Superadsorbent Ni–Co–S/SDS Nanocomposites for Ultrahigh Removal of Cationic, Anionic Organic Dyes and Toxic Metal Ions: Kinetics, Isotherm and Adsorption Mechanism

Novel adsorbent Ni–Co–S/SDS (nickel cobalt sulfide/sodium dodecyl sulfate) nanocomposites have been synthesized by a simple and eco-friendly approach using water as a solvent at low temperature. The prepared nanocomposites structure and morphology were studied by powder XRD, SEM, TEM, XPS, FT-IR, TGA, and also the surface area and surface charge of the adsorbents were measured by BET and ζ-potential. These nanocomposites showed an excellent adsorption property for both cationic {crystal violet (CV), rhodamine B (RhB), methylene blue (MB), Nile blue A (NB)}, anionic {methyl orange (MO) and Congo red (CR)} organic dyes and Cr(VI) metal ions. They exhibited maximum adsorption capacity 3598.23 mg g –1 for CR, 3284.08 mg g –1 for MO, 4417.79 mg g –1 for NB, 3598.23 mg g –1 for CV, 1451.64 mg g –1 for MB, 773.47 mg g –1 for RhB and 583.67 mg g –1 for Cr(VI) ions respectively, which are higher adsorption capacities than reported and exhibited an efficient adsorption property for both cationic and anionic dyes. Furthermore, nanocomposites showed adsorption efficiencies greater than 95% after regenerated and reused up to five times. Moreover, it followed pseudo-second-order kinetics and an isotherm best fit with the modified Zhu and Gu model. Based on the adsorption studies, FT-IR and ζ-potential measurements studies confirm that the hydrogen bonding and electrostatic interactions are the predominating factors for first step adsorption process and second step is hydrophobic interaction between adsorbates. Overall, remarkable adsorption capacity and reusability of Ni–Co–S/SDS nanocomposites elucidate the scope as an environmental remedy for industrial applications.