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 SBA15 (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.