Single-solute and bi-solute sorption of phenanthrene and dibutyl phthalate by plant- and manure-derived biochars

The spatial arrangement of biochar and the exact underlying interaction mechanisms of biochar and hydrophobic organic compounds both remain largely unknown. The sorption of dibutyl phthalate (DBP) and phenanthrene (PHE) to plant- and manure-derived biochars in both single- and bi-solute systems was investigated. The significant positive relation between surface polarity and ash content suggests that minerals benefit the external distribution of polar groups on particle surfaces. PHE and DBP sorption by the biochars was regulated by their surface polarity. The PHE generally displayed a pronounced enhancement of DBP sorption, likely resulting from the formation of biochar–PHE–DBP complexes, suggesting that DBP and PHE had different sorption sites on the biochars. The enhancement of Cd2+ (a soft Lewis acid) on DBP sorption implied that π–π interactions should not dominate DBP sorption by biochars. The influence of Cd2+ on PHE sorption by biochars would depend on the balance between suppressive sorption by Cd2+PHE bonding and enhanced sorption by Cd2+-complexed functionalities, and the amounts of Cd2+ adsorbed by biochars determined the relative role of increased sorption by Cd2+ in the overall PHE sorption. [Display omitted] •Sorption of DBP and PHE in single and binary systems was studied.•PHE and DBP sorption by the biochars was influenced by their surface polarity.•PHE could increase DBP adsorption on biochars.•Increased PHE adsorption by Cd2+ depends on the amount of sorbed Cd2+ by biochars.