Adsorption and co-adsorption of tetracycline and doxycycline by one-step synthesized iron loaded sludge biochar

Application of biochar as an adsorbent for wastewater treatment has obtained a tremendous research interest owning to their low cost and surface functionality. In this research, an iron loaded sludge biochar was successfully prepared through a simple and economical one-step modification hydrothermal method. The iron loaded sludge biochar possesses large amounts of surface organic functional groups (such as hydroxy, carboxyl and aromatic ring, etc.), smaller particle size (about 10 nm) as well as relative higher surface area (82.780 m2 g−1) than of the pristine one. The selective removal of two kinds of antibiotics by the prepared products was demonstrated. Experimental data was fitted to isotherm and kinetic models, and thermodynamic parameters were also calculated. In the single antibiotic system, the maximum adsorption amount of tetracycline (TC) and doxycycline (DOX) could reach 104.86 and 128.98 mg g−1 at 293.15 K, respectively. In the binary antibiotics system, there was an antagonistic effect between TC and DOX. Furthermore, the adsorption of TC was much more inhibited than that of DOX owning to its deferent steric hindrance of molecular structure.