Fabrication Of Carboxymethyl Chitosan-based Composite Microspheres And Its Adsorption Behavior For Dye Wasterwater

The pollution of industrial dye wastewater discharged from printing and dyeing,textile,leather and papermaking is one of the most urgent environmental problems.Adsorption is a simple and efficient method for the removal of this kind of dye wastewater.Carboxymethyl chitosan is a derivative of chitosan and has paid considerable attention because of the cheap price,abundant sources,and good adsorption effect on some dyestuff dyes.In this study,we used inverse suspension crosslinking reaction as preparation approach of droplets and natural carboxymethyl chitosan as raw material to prepare carboxymethyl chitosan microspheres(CCMSs),then we studied on the effects of single factor such as the dosage of emulsifier?ratio of water-ratio and stirring speed on the preparation of CCMSs.The results showed that microspheres with good morphology and good fluidity were obtained when glutaraldehyde was used as cross-linking agent,Span80 was 0.04g/mL,the ratio of water-ratio was 1/6,stirring speed was 800r/min,emulsification temperature was 60 C,emulsification time was 30min,the adsorption properties of anion and cation dyes were also studied.In order to increase the content of CCMSs active amino,a polydopamine layer was coated on the surface of carboxymethyl chitosan microspheres to form polydopamine modified carboxymethyl chitosan microspheres(PDA@CCMSs)by autoxidation polymerization of dopamine.The analysis results of SEM,FTIR and EDS showed that a large number of amino functional groups were covered on the surface of microspheres,which made PDA@CCMSs microspheres have higher adsorption capacity(qe=206mg/g)and quickening adsorption rate when removal of anionic dyes.In order to remove a specific dye from mixed dyes and increase the content of amino and carboxyl groups simultaneously,carboxymethyl chitosan/gelatin composite microspheres(CCGMSs)mixed with carboxymethyl chitosan and gelatin,have selective adsorption properties to anionic and cationic dyes.The adsorption results show that amino and carboxyl groups are the main groups for the adsorption of anionic and cationic dyes.The adsorption isotherm fitted the Langmuir equation while thermodynamic adsorption results were considered as strong proof of an adsorption exothermal process.