Preparation Of N-halamine Modified Silica Nanofibrous Membranes For Water Purification And Mercaptan Degradation

In recent years,due to the rapid development and progress of economy,the rapid improvement of industrial development speed,the establishment scale of various chemical plants is also correspondingly expanding,which leads to more and more pressure on sewage treatment in China’s cities,and the water pollution problem is increasingly serious.The sewage carrying a large amount of mercaptan pollutants not only seriously threatens human life and health safety,but also the odor in the sewage also causes serious harm to the surrounding environment.Therefore,there is an urgent need to take some measures to treat the mercaptan pollutants in sewage,so as to ensure the environment and human health from its harm.At present,the commonly used water purification technologies for wastewater treatment include physical adsorption,biodegradation,chemical degradation,etc.Among them,chemical degradation is a low investment,high efficiency and wide range of application.However,some degradation materials have problems such as low degradation efficiency and easy deactivation.N-halamine degradation materials have the advantages of high degradation efficiency and stability,safety,non-toxic and renewable,which make them have higher research and use value in the field of water purification.Among them,N-halamine nanofibrous materials are the research hotspot of scholars at home and abroad.Nanofibrous materials with larger specific surface area and porosity can increase the contact area between materials and mercaptan molecules,so as to improve the efficiency of mercaptan degradation.Therefore,it is of great significance to develop N-halamine nanofibrous materials with high mercaptan degradation efficiency and stability for water purification.In this project,1,4-dichloromethoxybutane was used to chloromethylate polyethersulfone（PES）to obtain chloromethylated PES.Then,5,5-dimethylhydantoin（DMH）was grafted onto chloromethylated modified polyethersulfone by nucleophilic substitution to prepare N-halamine grafted chloromethylated modified polyethersulfone nanofiber membrane through electrospinning technology and chemical grafting.However,due to the low active chlorine content（3200 ppm）,the degradation effect of the fibrous membranes on mercaptan is poor,which could not meet the needs of rapid degradation of mercaptan.Therefore,We synthesized a new haloamine material and grafted it on the nanofibrous membrane.The silica nanofibrous membrane with poly（vinyl alcohol）as template was prepared by electrospinning technology firstly,and then 5,5-dimethylhydantoin and3-chloropropyltriethoxysilane were used as raw materials to prepare organo silane halogen amine compound 5,5-dimethyl-3-（3’-triethoxysilyl propyl）hydantoin polymer（PSPH）,which was then covalently combined with silica nanofibrous membrane by chemical grafting process.Finally,N-halamine modified silica nanofibrous membrane with excellent mercaptan degradation performance was successfully prepared by chlorine bleaching process.The fibers in the prepared fibrous membrane are interconnected and highly intertwined to form a porous channel structure,which facilitates the flow of water.in addition,the prepared nanofibrous membranes have Excellent structural stability,high active chlorine content（7363 ppm）and uniform distribution,excellent degradation stability and chlorine bleaching renewable performance.Using dodecyl mercaptan as mercaptan template,the mercaptan degradation performance and water purification application of N-halamine modified silica nanofibrous membrane were studied.The results showed that the prepared fiber membrane could decompose dodecyl mercaptan by releasing oxidizing Cl⁺,and only 15 mg of fiber membrane could degrade 50 ppm dodecyl mercaptan in 30 minutes.In the application of dynamic water purification,the fiber membrane with a diameter of 20 mm can degrade nearly 100%of the initial concentration of 100 ppm dodecanethiol polluted water with high degradation efficiency and large treatment flux(the effective treatment flux is 25000 L·m^-2·h^-1).The successful preparation of these N-halamines modified silica nanofibrous membranes will provide a reference for the development of new multifunctional mercaptan degradation nanofibrous materials.