Construction Of Nitrogen-Sulfur-Doped Porous Biochar And Its Performance Research Of Activating Peroxymonosulfate

Recently,with the expansion of industry,the water pollution caused by many kinds of emerging pollutants discharged into water bodies in modern production has become increasingly serious.Among them,the pollution caused by antibiotics and endocrine disruptors is particularly prominent,while the traditional water treatment process has been unable to cope with the above pollutants.At present,sulfate radical-based advanced oxidation processes have become a hot research topic in the environmental field because of its strong adaptability and oxidation ability to remove most pollutants.Biochar,with its plentiful surface functional groups and a notably high specific surface area,has been widely used as carbon-based catalyst in activating peroxymonosulfate（PMS）.The heteroatomic doping can break the inertness of the original biochar,which is conducive to the activation of PMS to degrade organic pollutants.In this thesis,cheap and easily available biochar was used as raw material to prepare two kinds of biochar based nanomaterials by N/S co-doping,and their activating PMS performance and corresponding degradation mechanism were explored.The primary work contents are as follows:（1）Using shrimp shell-derived biochar as carbon source,potassium chloride（KCl）as hard template agent,and sulfur doped carbon nitnitide（S-C₃N₄）as external N and S sources,N/S co-doped biochar nanomaterials（BC-NS）were prepared by one-step hard template calcination at high temperature for PMS activation to degrade pollutants in water.The material showed excellent adsorption properties for sulfadiazine（SDZ）,and SDZ was completely removed by BC-NS/PMS system.The material showed outstanding removal effect to various pollutants,and had strong ability to resist environmental interference and stability.Through quenching experiment,EPR analysis and electrochemical test,it revealed the presence of free radical and non-free radical active substances in the reaction system,and the latter was predominant.Pyridine N,graphite N,thiophene S and C=O were regarded as active sites to promote the activation of PMS.（2）Fe,N and S co-doped porous biochar catalysts were synthesized by a simple impregnation-calcination process（Fe-NS@C）.Chitosan is used instead of shrimp shell as biomass carbon source,ferric chloride hexahydrate as an iron source,sulfur-doped carbon nitride introduces N and S heteroatoms from the outside.In addition,Fe@C,NS@C and Fe-N@C catalysts were prepared respectively,and the impacts of Fe doping,N and S doping on activating PMS to degradate bisphenol A（BPA）were systematically investigated.Under optimal conditions,Fe-NS@C/PMS system can completely degrade BPA（20 mg/L）within 5 min.In addition,Fe-NS@C not only has wide pH adaptability and high ability to resist environmental interference,but also maintains good degradation efficiency for different pollutants.The experimental results indicated that Fe,N,and S doping led to a noticeable improvement in the activation property of the catalyst for PMS,resulting in an enhanced removal efficiency of BPA.Additionally,the effects of N and S doping content on performance was further studied.By changing the doping amount of S-C₃N₄,biochar-based catalysts with different doping amounts of N and S were successfully designed,and their synergistic impacts were explored.In addition,it is found that the surface-binding free radicals(SO₄^·-和^·OH)play a dominant role in the system.Pyridine N and Fe-N_X are the main active sites in the system,while the active sites of thiophene sulfur also play a supporting role.