The sorption of organic contaminants on biochars derived from sediments with high organic carbon content.

Biochars were produced using a Dianchi Lake sediment at different temperatures and their sorption characteristics with five organic contaminants (with solubilities varied three orders of magnitude) were compared. Freundlich model showed satisfying fitting results of the sorption isotherms. Distinct decrease of nonlinear factors was observed for all five contaminants with pyrolysis suggesting wider energy distribution of the sorption sites after pyrolysis. No clear trend was observed between K(d) and the chemical properties of the five chemicals. Phenanthrene and sulfamethoxazole (SMX) showed increased sorption with increased pyrolysis temperature, while the sorption of bisphenol A (BPA), ofloxacin (OFL) and norfloxacin (NOR) in the original sediment was comparable to those in the thermally treated samples. Electrostatic repulsion played an important role in SMX sorption as suggested by its lowest hydrophobicity-normalized sorption coefficients among the five chemicals. Possible sorption mechanisms were discussed and the sorption of SMX and PHE on the produced biochars were compared with natural adsorbents (including soils, sediments, and inorganic mineral particles).