Interaction mechanisms of organic contaminants with burned straw ash charcoal

Black carbons (e.g., charcoal) have a great impact on the transport of organic contaminants in soil and water because of i strong affinity and ubiquity in the environment. To further elucidate their interaction mechanism, sorption of polar (p-nitrotoluen m-dinitrobenzene and nitrobenzene) and nonpolar (naphthalene) aromatic contaminants to burned straw ash charcoal under differe de-ashed treatments were investigated. The sorption isotherms fitted well with Freundlich equation, and the Freundlich N valu were all around 0.31–0.38, being independent of the sorbate properties and sorbent types. After sequential removal of ashes by aci treatments (HCl and HCl-HF), both adsorption and partition were enhanced due to the enrichment of charcoal component. The separate contribution of adsorption and partition to total sorption were quantified. The effective carbon content in ash charcoal functioned a adsorption sites, partition phases, and hybrid regions with adsorption and partition were conceptualized and calculated. The hybri regions increased obviously after de-ashed treatment. The linear relationships of Freundlich N values with the charring-temperature charcoal or biochar (the charred byproduct in biomass pyrolysis) were observed based on the current study and the cited publication which included 15 different temperatures (100–850°C), 10 kinds of precursors of charcoal/biochar, and 10 organic sorbates.