A novel eco-friendly fabricated keratin/nanosilica–carrageenan composite from rice straw and Periostracum serpentis for highly efficient Hg2+ removal in static and dynamic systems

Mercuric ions (Hg 2+ ) rank among the most poisonous metal ions, with their danger increasing significantly when transformed into methylmercury. A set of systematically designed static and dynamic trials was conducted to evaluate the ability of nanosilica/carrageenan (SC), keratin/carrageenan (KrC), and keratin/nanosilica-carrageenan (KrSC) composites to adsorb Hg 2+ ions from aqueous environments. KrSC porosity framework has been validated by various physicochemical techniques, featuring a pH PZC (4.1), specific surface area (239.9 m 2 /g), and a pore radius (2.4 nm), illustrating its impressive adsorption capability. Under specific batch conditions (25 °C, pH 4, and 2 g/L dose, 25 min), KrSC attained the greatest static adsorption capacity of 452.02 mg/g. Thermodynamic findings verified that Hg 2+ ions adsorb spontaneously by means of an exothermic mechanism. Over seven cycles, SC, KrC, and KrSC exhibited minimal performance declines (5.3%, 4.3%, and 2.8% respectively), implying strong reusability along with structural stability. Dynamic adsorption trials proved KrSC's highest capacity of 430.20 mg/g under specific conditions (flow rate = 8 mL/min, bed height = 2 cm, influent Hg 2+ concentration = 100 mg/L). Mercuric ions adsorption on KrSC in column trials was well-predicted by the Yoon-Nelson and Thomas models. Overall, KrSC exhibited impressive efficiency in capturing Hg 2+ ions, positioning it as a promising solution for detoxifying polluted water.