Removal of Tetracycline from aqueous solution using composite adsorbent of ZnAl layered double hydroxide and bagasse biochar

Abstract

A new composite adsorbent of biochar derived from bagasse and ZnAl-layered double hydroxide was produced by the in-situ growth method. The prepared biochars were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, the Brunauer–Emmett–Teller (BET) isotherms, Scanning electron microscopy (SEM), Energy Disperse X-ray (EDX) spectroscopic and Mular–Roberts titration analyses. The best Zn:Al molar ratio for the ZnAl-LDH/BGC composite to adsorb tetracycline was 3:1. The specific surface area of ZnAl-LDH/BGC31 was 456.39 m 2 /g compared to 404.05 m 2 /g for BGC. The optimal pH, contact time and initial TC concentration for TC adsorption were 6.0, 120 min and 25 mg/L, respectively. The ZnAl-LDH/BGC31 had a maximum adsorption capacity ( q m ) of 41.98 mg/g. The obtained data were analyzed with Langmuir, Freundlich and Tempkin isotherm models. Kinetic data were evaluated by using pseudo-first and pseudo-second-order kinetic models. The adsorption mechanism of ZnAl-LDH/BGC31 to remove TC was likely based on the pore-filling process, electrostatic attraction and π − π conjugate effect. ZnAl-LDH/BGC31 had significant adsorption capacity after five reusabilities. • ZnAl-layered double hydroxide bagasse biochar compositered (ZnAl-LDH/BGC31) was synthesized. • The maximum adsorption capacity ( q m ) of TC (41.98 mg/g) at pH 6 and 25 mg/L of initial TC. • Isotherm and kinetic model fitting indicated physisorption and chemisorption of TC. • The pore-filling process, electrostatic attraction and π − π conjugate effect were critical role in TC adsorption. • ZnAl-LDH/BGC31 adsorbent maintained its high adsorption ability up to 5 reusability.