ABSTRACT: In the present p aper, supermagnetic n anocomposite of self-doped polyaniline ( PANI) w as prepared by attaching hydrophilic thiacalix[4]arene tetrasulfonate protonic acid dopant as pendent groups to PANI backbone and was further m agnetized with Fe3 O4 via the coprecipitation m ethod. Thereafter, the stru ctural, m orphological, and magnetic properties of the nanocomposite were studied b y F ourier transform i nfrared, X -ray diff raction, scanning electron microscopy, t ransmission electron microscopy, atomic force m icroscopy, vibrating sample m agnetometer, and thermogravimetric analysis, and nanocomposites were further u sed for the removal of m etal ions from aqueous solutions. The adsorption capacity of self-doped nanoadsorbent t oward Cu(II), Cd(II), Co(II), and Cr(III) was investigated through batch adsorption techniques, and the extent of adsorption was m easured as a function of pH, i nitial metal i on concentration, and contact time. I t w as found that the metal i on removal reached maximum at p H 8.0 and remained constant after 60 m in. E xperimental d ata were fi tted t o the Langmuir, Freundlich, Redlich–Peterson, and Temkin equation models with the maximum adsorption capacity calculated as 294, 285.71, 277.7, and 285.7 mg g −1 from the Langmuir isotherm for Cu(II), Cd(II), Co(II), and Cr(III), respectively. T he kinetic study was carried out through pseudo–first-ord er, p seudo–second-ord er, Elovich kinetic, and intraparticle d iffusion m odels in which the related correlation coefficient for each kinetic model showed that the pseudo–second-order r ate equation w as better d escribed b y the adsorption process. The f our-probe conductivity m easurement technique revealed that m etal ion adsorption resulted in a r ather significant enhancement of conductivity with a 100 order of ,magnitude increment for the supermagnetic n anoadsorbent due t o charge d elocalization of absorbed m etal ions.
