PHOTODEGRADATION OF RHODAMINE B OVER TITANIUM DIOXIDE

Photodegradation of Rhodamine B over Titanium Dioxide

Photodegradation of Rhodamine B over Titanium Dioxide

Introduction

Contaminations of a water stream with industrial advances have become an issue of worldwide anxiety and health hazards by an endocrine disruptive chemical even at a reduced concentration has been more serious (Kim et al., 2001). Bisphenol-A (BPA), renowned as an endocrine disruptor, is a monomer used in the manufacture of numerous chemical products such as polycarbonate and epoxy resins. Epoxy resins have been used in many products such as the inward coating of nourishment cans, dental composites, and pharmaceutical consignment systems ( Ema et al., 2001; Bae et al., 2000). BPA has displayed estrogenic activity and alters metabolism kinetics, induces DNA damages, and results in telomeric associations simultaneously with chromosomal aberrations ( Haishima et al., 2001).

The degradation of organic compounds using a photocatalyst such as titanium dioxide (TiO2) in solution has attracted much attention as a promising procedure in water purification due to its easy handling and effectiveness (Tennakone and Kottegoda, 1996; Kuo and Lin, 2000). The purification with TiO2 as a photocatalyst in the presence of UV radiation has been renowned to have several advantages; productive removal of organic compounds dissolved or dispersed in water and inexpensive cost (Legrini et al., 1993).

The well-known standard of photooxidation is that UV illumination up on a photocatalyst excites to make electron and aperture pair (e-/h+) with high-energy state, which migrate to the particle surface and initiate a broad range of chemical reactions (Hoffmann et al., 1995). The valence band potential is positive sufficient to generate hydroxyl radicals at the surface and the conduction band potential is negative to decrease molecular oxygen. The hydroxyl radical is used as a mighty oxidizing agent to alter organic pollutants into CO2, H2O, and less harmful byproducts of a reduced molecular weight.

There have been some reports on the photodegradation of BPA by using TiO2 in the solution. Ohko et al. (2001) described that the photocatalytic degradation of BPA was presented in aqueous suspension of TiO2 particles under a UV radiation of 10 mW/cm2 for 20 h, where BPA concentration decreased from 175 to 0.04 µM in 10 h. Son et al. (2001) carried out the photocatalytic removal of BPA in a rotating oxidation-drum reactor, where the photocatalytic activity on TiO2 slim movie with a thickness of 455 nm was more productive than that of 285 nm.

Many other studies related to the photodegradation with TiO2 particles in solutions have been presented (Martyanov and Savinov, 1997; Lee et al., 2003; Liu et al., 2003; Matsunaga and Okochi, 1995). although, they have some difficulties to be solved. In case of suspended TiO2 particles, there are problems such as exponential decrease of the available light with distance from a light source due to the absorbance of UV light by particles themselves and recycle of TiO2 particles from treated wastewater. An alternative procedure of TiO2 immobilization decreases the photodegradation effectiveness per catalyst mass due to decrease in the available specific surface area of a photocatalyst and decrease of the ...