Catalytic wet oxidation of o-chlorophenol at mild temperatures under alkaline conditions

Wet oxidation of a 100 ppm aqueous solution of o-chlorophenol (o-CP) was performed in a lab-scale batch reactor using 3% Ru/TiO2 catalyst at 373 and 413 K, and a partial oxygen pressure of 0.1 MPa. The experiments were conducted by varying the initial pH values of o-CP solution from pH 6.3 to 9.8 and 11.8. From the results, it was revealed that the catalytic decomposition of o-CP occurred most effectively at 413 K and at the initial pH of 9.8. Complete decomposition and dechlorination of o-CP were almost achieved within 1 h, and about 85% of TOC was removed in 3.0 h. On the other hand, the catalytic wet oxidation of o-CP at a higher pH value of 11.8 was not effective in the removal of TOC. The incomplete removal of TOC at the initial pH of 11.8 is likely attributed to a low pKa of carboxylic acids formed during the wet oxidation of o-CP.