Preparation and heavy metal ion adsorption behavior of novel supermagnetic nanocomposite based on thiacalix[4]arene and polyaniline: Conductivity, isotherm and kinetic study

• We successfully synthesized a novel core–shell nano adsorbent of Fe3O4–polyaniline/modified thiacalix[4]arene via in-situ precipitation.
• Fine characterization was accompanied by accurate spectral characterization and morphological study.
• The sorption study was investigated through various well known isotherm and kinetic models.
• The conductivity measurements were implied after heavy metal sorption to confirm its super conductivity.

Supermagnetic nanocomposite of polyaniline thiacalix[4]arene (Fe3O4@PANI-AmAzoTCA[4]) was prepared by coprecipitation of aniline-diaminoazo thiacalix[4]arene copolymer (PANI-AmAzoTCA[4]) and in-situ generated Fe3O4 nanoparticles. Structural, morphological and magnetic properties of the nanocomposite was studied by nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Atomic force microscopy (AFM) and vibrating sample magnetometer (VSM), and further used for the removal of metal ions from aqueous solutions. The influence of pH, contact time and initial metal ion concentration on the adsorption efficiency was investigated. The heavy metal ion adsorption mechanism of the supermagnetic adsorbent was clarified through adsorption capacity investigation from the isotherm and kinetic point of view. The related correlation coefficient for each isotherm-model showed that the equilibrium adsorption behavior of Cd(II) ion can be applied to Langmuir model with the maximum adsorption capacity of 285.7 mg g−1 and for Cu(II), Co(II) and Cr(III) ions to Temkin model with the equal maximum adsorption capacity of 312.5 mg g−1. The experimental data of all metal ions fitted well with the pseudo-second-order rate equation. The four-probe technique revealed that metal ion adsorption resulted in a rather significant enhancement of conductivity with a 100 order of magnitude for the supermagnetic nanoadsorbent due to charge delocalization of absorbed metal ions.

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