The effect of extraction of labile organic fractions on surface properties of pyrochars

The changes in the properties of pyrochars and the possibility of their use as soil meliorants were evaluated. Pyrochars obtained from linden residues at fixed pyrolysis temperatures of 250°C, 450°C and 650°C and under isothermal conditions in the temperature range from 450°C to 650°C have been studied. Their labile fractions of organic matter extracted with Na₄P₂O₇-NaOH solution and hot water was investigated by UV-VIS spectrometry and after extraction cation exchange capacity of pyrochars was characterized. For the qualitative characteristics of the selected fractions, ratio of the absorption of a colored solution of organic matter at λ = 254 nm to the content of organic carbon was calculated. It was concluded, that the pool of water-soluble and alkaline-soluble organic matter of pyrochars is a mixture of organic compounds of uncertain qualitative composition, whose properties are determined by the pyrolysis temperature. Extraction of this water-soluble and alkaline-soluble organic matter leads to a change in cation exchange capacity of pyrochars. (paper)