[Sorption of p-Nitrophenol by Biochars of Corncob Prepared at Different Pyrolysis Temperatures]

Sorption of p-nitrophenol (PNP) on biochars prepared from pyrolysis of corncob in the temperature range of 200-600℃ (CC200-CC600) was investigated. Sorption mechanisms were discussed. Pyrolysis temperature showed a pronounced effect on properties of biochars. Decreases in molar H/C, O/C and (O+N)/C ratios were resulted from removal of H- and O-containing functional groups with increasing pyrolysis temperature, and produced biochars with low polarity and high aromaticity. The isotherms data were well described by the Freundlich model. Batch sorption experiments showed that the PNP sorption was strongly dependent on the properties of biochars. A linear relationship was observed between sorption parameters (n and K_F) and properties of biochars such as molar elemental ratios[H/C, O/C, and (O+N)/C]. The sorption and partition fractions were quantified by isotherm separation method. PNP sorption on biochar produced at 200℃ was linear due to partition on uncarbonized organic matter in biochar, while PNP sorption on biochars produced at 300-600℃ was nonlinear and adsorption-dominant for all the biochars via π-π electron donor-acceptor interaction and pore-filling.