Adsorption of Ciprofloxacin on to Bamboo Charcoal: Effects of pH, Salinity, Cations, and Phosphate

The adsorption of ciprofloxacin (CIP) by bamboo charcoal in aqueous solution was explored under varying pH, salinity, metal cations, and phosphate. The adsorption kinetics and adsorption isotherms were depicted well by the pseudo-second-order and Langmuir models, respectively. The maximum adsorption capacity (q(m)) was 36.02 mg g(-1) according to the Langmuir model. The CIP adsorption increased with increasing pH and reached the maximum adsorption amount at pH 5.5, then decreased with increasing pH. It indicated that cation exchange played an important role in CIP adsorption. The effects of metal cations (0.2 mM Cu2+, Zn2+, Cd2+, Pb2+, and Al3+)on the CIP adsorption are both pH and cation species dependent. Al3+ greatly increased the CIP adsorption on to bamboo charcoal at pH 3.5, 5.5, and 9.5 (p < 0.05). Pb2+ inhibited the CIP adsorption, while Cu2+ significantly enhanced the CIP adsorption at pH 3.5 and 5.5, but both showed insignificant effects at pH 9.5. The presence of phosphate enhanced the CIP adsorption at pH 3.5 and 5.5, while slightly inhibiting the CIP adsorption at pH 9.5. The adsorption mechanisms of CIP on to bamboo charcoal were ascribed to cation exchange, hydrogen bonding and metal bridging. These results suggest that bamboo charcoal has great potential to be used as an efficient material in CIP removal from aquatic environments. (C) 2017 American Institute of Chemical Engineers