Manganese Dioxide Modified Sludge Biochar Composite Activated Peroxymonosulfate To Remove Methylene Blue In Wastewater

The past several years has witnessed with the acceleration of Industrialization and urbanization,naturally,the production of municipal sewage and sludge in our country is also increasing.It is of great necessary to take harmless and recysling disposal treatment for municipal sludge to reduce the risk of secondary pollution to the environment due to the sludge contains a variety of toxic organic matter,pathogenic microorganisms but on the other hand contains a large number of organic matter.Advanced oxidation processes（AOPs）is a promising wastewater treatment method with the characteristics of simple operation,mild reaction,high efficiency and wide application.In this study,dewatered sludge from sewage treatment plant was used as a raw material to prepare sludge biochar and the sludge biochar was modified by MnO₂,Methylene Blue（MB）was selected as the target pollutant to verify the catalytic performance of the catalyst,the main results are as follows:（1）The sludge biochar（SBC）was synthesized by pyrolysis method in this research,MnO₂ and MnO₂@SBC composite materials with different MnO₂/SBC mass ratio（3%,5%,10%,20%）was prepared by co-precipitation method.When MnO₂/SBC mass ratio is greater than 5%,MB can be completely removed within 30min.The degradation kinetics of MB was more consistent with the pseudo-first-order kinetic model,and the catalytic performance of MnO₂@SBC was significantly higher than that of SBC and MnO₂ alone.（2）According to the characterization results of BET,SEM,EDS and XRD,MnO₂showed granular growth on the SBC surface and was successfully loaded on the SBC surface.The Zata potential characterization results shown that the isoelectric point of MnO₂@SBC is 3.79. MnO₂@SBC has a wide range of p H application at the p H of 5-9,and MB can be completely degraded within 30min.The recycling experiments showed that MB can be almost completely degraded within 180 minutes after five recycles in MnO₂@SBC/PMS catalysis system,indicated that the MnO₂@SBC has good stability and practical application.（3）In the radical quenching experiment,the addition of high concentrations of Et OH and TBA can significantly inhibited the degradation of MB in the MnO₂@SBC/PMS/MB degradation system,indicating that both SO₄^-· and ·OH The main reactive oxygen species;In addition,the UV-vis absorbance spectra of MB in the catalytic system showed thatthe strongest absorption peak of the reaction solution tends to migrate to a low-wavelength absorption peak as the reaction proceeds,and the specific process can be described as N-demethylation of methylene blue occurs at first,and then SO₄^-· and ·OH continue to attack the hydroxyl group of the aromatic ring in MB and its intermediates to make them degraded it into smaller molecules.（4）Compared the FTIR and XPS characterization of MnO₂@SBC before and after the reaction,the results show that the surface functional group-OH/-COOH of MnO₂@SBC can participates in activating PMS to generate active radicals and adsorb MB and its intermediate products.Besides,C-O,C=C,and C=O bond can participate in the adsorption of MB and its MB degradation intermediates through electrostatic adsorption.Furthermore,manganese dioxide main acts as oxidant during the MB degradation in MnO₂@SBC/PMS system.What’s more,Fe,Mn,and Al elments may participate in activating PMS,and there exist synergistic catalytic between these elements to improve the catalytic degradation efficiency.