Preparation Characterization And Applications Of Poly(2, 6-dimenthyl-1, 4-phenylene Oxide) Based Hollow Fiber Ion Exchange Membranes

Hollow fiber ion-exchange membrane is widely used in many areas such as protein separation and purification, removal of heavy metal ion and enzyme immobilization. Compared with hollow fiber membrane, preparation by direct spinning is much more difficult because of strong surface hydrophilicity, and its mechanical strength also decreases quickly. Thus, further chemical modification of base membrane is needed. For introducing ion exchange group, pre-graft of functional groups and crossliked groups are needed. Based on our previous study, we were focused on preparation and application of hollow fiber ion-exchange membrane, and poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) hollow fiber membrane with functional group was choosed as base membrane. Results are detailed as follows:(1) Amphoteric hollow fiber membranes (AHFM) were prepared from two seps including ethylenediamination and carboxylation, and used for proteins recovery and purification. FTIR spectra, amphoteric group density and cation-exchange capacity demonstrated that amino and carboxylic acid groups have been successfully introduced into the BPPO hollow fiber base membrane. Micrographs showed that there was no obvious difference on the cross-section morphology between the BPPO base hollow fiber and the prepared CEBPPO membrane, indicating modification of the membrane does not damage the pore structure. Then, the prepared amphoteric hollow fiber membrane was used for adsorption of lysozyme, and the results showed that the adsorption capacity increased with the increase of adsorption time and initial lysozyme concentration. In addition, the adsorption obeyed the Langmuir isotherm, and the maximum experimental lysozyme adsorption capacity was 4.00 mg/g, which was approximate to the calculated maximum data (3.85 mg/g). These above results indicated that the amphoteric hollow fiber membrane has been prepared successfully and used for protein separation and purification.(2) Hollow fiber cation-exchange membrane contained sulfonic acid groups were prepared via amination and sulfonation, and used for removing heavy metal ions. Firstly, amination and sulfonation processes were confirmed by FTIR and anion-exchange capacity, and the cation-exchange capacity, which was controlled by adjusting reaction time, reaction temperature, and reagent concentration, could reach 4.00 mmol/g. Scanning electronic microscopy (SEM) showed that the membrane's structure remained intact after such chemical modification. Secondly, the adsorption of hollow fiber cation-exchange membrane for heavy metal ions was examined for the first time using Cu2+ as a representative metal ion, the results showed that the adsorption capacity was controlled by adsorption time, initial Cu2+ concentration, pH and cation exchange capacity. In addition, the maximum adsorption capacity was 69.12 mg/g and the adsorption isotherm fit the Langmuir equation well. As for the generation of the prepared hollow fiber caiton exchange capacity, the regeneration ratio depends on the concentration of hydrochloric acid and regeneration time. These above results also showed that the hollow fiber cation exchange membrane has been prepared successfully and used for removing heavy metal ions.(3) Hollow fiber cation-exchange membranes (HFCEM) contained carboxylic acid groups were prepared by amination and carboxylation, and used for enzyme immobilization as a support. Micrographs of membranes indicated that the preparation processes does not damage the pore structure of the prepared membrane. Mechanical strength and water uptake analyses showed that the prepared membrane was hydrophilic and had good mechanical stability in the proper range of cation exchange capacity, which indicated that the prepared membrane was suitable for enzyme immobilization as a support. For evaluating immobilization efficiency of enzyme. Cellulase was chosen to be model enzyme, and influences of reaction conditions such as pH were fully investigated. The optimum immobilization conditions are as follows: EDC concentration,40 mg/mL; activation time,20 h; immobilization time,25 h; enzyme concentration,5.0 mg/mL; pH3.8. In addition, the stability of cellulase against pH and heat after immobilization was improved by immobilization, demonstrating that the prepared CBPPO membrane was suitable as a support for enzyme immobilization. Findings here can provide guidance for further exploration of this kind of membranes for enzyme immobilization.In conclusions, amphoteric hollow fiber membrane and hollow fiber cation-exchange membranes were prepared from BPPO hollow fiber base membrane, and used for protein separation and purification, enzyme immobilization and removal of heavy metal ions respectively, which indicated ion exchange group was introduced easily after pre-introductions of functional groups and crossliked groups...