Preparation Of The ?-Cyclodextrin And Thermal-Responsive Polymer Composite Electrospinning Fibers And Adsorption Performance

With the development of the urbanization and industrialization,the contaminants of wastewater have been increasingly serious.In particular,a mass of hardly degradable organic dye contaminants have seriously threatened the health and daily life of human.Therefore,the removal of organic dye contaminants in wastewater is an urgent problem to be solved.Of all the approaches,adsorption method has attracted increasing attention owing to its simple handling,low cost and high efficiency.Here,?-cyclodextrin(?-CD)was selected as adsorbent for its peculiar structure and modified with thermal-respective polymer for the fabrication of electrospinning fibers.The morphologies of fibers are maintained via a thermal crosslinking technology for further application of control adsorption in wastewater.The p(NIPAM-co-MAA)copolymers at the NIPAM/MAA monomer molars ratios of 1:0.2,1:0.6 and 1:1 were synthesized through the radical polymerization with 2,2'-azobis(2-methylpropionitrile)(AIBN)as initiator and methyl alcohol as solvent.Then,the synthesized copolymers were blend with?-CD(the mass ratio at 1.36:1)to fabricate the electrospinning fibers.Further,the fibers were treated at 180~oC for the thermal-esterification crosslinking reaction in vacuum drying oven for 4h to obtain the crosslinked fibers with the average diamete r of2.87±0.009?m.The fabricated copolymer and fibers were characterized by the ~1H-Nuclear Magnetic Resonance(~1H-NMR),Fourier Transform Infrared Spectrometer(FT-IR),Thermogravimetry(TG),Scanning Electron Microscope(SEM)and Contact Angle measurement(CA).The results suggested that the crosslinking reaction was realized to form ester groups,and the fibers showed the high thermostability.The SEM test indicated that the morphologies of the fibers have little change after the thermal crosslinking treatment,while the stability of the fibers morphologies was largely enhanced in water aqueous solution.Besides,the fibers showed temperature and pH responses after thermal crosslinking.From the CA test,the CA value of fibers underwent rapid increase at nearby 50~oC and finally reached to 146.77~o.And the water insoluble fraction of the fibers could be above 80%after being immersed in water in the pH range from 3 to 11.The negatively charged Rhodamine B(RhB)and positively charged Crystal Violet(CV)were selected as model contaminants to discuss the adsorption performance of the fibers.The fibers showed temperature and pH responsive adsorption behavior for RhB and CV,and the maximum adsorption capacity of CV was obviously higher than that of RhB.The fibers showed higher adsorption rate and the adsorption amount increased by 20%at 55~oC than that at 25~oC.Besides,the adsorption capacity of the fibers for CV increased with pH values increasing,and reached to the maximum at pH=9.From the adsorption isotherm of the fibers for CV,the maximum adsorption capacity increased from 1049.88 mg/g to 1253.78mg/g when the temperature increased from 25~oC to 55~oC.Besides,the adsorption process for CV fitted Langmuir isotherm model that means the monolayer adsorption through fitting analysis.And the adsorption process fitted the pseudo-second-order model.In addition,thermodynamic analysis showed that the adsorption was spontaneous and endothermic process.The cyclic regeneration efficiency of the fibers maintained about 80%even after four adsorption-desorption cycles.In conclusion,the fibers showed temperature/pH responsivities,good adsorption capacity for positively charged dyes,and potential application in the wastewater treatment.