Effectiveness comparison of octyltrimethoxysilane and hexadecyltrimethoxysilane functionalized on natural silica-coated magnetic materials for ciprofloxacin and chloramphenicol adsorption

Abstract

This article reports the synthesis of natural magnetic silica-coated material (NMM@SiO₂) functionalized with hydrophobic properties of octyltrimethoxysilane (OTMS) and hexadecyltrimethoxysilane (HDTMS). Characterization to confirm the success of OTMS and HDTMS functionalization on NMM@SiO₂ was performed, and the adsorption properties of ciprofloxacin (CIP) and chloramphenicol (CAP) on the materials were compared. The optimal conditions for CIP and CAP adsorption on both adsorbents were at pH 6, a contact time of 60 min for CIP and 90 min for CAP, and an initial concentration of 250 mg L⁻¹. The OTMS-functionalized adsorbent demonstrated a higher adsorption capacity than HDTMS-one, with capacities of 87.83 mg g⁻¹ for CIP and 56.44 mg g⁻¹ for CAP. The adsorption kinetics followed a pseudo-second-order model, and the adsorption isotherms were consistent with the Freundlich model. Thermodynamic parameters indicated a negative enthalpy change (ΔH), suggesting an exothermic reaction, a negative Gibbs free energy (ΔG), indicating spontaneity, and a positive entropy change (ΔS), suggesting increased randomness. The successful adsorption of CIP and CAP, achieved through introducing hydrophobic groups, promises alternative materials for CIP and CAP removal from water waste.