The Synthesis Of β-cyclodextrin-based Copolyme And Its Flocculated Decolorization Performances

flocculants for color removal are meaningful for the wastewater treatments and environmental protections. As a derivative from starches, beta-cyclodextrin (β-CD) has many advantages, such as eco-friendly aspect, renewability, biodegradability and low cost. Therefore, the modified products fromβ-CD have more potential in the area of flocculated decolorization.In this paper, a polymerizable monomer (β-CD-MAH) was obtained by the esterification between maleic anhydride (MAH) andβ-CD. Thereafter, copolymers ofβ-CD-MAH-TMAEMC as new flocculants for decolorization were synthesized by means of free radical copolymerization betweenβ-CD-MAH and the cationic monomer, N-trimethylaminoethylmethacrylate chloride (TMAEMC). The chemical structure, morphology and thermal stability ofβ-CD-MAH-TMAEMC were characterized by means of FT-IR, 1H-NMR, SEM photos and TGA curves. Besides, the cationic degree (α) and intrinsic viscosity ([η]) ofβ-CD-MAH-TMAEMC were determined by the measurements of zetal potenl, conductivity and viscosity. As a representative of anionic dyes, the reactive brilliant blue KN-R was applied for the flocculation experiments. And the decolrization performances ofβ-CD-MAH-TMAEMC and the interactions betweenβ-CD-MAH-TMAEMC and the reactive brilliant blue KN-R were studied in detail.The experimental results show that the anticipative chemical structure ofβ-CD-MAH-TMAEMC was achieved. Andβ-CD-MAH-TMAEMC was thermal stable during the normal flocculation processes. An increase in the feed composition of TMAEMC was helpful for increasing the copolymer composition of cationic units (α) and the copolymer's intrinsic viscosity ([η]). The optimum conditions for synthesis ofβ-CD-MAH-TMAEMC were 6/4 of the weight proportion betweenβ-CD-MAH and TMAEMC, 0.5 % of initiator (APS/SBS, 1/1, mol/mol) relative to the monomer weight, 45 ?C of temperature and time of 5 h. For the given flocculant/dye solution system, many conditions including the flocculant concentration, the pH of dye solution, the temperature of dye solution and the stirring modes had effects on decolorization. Under the condition of pH 7, room temperature and 0 g/L of NaCl, the dye solution at the concentration of 100 mg/L would be mostly decolorized (the highest decolrization efficiency of 95.45%) with the stirring mode of 170 r/min×5 min + 60 r/min×10 min. Accordingly, the optimum dosage of flocculant was 220 mg/L. On the other hand, under the condition of pH 10, room temperature and 40 g/L of NaCl, the dye solution at the concentration of 100 mg/L would be mostly decolorized (the highest decolrization efficiency of 84.43%) with the stirring mode of 120 r/min×5 min + 40 r/min×5 min. Accordingly, the optimum dosage of flocculant was 40 mg/L.The main mechanism for flocculated decolorization when the synthesized copolymer ofβ-CD-MAH-TMAEMC was added into the dye solution of reactive brilliant blue KN-R was electrostatic adsorption. Aside, other interactions such as covalent bond, H-bond and polymer bridging also contributed to the flocculated decolrization. With increasing the cationic degree of copolymer, the highest decolorization efficiency was improved and the corresponded flocculant dosage was reduced. The linear relationship between the reciprocalαand the optimum flocculant dosage was found. The relative molecular mass ofβ-CD-MAH-TMAEMC had a small role on the decolorization efficiency, but it had an important role on the formed focs'particle sizes. Larger flocs would formed whenβ-CD-MAH-TMAEMC with higher molecular mass was used, inducing faster sedimentation.