Synthesis Of Micro/Nano Structured Conducting Polymer/clay Composites And Their Application For Removal Of Cr(Ⅵ) In Aqoeous Solution

Due to the infeasibility of decomposition or destruction of heavy metal pollutants, permanent pollution will occur once heavy metal pollutants were discharged into the environment. At present, the pollution problem of heavy metal waste water becomes more and more serious in our country and many physical or chemical methods have also been applied to treat heavy metal wastewater. However, these methods are hard to at the same time satisfy the demands of a technique with all-around excellence such as high efficiency, low cost and no second contamination. In this paper, aniline and pyrrole were selected to composite with modified montmorillonite or sepiolite and conducting polymer/clay composites with micro/nano-structure were prepared by in situ polymerization. The structures of the nanocomposites were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy dispersive X-ray Spectroscopy(EDX), Fourier transform infrared spectroscopy(FT-IR) and X-ray diffraction(XRD). The adsorption performance of conducting polymer /clay nanocomposites for Cr( Ⅵ) ions in aqoeous solution was systematically studied. The main work and findings of this paper are as follows:(1) The montmorillonite was modified firstly by using a polymerizable polyhydroxy tertiary amine. Poly(2-acrylamido-2-methylpropanesulfonic acid) modified montmorillonite was prepared by a free radical graft copolymerization.Then, the flake-like polyaniline/montmorillonite nanocomposites were obtained by in situ chemical oxidation polymerization. The as-obtained nanocomposites were used for adsorption of Cr( Ⅵ) ions and exhibited excellent adsorption properties. The pseudo-second-order and Langmuir isothermal models can well describe the adsorption kinetics and adsorption isotherm, respectively. The maximum adsorption capacity of the polyaniline/montmorillonite nanocomposites for Cr(Ⅵ) was up to 167.78 mg/g at 25 ℃. The flake-like PANI/MMT adsorbent can be reused by regeneration.(2) Amphoteric polymer,(2-methacryloyloxyethyl) trimethyl ammonium chloride and methacrylate acid copolymer, was used to modify montmorillonite. The exfoliated polyaniline/montmorillonite nanocomposite and exfoliated polypyrrole/ montmorillonite nanocomposite were prepared by in situ chemical oxidation polymerization. Adsorption experiments were carried out to study the effects of formula, p H value, contact time, Cr( Ⅵ) concentration, adsorbent dose and temperature on the adsorption performance. The maximum adsorption capacity of Cr(Ⅵ) ions achieved 308.64 mg/g(polyaniline/montmorillonite) and 166.67 mg/g( polypyrrole/montmorillonite). The adsorption kinetics and adsorption isotherm followed the pseudo-second-order kinetic model and Langmuir isotherm, respectively. The adsorption process is endothermic, spontaneous. Polypyrrole/montmorillonite adsorbent can be reused for three adsorption-desorption cycles without significantly loss of its removal efficiency.(3) Polyaniline/sepiolite and polypyrrole/sepiolite nanofibers were prepared via in situ chemical oxidation polymerization by using the fibrous sepiolite as template. The effect of several parameters, namely formula, p H value, contact time, temperature, initial concentration of Cr(Ⅵ) and dose of adsorbent on the adsorption performance of Cr(Ⅵ) were studied in batch mode. The maximum adsorption capacity for Cr(Ⅵ) achieved 206.61 mg/g for polyaniline/sepiolit nanofibers and 302.11 mg/g for polypyrrole/sepiolite nanofibers. The adsorption kinetics and adsorption isotherm followed the pseudo-second-order kinetic model and Langmuir isotherm, respectively. And the adsorption processes were endothermic, spontaneous. The two kinds of nanofibers can be reused by regeneration.