Hydrothermal synthesis of magnetic sludge biochar for tetracycline and ciprofloxacin adsorptive removal

In this study, biochar derived from municipal sludge was activated by zinc chloride, which was first time used as the precursor for hydrothermal synthesis of magnetic sludge biochar (Fe/Zn-SBC) for tetracycline (TC) and ciprofloxacin (CIP) removal. The maximum adsorption capacity of Fe/Zn-SBC for TC and CIP were 145 mg g-1 and 74.2 mg g-1 at 25 °C, respectively. Kinetics, isotherms, thermodynamics and characterization analysis suggested that the adsorption process was dominated by pore filling, oxygen-containing groups complexation, π-π conjugation and hydrogen bonding. Fe/Zn-SBC had the high selective adsorption capacity for TC and CIP in a wide pH range and even at the high ionic strength. The magnetic sensitivity ensured its easy separation performance. The co-processing of ultrasound and ethanol could effectively regenerate the used Fe/Zn-SBC. Also, it exhibited great environmental safety in the pH range of 3 to 12. These superiority suggested that it is a promising adsorbent for antibiotics removal.