Study On Preparation Of Cellulose-based Composite Membrane And Its Catalytic Performance

The treatment of organic dyes in wastewater is important to solve environmental problems.Sulfate radical-based ad-vanced oxidation processes(SR-AOPs)have been proved to be an effective treatment for removing organic pollutants due to their good environmental applicability,high reactivity and thorough degradation.At present,peroxymonosulfate(PMS),as an oxidant,has been widely used to provide sulfate radicals(SO4·-).In the absence of catalyst,PMS reacts too slowly with pollutants.Cobalt and iron-containing transition metal oxides and novel cobalt-based metal-organic freamworks(MOFs)have been developed for activating PMS to degrade pollution.However,most of these catalytic materials are micro-nano level and powdery materials.This characteristic caused the problem that the catalytic materials were difficult to recover after the reaction.In order to solve this problem,there have been works using cellulose-based aerogels as the host material to support the catalytic material,which can effectively improve the recovery of the catalyst,and high porosity can ensure the effective contact between the dye and catalyst.However,aerogel materials have some problems such as longer preparation cycles and more energy consumption during drying.Our research found that cellulose-based membrane materials have higher porosity and surface area,while they are simpler to prepare,require less energy to dry,and can control the preparation conditions to obtain cellulose membrane of different thicknesses and sizes.Therefore,this paper proposes to composite a catalytic material with cellulose membrane to prepare cellulose-based composite membrane material as efficient catalysts for catalyzing PMS to degrade organic dye pollutants.To study the catalytic degradation performance of composite membranes under different pH,different PMS dosages,etc.,and analyze the catalytic degradation mechanism of composite membranes.The specific research content is as follows:(1)GO was selected as a substrate material for nucleation and growth of Fe3O4 particles.Fe3O4/RGO composites were prepared by the solvothermal method,which improved the agglomeration phenomenon of Fe3O4 particles.Then,Fe3O4/RGO composite material was introduced into the cellulose membrane by the doping method to prepare a Fe3O4/RGO/cellulose composite membrane.To study the catalytic degradation performance of composite membranes under different conditions.The catalytic results show that the Fe3O4/RGO/cellulose composite membrane/PMS system shows high catalytic activity,and can degrade 97%of MB molecules in 50 min without adjusting the initial pH of MB solution.Fe3O4/RGO/cellulose composite membrane also shows good pH applicability and can maintain high catalytic degradation performance over a wide pH range(4-9).At the same time,after the reaction is completed,the composite membrane can be quickly separated from the reaction system to achieve efficient separation and recovery of the catalytic material.In addition,the Fe3O4/RGO/cellulose composite membrane has excellent recycling performance and has practical application potential.(2)In order to improve the catalytic performance of the Fe3O4/RGO/cellulose composite membrane,a cobalt-based MOFs material ZIF-9 was introduced on the basis of Fe3O4/RGO to prepare a novel catalytic material and coded as ZIF-9@CA-Fe3O4/RGO.The same doping method was selected and introduced it into the cellulose membrane to obtain a ZIF-9@CA-Fe3O4/RGO/cellulose composite membrane.ZIF-9@CA-Fe3O4/RGO/cellulose composite membrane shows more efficient catalytic degradation performance than Fe3O4/RGO/cellulose composite membrane and ZIF-9/cellulose composite membrane,which can degrade 96%of MB molecules in 9 min without adjust the initial pH of the MB solution,indicating that the novel catalyst ZIF-9@CA-Fe3O4/RGO significantly improves the catalytic performance of Fe3O4/RGO after introduction of ZIF-9,and has higher degradation than single components performance.Besides,ZIF-9@CA-Fe3O4/RGO/cellulose composite membrane showed the same excellent pH applicability with Fe3O4/RGO/cellulose composite membrane.At the same time,after the reaction is completed,the composite membrane can be quickly separated from the reaction system to achieve efficient separation and recovery of the catalytic material.And the dynamic decolorization experiment showed that ZIF-9@CA-Fe3O4/RGO/cellulose composite membrane has certain practical application potential.In addition,GC-MS and EPR were used to analyze the mechanism of MB degradation in the composite membrane/PMS system.(3)In order to further simplify the preparation of high-performance catalytic membrane,and considering that MOFs have higher activity in catalysis.ZIF-67 particles were synthesized in a cellulose membrane by in-situ synthesis to obtain a ZIF-67/cellulose composite membrane.According to TG analysis,it can be known that the loading rate of ZIF-67 particles in the composite membrane can reach 7.06wt%.At the same time,ZIF-67/cellulose composite membrane showed excellent degradation performance.It can degrade 97%of MB and RhB in 1 min without adjusting the initial pH of the solution.The ZIF-67/cellulose composite membrane obtained by the in-situ synthesis method also has excellent pH applicability and can maintain catalytic activity over a wide pH range.At the same time,ZIF-67/cellulose composite membrane also has excellent recycling performance and can be separated from the reaction system quickly after the reaction,which has the potential for practical application.