| The traditional wastewater-treatment method had a lot of defects both in the treatment and economic efficiency. As an adsorbent, Chitosan had a shortage of acid dissolution, texture strength and was really hard to forming, therefore, there would be some chemical modification to Chitosan processing. However, the modified Chitosan which harbored excellent adsorption of metal ions was hard to granulated, meanwhile, lower proportion and slower settlement from solution made it difficult in applications, and the preparation cost was really high; Sepiolite was a kind of layered silicate which could be applied in dealing with wastewater of dye or heavy metal ions in the basis of its structure characteristics, ion exchange and adsorption properties. It was a promising and cheap water treatment agent, yet there were difficult problems in secondary utilization, and it was likely to produce secondary pollution.For both advantages and disadvantages of Chitosan and Sepiolite in water treatment, in this paper, Chitosan-g-poly(acrylic acid)/sepiolite composites were prepared by aqueous solution polymerization using Chitosan, AA, sepiolite as raw materials while APS was added as an initiator and N, N'-methylenebis-acrylamide was used as a crosslinker. The synthetic composites had a high water absorption rate as well as a high Pb(Ⅱ), Hg(Ⅱ) adsorption performance. The joining of sepiolite made the adsorption rate, gel strength ,acid and salt resistance of the resin improved a lot, meanwhile , it had totally reduced the cost of preparation.The main research contents and acquisition results in this paper was listed below:1. Used water absorbency rate and salt-water absorbency rate for reference, chose uniform design as a experimental method, the CTS-g-PAA/Sep composite was synthetized under the optimization condition, Test results showed that:the water absorbency rate reached 423.7g/g, and salt-water absorbency rate was 92.6 g/g. Compared to the comparison sample CTS-g-PAA, the salt resistance of the composites had greatly increased 2. XRF results showed that modified sepiolite had a less quantity of calcium impurities; FT-IR analysis showed that the AA, Chitosan and Sepiolite participated in the grafted polymerization reaction; XRD analysis showed that the Sepiolite layered structure had been opened up; SEM showed that the CTS-g-PAA/Sep composite contained abundant pores and was fairly to increase adsorption capacity; Thermal analysis tests showed that the thermal stability of CTS-g-PAA/Sep was greatly enhanced compared with Chitosan, it maintained a stable structure below 300℃; BET results showed that the specific surface area of CTS-g-PAA/Sep reached 82.168 m~2/g which was helpful for increasing adsorption amount.3. The adsorption of Pb(Ⅱ),Hg(Ⅱ) by CTS-g-PAA/Sep had been researched. The experiment about different synthesis conditions, pH and temperature affecting of adsorption performance was discussed; Adsorption isotherm was drew, four kind of adsorption isotherm models were used to fit the adsorption process, the result showed that the saturated Pb(Ⅱ) adsorption capacity of the composites was up to 286.95 mg/g, and Hg(Ⅱ) adsorption capacity reached 371.89 mg/g which was significantly higher than other mineral materials; The adsorption dynamics experimental suggested that the Pb(Ⅱ) and Hg(Ⅱ) adsorption balance of CTS-g-PAA/Sep was about 50 min which was superior to Chitosan, level 2 equation model was used for the interpretation of the Pb(Ⅱ) adsorption process, at the same time, level 1 equation model was used for the interpretation of the Hg(Ⅱ) adsorption process.4. Repeat adsorption and take off experiments showed that CTS-g-PAA/Sep had a better regeneration properties than Sepiolite. |
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