MIL-88A grown in-situ on graphitic carbon nitride (g-C3N4) as a novel sorbent: Synthesis, characterization, and high-performance of tetracycline removal and mechanism

The extensive and accumulative use of tetracycline (TC) in the environment has become a serious problem. In this study, MIL-88A/g-C3N4 micro-nano particles were successfully prepared through a simple, low-cost, one-step hydrothermal method for TC adsorption in water. At a pH of 7.0, the maximum adsorption capacity (154.51 mg.g(-1)) of MIL-88A/g-C3N4 is reached at room temperature. Owing to its porous structure and large pore size (>2.06 nm) of MIL-88A/g-C3N4, TC can be adsorbed on both external and internal surfaces. Kinetic and thermodynamic studies have shown that the pseudo-second-order kinetic and the Langmuir-Freundlich model can be used to describe the adsorption process, which is a spontaneous endothermic process. The mechanism study reveals that the TC adsorption process by MIL-88A/g-C3N4 is mainly through electrostatic interaction and the ion exchange of -COOH and -NH2 groups on MIL-88A/g-C3N4 to TC. After simple pickling and water washing, MIL-88A/g-C3N4 can still reach 83.1% of the original adsorption capacity after five cycles, which proves that MIL-88A/g-C3N4 can be a promising adsorbent. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.