Photocatalytic Remediation of Organic Pollutants in Water

Abstract

Water resource is the most precious resource for a human being that it is necessary to make the water resource to be clean and also non-toxic. Recently, water pollution becomes one of the most serious global issues, especially, water pollutions that contaminate various types of organic compounds, including pharmaceuticals and personal care products (PPCPs), persistent organic pollutants (POPs), and organic dyes. Photocatalysis as one of the advanced oxidation processes using reactive oxidative radicals or species to remediate the organic pollutants has drawn much attention recently.Photocatalysis is a process which a chemical reaction is accelerated in the presence of a catalyst on exposure to light. The possibility to utilize solar energy as a free energy from nature to solve the environmental problems is the key significance of photocatalysis. Homogeneous photocatalysis has many advantages, e.g., high oxidation properties. It is, however, not popular in various photocatalytic applications, because it is difficult to separate the photocatalysts from the solution, the photocatalysts have low potential to reuse, purification of products is necessary, and almost homogeneous photocatalysts absorb narrowly light within the solar spectrum. It has been proven that heterogeneous photocatalysis is one of the most potential methods for treatment of organic pollutants in water. Anyhow, relatively large band gap energy causes some limitations of metal oxide-based heterogeneous photocatalysts. Modifications of the electronic band can be achieved by doping and composites of semiconductors. Another modification technique in heterogeneous photocatalysts is the utilization of electrical potential in photocatalysis. The coated semiconductor photocatalysts are used as photoelectrodes in photo-electrocatalytic applications. In addition, the photocatalytic reactor configuration for wastewater treatment by heterogeneous photocatalysis can be classified as two main groups, including fixed bed reactor and slurry type reactor. Apart from the conventional photocatalytic reactors, the combination of photocatalysis with another treatment process has also been developed to overcome the specific obstacles in each case, such as a photocatalytic membrane reactor.