H3PO4 activated biochars derived from different agricultural biomasses for the removal of ciprofloxacin from aqueous solution

Biochars were prepared by the pyrolysis of various H3PO4 activated agricultural biomasses at 600 °C and subsequently used as adsorbents for the removal of ciprofloxacin (CIP) from aqueous solution. Peanut shell-based biochar (PSBC), corncob-based biochar (CCBC) and cotton-based biochar (CTBC) had high surface areas (571.0–1006.3 m2/g), well-developed pore structures (mesopores with large pore volumes) and available adsorption functional groups (C=C, C–N and C–O–C). The CIP adsorption onto the biochars was investigated by batch experiments (kinetics, isotherms, thermodynamics, pH, etc.). Thermodynamics calculations showed the spontaneous (ΔGθ<0) and endothermic (ΔHθ>0) nature of the mechanism. In particular, CCBC exhibited high adsorption capacity (120.6 mg/g) of CIP in real lake water and it also had significant removal efficiency of other common pharmaceutical contaminants from real lake environment, and even in a coexisting quintuple system. Finally, multiple interaction mechanisms of CIP adsorption onto aromatized biochar were explored combining characterization analysis and theoretical calculations. Elucidation of the mechanism of CIP adsorption onto biochar provides new insights into the assessment of the removal of pharmaceuticals from the aqueous environment.