In situ preparation of biochar/Bi4O5Br2 composite for ibuprofen removal under the synergistic effect of adsorption and photocatalysis and the underlying mechanism

The utilization of biochar to ameliorate the photocatalytic activity of a photocatalyst has been deemed as an effective route. In this work, a novel porous biochar/Bi4O5Br2 (pBC/Bi4O5Br2) composite was successfully synthesized for the removal of ibuprofen. The results demonstrate that the pBC/Bi4O5Br2 composite exhibits remarkable efficiency in ibuprofen removal. Notably, 20 % pBC/Bi4O5Br2 composite exhibits the highest photocatalytic activity, degrading up to 90 % of ibuprofen within 75 min light irradiation. Besides, the degradation constant of the 20 % pBC/Bi4O5Br2 composite is approximately 1.2 times that of the single Bi4O5Br2. Our investigation into photoelectrochemical properties reveals that the improved removal performance of pBC/ Bi4O5Br2 composite results from the synergistic interplay between adsorption and photocatalysis. This synergy leads to enhanced charge separation, improved light utilization ability, and the provision of more active sites to facilitate the photocatalytic reaction. Additionally, the degradation pathway and mechanism of the pBC/ Bi4O5Br2 composite were elucidated using HPLC-MS, capture experiments, and ESR measurements. The results indicate that the predominant active species involved in the removal are superoxide radicals (center dot O2  ), hydroxyl radicals (center dot OH) and hole (h+). Furthermore, the results revealed that the optimal pH for this reaction is 7, and the degradation efficiency of ibuprofen is inversely related to the dosage of ibuprofen while being positively related to the photocatalyst dosage.