Synthesis of Reusable Cyclodextrin Polymers for Removal of Naphthol and Naphthylamine from Water

As one group of important naphthalene derivatives, naphthol and naphthylamine, are diffusely employed as dye intermediates. The presence of naphthol and naphthylamine in water systems may pose risks to the environment and public health due to their carcinogenicity. In this study, four mesoporous polymers prepared by β-cyclodextrin derivatives and tetrafluoroterephthalonitrile were obtained, and applied to deal with 1-naphthylamine, 2-naphthylamine, 1-naphthol, and 2-naphthol from water. The impact of adsorption time, initial concentration of naphthol and naphthylamine, and temperature on the adsorption efficiency of the four polymers were explored separately. The four polymers present fast adsorption kinetics towards naphthol and naphthylamine, attaining 93%~100% of adsorption equilibrium uptake for 1-naphthol, 1-naphthylamine, 2-naphthylamine in 15 min, and 87%~90% of equilibrium uptake for 2-naphthol in 15 min. The kinetics could be depicted well by the pseudo-second-order kinetic model. The adsorption isotherms of the four polymers towards naphthol and naphthylamine accord with Redlich-Peterson or Sips model. The adsorption ratio increases fast with reducing the initial concentration of naphthol and naphthylamine, which suggest that these polymers are applicable to removing low concentration of naphthol and naphthylamine from water. The adsorption ratio of naphthol and naphthylamine in 5 mg/L, can achieve over 95% in 25 o C. In addition, the four polymers can be effortlessly recovered by a gentle and simple washing procedure with little reduction in performance. The adsorption performance of the four polymers towards the four naphthalene derivatives can be improved by increasing the adsorption temperature. In conclusion, the prepared β-cyclodextrin polymers exhibit rapid water treatment in removing the four low-concentration naphthalene derivatives with convenient regeneration and good reusability.