile industries. For this purpose, TiO2 nanoparticles are made as they show good photocatalytic activity in degradation of dyes into harmless products. Synthesis is done using titanium butoxide and 2-propanol. The particles formed were a little larger than 100 nm but after adding sodium lauryl sulphate as surfactant, the correct sized nanoparticles were formed. These nanoparticle which are TiO2 (Degussa, Aeroxide P25, 90% anatase) were used in degradation of dye using batch reactor in which glass cylinder was inserted with UV light source and was covered from top. Reactor was kept on stirrer and air was passed from the bottom. Different concentrated dye solutions were used for experimentation with changing amount of TiO2 and reactor time. Result showed that there is decrease in concentration of dye. Rate of degradation got slower with time and concentration. The amount of photo catalyst also affected the rate. Stirrer was stopped after some time; decrease in concentration was little affected. Form this experiment it was concluded that degradation of dye can be easily done for water which is highly concentrated with methylene blue dye. Even large amount of dye polluted water present in lake can be naturally degraded by UV light from sunrays and atmospheric air by just adding TiO2 nanoparticles. It can prove to be a very cost effective method.
Textile dyes and other industrial dyestiffs constitute one of the largest groups of organic compounds that represent an increasing environmental danger. About 20% of the total world production of dyes is lost during the dyeing process and is released in the textile effluents. The release of those colored waste waters into the environment is a considerable source of non aesthetic and dangerous pollution and eutrophication and can create further dangerous by products through oxidation, hydrolysis or other chemical reactions taking place in the wastewater phase. For the removal of pollutant dyes, traditional physical techniques like adsorption on activated carbon, ultra filtration, reverse osmosis, coagulation by chemical agents, ion exchange on synthetic adsorbents resins etc can generally be used efficiently. Nevertheless, they are non-destructive, since they just transfer organic compounds from water to another phase, thus causing secondary pollution. Consequently, regeneration of the adsorbent materials and post treatment of solid wastes, which are expensive operations, are needed. Due to the large degree of aromatics present in dye molecules and because of the stability of modern dyes, conventional biological treatment methods are ineffective for decolourization and degradation. Furthermore, the majority of dyes is only adsorbed on the sludge and not degraded. Chlorination and ozonation are also being used for the removal of certain dyes but in relatively fewer cases. They have often high operating costs and limited effect on carbon content. These are the reasons why Advanced Oxidation Processes (AOPs) have been growing in importance during the last decade since they are able to deal with the problem of dye destruction in aqueous system. AOPs were based on the generation of very reactive species such as hydroxyl radicals (•OH) that oxidize a broad range of pollutants quickly and non-selectively. AOPs such as H2O2/UV processes and TiO2 mediated photo-catalysis have been studied under a broad range of experiment conditions in order to reduce the colour and organic load of dye-containing effluent wastewaters. Among AOPs heterogeneous photo catalysis using TiO2 as a photo-catalyst appears as the most encouraging destructive technology. The key advantage of the process is its inherent destructive nature. It can be...
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