Hydrophobic modification of naturally magnetic silica with methyltrimethoxysilane for enhanced adsorption of chloramphenicol and ciprofloxacin

This study presents a successful synthesis of natural magnetic silica (NMM@SiO2) materials modified with hydrophobic groups for the adsorption of two antibiotics, chloramphenicol (CAP) and ciprofloxacin (CIP). The NMM@SiO2 was prepared using natural magnetic material (NMM) isolated from iron sand, silica extracted from quart sand, and methyltrimethoxysilane (MTMS) as the hydrophobic precursor. The synthesized materials were characterized using various analytical techniques, including FTIR, XRD, VSM, TGA, TEM, and SEM-EDX-Mapping. Subsequently, the synthesized materials were used to adsorb antibiotics from an aqueous solution using a batch system, and the antibiotic concentration in the solution was measured with UV-VIS spectrophotometry. The characterization results confirmed the successful incorporation of MTMS onto NMM@SiO2. The adsorption studies indicated that the optimum pH for CAP and CIP adsorption were 5 and 6, respectively, with the optimum contact time being 120 min for CAP and 90 min for CIP, and the initial antibiotic concentrations of 200 mg L−1. The NMM@SiO2 (1.5 g) modified with 0.4 g (3.0 mmol) of MTMS to obtain NMM@SiO2/C1(3) exhibit the highest adsorption capacities for both antibiotics (58.46 mg g−1 for CAP and 106.81 mg g−1 for CIP). For both antibiotics tested, the kinetics and the adsorption isotherms followed pseudo-second-order and Freundlich models, respectively. The thermodynamic study indicated a negative ΔH (exothermic), positive ΔS (increase in randomness), and negative ΔG (spontaneous) for CAP and CIP. These results highlight the successful performance of this hydrophobic-based natural material adsorbent and demonstrate its potential as an effective adsorbent for antibiotic adsorption in aquatic environments.