Preparation and Heavy Metal Ion Adsorption Behavior of Novel Supermagnetic Nanocomposite of Hydrophilic Thiacalix[4]arene Self-doped Polyaniline: Conductivity, Isotherm, and Kinetic Study

摘要

In the present paper, supermagnetic nanocomposite of self-doped polyaniline (PANI) was prepared by attaching hydrophilic thiacalix[4]arene tetrasulfonate protonic acid dopant as pendent groups to PANI backbone and was further magnetized with Fe3O4 via the coprecipitation method. Thereafter, the structural, morphological, and magnetic properties of the nanocomposite were studied by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, vibrating sample magnetometer, and thermogravimetric analysis, and nanocomposites were further used for the removal of metal ions from aqueous solutions. The adsorption capacity of self-doped nanoadsorbent toward Cu(II), Cd(II), Co(II), and Cr(III) was investigated through batch adsorption techniques, and the extent of adsorption was measured as a function of pH, initial metal ion concentration, and contact time. It was found that the metal ion removal reached maximum at pH 8.0 and remained constant after 60 min. Experimental data were fitted to the Langmuir, Freundlich, Redlich-Peterson, and Temkin equation models with the maximum adsorption capacity calculated as 294, 285.71, 277.7, and 285.7 mgg(-1) from the Langmuir isotherm for Cu(II), Cd(II), Co(II), and Cr(III), respectively. The kinetic study was carried out through pseudo-first-order, pseudo-second-order, Elovich kinetic, and intraparticle diffusion models in which the related correlation coefficient for each kinetic model showed that the pseudo-second-order rate equation was better described by the adsorption process. The four-probe conductivity measurement technique revealed that metal ion adsorption resulted in a rather significant enhancement of conductivity with a 100 order of magnitude increment for the supermagnetic nanoadsorbent due to charge delocalization of absorbed metal ions.