Acta Chimica Sinica ›› 2012, Vol. 70 ›› Issue (21): 2226-2231.DOI: 10.6023/A12030054 Previous Articles     Next Articles



王芬, 吴敏, 秦艳涛, 苗春存, 周少红, 倪恨美, 孙岳明   

  1. 东南大学化学化工学院 南京 211189
  • 投稿日期:2012-03-25 发布日期:2012-09-11
  • 通讯作者: 吴敏
  • 基金资助:
    项目受国家自然科学基金(No. 51073035)和江苏省教育厅高校科研成果产业化推进项目(No. JHB2011-2)资助.

Flocculation Kinetics of TiO2-enzyme Microfloccules

Wang Fen, Wu Min, Qin Yantao, Miao Chuncun, Zhou Shaohong, Ni Henmei, Sun Yueming   

  1. School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189
  • Received:2012-03-25 Published:2012-09-11
  • Supported by:
    Project supported by the National Natural Science Foundation of China (No. 51073035), and Educational Commission of Jiangsu Province (No. JHB2011-2).

TiO2-enzyme microfloccules were prepared by using titanium dioxide nanoparticles as immobilizing carriers, three kinds of polyacrylamide (nonionic, cationic and anionic polyacrylamide) as flocculants and papain as a model of enzyme. The effects of pH values, dosage and types of polyacrylamide (PAM) on the flocculation and sedimentation behaviour of TiO2-enzyme microfloccules were investigated. The SEM, EDS and particle size analyzer were used to characterize the morphology of TiO2-enzyme microfloccules. The results showed that an effective flocculation was formed among TiO2, papain and different types of PAM flocculant by hydrogen bonding interactions, electrostatic attractions, adsorption bridging action, etc. It was noted that the settling rate of TiO2-enzyme microfloccules, turbidity of the supernatant, floc size and compactness of resulting floccules were highly dependent on the PAM dosage. For three kinds of PAM, similar trends of flocculation kinetics were observed, a general increase in settling rates were relevant to decrease in turbidity. Attributed to high settling rates, strong flocculation with big size and stable floc occurred with the function of optimum PAM concentrations. But the optimum dosages were different. When the concentration was in the range of 75 mg稬-1 to 175 mg稬-1, nonionic PAM (nPAM) displayed the best flocculant performance in all kinds of PAM with a rapid settling rate and large floc size. Moreover, under excessive dosage condition, breakup of floc then occurred. Flocculation kinetics of TiO2-enzyme microfloccules also could be effectively controlled by changing the pH value of reaction system. Compared nPAM with cationic PAM (cPAM), the microfloccules by using nPAM displayed a high stability and compactness in a wide range of pH values. The settling rate and floc size by using cPAM showed a strong dependence on pH values. It indicated that the immobilized enzyme size could be regulated by the PAM dosage and pH value according to the enzyme structure and properties. Such porous and flexible microstructure was expected to provide the free space as much as possible for the access of substrate molecules to enzyme.

Key words: flocculation kinetics, settling rate, particle size distribution, nano TiO2, morphology