Design of a magnetically retrievable pectin-embedded MXene-Santa Barbara amorphous-15 network for high-performance removal of two β-lactam antibiotics from aqueous media

Antibiotic residues in aqueous media motivate the development of adsorbents that combine accessible adsorption sites with practical recovery. In this study, a magnetically retrievable hybrid nanoadsorbent (HNA) was prepared by integrating a pectin/polyacrylamide (Pec/PAAm) matrix with Ti3C2 MXene (MX), Santa Barbara Amorphous-15 (SBA-15), and SnFe2O4 magnetic nanoparticles (SFO MNPs). The material was characterized using spectroscopic, diffraction, thermal, microscopic, textural, magnetic, and electrokinetic analyses. The HNA exhibited a Brunauer-Emmett-Teller (BET) surface area of 132.52 m2 g-1, a total pore volume of 0.29 cm3 g-1, an average pore width of 8.85 nm, and a saturation magnetization of 0.71 emu g-1. Adsorption of amoxicillin (AMX) and cephalexin (CPX) was most favorable at pH 7 and 6, respectively, within the investigated pH range. At 298.15 K and an initial concentration of 140 mg L-1, the highest measured adsorption capacities within the investigated concentration range were 276.49 mg g-1 for AMX and 253.53 mg g-1 for CPX, using 0.004 g of HNA and selected contact times of 15 and 20 min, respectively. Equilibrium data were best described by the nonlinear Freundlich model, consistent with an energetically heterogeneous distribution of apparent adsorption affinities. Direct kinetic fitting identified the Weber-Morris intraparticle-diffusion (WM-ID) model as the closest descriptor for AMX, while WM-ID and pseudo-second-order (PSO) fits were closely comparable for CPX. Post-adsorption characterization showed that the principal diffraction and magnetic features remained detectable, while surface topography, N2-accessible texture, and zeta potential changed measurably. The HNA remained magnetically responsive and retained measurable adsorption performance through three regeneration/reuse cycles. A preliminary evaluation using Caspian Sea water spiked with known concentrations of AMX and CPX showed measurable adsorption in a more complex real-water matrix.