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ADSORPTION-PARTITIONING UPTAKE OF NINE LOW-POLARITY ORGANIC CHEMICALS ON A NATURAL SORBENT. (R825406)
Citation:
Xia, G. S. AND W. P. Ball. ADSORPTION-PARTITIONING UPTAKE OF NINE LOW-POLARITY ORGANIC CHEMICALS ON A NATURAL SORBENT. (R825406). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 33(2):262-269, (1999).
Description:
Sorption of comparatively nonpolar organic chemicals by natural solids not
only can be predominated by partitioning with organic matter but also can
reflect a substantial contribution from adsorption at low relative
concentration. Sorption of nine polycyclic aromatic hydrocarbons (PAHs) and
chlorinated benzenes (CBs) was investigated on a subsurface aquitard through
batch study, with results interpreted by a composite adsorption-partitioning
model. For both PAHs and CBs, the low-concentration adsorption slope and the
coefficient for partitioning each correlated well with Kow;
however, PAHs consistently sorbed more strongly than CBs at given
Kow. For all chemicals, adsorption contributions were only
important at low relative concentration and could be successfully modeled by
assuming either Langmuir-type or Polanyi-type isotherms. Isotherms for all
liquid chemicals fell on a single isotherm when plotted on a Polanyi basis
(adsorbed volume per mass of sorbent versus adsorption potential density),
providing evidence that a pore-filling phenomenon is involved. Adsorbed volumes
of solid chemicals were observed to be less than those of liquids at the same
adsorption potential density, consistent with a reduction in packing efficiency
and as previously reported for activated carbons. These results suggest that the
adsorption contribution is from pore filling within microporous solids.