Experimental Study On Coagulation-Modified Shell/La-Fe-TiO₂ Photocatalytic Oxidation Of Pyridine Wastewater

In the process of coal chemical industry production,a large number of nitrogen-containing heterocyclic compounds?NHCs?are produced,which are of great biological toxicity,difficult to handle,easily soluble in water,alcohol,etc.and easily cause teratogenic,carcinogenic and mutagenesis,which are harmful to the environment and human health.and can only be discharged into water body after efficient and stable treatment.Degradation research by coagulation sedimentation pretreatment combined with ultraviolet photocatalytic oxidation provides theoretical reference for further treatment of NHCs in coal chemical wastewater.Using pyridine to simulate typical nitrogen-containing heterocyclic compounds as target pollutants,a combined static and dynamic test method was used to investigate the coagulation-modified shell/La-Fe-TiO₂photocatalytic oxidation process for typical nitrogen-containing heterocyclic Treatment effect of compounds and adsorption performance of composite materials.The research contents mainly include:determining the optimal test conditions for the coagulation treatment stage and the photocatalytic oxidation stage,investigating the factors affecting the treatment of typical nitrogen-containing heterocyclic compounds,studying the factors affecting the adsorption of composite photocatalytic materials,kinetics and thermodynamics,examining Use process static test and dynamic test operation treatment effect.Three coagulants were used for coagulation pretreatment of pyridine wastewater.Based on coagulation tests,it was found that PAFC coagulation treatment had the best effect and the best reaction conditions:the dosage of PAFC was 300 mg/L,and the dosage of PAM was 3mg/L,p H was controlled to 8 and precipitation was 30 min.At this time,50mg/L pyridine-containing wastewater was coagulated,and the average removal rate of pyridine reached 13.65%.The test results of modified shell/La-Fe-TiO₂photocatalytic oxidation of pyridine wastewater showed that the optimal reaction conditions were:modified shell/La-Fe-TiO₂800mg/L,maintained at p H 8,temperature 35?and light intensity 600W.At this time,the photocatalytic oxidation of 50mg/L pyridine wastewater for 3h,the degradation rate of pyridine reached 77.23%,and the removal rate of TOC reached 52.15%.The modified shell/La-Fe-TiO₂has better catalytic performance than La-Fe-TiO₂,and the degradation process conforms to the first-order reaction kinetic equation with a correlation coefficient of 1.The comparison of the adsorption experiments of the modified shell and the modified shell/La-Fe-TiO₂found that under the conditions of 25mg/L pyridine concentration,35?and200r/min oscillation speed,the adsorption kinetic curves of the two materials are in line The first-order kinetic equation has second-order adsorption rate constants of 0.9632 g/?g·min?and 23.2397g/?g·min?,respectively.The thermodynamic curves of the two adsorbent materials follow the Frundlich equation,which are all spontaneous endothermic reactions,and the composites have stronger adsorption power.Through static tests,the coagulation-photocatalytic oxidation combined treatment of pyridine wastewater is more effective than the coagulation wastewater treatment alone and the photocatalytic oxidation treatment wastewater alone.The average degradation rate of pyridine and the average removal rate of TOC are 94.68%and 83.32%,respectively,which is higher than that of coagulation treatment alone.It increased by 81.03%and 70.37%,respectively,and increased by 17.45%and 30.39%respectively compared with the photocatalytic oxidation treatment alone.Through dynamic experiments,the average degradation rate of pyridine and the average removal rate of TOC of pyridine wastewater by coagulation-photocatalysis treatment were obtained through dynamic tests.They are 88.11%and 77.02%,respectively,the dynamic treatment effect was slightly lower than the static test effect.Pretreatment combined with coagulation can reduce the subsequent processing load and lay a good foundation for the complete degradation of nitrogen-containing heterocyclic compounds.Utilizing the characteristics of strong oxidizing ability of oxidants in photocatalysis,the ring-opening denitrification will be achieved,and finally complete mineralization will be achieved,which will make it lose its toxicity.The study of degradation by coagulation pretreatment combined with photocatalytic oxidation is of great significance for gradually eliminating its harm to the environment and human beings,maintaining ecological environment,and achieving"zero discharge"of coal chemical wastewater.