Study On Catalytic Wet Oxidation Of Semi-Coking Wastewater

Semi-coking wastewater is a representative industrial organic wastewater with high concentration and many un-biodegradable substances, which will be discharged into water body if it is let out into river without disposing. Currently, the biochemical treatment method is widely adopted to treat semi-coking wastewater, but it needs high investment and treated water failed to meet the appropriate national standards. In this paper,catalytic wet air oxidation is used to treat simi-coking wastewater. Catalytic wet air oxidation(CWAO) is an efficidet technology to treat hard biodegradable organic wastewater with high concentration. The key of this technology is preparation of a low cost and high activity catalysts. Therefore, this paper aims to study the preparation of catalysts for CWAO and treat semi-coking wastewater with this catalysts.Operation condition was investigated for wastewater treatment, and the better operation condition was obtained preliminary.First, in a series transition metals including Cu, Mn, Zn, Fe, Co, Cr and Ni, the best activated metal Cu is selected as the first active component of catalysts for treating simi-coking wastewater by CWAO. And the catalyst CuO/γ-Al₂O₃ was prepared by impregnating process. Effect of the load of Cu on catalytic activity was investigated according to CODcr removal of wastewater.In order to improve the catalytic activity and stability, the second active component Mn and the structural promoter Ce were selected and added, that is preparation of catalyst CuO-MnO₂-CeO₂/γ-Al₂O₃. Effect of influencing facrots on catalytic activity and stability was investigated , including calcination temperature, calcination time, carrier's particle size and Ce content. The catalysts was characterized by BET and XRD to research the effect mechanism. From experiments,the best preparation condition was obtained:the load of Cu is 5%, Cu:Mn = 2:1, the load of Ce is 1.5%, calcination temperature is 600℃and calcination time is 4.5 h.Treating semi-coking wastewater by CWAO with self-made catalysts. Comparing the wet oxidation and catalytic wet air oxidation showed that CuO-MnO₂-CeO₂/γ-Al₂O₃ was an alternative catalyst for treating semi-coking wastewater by CWAO. The CODcr removal of wastewater was up to 77.8% by CWAO from 17.3% by WAO.Then, effect of influencing facrots on CWAO was investigated ,including reaction temperarure,oxygen partial pressure,stirring speed, pH and catalyst dosage. The optimal catalytic oxidation condition: reaction temperarure was 150℃, oxygen partial pressure was 1.6 Mpa, stirring speed was 500 r/min and pH = 8. Under the condition,the CODcr removal got 77.8% and color removal was 80.6%.