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Water pollution and its efficient treatment is the major aspect of concern among environmental issues. A wide variety of organic pollutants are introduced into the water system from various sources such as industrial effluents, agricultural runoff and chemical spills (Cohen et al., 1986; Muszkat et al., 1994). Their toxicity, stability to natural decomposition and persistence in the environment have been the cause of much concern to the societies and regulation authorities around the world (Qamar et al., 2009).
Over the last few years the presence of pharmaceuticals, a large group of human and veterinary medicinal compounds in the aquatic ecosystem is considered as an emerging environmental problem due to their continuous input and persistence even at low concentrations. This may constitute in the long term a potential risk for aquatic and terrestrial organisms (Klavarioti et al., 2008).
Many of these pharmaceuticals like antibiotics may cause long-term and irreversible change to the micro-organisms genome, making them resistant in their presence; moreover, they may also disrupt the human endocrine system (Bredhult et al., 2007).
Chloramphenicol is a bacteriostatic antimicrobial compound, introduced into clinical practice in 1949 and it was the first antibiotic to be manufactured synthetically on a large scale (Al-Rimawi et al., 2011). Chloramphenicol (CAP) as a representative antibiotic is applied to inhibiting Gram-positive and Gram-negative bacteria and is used in eye drops or ointment for the treatment of bacterial conjunctivitis (Vigh et al., 1976). Its residual parts with metabolites from the excrement of human and animals get into the surface water and ground water after the sewage treatment (Junwei et al., 2010). Environmental presence of chloramphenicol has gained importance because it is related to abnormal physiological processes such as cancer, development of antibiotic resistant bacteria and increased toxicity of chemical mixtures (Jia-xin et al., 2010.). Due to this, researchers have been trying to find out techniques for degradation and inactivation of CAP. Its structure is shown in Figure 1.
Conventional methods of water treatment are disadvantageous, due to high cost as well as problem of sludge disposal. Advanced oxidation processes (AOPs), based on formation of hydroxyl and other free radicals have been considered the best methods for removal of such compounds due to mild operation condition and low costs. AOP which uses the semiconductor such as TiO2 as photo catalyst to mineralize toxic organic chemicals, has shown the best effects, as the catalyst itself is inexpensive, commercially available at various crystalline forms and particle characteristics, non-toxic and photo chemically stable (Doll et al., 2004). UV-irradiated TiO2 behaves as a total oxidation catalyst in water because of the photogeneration of OH∙ radicals by neutralization of OH− surface groups by positive photo-holes; hence a large variety of organics could be totally degraded into CO2 and harmless inorganic anions (Herrmann et al., 1999).