Study On Photocatalysis-ozone Degradation Of Phenolic Wastewater In Spinning Disk Reactor

Phenolic wastewater mainly comes from pharmaceutical,coal chemical,resin and other industries,which is carcinogenic,teratogenic and mutagenic.And its characteristics of difficult degradation have become a major problem in the treatment of phenolic wastewater.Advanced oxidation processes（AOPs）are widely used in the treatment of phenolic wastewater.Studies have shown that it is difficult to achieve the effect of efficient and green degradation by using AOPs alone.The coupling of two or more oxidation methods has become a research hotspot.The photocatalysis has the advantages of mild conditions,good stability,non-toxicity and no secondary pollution.Ozonation has been widely studied because of its high redox potential,oxidation efficiency and biochemical performance.The combination of photocatalysis and ozonation technology can not only restrain the recombination of electron-hole pairs and improve the photocatalytic efficiency,but also accelerate the decomposition of ozone and improve the utilization rate of ozone,achieving the purpose of efficient degradation of organic pollutants.In this study,a new type of process intensification device—spinning disk reactor（SDR）was used as a photocatalytic reactor.Ti O₂and Zn O-Ti O₂catalysts were prepared by sol-gel method.The photocatalyst film supported on SDR was prepared by impregnation-pull-drying-calcination method.The degradation of phenolic wastewater by supported photocatalyst coupled with ozonation in SDR was studied.A detailed study of the photocatalytic degradation process in SDR was conducted.The study found that the degradation rate of phenol reduced with the increase of rotational speed,and the degradation rate increased with the increase of flow rate.The best photocatalytic performance of 5%Zn O-Ti O₂was achieved at the p H was 2,the rotational speed was 60 rpm and the flow rate was 60 L/h.The removal rate of phenol was 74.6%and mineralization rate was 62.4%within 120 min,which were 32.2%and 25.4%higher than that of pure Ti O₂,respectively.There was no significant decrease in catalytic efficiency after regeneration of the used catalysts by washing with 8 m L/L H₂O₂solution.A detailed study of the photocatalytic ozonation degradation process in SDR was conducted.Using 5%Zn O-Ti O₂as the photocatalyst and phenol solution with initial concentration of 100 mg/L as the targeted pollutant,the influence of various factors on the treatment effect was investigated.The results showed that the degradation rate and mineralization rate of phenol reached 100%and 83.4%after 50 min when p H value was 6,rotational speed was 60 rpm and flow rate was 60 L/h under UV irradiation.The results of photocatalysis,ozonation and photocatalytic ozonation in SDR showed that compared with single photocatalysis and ozonation,the removal rate of the coupling technology increased by 69.3%and 34.7%,respectively after 50 min,and the mineralization rate increased by56.7%and 62.9%,respectively.This indicated that photocatalytic ozonation had synergistic effect and significantly enhanced the treatment effect of phenolic wastewater.Using tert-butyl alcohol（TBA）,p-benzoquinone（BQ）and ethylenediaminetetraacetic acid disodium salt（EDTA-2Na）as radical trapping agents,the experimental results showed that the degradation rates decreased by 22.61%,5.37%and 6.59%compared with that without the addition of trapping agents,indicating that hydroxyl radicals（·OH）played a dominant role in the degradation process,superoxide radicals（·O₂^-）and photogenerated cavities（h⁺）played a secondary role.