Nanogel and superparamagnetic nanocomposite based on sodium alginate for sorption of heavy metal ions

• Nanogel and superparamagnetic nanocomposite synthesized based on sodium alginate.
• Sorption of heavy metal ions by synthesized nanoadsorbents was investigated.
• Thermal stability of synthesized nanoadsorbents was investigated by TGA and DSC.
• The sodium alginate nanocomposite showed the characteristics of superparamagnetism.

Novel sodium alginate supported tetrasodium thiacalix[4]arene tetrasulfonate (TSTC[4]AS-s-SA) nanogel was prepared using sodium alginate nanoparticles. Then, superparamagnetic nanocomposite of sodium alginate (Fe3O4@TSTC[4]AS-s-SA) was fabricated from coprecipitation of sodium alginate supported tetrasodium thiacalix[4]arene tetrasulfonate and in situ generated Fe3O4 nanoparticles. Structural, morphological, surface, thermal and magnetic properties of the nanoadsorbents were studied by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM), respectively. Adsorptions of Cu(II), Cd(II), Pb(II), Co(II), Ni(II) and Cr(III) ions onto nanoadsorbents were studied in aqueous condition at pH = 7. The results indicated that incorporation of thiacalix[4]arene tetrasulfonate and Fe3O4 into sodium alginate nanoparticles increased the adsorption capacity of sodium alginate bioadsorbents, and led to the magnetic property. The TSTC[4]AS-s-SA nanogels consist of rod-like structure with an average diameter of 50 nm.