Magnetic carrageenan gum-grafted-polyacrylamide nanocomposite for uptake of cationic dyes from the aquatic systems

Using an ex-situ growth approach, this research fabricated k Carrageenan/Polyacrylamide@magnetite nanocomposites (NCs), (k-Car/PAM@Magnetite NCs). The k-Carrageenan (k-Car) backbone was modified through graft polymerization of acrylamide (PAm) via radical polymerization using ammonium persulfate (APS) as the initiator. N'-N' methylenebisacrylamide (MBAA) was used as the cross-linking agent, and magnetic nanoparticles (MNPs) were incorporated to impart magnetic properties. The successful synthesis of the k-Car/PAM@Magnetite NCs was confirmed through various analyses, including FT-IR, FESEM, EDS, XRD, VSM, BET, TGA, and Zeta. The adsorption effectiveness of the NCs for removing methylene blue (MB) and rhodamine B (RhB) from wastewater was evaluated by optimizing experimental parameters such as pH, adsorbent dosage, agitation time, and initial dye concentration. The NCs demonstrated a maximum adsorption capacity according to the Langmuir Isotherm (Q_max) of 204.082 mg. g⁻¹ for MB and 200 mg.g⁻¹ for RhB using 0.004 g of NCs.The adsorption data fit the Freundlich non-linear isotherm model well, and the kinetic data followed a pseudo-second-order (PSO) model. It is evident from the thermodynamic parameters that adsorption is an endothermic process that is spontaneous and favourable. The k-Car/PAM@Magnetite NCs also exhibited excellent regeneration capabilities, maintaining high adsorption efficiency after three consecutive adsorption-desorption cycles.