Humic acid complexation of basic and neutral polycyclic aromatic compounds

K. G. Karthikeyan; Jon Chorover

doi:10.1016/S0045-6535(02)00186-8

Humic acid complexation of basic and neutral polycyclic aromatic compounds

K. G. Karthikeyan, Jon Chorover

Research output: Contribution to journal › Article › peer-review

28 Scopus citations

Abstract

Complexation by humic acid (HA) of basic (quinoline) and neutral (naphthalene) polycyclic aromatic compounds (PACs) was compared using fluorescence spectroscopy and equilibrium dialysis (ED). These compounds sorb to HA via cation exchange and hydrophobic interactions, respectively. Ionization of quinoline strongly affects its sorption to HA; maximum sorption is observed at pH close to log K_b (4.92), and competition with H⁺ and electrolyte cation (Li⁺) is evident. Spectroscopic experiments indicate that quinolinium (QH⁺) cation fluorescence is quenched via a static mechanism (i.e., a dark complex is formed) when the protonated form is adsorbed via ion exchange to HA. The extent of sorption, calculated from fluorescence data using the Stern-Volmer equation, was compared to independent ED measurements. Although both methods indicated the same trends with solution chemistry, fluorescence quenching data suggested more extensive complexation than that measured using ED. In contrast to ionizable PACs, studied here and previously, interaction of naphthalene with HA is unaffected by changes in solution conditions (pH, ionic strength).

Original language	English (US)
Pages (from-to)	955-964
Number of pages	10
Journal	Chemosphere
Volume	48
Issue number	9
DOIs	https://doi.org/10.1016/S0045-6535(02)00186-8
State	Published - 2002

Keywords

Complexation
Dialysis
Fluorescence spectroscopy
Naphthalene
Quinoline

ASJC Scopus subject areas

Environmental Engineering
Environmental Chemistry
General Chemistry
Pollution
Public Health, Environmental and Occupational Health
Health, Toxicology and Mutagenesis

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10.1016/S0045-6535(02)00186-8

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title = "Humic acid complexation of basic and neutral polycyclic aromatic compounds",

abstract = "Complexation by humic acid (HA) of basic (quinoline) and neutral (naphthalene) polycyclic aromatic compounds (PACs) was compared using fluorescence spectroscopy and equilibrium dialysis (ED). These compounds sorb to HA via cation exchange and hydrophobic interactions, respectively. Ionization of quinoline strongly affects its sorption to HA; maximum sorption is observed at pH close to log Kb (4.92), and competition with H+ and electrolyte cation (Li+) is evident. Spectroscopic experiments indicate that quinolinium (QH+) cation fluorescence is quenched via a static mechanism (i.e., a dark complex is formed) when the protonated form is adsorbed via ion exchange to HA. The extent of sorption, calculated from fluorescence data using the Stern-Volmer equation, was compared to independent ED measurements. Although both methods indicated the same trends with solution chemistry, fluorescence quenching data suggested more extensive complexation than that measured using ED. In contrast to ionizable PACs, studied here and previously, interaction of naphthalene with HA is unaffected by changes in solution conditions (pH, ionic strength).",

keywords = "Complexation, Dialysis, Fluorescence spectroscopy, Naphthalene, Quinoline",

author = "Karthikeyan, {K. G.} and Jon Chorover",

note = "Funding Information: Research supported by the U.S. Department of Energy, Office of Biological and Environmental Research, Joint Bioremediation Program, Grant no. DE-FG02-97ER62356. We are grateful to Dr. Mark Maroncelli, Department of Chemistry at Penn State for providing access to the fluorescence spectrometer and to Mary Kay Amistadi for extraction and purification of the HA. ",

year = "2002",

doi = "10.1016/S0045-6535(02)00186-8",

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pages = "955--964",

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T1 - Humic acid complexation of basic and neutral polycyclic aromatic compounds

AU - Karthikeyan, K. G.

AU - Chorover, Jon

N1 - Funding Information: Research supported by the U.S. Department of Energy, Office of Biological and Environmental Research, Joint Bioremediation Program, Grant no. DE-FG02-97ER62356. We are grateful to Dr. Mark Maroncelli, Department of Chemistry at Penn State for providing access to the fluorescence spectrometer and to Mary Kay Amistadi for extraction and purification of the HA.

PY - 2002

Y1 - 2002

N2 - Complexation by humic acid (HA) of basic (quinoline) and neutral (naphthalene) polycyclic aromatic compounds (PACs) was compared using fluorescence spectroscopy and equilibrium dialysis (ED). These compounds sorb to HA via cation exchange and hydrophobic interactions, respectively. Ionization of quinoline strongly affects its sorption to HA; maximum sorption is observed at pH close to log Kb (4.92), and competition with H+ and electrolyte cation (Li+) is evident. Spectroscopic experiments indicate that quinolinium (QH+) cation fluorescence is quenched via a static mechanism (i.e., a dark complex is formed) when the protonated form is adsorbed via ion exchange to HA. The extent of sorption, calculated from fluorescence data using the Stern-Volmer equation, was compared to independent ED measurements. Although both methods indicated the same trends with solution chemistry, fluorescence quenching data suggested more extensive complexation than that measured using ED. In contrast to ionizable PACs, studied here and previously, interaction of naphthalene with HA is unaffected by changes in solution conditions (pH, ionic strength).

AB - Complexation by humic acid (HA) of basic (quinoline) and neutral (naphthalene) polycyclic aromatic compounds (PACs) was compared using fluorescence spectroscopy and equilibrium dialysis (ED). These compounds sorb to HA via cation exchange and hydrophobic interactions, respectively. Ionization of quinoline strongly affects its sorption to HA; maximum sorption is observed at pH close to log Kb (4.92), and competition with H+ and electrolyte cation (Li+) is evident. Spectroscopic experiments indicate that quinolinium (QH+) cation fluorescence is quenched via a static mechanism (i.e., a dark complex is formed) when the protonated form is adsorbed via ion exchange to HA. The extent of sorption, calculated from fluorescence data using the Stern-Volmer equation, was compared to independent ED measurements. Although both methods indicated the same trends with solution chemistry, fluorescence quenching data suggested more extensive complexation than that measured using ED. In contrast to ionizable PACs, studied here and previously, interaction of naphthalene with HA is unaffected by changes in solution conditions (pH, ionic strength).

KW - Complexation

KW - Dialysis

KW - Fluorescence spectroscopy

KW - Naphthalene

KW - Quinoline

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Humic acid complexation of basic and neutral polycyclic aromatic compounds

Abstract

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