Adsorption of tetracycline using one-pot synthesis zirconium metal-organic framework (UiO-66) decorated hydroxyapatite

Abstract

Tetracycline (TC) is considered to be one of the commonly preferred antibiotics in the pharmaceutical industry. On the other hand, in order to eliminate the increasing environmental pollution associated with TC, the researchers are studying promising methods for its removal from water. In the present investigation, a novel zirconium metal–organic framework (UiO-66) decorated hydroxyapatite (HAp) composite adsorbent was synthesized by one-pot technique for the removal of TC from water. The proposed composites were prepared by proportioning different quantities by mass (10 %, 30 % and 50 %) of UiO-66 with HAp. The samples were characterized by various analyzes such as XRD, TGA, SEM, FT-IR and BET/N2. The adsorption process was conformed to the Langmuir isotherm model, which is a monolayer model. HAp and UiO-66@HAp composites were compared on the basis of maximum TC adsorption capacity (qmax) and the best qmax was obtained as 218.68 mg g−1 for 30UiO-66@HAp composite. Adsorption kinetics was optimized with linear pseudo second order and Elovich models, additionally the equilibrium time was determined as 300 min. Maximum adsorption was reached in the range of pH 4–8 while adsorption efficiency diminished below pH 4. Thermodynamic analysis reveals that TC adsorption is a spontaneous, favourable and endothermic process. The reusability of the 30UiO-66@HAp was perfect and the removal was 82.5 % even after 7 adsorption cycles. It also performed well with TC solutions prepared in different water matrices, with a clear reduction only with increasing HA concentration. It also showed a remarkable potential in the removal of different antibiotics and organic dyes. The synthesised 30UiO-66@HAp exhibited a favorable adsorption capacity and stable operating performance. It is expected to be utilized in the future wastewater treatment processes in industrial applications.