In-situ uniform growth of ZIF-8 on 3D flower-like NiCoLDH microspheres to enhance tetracycline and doxycycline removal from wastewater: Anti-interference and stability tests

Abstract

Herein, we developed a novel recyclable three-dimensional (3D) flower‑like NiCoLDH@ZIF-8 microsphere (LDH@ZIF-8) with hierarchical pores through in-situ uniform growth of nano-sized ZIF-8 on NiCoLDH, and applied to efficiently remove tetracycline (TC) and doxycycline (DC) from wastewater. Compared with pristine NiCoLDH, the adsorption capacity of LDH@ZIF-8 for TC and DC was increased about 6 and 5 times, respectively. The experimental results suggest that LDH@ZIF-8 exhibits ultra-high adsorption performance for both TC and DC. The maximum adsorption capacities reached 612.1 and 730.0 mg/g at 303 K, respectively, which are much higher than those of most reported adsorbents. The adsorption process of LDH@ZIF-8 can be well described by Elovich and Sips models. In addition, LDH@ZIF-8 displays outstanding anti-interference ability to various ions and organic compounds in effluent. Additionally, the surfactant species and concentrations have an obvious influence on TC and DC adsorption. Furthermore, the adsorption mechanisms of LDH@ZIF-8 are systematically explored based on FT-IR, XPS, and DFT calculations. More importantly, LDH@ZIF-8 exhibits high removal rate of TC and DC from real water systems, and performs excellent reusability and water stability, indicating LDH@ZIF-8 can be used to remove antibiotics in real wastewater without secondary pollution.