Preparation Of Cross-linked Carboxymethyl Starch And Study On Adsorption Properties Of Dyes And Heavy Metal Ions

Using corn starch as raw material and epichlorohydrin as crosslinking agent,crosslinked starch(CS)was synthesized under alkaline conditions.Crosslinked carboxymethyl starch was prepared by solvent method with CS as raw material and chloroacetic acid as etherification agent.The preparation process of CS was investigated by single factor experiment.CCMS was synthesized by CS with high,medium and low crosslinking degrees(the sedimentation was 0.52,0.66 and 1.32,respectively).The experimental results showed that CS with sedimentation of 0.52 was achieved when the epichlorohydrin volume and NaOH quality were 4.5mL and 1.5 g,alkalization was proceeded at 50?for 8h.The preparation condition of CS with sedimentation of 0.66 was as follows:epichlorohydrin volume of 1.5mL,1.5g of NaOH,50 ? of reaction temperature,8h of reaction time.The preparation condition of CS with sedimentation of 1.32 was that the 4 conditions werel.5mL?3g?50? and 8h,respectively.The single factor experiment and orthogonal test of CCMS synthesis showed that the dosage of NaOH and the amount of chloroacetic acid had a significant effect on the substitution degree of CCMS,and the reaction temperature had no significant effect on it.Considering the cost of raw materials,the optimum preparation conditions for CCMS were n(NaOH):n(chloroacetic acid)=1.2,n(chloroacetic acid):n(starch)=1.0,and reaction temperature of 50 ?.The differences in grain morphology and internal structure of corn starch and CCMS were investigated by analysising of SEM,FTIR and XRD.The results showed that after cross-linking and etherification,the crystalline region of CCMS was destroyed,and a large number of carboxyl groups were introduced on macromolecular chains.The macroscopic performance was the increase of particle size,the increase of surface roughness and the appearance of many groove marks on the surface.The influence of substitution degree on the physical and chemical properties of CCMS was analyzed by measuring the solubility,expansion and transparency of CCMS with different substitution degree.The test results showed that the carboxyl content in the starch increased with the increase of CCMS substitution degree,so the solubility and expansion force increased,and the transmittance increased.The adsorption and regeneration properties of CCMS to methylene blue were investigated by adsorption and regeneration experiments of CCMS to cationic dye(MB).The results showed that the adsorption of CCMS to MB was basically balanced about 20min.The substitution degree had significant influence on adsorbability of CCMS,and the crosslinking degree had little influence on its adsorption.At the same crosslinking degree,the adsorbability of CCMS increased with the increase of substitution degree.When the substitution degree was the same,the degree of crosslinking increased,and the adsorption amount of CCMS increased slightly.The regenerative of CCMS to MB was not ideal.Through the adsorption and regeneration experiments to Zn(?)and Co(?),the adsorption and regeneration properties of different adsorbents on metal ions were compared.The experimental results showed that the adsorption of CCMS on Zn(?)and Co(?)was basically balanced by 30min.With the increase of substitution degree,the adsorption capacity of CCMS on Zn(?)and Co(?)increased first and then decreased slowly.The adsorption performance of CCMS on heavy metal ions was higher than that of zeolite,activated carbon and 110 resin.CCMS had a certain cycle regeneration on Zn(?)and Co(?),but less than 110 resin.Crosslinking help to improve the recycling performance of CCMS on dyes and metal ions.