Experimental Study On Decomposition Of Aromatic Toxic Substances In Coal Chemical Wastewater By Carbon-based Materials

Coal chemical wastewater is a typical high-concentration toxic and hazardous industrial organic wastewater.The water quality is complex and variable.If it is discharged directly without treatment or the treatment is insufficient,it will bring high risks to the environment and human health.In this paper,advanced oxidation technology was used to eliminate the aromatic toxic substances,which provided a theoretical basis for the prevention and control of aromatic toxic substances in coal chemical wastewater.In this paper,using organic salt and biomass carbon as carbon source,carbon materials with catalytic properties were prepared by high temperature carbonization and hydrothermal method.The catalytic performance of carbon materials was improved by hetero atom doping for the removal of aromatic toxic substances?phenol and pyridine as target toxic substances?.The influencing factors and reaction mechanism of carbon materials to degrade toxic substances were explored.These experimental results provide important basic data for the degradation of organic toxic substances.The main research contents are as follows:?1?Porous carbon materials were prepared by high temperature carbonization,nitrogen and sulfur co-doping method using calcium citrate as carbon source.The physical and chemical surface properties of carbon materials were investigated by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,nitrogen adsorption-desorption curve,X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?;the degradation performance of nitrogen and sulfur-doped carbon materials?NS-CCa800?on toxic substances was evaluated by catalytic oxidation experiments of phenol.The results show that the prepared carbon material has high specific surface area(886-1935m² g^-1)and well-developed pore structure(pore volume5.08-12.87cm³ g^-1).The doping of nitrogen and sulfur effectively improves the catalytic performance of porous carbon;when the mass ratio of porous carbon to thiourea is 1:0.3?NS-CCa800-3?,the removal effect of phenol is the best?after 40 minutes of reaction,the removal rate of phenol can reach 91%?.According to the free radical quenching experiment,the digestion process of organic toxic substances is combined by free radical pathway and non-free radical pathway.?2?Biomass carbon materials were prepared by using hydrothermal carbonization and iron ion doping method with glucose as the carbon source.The physical structure and surface chemistry of carbon materials were characterized by scanning electron microscopy?SEM?,EDS,XPS and fourier transform infrared spectrum?FTIR?.Visible light enhanced Fenton-like degradation of pyridine was carried out to investigate the performance of different catalytic systems for the digestion of pyridine.The effects of H₂O₂ content and pH of the reaction solution were used to analyze the pyridine digestion performance,and the stability and reusability of the catalyst were evaluated.The results show that the surface of the carbon material after hydrothermal carbonization?HTC?is rich in oxygen-containing functional groups?hydroxyl,carbonyl and carboxyl groups?;trivalent iron ion?Fe?III??forms a complex with oxygen-containing functional groups on the surface of carbon spheres;when the pH of the solution is near neutral?pH=6?and the content of H₂O₂ is 80 mM,the removal rate of pyridine by Fe?III?-HTC/H₂O₂/Vis system exceeds 95%;after repeated use of Fe?III?-HTC four times,the removal rate of pyridine was still up to reach 70%.Under visible light,the charge transfer of HTC and Fe?III?forms Fe?II?to activate H₂O₂ and generate hydroxyl radicals?·OH?,which play a major role in the reaction system.