Effect Of Co-existing Anions In Coke Tailwater On Catalytic Ozonation Of Characteristic Organics

Heterogeneous catalytic ozonation technology has good prospects in the field of deep treatment of coke waste water due to its advantages of green,high efficiency and no secondary pollution.Factors affecting the effectiveness of non-homogeneous catalytic ozonation,in addition to catalysts and environmental factors,are of increasing interest,as are the co-existing anions in the wastewater.In this thesis,a series of studies were conducted to investigate the effect of the metal oxide TiO₂on the effectiveness of catalytic ozonation technology for the removal of organic pollution,using the metal oxide TiO₂as the catalyst and the characteristic organic quinoline in coke tailwater as the target organic pollutant,focusing on the widespread presence of Cl^-,Br^-and SO₄^2-and the natural inorganic anions CO₃^2-,HCO₃^-and PO₄^3-in coke tailwater.The main contents and results are as follows:（1）To investigate the effect of the common anions Cl^-,Br^-and SO₄^2-and the natural inorganic anions CO₃^2-,HCO₃^-and PO₄^3-on the degradation efficiency of quinoline and COD in coke tailwater at different concentration gradients.The results showed that Cl^-had an insignificant inhibitory effect on ozonation alone and TiO₂-catalyzed ozonation of quinoline,and the higher the Cl^-concentration,the lower the removal of quinoline and COD;Br^-has a stronger inhibitory effect on the efficacy of catalytic ozonation than Cl^-,and high concentrations of Br^-can reduce the removal rates of quinoline and COD in catalytic ozonation by 20.71%and 32.63%,respectively,which can be attributed to the scavenging ofO₃and OH·by Cl^-and Br^-leading to the formation of Cl·,Cl₂^-·,Br OH^-·,Br^-·and Br₂^-·and other less reactive radicals;SO₄^2-has no significant effect on catalytic ozonation efficacy;The natural inorganic anions inhibit the catalytic ozonation degradation efficiency in the order of PO₄^3->HCO₃^->CO₃^2-,which can be attributed to the generation of selective radicals such as CO₃^-,HCO₃^-and PO₄^3-;（2）For the TiO₂-catalyzed ozonation system in the presence of Br^-coexistence,the experimental conditions were optimised using a single-factor experiment with an initial pH of 9,an ozone concentration of 3 mg/L and an optimum catalyst dosage of 2g;The results of orthogonal experiments showed that the influence of environmental factors on the efficacy of Br^-suppressed catalytic ozonation was in the order of initial pH>catalyst dosage>ozone concentration;Following this,the effect of other anions on Br^-inhibition was examined,the addition of Cl^-to quinoline wastewater containing Br^-could improve the efficacy of catalytic ozonation and reduce the inhibition effect of Br^-;And when SO₄^2-was added to quinoline wastewater containing Br^-,the synergistic inhibition of Br^-and SO₄^2-leads to a more significant inhibition of catalytic ozonation efficacy,reducing catalytic ozonation efficacy;（3）In order to investigate the inhibition mechanism of single Br^-on the catalyst and the combined inhibition mechanism of Br^-and SO₄^2-,the influence of the presence of a single Br^-and the coexistence of Br^-and SO₄^2-on the surface properties of the catalysts was analysed using XRD,Raman,SEM,XPS and FTIR characterisation methods.The results showed that the Br^-impacted catalysts were crystallographically unchanged,with material deposited on their surfaces,the content of adsorbed oxygen and the rate of electron transfer on the catalyst surface decreased and reduced,the concentration of surface hydroxyl groups became lower,the leaching of surface metal ions increased,and therefore the catalytic activity decreased;Similar to Br^-,Br^--co-SO₄^2-also does not change the crystalline shape of the catalyst,but has an effect on the surface morphology,surface adsorbed oxygen content and electron transfer rate,surface hydroxyl concentration and metal ion leaching of the catalyst to a greater extent than Br^-alone,and thus Br^--co-SO₄^2-has a stronger inhibitory effect on the catalytic ozonation efficacy;（4）In order to investigate the inhibition mechanism of the catalytic ozonation process by single Br^-and Br^-in conjunction with SO₄^2-,the reactive radicals in the two systems were examined separately in this study using masking experiments.The results showed that the main reactive oxygen species OH·,O₂^-·and ¹O₂in the TiO₂-catalyzed ozonation of the quinoline system played an auxiliary degradation role;When Br^-coexists,the depletion of OH·by Br^-and the generation of its secondary radicals inhibit the catalytic ozonation efficiency and lead to a change in the dominant radical in the system,when ¹O₂and ¹O₂play a dominant role in the oxidative degradation of quinoline.When Br^-and SO₄^2-coexist,SO₄^-·is the important reactive species;furthermore,a possible pathway for quinoline degradation is suggested in conjunction with the analysis of reactive radicals and intermediates in the system,and the results suggest that the coexistence of Br^-in the wastewater may lead to the production of more toxic brominated by-products.This thesis has 43 figures,14 tables and 127 references.