Study On Advanced Treatment Of Oil Refinery Wastewater By Catalytic Ozonation Oxidation

Refinery wastewater has the characteristics of large amount of quantity,high concentration of pollutants,complex composition and non-Biodegradabilit y.“Petroleum refining industrial pollutants emission standards”（GB31570-2015）wasput into effect on July 2015.The traditional treatment of“oil separating+a ir flotation+biodegration”can hardly meet the relevant regulation because the waste water discharge standards of COD_cr is raised to 60mg/L.Thus,it is of great importance to develop the economic efficient advanced wastewater treatment technology.In this paper,the self-made ceramsite catalyst was used to study ozone catalytic oxidation of the biochemical effluent from an oil refinery in Wuhan.Taking the removal rate of COD_cr as the evaluation index,the preparation process of the new ceramsite catalyst and the advanced treatment of refinery wastewater by ozone catalytic oxidation were studied.The catalysts were characterized by SEM,XRD,BET,FT-IR,and the degradation mechanism of ozone catalytic oxidation was discussed.The main conclusions are as follows:（1）The ozone catalyst,taking single transition metal salt solution as the active component,was prepared by high temperature calcination.The order of the catalytic activity is MnOx/ceramsite>FeO x/ceramsite>CuO/ceramsite>ZnO/ceramsite.（2）In the ozone ceramsite catalysts which were prepared with two-component transition metal nitrates as active matter,the order of the catalytic activity is Mn-Fe/ceramsite>Mn-Cu/ceramsite>Mn-Zn/ceramsite.And the catalytic activity of the two components is better than that of the single component.（3）The optimum catalyst preparation conditions are:Mn（NO₃）₂ and Fe（NO₃）₃（molar ratio of 1:1）is taken as the active component,the loading of active component is 7%,the calcination temperature is 1150℃,the calcination time is 10min.（4）SEM test results show that there are many holes in the surface of the catalyst.XRD results show that there exsists Mn₃O₄ crystals in the catalyst.（5）In such conditions:the volume of biochemical refining wastewater was 250mL,the ozone dosage was 7.71 mg/min,Mn-Fe/ceramsite catalyst dosing quantity was2 g,the initial pH of the wastewater was 9,the reaction time was 25 min,the COD_cr of wastewater decreased from 90 mg/L to 43 mg/L,the removal rate achieved 53%.The effluent reached the country’s new emission standards（≤60mg/L）.（6）In the process of ozone catalytic oxidation,tert-butanol was added as a capture agent for.OH,the removal efficiency of COD_cr in refinery wastewater decreased significantly.It is proved that the ozone oxidation process in the study is free radical process.