Effect Of Background Water Matrix On The Removal Of Sulfonamide Antibiotics By Catalytic Oxidation Of Composite Membrane

As a typical organic micro-pollutant,SMX is widely detected in water.Long-term residues of organic micro-pollutants are likely to cause the production of resistance genes,so it is particularly necessary to develop a suitable method to remove it.The combination of persulfate and heterogeneous metal-free catalyst,the carbon nano-material activated PS（CNMs/PS）system,has good oxidation efficiency,low operating energy consumption and no metal dissolution risk.The reaction mechanism of CNMs/PS to degrade organic pollutants is complex,which is mainly divided into radical pathway and surface catalytic oxidation.The type of CNMs,inorganic salt ions,background organic matter and other factors impact the treatment efficiency of the system.Carry out functional design of CNMs,form rGO/CNTs and NG/rGO/CNTs composite membranes by filtration coating method,and it is a feasible way to remove pollutants under complex matrix by combine the synergistic effect of adsorption and catalytic oxidation.It would become an important process in the industrial application of CNMs/PS in the future.In order to further study the catalytic oxidation mechanism and pollutant degradation path of the composite membrane,this study deeply analyzed the reaction mechanism of two CNMs composite membrane systems with a load of 8 g·m^-2,NG/rGO/CNTs and rGO/CNTs composite membranes.Adding 2 mmol·L^-1 PDS,NG/rGO/CNTs composite membrane has stronger catalytic performance than rGO/CNTs composite membrane.MeOH,NaHCO₃,KI are used to quench free SO₄^·-,·OH,¹O₂ and surface complex SO₄^·-.The test found that the inhibitory effect on the removal of SMX is:MeOH<NaHCO₃<KI,indicating that NG/rGO/CNTs and rGO/CNTs membranes have both radical pathway and surface catalytic oxidation,but the dominant is surface catalytic oxidation.The introduction of NG enhances the catalytic oxidation of the surface.After five times of reuse,the SMX removal rate of NG/rGO/CNTs was 85.1%,which was significantly higher than the 65.8%of rGO/CNTs,showing better durability.In order to further study the engineering application value of the composite membrane,a 16 g·m^-2 NG/rGO/CNTs composite membrane was selected,and the effect of different background water matrix on the composite membrane’s catalytic oxidation degradation of SMX was studied.The results show that the removal rate of SMX can still reach 96%when tap water with the lower concentration of organic matter is used as the background water after the reaction for 24 hours.While the higher organic matter content,the surface water,the effluent of aerobic tank and the effluent of anaerobic tank are the background water,at this time,the removal rate of SMX was significantly suppressed by 31.7%,47%,and 17.1%,respectively.And through three-dimensional fluorescence,it is found that protein-like substances,fulvic acid-like substances and humic acid-like substances in the background water organic matter are all involved in the catalytic oxidation process.By studying the influence of membrane fouling on the in-situ catalytic oxidation,it was found that for the NG/rGO/CNTs composite membrane,after being pre-contaminated by tap water,surface water,aerobic tank effluent,and anaerobic tank effluent,after 24hours of catalytic oxidation,the SMX removal rate can still be maintained above 84%.The in-situ catalytic oxidation system of the composite membrane is analyzed.After the membrane is polluted by organic matter,macromolecular organic matter and some small molecular organic matter are trapped in the upper layer of the membrane through pore sieving and adsorption.The lower part of the membrane is less polluted and it can maintain high-efficiency catalytic activity,so that SMX maintains a high removal rate.This thesis deeply analyzed the in-situ catalytic oxidation mechanism of carbon nanomaterial composite membrane,and studied the influence of background water and membrane pollution on the in-situ catalytic oxidation mechanism of composite membrane,which laid the foundation for the future engineering application of the functionalized composite membrane.