Co-doped metal–organic framework MIL-125(Ti) derivate for efficient adsorption of tetracycline hydrochloride from water

Metal-organic framework (MOF) based materials have aroused much research interest owing to their unique structural features in the field of environmental purification. Herein, a MOF derivate of Co-MIL-300 was prepared by sintering the cobalt-modified MIL-125(Ti) (Co-MIL) precursor at 300 °C in an air atmosphere and used as adsorbent to remove tetracycline hydrochloride (TCH, a typical emergent pollutant) from water. The Co-MIL-300 adsorbent possesses a large specific surface area, the rich surface oxygen-containing groups, the benzene-ring structure with rich π-electrons and surface cobalt ions benefiting for TCH adsorption. The TCH adsorption on Co-MIL-300 satisfies the pseudo-second-order kinetic model and Langmuir mode well, and is found to be a spontaneous endothermic and monolayer chemical adsorption process based on covalent bonding (such as π-π conjugation interactions, hydrogen bonding, π-cation interactions, coordination bonding) adsorption mechanism. Co-MIL-300 reveals a much higher adsorption capacity than Co-MIL (2.3 times of the latter) with qmax = 321.5 mg⋅g−1 at 30 °C, and it also keeps a high adsorption capacity in a wide pH range (pH = 2–11). The coexisting CO32–, PO43-, Al3+ and Fe3+ ions can greatly inhibit TCH adsorption. Most of its adsorption capacity can be recovered in five cycles after regeneration, showing great application potential for antibiotics removal.