Study on the adsorption performance of carbon-magnetic modified sepiolite nanocomposite for Sb(V), Cd(II), Pb(II), and Zn(II): Optimal conditions, mechanisms, and practical applications in mining areas

Abstract

A carbon-magnetic modified sepiolite nanocomposite (γ-Fe₂O₃/SiO₂-Mg(OH)₂@BC) was synthesized using a hydrothermal method, consisting of γ-Fe₂O₃, activated sludge biochar (BC), and alkali-modified sepiolite. Its ability to remove heavy metals such as Sb(V), Pb(II), Cd(II), and Zn(II) was investigated through adsorption experiments. Using response surface optimization, the optimal adsorption conditions were determined: adsorption time = 3.78 h, pH = 2.63, initial concentration = 15.78 mg/L, temperature = 35.14°C, and adsorbent dosage = 100.71 mg. Characterization results revealed that the main adsorption mechanisms included complexation, π-π interactions, and electrostatic attraction. Kinetic and isotherm model analyses indicated that the adsorption process of γ-Fe₂O₃/SiO₂-Mg(OH)₂@BC adhered to the pseudo-second-order kinetic model and the Freundlich isotherm model, primarily involving multilayer chemical adsorption. The application of this composite material in complex aquatic environments in antimony mining areas demonstrated promising practical results, as well as excellent regeneration performance. This study provides technical and theoretical support for the treatment of complex heavy metal wastewater in antimony mining areas and lays a foundation for the development of novel carbon-magnetic modified nanocomposite adsorbents.