Comprehensive evaluation of antibiotic tetracycline and oxytetracycline removal by Fe-metal organic framework/biopolymer-clay hydrogel

Tetracycline (TC) and oxytetracycline (OTC) are antibiotic compounds increasingly detected in various water sources. In this study, Fe-metal organic framework incorporated biopolymer-clay hydrogels (CAMIL-MMT and CAMIL-SEP) were prepared to remove TC and OTC from water. The physicochemical properties of the as-prepared hydrogels were thoroughly characterized, and the effect of various operating parameters on the adsorption performance was systematically examined. The CAMIL-MMT hydrogel showed the maximum adsorption capacity for TC and OTC (24.59 and 26.14 mg/g, respectively) compared to the CAMIL-SEP and other forms of biopolymer hydrogel precursors. The effects of the contact time and initial concentration on TC and OTC adsorption by CAMIL-MMT and CAMIL-SEP hydrogels were well suited to the pseudo-second-order kinetics and Freundlich isotherm models. The adsorption performance of CAMIL-MMT and CAMIL-SEP hydrogels slightly decreased with an increase in solution pH, while it was not much influenced by the co-existing anions. The thermodynamic study indicated that the reactions for the uptake of TC and OTC were spontaneous and highly favorable. Moreover, the as-synthesized CAMIL-MMT and CAMIL-SEP hydrogels demonstrated strong potential for reuse in TC and OTC removal with high reusability and strong stability. The photocatalysis study revealed that residual TC and OTC after adsorption could be further degraded by CAMIL-MMT and CAMIL-SEP hydrogels under visible light irradiation. From the above-mentioned results, the as-synthesized CAMIL-MMT and CAMIL-SEP hydrogels are promising to be considered alternative materials for the adsorptive and photocatalytic removal of TC and OTC in practical application of water and wastewater treatment.