Role of dissolved humic substances surrogates on phthalate esters migration from sewage sludge.

The facilitated transport of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP), the priority endocrine disrupting chemicals in sludge, by dissolved humic substances (HS) was evaluated by batch extraction. The DBP, much less hydrophobic than DEHP, was inclined to migrate from sludge matrix into humic substances solutions, while the DEHP could not migrate facilitated by most humic and fulvic acids solutions, except the humic acid surrogate of high humification. This result revealed that the affinity of DEHP in sludge matrix exceeded DBP and was not susceptible by weak HS. The hydrophobic property controlled the association of phthalic acid esters on sludge residual phases. Migration rate of DBP was positively correlated to the weight-average molecular weight of HS surrogates and the aromatic extents of HA. Some functional groups in HS molecules benefited to the facilitated transport of DBP.