Fabrication And Pervaporation Applications Of Thin Film Composite(TFC) Hollow Fiber Membranes Modified With Phytic Acid-metal Coordination Complexes

Biofuels,especially bioalcohols,have received more and more attention in recent years,with the increasing exhaustion of traditional energy sources.Pervaporation,a new membrane-based separation technology,has emerged to be a promising technology to separate bioalcohols from alcohol dehydration with high efficiency,low cost and environmental friendliness.The high-performance membrane determines the whole pervaporation separation efficiency.Thin film composite membranes（TFC membranes）have gained growing attention in pervaporation applications recently,due to their simple preparation,higher flux and optimized structure design.However,due to the poor hydrophilicity and relative loose microsructure of the polyamide selective layer,especially for hollow fiber TFC membrane,the separation effciency is generally too low to meet the separation requirement for bioethanol purification.In this work,a series of phytic acid（PA）-metal coordination complexes are employed to modify the TFC membrane through surface modification and interlayer modification.The effects of the surface modification and interlayer modification on the physicochemical properties of TFC membranes and pervaporation performance for ethanol dehydration are investigated systematically.This strategy provides a new idea for the improvement of hollow fiber TFC membrane for pervaporation.Firstly,surface modification onto the TFC membrane through phytic acid-metal（PA-M）is performed.With the presence of the amide groups on the surface of pristine TFC membrane,the metal ions are successfully anchored on the membrane surface,which further allow the successful introduction of PA onto the membrane surface by the coordination interaction with grafted metal ions,forming a PA-M self-assembly layer.The successful surface modification of PA-M on the TFC membrane is confirmed via various characterization techniques,and the impacts of the PA-M on the surface properties and microstructures of the modifed membranes are explored.The amount of metal ions anchored on the membrane surface and the coordination abilities of different PA-M complexes are studied by the potentiometric titrimeter test and ICP-OES.The results find that the introduction of the PA on the membrane surface can improve the separation performane of TFC membranes,especailly for those modified with Fe³⁺,Cu²⁺and Zn²⁺-based PA coordination complexes.In addition,the PA-M self-assembly circle is also varied to study its effect on the pervaporation performance of the modified TFC membranes.Finally,the optimized TFC membrane has achieved the advanced level of separation factor in the existing reports,and has obtained excellent performance for pervaporation ethanol dehydration.In the second work,the PA-Fe coordination complex is further employed as the interlayer to modify the TFC membranes.With metal coordination interaction,the formed PA-Fe interlayer bonds well with the substrate and selective layer,therefore resulting in an optimized micro-structure of selective layer.Through a series of characterizations,the successful formation of PA-Fe interlayer is confirmed and its impact on the physicochemical properties of the membrane surface has been discussed.The pervaporation performance of corresponding TFC membrane with PA-Fe interlayer of various self-assembly circles are investigated.What’s more,the potential of other organic phosphates and metal ions for the interlayer fabricating are also explored,and all of them show enhanced performance.The developed TFC membranes with PA-M interlayer exhibit superior pervaporation performance to most other reported membranes,suggesting its great potential for pervaporation applications with this green and versatile modification strategy.