Biodegradability enhancement of coking wastewater by catalytic wet air oxidation using aminated activated carbon as catalyst

Abstract

The catalytic wet oxidation (CWO) under mild conditions was employed for pre-treatment of low-biodegradable coking wastewater. The catalysts were a commercial activated carbon (AC) and its ammonia-treated samples at various temperatures and were characterized by N2 adsorption/desorption and X-ray photoelectron spectroscopy. The CWO experiments and pilot tests were performed in fixed bed reactors at 140–160°C and 0.2–1MPa of oxygen partial pressure. The amination introduced nitrogen-containing functional groups into the AC surface and decreased acid oxygen-containing functional groups. The ACs aminated at 450 and 650°C showed higher activity than their parent counterpart. It was suggested that nitrogen-containing functional groups contributed to the enhanced activities compared the activities, surface chemistry and porosity of ACs with and without amination. The BOD/COD ratio increased from 0.23 of the untreated wastewater up to 0.84 of the effluents of pilot tests. Higher COD removal of anoxic digestion experiments also indicated the biodegradability enhancement of coking wastewater after the CWO treatment.