Removal of pharmaceutical residues from wastewater by woodchip-derived biochar

The aim of this study was to evaluate the effectiveness of wood-derived biochar for the removal of 18 pharmaceutical compounds (PCs) from untreated municipal wastewater (WW). The WW samples were analyzed by an HPLC-Q-Orbitrap-HRMS method. Two aliquots of WWs were incubated with biochar sorbent for 2 h and 7 d. The highest absolute removal of PCs was achieved for ibuprofen and caffeine (2.6 and 13.2 mg L^–1 after 7 d, respectively). The highest removal efficiency after 2 h incubation was detected for erythromycin (72.0% ± 12.7 %) while lower degree of removal was observed for other compounds with much higher initial concentrations. The results indicated that a 2 h sorption process on biochar may be insufficient and 7 d incubation is preferred for quantitative removal of xylazine, metoprolol, and azithromycin. However, the sorption of ketoprofen, diclofenac, ibuprofen, sulfamethoxazole, and simvastatin on biochar was more effective during the first 2 h than during the following 7 d. Regression analysis revealed a strong correlation (R²~0.9) between the absolute amounts of the removed PCs and their initial concentrations. In this respect, the removal of the last traces of PCs from WW is expected to present technological challenges.