Effects of Cations on Complexation of Naphthalene by Water-Soluble Organic Carbon
- Samuel J. Traina *,
- Donna A. Spontak and
- Terry J. Logan
The effects of cation type (Na, Ca, or Al), pH, and stoichiometric ionic strength (Is) on the complexation of naphthalene (in ClO−4 media) by water-soluble soil organic matter extracted from a muck soil (Euic, mesic Typic Medisaprist) were investigated with a fluorescence quenching technique. Decreases in the intrinsic fluorescence of the naphthalene, resulting from additions of water soluble soil organic matter (0–28 mg L−1 C expressed as water-soluble organic carbon or WSOC) were used to calculate conditional naphthalene-WSOC stability constants (cKoc) for each of the electrolyte systems investigated. For all cases, increased aqueous concentrations of WSOC caused an increase in the formation of naphthalene-WSOC complexes. Changes in pH value from 1.5 to 7.3 (in the presence of 0.05 mol L−1 NaClO4) and changes in Is from 0.05 to 0.5 mol L−1 [in the presence of either Ca(ClO4)2 or Al(ClO4)3] had no effect on the binding of naphthalene by WSOC. In homoionic systems of either NaClO4, Ca(ClO4)2, or Al(ClO4)3) (for Is = 0.05 mol L−1), the formation of naphthalene-WSOC complexes decreased in the order Na = Ca > Al. The effect of Al on the binding of naphthalene by WSOC may have resulted from changes in the physical, polymeric structure of WSOC molecules caused by the presence of Al as a counter ion.
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