Degradation of organochlorinated pollutants in water by catalytic hydrodechlorination and photocatalysis

The degradation of chlorinated herbicides (MCPA and 2,4-D) and 4-chlorophenol (4-CP) by photocatalytic oxidation (PCO) and the combination of catalytic hydrodechlorination (HDC) and photocatalysis, at ambient conditions, has been studied. Commercial TiO2 (P25) and Pd/Al2O3 catalysts were used for PCO and HDC, respectively. MCPA and 2,4-D were transformed upon photo-oxidation to intermediate products and almost total mineralization was achieved. However, in the case of 4-CP, a conversion of only 82% of chloride formation and 87% TOC were obtained. In spite of the fact that the HDC reaction resulted in a total dechlorination of organochlorinated pollutants combined with an important decrease of the effluent ecotoxicity, the percentage of mineralization obtained in the combined process (HDC-PCO) was slightly lower than in the PCO treatment. Thus, the HDC-PCO process is not justified versus a single PCO treatment. (C) 2015 Elsevier B.V. All rights reserved.