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

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 m2/g compared to 404.05 m2/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 (qm) 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.