In-situ immobilization of ZIF-67 on wood aerogel for effective removal of tetracycline from water

Abstract

Metal-organic framework (MOF) materials have been extensively studied in the removal of pollutants in wastewater. However, MOFs, which are usually in powder form, suffer from complex separation that hinder their practical application. Herein, a composite adsorbent material, ZIF-67@WA (wood aerogel), has been successfully fabricated through in-situ anchoring of ZIF-67 rhombic dodecahedron on the wood aerogel obtained by selectively removing lignin and hemicellulose from natural wood. WA with lamellar structure provided sufficient attachment sites for ZIF-67, and the content of ZIF-67 in the composite reached 32.65 wt%. ZIF-67 with 1 μm in grain size maintained its crystallinity when it was introduced to the surface of WA. The effects of pH, contact time, initial concentration, temperature, coexisting ions and humic acid on tetracycline (TC) adsorption were investigated. The composite showed excellent TC adsorption capacity (273.84 mg·g−1 at 298 K), which was comparable to most previously reported adsorbents. Pseudo-second-order kinetic model and Langmuir isotherm model described the adsorption process well. Adsorption thermodynamic studies implied that the adsorption process was spontaneous and endothermic. Furthermore, the possible adsorption mechanism was proposed. The TC removal efficiency dropped from 94.09% to 80.27% after 3 cycles, revealing the composite could be recycled. The leaching of cobalt was measured to be within the permissible range, indicating that no serious secondary contamination would be caused during using the composite. The superior adsorption performance coupled with compressibility, light weight and facile separation gave ZIF-67@WA the potential to effectively remove TC from water.