Novel BiOBr by compositing low-cost biochar for efficient ciprofloxacin removal: the synergy of adsorption and photocatalysis on the degradation kinetics and mechanism insight

C/BiOBr composite materials were synthesized via a simple one-step solvothermal method, with C derived from biochar, which was prepared from the low-cost straw. The samples were characterized by SEM, XRD, XPS and PL. The 2% C/BiOBr composite material showed a noticeable adsorption and photocatalysis synergistic effect to remove CIP. The adsorption rate and degradation rate were 1.45 times and 1.8 times that of BiOBr. The adsorption kinetics and isotherms of CIP on C/BiOBr were analyzed with the pseudo-second-order kinetic and Langmuir models. The degradation efficiency was 96.8% after 60 min of irradiation. High stability and degradability were still maintained after four cycles. The Bi-O-C bond accelerated electron transition and inhibited the rapid photogenerated electron pair recombination. In the degradation process of CIP, ˙O₂ ^- and h⁺ played a significant role. Experiments proved that C/BiOBr is practical and feasible for the degradation of CIP under the synergistic effect of adsorption and photocatalysis.