Pyrolysis Temperature-Dependent Changes in the Characteristics of Biochar-Borne Dissolved Organic Matter and Its Copper Binding Properties

The dissolved organic matter (DOM) samples from biochars produced from Jerusalem artichoke stalks by pyrolysis at 300, 500, and 700 °C were characterized using a combination of spectroscopic techniques. Additionally, the binding affinities (long KM) and the complexation capacities (CL) of the DOM samples with Cu(II) were calculated to assess their Cu binding properties. The biochar-borne DOM contained mainly humic-like components (C1–C3) with a small amount of a protein-like component (C4). As the charring temperature increased, the concentrations of released DOM decreased. The low temperature biochar-borne DOM was found to have more carboxyl groups than its high temperature counterparts, and thus it had larger CL values. In contrast, the high temperature biochar-borne DOM had larger long KM values. Low temperature biochars, if applied in a large quantity, would alter copper mobility in the environment because of their high DOM contents and large copper binding capacities.