Preparation Of Aminated Crosslinked Chitosan Microspheres And Their Adsorption Properties On Acid Azo Dye

Acid azo dye is widely applied in fiber,paint,plastic and rubber due to its simple synthesis methodology,low cost and outstanding dyeing properties.However,because of its toxicity,high stable chemical properties,and complex composition,it brings great difficulties in the dyes wastewater treatment.The adsorption method is one of most common method for dyes wastewater treatment.Chitosan containing an abundance of free amino and hydroxyl groups,which make it having excellent adsorption properties for acid azo dye.Unfortunately,chitosan is easily dissolved in acidic solution when it is used as adsorbent in dyes wastewater treatment.In order to improve the acid resistance and adsorption performance of chitosan,three aminated crosslinked chitosan microsphere adsorbents including ethylenediaminepropionyl crosslinked chitosan microspheres(EAGCS),polyethyleneimine modified crosslinked chitosan microspheres(PEI-GCS)and hyperbranched polyamideamines modified crosslinked chitosan microspheres(HPAMAM-GCS)were prepared.The adsorption properties of these three adsorbents for methyl orange(MO)and acidic chrome blue K(ACB-K)in simulated dyes wastewater was systematically studied,and the results are listed follows:(1)Using acryloyl chloride as bridging agent,EAGCS and PEI-GCS were prepared by grafting ethanediamine and polyethyleneimine into crosslink chitosan microspheres(GCS).The chemical structure of EAGCS and PEI-GCS were confirmed by Fourier transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS).Scanning electron microscope(SEM)showed that these microspheres were uniform spheres.(2)The effects of pH value of simulated dyes wastewater,temperature,initial concentration and adsorbent dosage on the adsorption performance of EAGCS and PEI-GCS to MO and ACB-K were systematically investigated.The results showed that the adsorption capacity of EAGCS and PEI-GCS to MO were 545.40 mg·g-1 and 622.27 mg·g-1 respectively,EAGCS and PEI-GCS to ACB-K were 439.18 mg·g-1 and 509.76 mg·g-1 respectively.Furthermore,the kinetic and isothermal adsorption model studies suggested that this adsorption kinetics were pseudo-second-order,which were fit to Langmuir and Freundlich isothermal adsorption model.(3)HPAMAM were synthesized by using ethylenediamine(EDA)and N,N'-methylene double acrylamide(MBA).Their structures were characterized by FT-IR,1H-NMR and 13C-NMR.Under optimal synthesis condition,Gel permeation chromatography(GPC)showed that the average molecular weight(Mw)and polydispersity index(PDI)of HPAMAM were 1.5x104 g·mol-1 and 5.79 respectively.Then,HPAMAM-GCS were prepared by grafting HPAMAM into GCS,which was confirmed by FT-IR and XPS.In adsorption tests,the adsorption capacity order for MO and ACB-K was HPAMAM-GCS>PEI-GCS>EAGCS>GCS.