Studies On Preparetion Of Cross-Linked Amino Konjac Glucomannan And Its Adsorption Properties Of Cu(Ⅱ), Ni(Ⅱ), Cr(Ⅵ)

Natural polysaccharides are with a large number of active groups such as-OH and-NH2, rich in raw materials and easy to get. Its own or that can be prepared by modification are of certain adsorption capacity. KGM is one of natural polysaccharides similar with starch, cellulose, chitosan. Acording to its own characteristics, it has been widely used in food and chemical industry. It is a natural material with environmental effects.In this paper, ACKGM were prepared to be used in adsorption Cu(Ⅱ), Ni(Ⅱ), Cr(Ⅵ). The structure and surface morphology of each product were characterized using Infrared Spectrum, Scanning Electron Microscopy and X-diffraction.(1) The optimum conditions of the crosslinking, etherification, amination reaction were discussed. The settlement plot of CKGM was 53.5, that was prepared while the solvent concentration of isopropyl alcohol was 15%, the molar ratio of NaOH and konjac glucomannan was 1:2, the molar ratio of epichlorohydrin and konjac glucomannan was 1:1, the reaction temperature was 50℃, the reaction time was 6h; The CHKGM was prepared by CKGM and epichlorohydrin while the water rate of CKGM was 11～13%, the mol catalyst ratio of HClO4 and CKGM was 0.03:1, the reaction temperature was 80℃, the reaction time was 8h. The highest content of Cl and DSCl of CHKGM was 0.0503,0.2642 respectively. Cross-linked amino konjac glucomannan were prepared with Konjac glucomannan and amine agent which was ethylenediamine, diethylenetriamine, triethylenetetramine when the molar ratio dose of-NH2 of amine agent and CHKGM was 4:1, the reaction temperature was 60℃, the reaction time was 4h, the DSN of EACKGM,DACKGM,TACKGM was 0.0522,0.07695,0.1228 respectively.(2) EACKGM, DACKGM and TACKGM were applied to adsorption of Cu(Ⅱ), Ni (Ⅱ), Cr (Ⅵ), the order of the adsorption capacity was TACKGM> DACKGM> EACKGM. The affects on adsorption properties of TACKGM of the pH value of solution, dosage of TACKGM, the initial concentration of solution, adsorption time and adsorption temperature were discussed. The adsorption properties of Cu(Ⅱ), Ni(Ⅱ), Cr(Ⅵ) on TACKGM were 18.38mg·g-1,5.173 mg·g-1,21.51mg·g-1 respectively at 30℃.(3) The thermodynamics and dynamics of adsorption Cu(Ⅱ), Ni (Ⅱ), Cr (Ⅵ) on TACKGM were discussed, which provided their theoretical basis for the development and applications of TACKGM. The isothermal adsorption process of adsorption Cu(Ⅱ) and Ni(Ⅱ) could be described with the Langmuir model and the isothermal adsorption process of adsorption Cr (VI) could be described with Langmuir model or Freundlish model. By fitting the thermodynamic parameters of isotherm data, the adsorption process of adsorption Cu(Ⅱ), Ni(Ⅱ) was spontaneous, endothermic, entropy increasing while he adsorption process of adsorption Cr(Ⅵ) was spontaneous, exothermic and entropy decreasing; Compared with the pseudo-first order kinetic model, the pseudo second order kinetics model was more suitable for describing the process of adsorption Cu(Ⅱ), Ni(Ⅱ) Cr (Ⅵ) on TACKGM. The adsorption capacities obtained by fitting pseudo second order kinetics model were similar with the adsorption capacities obtained by experiments.(4) Desorption Cu(Ⅱ), Ni(Ⅱ)of TACKGM by 1% hydrochloric acid, adsorbent recycling rate was high, the adsorption capacities of regenerated TACKGM could reach the 80% of the original absorption capacities through desorpting for three times; Desorption Cr(VI) of TACKGM by 1% NaOH,1% hydrochloric acid and 3% ammonia solution respectively, it was difficult to resolve Cr (VI) from the adsorbent, desoption capacity was less than 5%.(5) Combination of the IR spectrum, the adsorption thermodynamics and kinetics, it suggested that the adsorption mechanismof Cu(Ⅱ), Ni(Ⅱ), Cr(Ⅵ) adsorption on TACKGM. The adsorption mechanisms of Cu(Ⅱ), Ni(Ⅱ) on TACKGMwere shown as: the adsorption was better in line with single-molecule layer adsorption, that concluded chemical adsorption and intergranular diffusion; The force between Cr(Ⅵ) and TACKGM were minly the electrostatic attraction, while there was intergranular diffusion; The adsorption mechanisms of Cu(Ⅱ), Ni(Ⅱ), Cr(Ⅵ) on TACKGM were the interaction results of physical adsorption and chemical adsorption.The adsorbent named ACKGM will be an friendly and environmentally material, which will be used in solid phase extraction and enrichment of Cu (Ⅱ), Ni (Ⅱ), Cr (Ⅵ).