PMS Activation Through Fe/Mn Composites For Removal Of Organic Matters From Water

In view of the current situation of serious shortage of water resources in the world,it has been proved to be an effective way to carry out advanced treatment for wastewater to reuse.However,dye wastewater accounts for a relatively high proportion in the current wastewater discharge and causes great harm.Therefore,this study selected dye wastewater as the target water for further treatment.Peroxymonosulfate?PMS?Advanced Oxidation Processes?AOPs?has strong oxidation ability,environmental protection and wide application range,so it was selected in this paper to treat the actual dye wastewater.In this paper,the heterogeneous iron manganese composite catalyst material with high economy and good catalytic effect was used as the PMS activator to generate the active free radical SO₄·^-to oxidize the polluted water to achieve advanced treatment.In the process,Fe-Mn-LDHs,magnetic MnO₂/MnFe₂O₄ nanocomposites and magnetic Fe₂O₃/Mn₂O₃ three kinds of ferromanganese composites were mainly prepared.The simulated wastewater,such as octadecylamine,Rhodamine B and tartrazine solution,was treated by activated PMS,and the possible degradation mechanism of each reaction system was explored.In the end,the advanced treatment for dye wastewater from the paint factory was carried out by using the magnetic Fe₂O₃/Mn₂O₃/PMS system.The specific work is as follows:Firstly,Fe-Mn-LDHs with Fe/Mn mole ratio 1:1 was prepared by the coprecipitation method,and the morphology,crystal structure,element content and surface ion state of the material were studied by various characterization techniques.Then,Fe-Mn-LDHs was used to activate PMS to remove the simulated pollutant ODA from the aqueous solution,and the effects of various environmental factors on the reaction system were explored,including the concentration of catalytic materials and PMS,temperature and pH value,as well as the addition of common substances in the natural water.In addition,the structure and catalytic stability of Fe-Mn-LDHs,the possible degradation mechanism and pathway of ODA were all studied.The results show that Fe-Mn-LDHs with Fe Mn molar ratio 1:1 has good activation performance for PMS.The system can remove 85%of ODA?10mg/L?in aqueous solution within5min,which is significantly higher than that of pure PMS,and the removal efficiency reaches the highest under the alkaline condition.In the experiment of adding natural substances,NOM,NO^3-and CO₃^2-inhibited the degradation of ODA,while Cl^-promoted it.The experimental results of cycle degradation and metal ion leaching show that Fe-Mn-LDHs has good structural and catalytic stability.Finally,based on the result of XPS and GS-MS technology,the possible degradation mechanism and path of ODA were proposed,which has great value in practical application.In order to further improve the advanced oxidation technology of activated PMS and optimize the way of catalyst recovery,the magnetic MnO₂/MnFe₂O₄ nanocatalyst material was prepared by two-step hydrothermal method for the first time,and the proportion of Fe/Mn in the material was optimized.Then,the physical and chemical properties of the material,such as morphology,crystal structure,element ratio,magnetic properties,specific surface area and particle size distribution,as well as the change of surface ion state,were studied by using a variety of characterization techniques.Then,the prepared magnetic MnO₂/MnFe₂O₄ nanocomposites were used to activate PMS to oxidize and degrade the simulated pollutant Rh B in water,and the effects of various environmental factors on the reaction system were systematically discussed.Finally,we carried out four times of cyclic degradation experiments on the catalytic material to explore its structure and catalytic stability.The results show that the magnetic MnO₂/MnFe₂O₄ nanocomposites with a molar ratio of 7:1 has excellent activation ability for PMS.In the degradation experiment of organic dye Rh B,the removal rate of 5 min was 99%,and the pH that without adjusted was benefit for the degradation.The stable crystal structure and catalytic performance of the nanocomposite were confirmed by the circulation experiment of the catalyst.Due to the existence of magnetic MnFe₂O₄ particles,the catalyst shows good magnetism in aqueous solution,and could be easily separated under the influence of external magnetic force.This is conducive to the recovery and reuse of the catalyst,and to a certain extent,alleviates the secondary harm to the environment,which is of great significance in practical application.For further optimizing the preparation method of PMS activator,a relatively simple method was used to prepare the magnetic Fe₂O₃/Mn₂O₃ catalytic material,and its iron manganese ratio was optimized concurrently.Then,the morphology,crystal structure,element ratio and surface ion state evolution of the material were studied by characterization techniques.Then we used the composite to activate PMS to oxidize and degrade TTZ in water,and explore the influence of various environmental factors on the reaction system.And then verified the stability of its structure and catalytic performance.In addition,Fe-Mn-LDHs,magnetic MnO₂/MnFe₂O₄ and magnetic Fe₂O₃/Mn₂O₃ composite materials were used to activate PMS to degrade the actual wastewater discharged from an organic dye plant in Lanzhou,and the magnifying test of actual wastewater degrading was carried out by selecting the dominant catalyst.The results show that Fe₂O₃/Mn₂O₃ catalyst with molar ratio of 3:2 has the maximum PMS activation ability,and the 10mg/L TTZ removal rate reaches 97.3%within 30 min.It was also found that both the HO·and SO4·^-played an important role in the degradation process,and HPO₄^2-,HCO₃^-,NO₃^-and NOM showed inhibition on the degradation experiment,while Cl^-promoted it.In addition,the magnetic Fe₂O₃/Mn₂O₃ composite has good structural stability and recycling performance.Finally,in the experiments that used three kinds of Fe-Mn composite catalyst to activate PMS system for the degradation of the actual dye wastewater,they all showed excellent degradation performance and achieved good removal effect for COD in the actual dye wastewater under the same conditions.The COD removal rates of Fe-Mn-LDHs,magnetic MnO₂/MnFe₂O₄ and magnetic Fe₂O₃/Mn₂O₃ were 49.5%,58.6%and65.9%respectively within 120 min,while that of pure PMS were only 17.6%.In addition,in the cyclic degradation experiments,it is also confirmed that the Fe₂O₃/Mn₂O₃/PMS has good structural stability and reusability in the treatment of actual dyeing wastewater.At last,the COD removal efficiency of 10 L dye wastewater was 58.4%in 120 min in the expanded experiment of Fe₂O₃/Mn₂O₃/PMS system.This proves the rationality of the reaction system and the feasibility of its practical application,it also proves that the system has good reproducibility and reliability,and provides valuable data support and theory for future engineering application.