| At present,with the vigorous development of industrial technology,the discharge of industrial wastewater shows a rapid growth trend.Among them,organic dye wastewater is an important part of industrial wastewater,which usually has the characteristics of complex composition,high chroma,difficult natural purification and long purification cycle,and have caused great harm to water and ecological environment.For example,benzene,naphthalene,anthracene,quinone and other color groups in the molecular structure of organic dyes will change the color of water,thus interfering with the transmission of sunlight,affecting the photosynthesis of aquatic plants;In addition,organic dye molecules tend to chelate easily with heavy metal ions and can be enriched in aquatic animals,which will further cause toxicity if ingested by humans.Nowadays,the conventional method of treating organic dye wastewater is physical method,including adsorption method,filtration method and so on.However,these physical methods can only physically separate or enrich the pollutants in the adsorbent,but cannot completely decompose the organic dye molecules,and may cause a secondary pollution.Therefore,an efficient and environmentally friendly method is urgently needed to treat organic dye wastewater.At present,heterogeneous catalysis based on metal nanocatalysts has been widely studied in the application of organic dye reduction treatment.However,metal nanocatalysts are faced with disadvantages such as small intrinsic particle size,easy agglomeration and difficulty in recovery,which will reduce their catalytic efficiency and increase their cost,thus greatly limit their application in practical scenarios.This research is based on polymer-based non-woven new materials,combined with the hot pressing process and in-situ reduction strategy of fiber surface nano hybrid technology,innovatively prepared two kinds of novel non-woven catalytic materials with high catalytic performance,systematically studied the micro-nano structure characteristics of them and the effects of fiber interface functionalization,hot pressing and in-situ nano hybridization on the structure and properties of the materials were revealed.Taking the catalytic reduction reaction of organic dyes as a model,the catalytic reduction performance,service stability and reuse performance of organic dyes（such as methylene blue）in intermittent and continuous flow catalytic mode were studied in detail.The specific work content can be divided into the following two parts:Firstly,A mussel inspired interface modification strategy was adopted to introduce polydopamine nano-functional coating on the surface of polyethylene terephthalate/polyethylene（PET/PE）shelth-core fiber,and introduced hydroxyl and other active functional groups on the surface at the same time to further in-situ reduce the silver（Ag）salt precursor into Ag nanoparticles,and realized the interface hybrid loading.Scanning electron microscopy（SEM）,X-ray energy dispersive spectroscopy（EDS）,X-ray photoelectron spectroscopy（XPS）and other characterization of the materials proved that the loading of Ag nanoparticles（50-100 nm）on PET/PE shelth-core fibers was successfully realized.In addition,reduction of methylene blue by NaBH4 was used as a model reaction,and the catalytic reduction performance of organic dyes was studied on the nano Ag supported non-woven（NWF/Ag）composites under batch and flow reaction conditions.The results showed that:（1）NWF/Ag composite material has good catalytic activity,and the model reaction of catalytic reduction of methylene blue by NaBH4 shows first-order kinetic characteristics;The kinetic constant of the reaction increased with the increase of the nano-Ag loading,and reached a maximum of 0.29 min-1 under experimental conditions.（2）Two different types of flow catalytic reactor（filter type flow reactor and channel type flow reactor）were assembled based on NWF/Ag composite material to test the performance of the flow catalytic reaction.The results of flow catalytic reaction showed that the catalytic efficiency of the reactor decreases first and then tends to be stable with the increase of the flow rate of the reaction solution.The catalytic efficiency can be significantly improved by reducing the flow rate or increasing the reaction contact time.For example,when the concentration of methylene blue solution is 24 mg/L,the catalytic efficiency of more than 98% can be obtained by controlling the flow time to 270 s in the channel type flow catalytic reactor.The stability test results showed that the catalytic efficiency of the flow catalytic reactor can remain above 85% after continuous treatment of 200 mL methylene blue solution.More importantly,the prepared NWF/Ag composite showed good catalytic reduction performance for a variety of organic dyes and their mixtures.Secondly,a sandwich structure of non-woven fabric/Fe3O4/Nano Silver（NWF/Fe3O4/Ag）magnetic responsive composites was prepared by hot pressing and in-situ reduction strategy.The material preparation process is mainly divided into two steps: first,Fe3O4 nanoparticles are filled into the inner layer fiber of non-woven fabric by hot-pressing method based on the self-bonding property of PET/PE two-component non-woven fiber.Then,the polydopamine functional coating was introduced on the surface of the non-woven fiber.Finally,Ag nanoparticles were synthesized by in-situ reduction of Ag precursor and loaded on the surface of fiber to obtain NWF/Fe3O4/Ag composites.SEM,XPS,X-ray diffraction（XRD）and other characterization of the material showed that Fe3O4 nanoparticles（≈ 246 nm）and Ag nanoparticles（50-200 nm）were successfully loaded on PET/PE two-component non-woven fabric.Subsequently,the catalytic experiment also used the reaction of reduction of methylene blue by NaBH4 as a model to study the catalytic reduction performance of organic dyes of the obtained NWF/Fe3O4/Ag composite.The results showed that:（1）NWF/Fe3O4/Ag composite showed high catalytic activity in the catalytic reduction reaction of methylene blue.A 7 cm×7 cm NWF/Fe3O4/Ag composite could completely discolor 100 mL12mg/L methylene blue solution within 15 min.（2）NWF/Fe3O4/Ag composites show non-first-order kinetic characteristics in the catalytic reduction of methylene blue by NaBH4,revealing that the removal of methylene blue in the system is coordinated by Fe3O4 nanoparticles and Ag nanoparticles.（3）The magnetic saturation strength of NWF/Fe3O4/Ag composites is up to 31 emu/g,it can be separated and recovered from the post-reaction solution in the presence of an external magnetic field.In addition,the catalytic efficiency of above 86% can be maintained after 8 times of repeated catalytic reduction of methylene blue solution. |
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