Nanocomposites of zero-valent iron@biochar derived from agricultural wastes for adsorptive removal of tetracyclines.

Tetracycline antibiotics as the emerging pollutants had been drawn abroad increasing concerns. An agricultural waste, the lignocellulosic hazelnut shell, was used as the carbon source to prepare the nanocomposites of zero-valent iron@biochar by pyrolytic reduction method at 1123 K for 2 h in N2 atmosphere. The adsorptive removal of tetracycline, oxytetracycline and chlortetracycline by the zero-valent iron@biochar from aqueous solution was investigated by batch method. The optimal experimental conditions were found to be at pH 6-7 with a contact time of 40 min. The adsorbed amounts of oxytetracycline, chlortetracycline and tetracycline at 298 K were 52.7, 42.5 and 39.1 mg g-1, respectively. Adsorption process of three antibiotics by the nanocomposite pursued Langmuir and pseudo-second-order equations. Thermodynamic parameters illustrated that the adsorption was spontaneous and endothermic intrinsically. The high removal efficiencies up to 95% of the zero-valent iron@biochar for oxytetracycline and chlortetracycline from the culture wastewaters had opened the potential applications for the removal of the antibiotics.