Carbon dioxide activated biochar-clay mineral composite efficiently removes ciprofloxacin from contaminated water - Reveals an incubation study

Abstract

Ciprofloxacin, a second-generation synthetic fluoroquinolone derivative widely used in human and veterinary medicines, has the potential to pose a serious risk to aquatic organisms and humans. The current research investigated the removal of ciprofloxacin using biochar treated with clay mineral and subsequently activated with carbon dioxide (CO2) produced at two different pyrolysis temperatures (350 and 650 °C). Batch adsorption experiments were carried out to assess the removal efficiency of ciprofloxacin by as-synthesized materials. The effects of various factors, such as pH, contact time, adsorbent dose, initial ciprofloxacin concentration, and temperature were studied during the removal process. The physicochemical characterization results verified the successful loading of clay minerals on biochar. Non-linear adsorption models were employed to understand the nature of adsorption processes however, the Pseudo-second-order kinetic and Freudlich and Redlich Peterson isotherm models best fitted with the adsorption data. These findings indicated that the adsorption did not follow an ideal monolayer adsorption suggesting hybrid chemical adsorption process that was spontaneous and endothermic. The maximum adsorption (50.32 mg g−1) of ciprofloxacin was achieved by CO2 activated biochar-clay mineral composite prepared at 350 °C, and was almost two times higher than the pristine biochar at neutral pH and 40 °C. The possible proposed mechanisms involved for the removal of ciprofloxacin were electrostatic attraction, cation exchange, pore-filling effect, and π-π interactions. Our findings demonstrate that application of CO2 activated biochar-clay mineral composite is a promising technique for efficient removal of ciprofloxacin from aqueous solution.