| The heavy metal ions are paid more and more attention because of they are toxic, they can not be degraded and they are polluted to the environment. When researching how to treat with such waste water we come to an agreement that, the effective management should be efficient, convenient, and won't bring second contamination. To remove the heavy metal ions several chemical techniques are used widely nowadays, such as Chemistry subsidence, Ionic exchange and Adsorption etc. But for the complexed heavy metal ions, remove them thoroughly through traditional method is very difficult. So the research to develop economy effective heavy metal wastewater processing technology has the good application prospect.Chitosan is a biopolymer, which contains high contents of amino and hydroxyl active functional groups, can be conjugated with heavy metal ions. And because of its advantages such as nontoxic, no second contamination, easy to depolymerize, it is paid more and more attention by scientific researchers. AT the same time, chitosan has some disadvantages such as low molecular weight, high cost and so on, so we have to modify it.This article mainly including two parts: first, graft copolymerization of chitosan; second, remove of heavy metal ions with the polymer.We take chitosan, acrylamide, acrylic acid as raw material synthesize triplex graft copolymerization which containing -OH,-NH2 and–COOH. The grafted copolymers are characterized by scanning electro-microscope, infrared and thermogravimetry. It testified that the acrylamide, acrylic acid are successfully grafted onto the chitosan.From the grafting ratio,grafting efficiency we can draw the conclusion: The optimum technological condition to synthesize the copolymerization was as follows: the concentration of initiator is 6mmol/L,the ratio of acrylic acid in the monomer is 10%,m(chitosan):m(arcyamide+acrylic acid)=1:3,the temperature is 45oC,time of adding acrylic acid is 1.5 hours, after adding acrylic acid the reaction time is 1 hour, n(NaHSO3):n(K2S2O8) is 1:4. Study the adsorption of the graft copolymerization to Cu2+, Zn2+ and Pb2+. Various factors affect the adsorption including pH, adsorption time, temperature of the adsorption solution, the amount of the sorbent, the concentration of the heavy metal ion, etc. From ratio of heavy metal removement we drew conclusions as follows: 1 The experiment tells us that the same grafting copolymerization product show different adsorptive capacity to heavy mental ions, in which to copper 16# product show the best adsorption effect, to zinc 2# product show the best adsorption effect, to copper 6# product show the best adsorption effect.2 Value of the solution pH influence adsorption effect. For copper and zinc the best solution pH value are at 6, for lead the best solution pH value is at 5.3 Adsorbent dosage affects the remove of the heavy metal. The more adsorbent we use, the higher the removement ratio is. The more adsorbent we use, the lower the adsorption capacity is. When the heavy metal concentration is at about 10mg/L,the equilibrium adsorption capacity is about 25mg/g.When the heavy metal concentration is at about 50mg/L and 100mg/L, the equilibrium adsorption capacity of the graft compolymerization to zinc and lead is at about 40mg/g,to copper the equilibrium adsorption capacity is about 5mg/g.4 Adsorption dynamics indicated that, at the start period, the adsorption capacity increase quickly, approximately 30 minutes later the adsorb speed is slowing-down. And then will achieve the adsorption equilibrium gradually.5 The adsorption isothermal indicated that, the adsorption to the choosed three kinds of heavy metals all follow Langmuir adsorption characteristic.6 The temperature also influence adsorption effect, in the 12oC to 25oC scope, the adsorption capacity increases gradually. When the temperature elevates again, the adsorption capacity starts to reduce.7 The adsorption capacity of the graft copolymerization to the copper surpasses the zinc and lead obviously. |
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