Comparative Experimental Study Of UV/PS And UV/H₂O₂ Degradation Of Quinoline In Coal Chemical Wastewater

As a typical nitrogen-containing heterocyclic compound,quinoline is widely present in the secondary biochemical effluent of coal chemical industry wastewater.Once discharged into the environmental system,it will have a toxic impact on the environment and humans.Photochemical oxidation technology is widely used in the treatment of nitrogen-containing heterocyclic compounds.At the same time,relevant studies have shown that the combination of transition metal activation technology on the basis of photochemical oxidation technology can improve its effect of degrading pollutants.In this study,ultraviolet light?UV?activated persulfate and hydrogen peroxide?UV/PS and UV/H₂O₂?two oxidation technologies based on photochemical reaction were used to degrade quinoline.The dosage of oxidant and the initial pH of the solution The effect of the degradation of quinoline was also investigated.The effect of Fe²⁺on the degradation of quinoline by the two systems was also investigated.Finally,the two oxidation technologies are compared,and the optimal reaction system is selected to measure the rate constant of the reaction between free radicals and quinoline.The research results are as follows:?1?In the UV/PS system,when the initial concentration of quinoline is C₀=15mg/L,the ultraviolet light intensity is I₀=8.96mW/cm²,and the reaction temperature is 25?,the optimal oxidation conditions are:[PS]:[QL]=20,pH=7,[Fe²⁺]:[PS]=1:33.After 60minutes of reaction,the removal rate of quinoline was 90.92%,and after 120 minutes of reaction,the removal rate of TOC was 62.33%.?2?In the UV/H₂O₂ system,when the initial concentration of quinoline is C₀=15mg/L,the ultraviolet light intensity is I₀=8.96mW/cm²,and the reaction temperature is 25?,the optimal oxidation conditions are:[H₂O₂]:[QL]=40,pH=7,[Fe²⁺]:[H₂O₂]=1:65.After 60 minutes of reaction,the removal rate of quinoline was 90.90%.After 120minutes of reaction,the removal rate of TOC was 65.07%.?3?Comparing the degradation effects of quinoline by the two technologies under their respective optimal reaction conditions,it was found that the degradation rate of quinoline by the Fe²⁺/UV/PS system was slightly higher than that of Fe²⁺/UV/H₂O₂ technology.Controlling other reaction conditions remains the same.When adding the same amount of oxidant or the same amount of Fe²⁺to the reaction system,it was found that the degradation rate of quinoline by Fe²⁺/UV/PS is slightly higher than that of Fe²⁺/UV/H₂O₂ technology.At the same time,Fe²⁺/UV/PS consumes less electricity than Fe²⁺/UV/H₂O₂,and has a lower economic cost.?4?In the Fe²⁺/UV/PS system,quenching experiments verify that both SO₄^-·and·OH radicals are present in the system.According to the probe compound method,nitrobenzene and benzoic acid are used with the two radicals.The second-order rate constants of the reaction were used to calculate the contents of the two kinds of free radicals,and the rate constants of the reaction between the free radicals and quinoline were measured according to the calculated free radical contents:k_·OH,_QL=6.86×10⁹M^-1·s^-1,k_SO4-·,_QL=8.37×10⁹M^-1·s^-1.