Preparation And Separation And Adsorption Properties Of Knitted Tube Composite β-CD/CS Porous Membrane

With the continuous development of industrialization,the problem of water pollution has become increasingly serious.For the pollution of organic matter and heavy metals,we aim to obtain a separation membrane material with adsorption properties.In this paper,chitosan（CS）andβ-cyclodextrin（β-CD）were used as the film-forming matrix,polyethylene glycol（PEG）as the pore forming agent,glutaraldehyde as the crosslinking agent to improve the water stability,and knitted tube as the reinforcement to improve the mechanical properties.The knitted tube compositeβ-cyclodextrin/chitosan（β-CD/CS）porous membrane was prepared by non solvent induced phase separation（NIPS）and dip coating crosslinking.Its preparation process,separation performance,adsorption performance and adsorption mechanism were studied.At first,the knitted tube composite CS porous membrane was prepared,and the optimum concentration of CS base membrane was discussed.The results showed that the optimal concentration of chitosan casting solution was 7 wt%.The tensile test shows that the mechanical properties of CS membrane were poor,and the composite of the knitted tube obviously enhances the breaking strength and elongation at break of the membrane,which showed that the knitted tube as the support material,significantly improved the mechanical properties of the membrane.Then,based on NIPS method and dip coating crosslinking method,the knitted tube compositeβ-CD/CS porous membrane was prepared.The effects of differentβ-CD content and glutaraldehyde crosslinking time on the membrane properties were investigated by SEM,contact angle,water flux,rejection rate,stretching and adsorption experiments.The optimal preparation parameters were obtained:β-CD content was 3.5 g and crosslinking time was 10 min.Through SEM,it can be seen that the surface of the knitted tube compositeβ-CD/CS porous membrane was more uneven and wrinkled,which greatly increased the specific surface area of the membrane and improved the adsorption performance of the membrane.FTIR analysis showed that CS andβ-CD were successfully crosslinked by glutaraldehyde.The effect of adsorption time and initial concentration on the adsorption performance were studied by single factor adsorption experiment.The results showed that the optimal adsorption time and adsorption rate of phenolphthalein were 60 min and 85%,respectively.The results showed that the adsorption of phenolphthalein on the knitted tube compositeβ-CD/CS porous membrane was dominated by monolayer adsorption and coexisted with multi-layer adsorption.The adsorption kinetics of phenolphthalein on the knitted tube compositeβ-CD/CS porous membrane followed the Double constant and Elovich model,which showed that the adsorption process was the synergistic effect of host-guest interaction fromβ-cyclodextrin,non-uniform diffusion and porous network capture.The best adsorption time of Cu²⁺on the knitted tube compositeβ-CD/CS porous membrane was 240 min and the best adsorption rate was 97%.The adsorption was in accordance with Langmuir isotherm adsorption model,which indicated that the adsorption process of Cu²⁺on the knitted tube compositeβ-CD/CS porous membrane was single molecular layer adsorption.The adsorption kinetics can be described by the quasi second-order kinetic equation,which showed that the adsorption process of Cu²⁺on the knitted tube compositeβ-CD/CS porous membrane was mainly chemical adsorption.In order to study the cyclic regeneration performance of the membrane,the adsorbed membrane was desorbed by desorbent.In order to study the recycling performance of the membrane,the adsorbed membrane was desorbed with a desorbent.After 5 adsorption-desorption cycle experiments,the adsorption recovery rate of the knitted tube compositeβ-CD/CS porous membrane was above 80%.