| In this paper, the crosslinked amino starch(TTACS) was synthesized by corn starch through three-steps with cross-linking, oxidizing and aminating. And the optimal synthesis condition of oxidized starch and amino-starch were also determined. At the same time, adsorption of Ni(Ⅱ), Cr(Ⅵ) by TTACS was studied at factors of pH, the adsorbent dosage, initial concentration of Ni(Ⅱ), Cr(Ⅵ) in solutions, adsorption time; adsorption isotherm, adsorption kinetics, adsorption regeneration and dsorption mechanism were also explored. Moreover, the adsorption of dye K-2BP was researched.1. The oxidized starch was prepared by H2O2 through two methods with containing catalyst and without catalyst. Using acid-catalyzed amine method measure the content of carbonyl, the content of carboxyl was determined by starch thermal paste titration. The synthesis conditions of with catalyst oxidation reaction were as follows:reaction time 3h, reaction temperature 45℃, pH5,2mLH2O2 and the mount of catalyst was 0.02%, the carbonyl content of oxidized starch obtained in this condition was 1.42%; the synthesis conditions of without oxidation reaction were as follows:the water content 15%, pH6, 2mLH2O2, reaction temperature 35℃and reaction time 3h under this condition, the carbonyl content of oxidized starch is 2.75%.2. By comparison with nitrogen content of amino starch which prepared respectively by with catalyst and without catalyst oxidation starch, using the higher nitrigen content with catalyst oxidized starch as raw mateiral to discuss the preparation of amino starch conditions. The molar ratio of ethylenediamine and OCS is 2:1, reaction temperature 45℃, ethylenediamine concentration 1.0mol/L, pH7, reaction time 3h and ethanol as a solvent, respectively using ethylenediamine, diethylenetriamine, triehylenetramine as aminating agent prepared the amino starch(EDACS, TDACS, TTACS), which the nitrogen content was 1.37%,1.69%,2.36%, respectively.3. We study the factors of pH, TTACS dosage, ions initial concentration and adsorption time of the influence of its adsorption behavior. In addition, we also compare with the adsorption of Ni(Ⅱ), Cr(VI) by different modified starchs, which indicated that the adsorption ability order for Cr(VI) was TMACS>AS>TTACS>DTACS>EDACS >OCS; the adsorption ability order for Ni(Ⅱ) was TMACS>TTACS>EDACS> DTACS>OCS.4. From the adsorption dynamic of amino starch(TTACS) for Ni(Ⅱ), Cr(Ⅵ), we know that amino starch(TTACS) adsorption for Ni(Ⅱ), Cr(Ⅵ) was more fit to second-order kinetics model. Through the research of adsorption isotherm for Ni(Ⅱ), Cr(Ⅵ), while the adsorption isotherm of amino starch(TTACS) for Ni(Ⅱ), Cr(Ⅵ) was likely to be Langmuir isotherm model. During the thermodynamic calculation, we got the preliminary judgment that TTACS adsorption for Ni(Ⅱ) is a spontaneous, non-flammable and entropy increase process; while adsorption for Cr(Ⅵ) is a spontaneous, exothermic and entropy decrease process. The adsorption regeneration showed that its adsorption for Ni (Ⅱ) can be reused, while for Cr (Ⅵ) poor recycled.5. According to the IR and XRD spectrums of adsorbent adsorption before and after, adsorption isotherm, adsorption dynamic and regeneration adsorption, we could initially presume that the TTACS adsorption for Ni(Ⅱ), Cr(Ⅵ) were mainly physical adsorption along with chemical adsorption.6. Cross-linked amino starch(TTACS) can adsorb the dye K-2BP, and the adsorption may be based on electrostatic interactions and sequestration cooperation, it has maximum absorption capacity at pH9. Moreover, in the presence of low concentration metal ions, the adsorption capacity of K-2BP decreased, this belong to the synergy of metal ions. |
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