CCS Haryana Agricultural University,
Keywords: environment, hazardous, pollutants, nano-material, photo-catalytic, semiconductor
Summary:Abstract- Our environment is being polluted by toxic organic as well as inorganic chemicals through industrial effluents and municipal sewage discharge. These chemicals including dyes, pesticides and heavy metals are not only hazardous to human health but also degrade the eco-system. The usual micro-filtration, adsorption and chemical/biological methods used for the treatment of water contaminated with these pollutants are inefficient and also generate a large amount of sludge as solid waste that requires a secondary treatment. Photo-catalytic degradation of pollutants over semiconductor nano-material, using solar radiation, is a cost-effective and environment friendly alternative. Commonly used high band gap semiconductors: titanium oxide (TiO2) or Zinc oxide (ZnO) nanoparticles as photo-catalyst for purifying polluted water or air are photo-sensitive only in the ultra-violet region of radiation and less efficient under visible light. But the high cost of UV source involved, restricts their use at commercial scale for water treatment. Therefore, in order to lower down the cost of photo-catalytic process, different strategies have been adopted to render the high band photo-catalysts visible light - responsive and thus harvesting the inexpensive solar radiation. This paper highlights such strategies including: optimizing photo-catalyst’s size and morphology, doping metals and non-metals, compositing two or more photo-ctalysts and use of sensitizers.