Preparation Of New Starch Chelating Agent And Its Adsorption On Cd (Ⅱ)

Starch glycidyl methacrylete (GMA)-grafted copolymers (St-g-GMA) were synthesized by using the thermal treatment polymerization method, in which corn starch and GMA were introduced as raw materials and potassium persulfat as initiator. Subsequently, St-g-GMA was modified by Glycine (Gly),5-aminosalicylic acid (5-ASA) and Glycine and 5-aminosalicylic acid (Gly/ASA) into Glycine-modified starch (St-g-GMA-Gly), aminosalicylic acid-modified starch (St-g-GMA-AS A) and Glycine and 5-aminosalicylic-modified starch (St-g-GMA-Gly/ASA), respectively. The main contents are as follows:1, The optimal technology of starch-grafted copolymerization and functional modification was studied in the experiment:The optimum reaction condition was v(GMA):m (starch)=1.5,m (potassium persulfate):m (starch)=3%, reaction temperature:333 K, reaction time:1.5h. Under this condition, grafting percentage, grafting efficiency and epoxy value could reach 95%,94% and 4.3 mmoL/g,respectively.Meanwhile,the impact of the material ratio, reaction time and temperature on the nitrogen content of St-g-GMA-Gly and the adsorption capacity of Cd (â…¡) were studied as well. The optimum reaction condition for St-g-GMA-Gly was: m (St-g-GMA):m (Gly)= 1:2, reaction time:15 h, and reaction temperature:343 K. The results of Elemental Analyzer and Atomic Absorption Spectrometer characterization showed that the nitrogen content and adsorption capacity of St-g-GMA-Gly were 3.8% and 78 mg/g, respectively. The optimum reaction condition for St-g-GMA-ASA was:m (St-g-GMA):m (ASA)=1:3,reaction time:18 h, reaction temperature:363 K, respectively. Analysis of FT-IR, SEM and Elemental Analyzer confirmed the successful grafting and modification process. The nitrogen content and adsorption capacity of St-g-GMA-ASA were 3.0% and 52 mg/g, respectively.2, Static adsorption experiments were carried out to study the adsorption kinetics and isothermal adsorption behavior for Cd(â…¡) in aqueous solution of the modified St-g-GMAs (St-g-GMA-Gly, St-g-GMA-ASA and St-g-GMA-Gly/ASA). The effects of pH, adsorption time, initial concentration and adsorption temperature of were discussed.he results showed that the adsorption process for Cd(â…¡) of the three modified St-g-GMAs were all in accordance with the second-order kinetic model and the adsorption isotherm was in better agreement with the Freundlich model than the Langmuir model. The effects of pH and initial concentration of Cd(â…¡) in aqueous solution greatly influenced the adsorption behavior, and the adsorption process was more easier at room temperature. With the increase of the content of modifier, the adsorption capacity for Cd(â…¡) of St-g-GMA-Gly and St-g-GMA-ASA increased. St-g-GMA-ASA exhibited a better adsorption effect on Cd(â…¡) When similar modifier content was uesd. Under the same condition, St-g-GMA-Gly and St-g-GMA-ASA on Cd(II) had higher equilibrium adsorption capacity, which were 130 mg/g and 149 mg/g, respectively.3, St-g-GMA-Gly and St-g-GMA-ASA prepared under the optimal condition had larger adsorption capacity. On basis of this, St-g-GMA was modified by the blend of glycine and 5-aminosalicylic acid, obtaining a modified product (St-g-GMA-Gly/ASA), which showed a lower adsorption capacity for Cd(II).