Cetyltrimethylammonium bromide functionalized silica nanoparticles (MSN) synthesis using a combined sol-gel and adsorption steps with enhanced adsorption performance of oxytetracycline in aqueous solution

Abstract

The cetyltrimethylammonium bromide (CTAB)-functionalized silica nanoparticles (MSN) were prepared using a combined sol-gel and adsorption steps. The nitrogen adsorption-desorption surface analysis shows the MSN has a lower surface area than the unmodified (or free) silica nanoparticles (FSN). The energy dispersive X-ray (EDX) and Fourier transform infrared (FTIR) analysis confirmed the presence of CTAB in MSN with maximum CTAB coverage of (0.74 ± 0.04) mmol/g. The maximum adsorption capacity of oxytetracycline (OTC) onto MSN performed in the batch adsorption process, Qe.max is 449.89 µmol g⁻¹, which is higher than FSN (57.06 µmol g⁻¹). The adsorption depends on pH value, OTC concentration, temperature, and contact time. The thermodynamic parameters indicate the process as exothermic in nature and spontaneous. The isotherm data fits well with the Redlich-Peterson model, while the pseudo-second order (PSO) kinetic model is found to be suitable to describe the kinetic data with the film diffusion as the rate-limiting step. The electrostatic, hydrogen bonding and hydrophobic interactions are mainly responsible for the OTC adsorption onto the synthesized adsorbents. The reusability studies found that the adsorbent could be recycled without drastic adsorption capacity reduction. The successful decoration of the CTAB onto the surface of the silica nanoparticles provides an effective method in the development of promising adsorbents for antibiotic removal from wastewater.