One-pot synthesis of Al-containing mesoporous silicas in a mildly acidic condition for efficient tetracycline adsorption

Tetracycline (TC), one of the widely used antibiotics in wastewater, has caused serious interferences in human health and ecological balance. Herein, a series of Al-containing mesoporous silicas (Al–SiO₂) were direct synthesized from mildly acidic solutions in which the acidity was self-generated by the AlCl₃ precursor. Structure characterizations disclose that Al–SiO₂ has both of long-range well-ordered and short-range ordered mesopores, large surface area (723–876 cm² g⁻¹), high pore volume (0.83–1.06 cm³ g⁻¹), and a small number of Al species (0.44–1.10 wt %) in it. In batch tests, all Al–SiO₂ materials present fast uptake and high removal efficiency (RE) towards high concentrated TC (C₀ = 80 mg L⁻¹, RE = 60–83%). Among them, the sample synthesized with rAl/Si = 1.0 displays the largest TC adsorption capacity (74.6 mg g⁻¹), which is much higher than conventional SBA-15 (13.2 mg g⁻¹), porous Al₂O₃ (27.8 mg g⁻¹) and industrial SiO₂ (3.4 mg g⁻¹). Meanwhile, the Al–SiO₂ possesses favorable removal efficiency in neutral pH range (pH = 5.0–7.0, RE > 77%), quite good selectivity to tetracycline and quinolone antibiotics, excellent cycling stability in the removal of TC (RE = 74% after six cycles). This study provides a simple and facile method for the synthesis of heteroatom-containing mesoporous adsorbents for the removal of antibiotics in wastewater.