Abstract

LOPEZ-OJEDA, Gonzalo Cuauhtémoc et al. Photoelectrochemical oxidation of phenol and 4-chlorophenol using a titanium electrode coated with a TiO₂ film. Rev. Int. Contam. Ambient [online]. 2011, vol.27, n.1, pp.75-84. ISSN 0188-4999.

The aim of this work was to evaluate the performance of a photoelectrochemical system for the degradation of phenol and 4-chlorophenol in aqueous solutions. Experiments were carried out in a 1.5 L cell using a titanium electrode coated with titanium dioxide (TiO₂) as anode. The anode was prepared by immobilizing TiO₂ (Degussa P25) on a titanium substrate using an electrophoretic deposition method, followed by heat treatment at 450 ºC. The TiO₂ film was characterized using scanning electron microscopy (SEM); a uniform surface was observed all over the titanium substrate. This electrode was utilized as the anode of a photoreactor for the oxidation of phenol and 4-chlorophenol under acidic conditions and an ultraviolet lamp. Results showed a rapid transformation of phenol and 4-chlorophenol by the action of hydroxyl radicals yielded from water. It was found that at low concentrations (50-100 mg/L) both compounds were significantly degraded (80-100 %), however, at higher initial concentrations (300-500mg/L), by-product formation of phenol and 4-chlorophenol oxidation imparted a dark color to the solutions, which hindered light transmission to the catalyst and interfered with the reaction mechanism. Attempts to degrade by-products by applying other potentials in the experiments of concentrations greater than 300 mg/L did not succeed. Removals of total organic carbon (TOC) higher than 80 %, showed that the photoelectrochemical oxidation system was effective in mineralizing phenol and 4-chlorophenol at concentrations lower than 100 mg/L. Future studies will focus on evaluating the photochemical oxidation system as a pre-treatment for a biological process used for the treatment of wastewater with high phenol and 4-chlorophenol concentrations.

Keywords : photoelectrocatalysis; photocatalysis; phenol; 4-chlorophenol; photoanode; TiO₂; UV light.

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