Advanced Treatment Of Biologically Pretreated Papermaking Wastewater By Activated Persulfate Using CuO@Biochar And Heat

Most of the pollutants in papermaking wastewater contain benzene ring and other difficult degradable structures,and have strong"three causes"effect.The biochemical effluent still has problems such as high chemical oxygen demand(COD),high chromaticity and high toxicity,which need to be treated in depth.Activated persulfate oxidation has the advantages of high oxidation and good stability,which needs further study in the preparation and recovery of heterogeneous catalytic materials.In this study,taking the effluent from the biochemical treatment of papermaking wastewater as the object,the preparation and characteristics of biochar supported copper oxide were studied by using the method of biochar supported copper oxide and activation of persulfate by heating.The effects of the mass ratio of biochar to copper oxide,the dosage of catalyst,the dosage of persulfate(PDS),p H,temperature and other factors on the advanced treatment of papermaking wastewater by activated persulfate were analyzed.The composition changes of papermaking wastewater before and after advanced treatment were investigated and the reaction mechanism was revealed.The main research conclusions and analysis are as follows:In this study,we prepared biochar from the branches of Indus chinensis and made copper oxide attach to the biochar,and finally prepared a heterogeneous catalyst.Using X-ray diffraction analysis,electron microscopy-energy spectrum analysis,Fourier infrared spectrum analysis,specific surface area analysis and other techniques,it is found that copper oxide is mainly attached to the biochar by the way of physical deposition,and forms a new chemical bond to connect each other.It was also found that the surface of the biochar supported copper oxide material was rough,with a relatively developed pore structure and specific surface area.In the single factor experiment of the advanced treatment of papermaking biochemical effluent by the catalyst combined with thermally activated persulfate,the best treatment effect is achieved when the mass ratio of biochar to copper oxide is 1:5,the dosage of catalyst is 2g/L,the initial p H is 5,the concentration of PDS is3mmol/L,and the thermal activation temperature is 70?.Under these conditions,the removal rate of COD can reach 58.2%,and the removal rate of chroma can reach77.3%.At the same time,the study found that CuO@BC combined with thermally activated PDS showed higher removal effects of COD and chroma in a wide p H range(4-8).Under the optimal conditions,CuO@BC combined with thermally activated persulfate system follows the quasi-second order reaction kinetics.After the catalyst has been used repeatedly for 5 times under the optimal reaction conditions,the degradation effect of the wastewater is relatively stable,and the appearance of the catalyst has no obvious change,so it has a good reusable value.Using gas chromatography-mass spectrometry analysis,three-dimensional fluorescence spectroscopy,ultraviolet-visible spectroscopy,infrared spectral analysis of papermaking wastewater before and after treatment were two heavy water organic component analysis,the results showed that aromatic compounds in raw water,fulvic acid,humic acid,such as reducing refractory organic matter content,The UV₂₅₄ decreased from 1.0619 to 0.3334,and the chromogenic groups and organics with simple structure were also degraded.In the biodegradability analysis,the BOD₅/COD of the wastewater increases from 0.08 to 0.24,that is,most of the organic matter removed is difficult to be degraded by microorganisms.The mechanism analysis based on the capture test of active factor showed that sulfate radical and superoxide radical played the main role in this process,and mono-line oxygen also played a certain role.The research results of this study is expected to heterogeneous catalytic thermal activation persulfate application in papermaking wastewater deep treatment provides a new technical ideas,as the phoenix tree branches biochar load copper oxide provides the theory basis for the application of composite materials,across sulfate advanced oxidation technology depth treatment of papermaking wastewater and garden waste recycling is of great significance.