Binding of Polychlorinated Biphenyls to Aquatic Humic Substances:  The Role of Substrate and Sorbate Properties on Partitioning

Abstract

Two ortho-(2,2′,5 and 2,2′,5,6′) and a non-ortho-(3,3′,4,4′) substituted polychlorinated biphenyl (PCB) congeners were used to study the effects of sorbate structure in binding processes to two lacustrine fulvic acids. Binding constants were determined by solubility enhancement of the solutes by the fulvic acids. The binding of the orthotrichlorobiphenyl was significantly less than the non-orthosubstituted tetrachlorobiphenyl to both fulvic acids. Surprisingly, the measured ortho-trichlorobiphenyl binding constant to both fulvic acids was approximately the same as the ortho-substituted tetrachlorobiphenyl. The effect of the chlorines in the ortho position inhibits free rotation around the 1,1′ carbon bond, thereby making the molecule less able to interact effectively with the fulvic acid substrate relative to its non-ortho-substituted congeners. Finally, binding of all three PCBs to the Great Dismal Swamp fulvic acid was significantly higher than for the Pony Lake sample. This observation is attributable to the former substrate's higher degree of aromaticity and polarizability, which can potentially interact more favorably with the PCBs through an increase in van der Waals type interactions.

A Novel Polyaniline Titanium Oxide Sawdust Composite Adsorbent for Polychlorinated Biphenyls

“…). A similar relationship where a lower adsorption capacity for the highly chlorinated PCB mixtures, in comparison with the less chlorinated ones, has been reported elsewhere [52]. An observation of preferential coplanar sorption was also reported elsewhere for PCB interaction with humic substrates [53].…”

“…6). This kinetic model is associated with chemisorption mechanism as argued in past literature where Pirbazari and Weber [52] mentioned that adsorption of PCBs on carbon may be predominantly chemisorption. In the case of PCB 101, the kinetic model that explained the nature of adsorption process here was found to be intraparticle diffusion model which suggested a possible diffusion limited step during adsorption.…”

Removal of phenol from water by adsorption–flocculation using organobentonite

“…The shape of the adsorption isotherms of TMA-, TEA-, and TMH-bentonites are S-type isotherms in Giles' classification, suggesting that the adsorbate-adsorbate interaction is stronger than the adsorbate-adsorbent interaction. The relatively high affinity between phenol and BTMA-and BTEA-bentonite is probably the result of the phenol molecules interacting favorably with the benzene ring in BTMA and BTEA ions through increased p2p type interactions [10,11]. Meanwhile, the saturated uptake of phenol by BTMA-bentonite (34 mg g À1 ) is considerably higher than that by BTEAbentonite (21 mg g À1 ), presumably due to the smaller size of the BTMA ion.…”

A New Perspective on the Apparent Solubility of Dissolved Black Carbon

“…This approach allowed for the assessment of the widest possible range of modeled K ow values for each DBC formula pair. Structural planarity enhances the partitioning of hydrophobic organic compounds to humic substances (Gauthier et al, 1987;Chin et al, 1997;Uhle et al, 1999). Since we hypothesize DBC molecules to participate in such hydrophobic interactions with DOM, we sought to maximize the structural planarity of proposed DBC structures in the current study.…”