7 application of nanochemicals for ef fl uent

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7 Application of Nanochemicals for Ef fl uent Treatment Nanoscience is the fi eld of science which deals with the study of materials at the nanoscale. The smaller size of nanomaterials highly in fl uences their properties as compared to their bigger counterparts. Nanotechnology is an application of nanoscience and it deals with the control, integration and manipulation of various atoms and molecules to form different materials at the nanoscale (Hornyak et al. 2008 , 2009 ). The past decade has been subjected to drastic increase in the appli- cation of nanotechnology in applied science, especially in the area of water puri fi cation, opening up a new potential alternative to treat wastewater more ef fi - ciently and cost-effectively (Baruah et al. 2012 ; Baruah and Dutta 2016 ) Some of the key advantages of nanochemicals include their small size, high reactivity, high accuracy and most importantly, their capability to be produced by environment-friendly techniques, most of which are potentially cost-effective as well. Two of the promising applications of nanochemicals for wastewater treatment in textile industries are: Photocatalysis Nanosorbents. 7.1 Photocatalysis Photocatalysis is a process which can be de fi ned as a change in the rate of a chemical reaction or its initiation under the action of ultraviolet, visible, or infrared radiation in the presence of a substance the photo catalyst that absorbs the light and is involved in the chemical transformation of the reaction partners (McNaught and Wilkinson 1997 ). It is a process which is used to degrade pollutants in wastewater. A nanostructured catalyst medium which is sensitive to exposure to light is mainly employed. The catalyst medium usually in use is a semiconductor material, which generates an electron hole pair upon absorption of light with energy higher than its band gap energy. The electron hole pair then reacts with water to produce highly reactive Nanochemicals and Ef fl uent Treatment in Textile Industries 79
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oxidizing and reducing radicals, such as super oxides, hydroxyl ions or other radicals. These radicals then degrade any organic/inorganic pollutant molecules present in the contaminated water through some secondary reactions. Photocatalysis is a surface phenomenon and its general mechanism is a complex process, which involves fi ve basic steps (Pirkanniemi and Sillanp ää 2002 ). Reactants diffusing to the surface of the catalyst Reactants getting adsorbed on the surface of the catalyst Reaction taking place at the surface of the catalyst Products undergoing desorption from the surface of the catalyst Products diffusing away from the surface of the catalyst. Nanostructured semiconductor materials possess higher surface area which enables them to have better photocatalytic properties compared to their larger bulk counterparts. This property makes it possible for the generated electrons and holes to be available at the surface of the nanophotocatalyst rather than to be available in the bulk of the material. An ideal photocatalyst should exhibit the following
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  • Fall '19
  • N. Gokarneshan

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