| With the rapid development of pringting and dyeing industry in our country, more and more printing and dyeing wasterwater is discharging into environmental water,which has seriously polluted ecological environment. Therefore, the study about dye wastewater treatment method and technology has become the focus of attention. By virtue of its outstanding advantages, such as simpler operation, higher treatment efficiency and faster rate, adsorption method has been playingd an important role in wastewater treatment. However, adsorption method also possesses some defects,including higher production cost. In addition, some adsorbents are difficult to be biologically degraded and easily initiate secondary pollution. So, in this present thesis,we selected chitosan and cellulose, which were the most abundant in nature, cheaper and biodegradable natural polymers, as base materials to prepare environmentfriendly, cheaper and efficientive dye-adsorbents. By modification of chitosan and cellulose with grafting polymerizations and composition with inorganic natural polymer bentonite, several new-style adsorbents were successfully prepared.This thesis consists of following four parts:Chapter 1. Advances of application investigations of the adsorption method in wastewater treatment were reviewed, in particular, applications of the natural polymer materials chitosan and cellulose in the preparation of dye adsorbents were introduced.Chapter 2. A new composite adsorbent PMAA-g-CTS/BT was synthesized using chitosan(CTS), bentonite(BT) and the functional monomer methyl acrylic acid(MAA)as raw materials through a grafting polymerization procedure and its structure and morphology were characterized by infrared spectroscopy(IR), scanning electron microscopy(SEM) and X-ray powder diffraction(XRD) and so on. And the adsorption performance of the composite adsorbent to cationic dyes Methylene blue(MB) and Malachite green(MG) were also studied and some factors on the adsorption coefficiency were discussed. The results indicated that the adsorbent could rapidly and highly effectively remove cationic dyes. The highest decolorization rates for MB and MG respectively reached 97.9% and 98.9% and saturated adsorption capacities respectively arrived at 330 mg.g-1and 109 mg.g-1, which were obviously better thanthose of the previously reported similar adsorbents. In addition, the adsorption kinetics and isotherms were also studied. It was found that the two sorption processes were better fitted by pseudo-second-order equation and the Langmuir equation. The thermodynamic study indicated that the adsorption processses were spontaneous endothermic reactionsChapter 3. To further improve the adsorption performance of chitosan based adsorption material, in this chapter, PAA-g-CTS/BT composite adsorbent was prepared with a similar method, only by changing the functional monomer as acrylic acid. As a result, the sorption performance of the prepared composite adsorbent for the cationic dyes Crystal violet(CV) was remarkablly improved. It was found that the saturated adsorption capacity of the composite adsorbent to CV reached 800 mg.g-1, 5.33 times higher than that of PMAA-g-CTS/BT, and that of Na OH neutralized PAANa-g-CTS/BT even reached 2100 mg.g-1, 14-folds higher than PMAA-g-CTS/BT. The possible mechanism was speculated.Chapter 4. A new intelligent hydrogel PAA-g-CMCNa/BT was prepared by supporting of carboxymethy cellulose grafted acrylic acid onto bentonite substrate characterized IR, XRD and SEM. Its swelling and deswelling switching behaviours in different temperatures, p H values and salt solutions also investigated in detail. The results indicated that the hydrogel possessed good p H-sensitivity and salt-sensitivity,which promised a potential application in drug diversity system. In addition, its adsorption behaviour to MB was studied,it was found that the hydrogel possessed a high adsorption capacity for the dye. When the initial concentration of MB was160 mg.g-1, the equilibrium adsorption amount reached 495.3mg.g-1. |
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