Catalytic wet air oxidation of Kraft bleach plant effluents in a trickle-bed reactor over a Ru/TiO2 catalyst

Catalytic wet air oxidation of two acidic and alkaline Kraft bleach plant e ffluents (total organic carbon (TOC) content 1138 and 1331 mg l(-1),respect ively) was investigated in a trickle-bed reactor at T = 463 K and oxygen pa rtial pressure of 8 bar. The reactor packed with titania or titania-support ed ruthenium catalyst was operated in a low-interaction (LIR) trickle-how r egime either in continuous-flow or batch-recycle mode. In the off-gas, no c arbon monoxide was detected in any of the runs. When the catalytic bed was composed of TiO2 particles, moderate abatement of organic compounds from th e bleach plant effluents was observed (TOC conversions up to 46 and 26%, re spectively). The removal of parent organic material was further enhanced by deposition of metallic ruthenium (3 wt.%) on the titanium oxide support. I n that case, the once-through oxidation produced decolorized outlet streams with TOC conversions as high as 89 and 88%, respectively These values furt her increased to 98 and 95%, respectively by running the trickle-bed reacto r in the batch-recycle mode of operation; the residual carbon content in tr eated effluents was found in the form of acetic acid. No leaching of Ru or Ti was detected by ICP-AES analysis to the detection limits of 0.2 and 0.1 mg l(-1), respectively. (C) 2001 Elsevier Science B.V. All rights reserved.