Nanocomposite magnetic hydrogel based on κ-carrageenan and acrylic acid for the removal of Cd(II), Co(II), Cu(II), and Ni(II); Efficient adsorption enhanced by activated carbon and magnetic nanoparticles.

A novel nanocomposite magnetic hydrogel was synthesized based on κ-carrageenan, acrylic acid, and activated carbon as an absorbent for removing heavy metal ions from aqueous solution. FT-IR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibration sample magnetometer (VSM) were employed to confirm the structure of the nanocomposite hydrogels. The effects of contact time, pH, particle size, temperature, and metal ion concentration on the metal ion adsorption were investigated. The selectivity of the nanocomposite hydrogel for metal ions adsorption was determined in the sequence of Ni > Cu > Co > Cd. Adsorption of the heavy metal ions from aqueous solution by the nanocomposite magnetic hydrogel was analyzed using Langmuir and Freundlich models. The adsorption capacity by the Langmuir model was found to be 156.25, 294.11, 454.54, and 285.71 mg/g for Ni, Co, Cd, and Cu, respectively. The reusability experiments indicated that about 60 % of initial adsorption can be achieved after 6 cycles.