Tetracycline removal from aqueous solutions using zeolitic imidazolate frameworks with different morphologies: A mathematical modeling

Concerns about environment pollution by antibiotics raised notable attention. In this context, metal-organic frameworks (MOFs) can produce an excellent platform for toxicant removal from water environments. In the current investigation, eight MOFs (ZIF-67-NO3, ZIF-67-CI, ZIF-67-SO4, ZIF-67-OAC, ZIF-8-Octahedron, ZIF-8-Leaf, ZIF-8-Cuboid, and ZIF-8-Cube) with different chemical and textural compositions were synthesized, and furthermore, the adsorption of Tetracycline (TC) by them was evaluated. Also, the key experimental conditions were modeled using response surface methodology (RSM). Among the prepared MOFs, the highest tendency for TC removal was nominated to ZIF-67- Acetate (ZIF-67-OAC). By model optimization approach, the optimum system conditions as contact time, adsorbent dosage, pH and adsorbed antibiotic concentration were reported as 26.8 min, 0.63 a, 5.9, and 74.6 mg/L, respectively. The proposed equilibrium model showed that the TC accumulated on ZIF-67-OAC surface is reversible in multilayer with the highest monolayer capacity of 446.9 mg/g. Furthermore, based on separation factor (K-L), TC adsorption is more favorable at a higher amount of MOFs added. Moreover, according to the fitted kinetic model, the process was controlled by chemisorption. ZIF-67-OAC shows excellent structural stability during mechanical agitation in an aqueous environment, and the TC removal capacities of regenerated adsorbent did not change considerably at the end of cycle 4 compared to the first cycle. Considering the findings among the examined MOFs, the ZIF-67-OAC can be approached as a promising adsorbent for the removal of antibiotics from aqueous environments. (C) 2018 Elsevier Ltd. All rights reserved.