Synthesis Of Rosin-based Anionic Exchange Resin And Its Adsorption Performance On Pigment Products Of Sugar Juice

The colored substances in the sugar juice will reduce the quality of the sugar produced,so it is necessary to decolorize the sugar juice in the process of sugar production.At present,styrene resins are widely used in sugar enterprises for decolorization of sugar juice,but styrene resins may have carcinogenic styrene monomer residues,which may cause food safety risks when used in sugar purification.Therefore,it is necessary to develop a new environment-friendly and safe decolorizing resin to replace the existing styrene ion exchange resin for decolorization of sugar juice in sugar industry.Using hydrogenated rosin(?-acryloxy ethyl)ester(HREGA)as monomer,dimethylaminoethyl methacrylate(DEAEMA)as functional monomer and ethylene glycol dimethacrylate(EGDMA)as cross-linking agent,the rosin-based anionic exchange resin(RAER)was prepared by suspension polymerization as a new decolorizing resin for sugar juice.The RAER was used to adsorb alkaline degradation products of hexoses(HADPs)and gallic acid(GA).The research contents were as follows:(1)The effects of different monomer ratios and pore-forming agents on the structure and morphology of the rosin-based anionic exchange resin(RAER)were discussed.The RAER was characterized by Fourier transform infrared spectrometer(FT-IR),scanning electron microscope(SEM),nitrogen physical adsorption apparatus(BET)and synchronous thermogravimetric analyzer(TGA).The optimal pore structure of the RAER with the specific surface area of 18.47m~2·g^-1,the pore volume of 0.15 cm~3·g^-1,the range of pore size distribution of5-180 nm and the average pore diameter of 26.31 nm,were obtained under the conditions that:HREGA,the molar ratio of the cross-linking agents(EGDMA)and DEAEMA was 0.2:4:8,and PPG was used as the porogen.The synthesized material has high mechanical strength and excellent thermal stability.In vitro cytotoxicity tests were conducted using the CCK-8 assay and LIVE/DEAD cell viability assay with GES-1 cells(human gastric epithelial cells)to evaluate the food safety of RAER.The cell viability could still reach up to 95.82%even after72 hours when the sample concentration was as high as 100?g·m L^-1.These results suggest that the RAER has ideal biocompatibility(food safety)and is a green(nontoxic)safe decolorizing resin for sugar juice.(2)The optimum conditions for the removal of HADPs using RAER were determined by static adsorption experiments,in which the affects of adsorption conditions(e.g.RAER dosage,temperature,time and p H value)on the adsorption performances were investigated.The results showed that the removal rate of HADPs for the decolorization was up to 100%(experimental conditions:RAER dosage,0.05 g·m L^-1;temperature,343 K;p H,7.0;initial HADPs concentration,100 mg·L^-1).After 20 times of regeneration,the decolorization rate of RAER to HADPs was still 92.18%.Studies on the kinetics,isotherms and thermodynamics of HADPs adsorption by RAER.The results showed that the adsorption of HADPs by RAER accorded with pseudo-second-order kinetic model(R~2?0.99)and Freundlich isotherm model(R~2?0.98),?H=62.32 KJ·mol^-1.It indicated that the adsorption mechanism was a Heterogeneous and endothermic process dominated by the adsorption in active sites.The RAER-HADPs(RAER after adsorption of HADPs)was characterized by FT-IR,SEM,BET and TGA.The results showed that the pores of the RAER-HADPs have been filled with macromolecular HADPs.The specific surface area,pore volume and average pore diameter of RAER-HADPs are 15.48 m~2·g^-1,0.13 cm~3·g^-1and 23.40 nm respectively.Compared with RAER,the content of N on the surface of RAER-HADPs was decreased from 15.58%to 10.81%,which was due to the ion exchange reaction between the adsorbent and the adsorbate by tertiary amine.Electrostatic attraction(ion exchange)existed in the adsorption of HADPs was conducted by the results of RAER and HADPs Zeta potentials.(3)The optimum conditions for the removal of GA using RAER were determined by static adsorption experiments,in which the affects of adsorption conditions(e.g.RAER dosage,time and p H value)on the adsorption performances were investigated.The results showed that the removal rate and the equilibrium adsorption capacity of GA for the decolorization was 94.67%and76.55 mg·g^-1(experimental conditions:RAER dosage,0.005 g·m L^-1;p H,3.0;initial GA concentration,400 mg·L^-1).After 10 times of regeneration,the decolorization rate and the adsorption capacity of RAER to GA was still 82.24%and 65.44 mg·g^-1.Studies on the kinetics and isotherms of GA adsorption by RAER.The results showed that the adsorption of GA by RAER accorded with pseudo-second-order kinetic model(R~2?0.99)and Freundlich isotherm model(R~2?0.98).It indicated that the adsorption mechanism was a Heterogeneous process dominated by the adsorption in active sites.The RAER-GA(RAER after adsorption of GA)was characterized by FT-IR,SEM,BET and TGA.The results showed that the pores of the RAER-GA have been filled with a large number of small GA.The specific surface area,pore volume and average pore diameter of RAER-GA are 16.56 m~2·g^-1,0.12 cm~3·g^-1and 23.75 nm respectively.Compared with RAER,the content of N on the surface of RAER-GA was decreased from15.58%to 5.42%,which was due to the ion exchange reaction between the adsorbent and the adsorbate by tertiary amine.