Sorption of polychlorinated biphenyls onto biochars derived from corn straw and the effect of propranolol

The sorption of three polychlorinated biphenyls (PCBs) in single-solute and bi-solute systems in the presence of propranolol was studied on biochars at pyrolyzing temperatures of 200°C (BC200) and 700°C (BC700). Hydrophobicity and molecular planarity played a major role in PCB sorption onto BC200 and BC700, respectively. The steric hindrance caused by non-planarity made the strong specific sorption sites on BC700 less accessible to nonplanar PCBs. In bi-solute systems for BC200, propranolol monomers at an initial concentration (Cinit) of 0.8mg/L inhibited the sorption of PCB4 by competing for sorption sites. Propranolol at Cinit larger than 1.2mg/L could form hemimicelle structures on the biochar surface, providing a favorable phase for PCB4 partitioning, thereby increasing Koc up to 1.15 times. For BC700, propranolol prohibited PCB4 sorption mainly by pore-blocking, with the log Koc being reduced from 4.92 to 3.94. This study informs the application of biochar in mixture-contaminated environment.