Cellulose-based Electrospun Nanofibers Supported Metal-Organic Frameworks Catalysts And Their Applications In The Complex Wastewater Treatment

At present,the efficient treatment of organic wastewater is one of urgent environmental issues that should be solved,in particular for the complex multiphase organic wastewater,containing dyes,oils,bacteria and heavy metals,which will lead to a greater risk to the environment and human health.Traditional adsorption,filtration or catalytic materials as well as their treatment methods are difficult to realize the synchronous treatment of the above complex organic wastewater.Therefore,the development of high-performance,sustainable and low-cost multifunctional water remediation materials and technology has attracted intensive interest.Metal-organic frameworks(MOFs)have the characteristics of large specific surface area,high porosity and easy modification,which can be well used in the adsorption and catalytic degradation of water pollutants.However,as kind of powder catalysts,MOFs are difficult to be effectively recovered from water and their catalytic activities are decreased due to their readily agglomeration.Cellulose fiber,as natural biomass material,features abundant surface functional groups,low cost and easy modification,which can become a good carrier for MOFs,promoting the dispersion of MOFs in order to improve the catalytic performance.Besides,it can also endow material with recyclability,which is conducive to industrial preparation of high-performance biomass water remediation material.In this study,we used cellulosic biomass as the substrate to prepare electrospinning nanofiber membrane(ENM)and electrospinning nanofiber aerogel(ENA).Then immobilized the MOFs(such as HKUST-T,MIL-100(Fe),ZIF-67)with catalytic or antibacterial effect on the fibers by in-situ synthesis method.Using trifluoroacetic acid(TFA)and dichloroethane(DCE)as solvent system to dissolve pure dissolved pulp for dry spinning,polyethylene oxide(PEO)and copper acetate(Cu(OAc)2)were selected as fiber thickener and MOFs binding site to prepare HKUST-1 nanocellulose fiber composite membrane material(CF@HKUST-1),and its application in multifunctional water remediation was discussed.The results show that the introduction of PEO and Cu(OAc)2 helps HKUST-1 to attach to the nanofibers,and the maximum loading capacity can reach 16.1%.In addition,CF@HKUST-1 has high oil-water separation efficiency,with 98%oil-water separation efficiency for rapeseed oil from wastewater and also has good utilization performance.Moreover,using Escherichia Coli as simulation bacteria,the results showed that CF@HKUST-1 composite showed excellent antibacterial performance.A core-sheath β-FeOOH@MIL-100(Fe)/CeP composite membrane was prepared using electrospun cellulose acetate/polyvinylpyrrolidone(CA/PVP)nanofiber as the skeleton core and β-FeOOH@MIL-100(Fe)heterostructure as the photocatalytic sheath.The core-sheath structured ENM has ultrahigh MIL-100(Fe)loading(78 wt%),large surface areas(1105 m2/g)and well-dispersed(3-FeOOH nanorods.Thanks to these porous and hydrophilic MIL-100(Fe),along with a robust photocatalysis-Fenton synergy from(3-F eOOH@MIL-100(F e),the as-prepared ENM shows outstanding performances with simultaneous high removal efficiency for oils(99.5%),dyes(99.4%)and Cr(VI)(99.7%).Additionally,the photocatalytic ENM can achieve a long-term reuse owing to its inherent self-cleaning function.Finally,SiO2 supported electrospun acetate cellulose nanofiber composite membrane material(CA@Si ENM)was prepared by using electrospun nanofiber as substrate and modified by doping TEOS.To further raise the overall performance of composite material,the above silane modified electrospun nanofibers were homogeneously dispersed and used as skeletons for in situ synthesis and anchoring MOFs(ZIF-67).The as-prepared electrospun nanofiber(ENF)-based aerogel(CA@Si@ZIF-67)was subjected to thermal treatment(T)to obtain the electrospun nanofiber aerogel of T-CA@Si@ZIF-67 ENA(T-ENA)with an enhanced mechanical stability.The structure conversion from 2D to 3D has been successfully realized,and it has been applied to the treatment of oil and drug residues in multiphase organic wastewater.The results show that thermal treatment can strengthen the network crosslinking between SiO2 and electrospun fiber in T-ENA,not only enhance the mechanical stability and hydrophobicity of composite aerogel,but also ensure its high porosity(>98%)and low density(=10 mg/cm3).Due to its good hydrophobicity,porosity and mechanical properties,T-ENA showed good adsorption and separation(≥99.3%)and excellent recycling and reuse properties for oil stains in wastewater.At the same time,due to the effective dispersion and immobilization of porous active ZIF-67 catalyst in T-ENA,the efficient activation of permonosulfate was promoted,and the complete degradation of carbcarbazepine(CBZ)residues in wastewater was achieved within 20 min.