Factors influencing inapplicability of cosolvency-induced model on organic acid sorption onto humic substance from methanol mixture

Minhee Kim, Juhee Kim, Jeong-Gyu Kim, Seunghun Hyun

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1 Citation (Scopus)

Abstract

Applicability of cosolvency model for describing the sorption of organic acids to humic substance was investigated by analyzing dataset of sorption (K<inf>m</inf>) and solubility (S<inf>m</inf>) of selected solutes (benzoic acid, 1-naphthoic acid, 2,4-dichlorophenoxyacetic acid, and 2,4,6-trichlorophenol (2,4,6-TCP)) as a function of pH<sup>appCME</sup> (apparent pH of liquid phase) and f<inf>c</inf> (methanol volume fractions). For all solutes, the K<inf>m</inf> decreased with f<inf>c</inf> with the K<inf>m</inf> reduction being less than the S<inf>m</inf>-based prediction. The slope of log K<inf>m</inf>-f<inf>c</inf> plot in the three organic carboxylic acids was well correlated with their cosolvency power, whereas the data of organic phenolic acid (2,4,6-TCP) was placed above the trend, indicating the different actions of functional groups. The occurrence of Ca<sup>2+</sup> bridge between carboxylate and negatively charged humic surface may explain this phenomenon. Normalizing the K<inf>m</inf> to the corresponding S<inf>m</inf> (α′ = K<inf>m</inf>/S<inf>m</inf>) was not in unity over the pH<sup>app</sup>-f<inf>c</inf> range but decreased with f<inf>c</inf>, indicating a possible structural modification of sorption domain favoring extra sorption. For a given solute, the α′ of neutral species was always greater than that of anionic species, showing that extra interaction will be likely at pH<sup>app</sup> <pK<inf>a</inf> − 2 when both solute and sorbent are uncharged. In short, the knowledge of cosolvent-enhanced solubility is incapable of describing sorption of organic acids by humic substance in methanol/water mixtures. Modification of humic structure and hydrophilic interaction (such as Ca<sup>2+</sup> bridge and same-charge repulsion) is considered a relevant process that possibly restricts the applicability of the cosolvency model.

Original languageEnglish
JournalEnvironmental Science and Pollution Research
DOIs
Publication statusAccepted/In press - 2015 Jun 2

Fingerprint

Humic Substances
Organic acids
humic substance
organic acid
Solubility
Methanol
methanol
Sorption
sorption
solute
2,4-Dichlorophenoxyacetic Acid
Acids
Benzoic Acid
Carboxylic Acids
Hydrophobic and Hydrophilic Interactions
acid
solubility
Water
Benzoic acid
2,4 dichlorophenoxyacetic acid

Keywords

  • Cosolvency
  • Humic substance
  • Hydrophobic organic acid
  • Sorption

ASJC Scopus subject areas

  • Environmental Chemistry
  • Health, Toxicology and Mutagenesis
  • Pollution

Cite this

@article{9071179e815f483c8ea23816695d29e4,
title = "Factors influencing inapplicability of cosolvency-induced model on organic acid sorption onto humic substance from methanol mixture",
abstract = "Applicability of cosolvency model for describing the sorption of organic acids to humic substance was investigated by analyzing dataset of sorption (Km) and solubility (Sm) of selected solutes (benzoic acid, 1-naphthoic acid, 2,4-dichlorophenoxyacetic acid, and 2,4,6-trichlorophenol (2,4,6-TCP)) as a function of pHappCME (apparent pH of liquid phase) and fc (methanol volume fractions). For all solutes, the Km decreased with fc with the Km reduction being less than the Sm-based prediction. The slope of log Km-fc plot in the three organic carboxylic acids was well correlated with their cosolvency power, whereas the data of organic phenolic acid (2,4,6-TCP) was placed above the trend, indicating the different actions of functional groups. The occurrence of Ca2+ bridge between carboxylate and negatively charged humic surface may explain this phenomenon. Normalizing the Km to the corresponding Sm (α′ = Km/Sm) was not in unity over the pHapp-fc range but decreased with fc, indicating a possible structural modification of sorption domain favoring extra sorption. For a given solute, the α′ of neutral species was always greater than that of anionic species, showing that extra interaction will be likely at pHapp a − 2 when both solute and sorbent are uncharged. In short, the knowledge of cosolvent-enhanced solubility is incapable of describing sorption of organic acids by humic substance in methanol/water mixtures. Modification of humic structure and hydrophilic interaction (such as Ca2+ bridge and same-charge repulsion) is considered a relevant process that possibly restricts the applicability of the cosolvency model.",
keywords = "Cosolvency, Humic substance, Hydrophobic organic acid, Sorption",
author = "Minhee Kim and Juhee Kim and Jeong-Gyu Kim and Seunghun Hyun",
year = "2015",
month = "6",
day = "2",
doi = "10.1007/s11356-015-4742-x",
language = "English",
journal = "Environmental Science and Pollution Research",
issn = "0944-1344",
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T1 - Factors influencing inapplicability of cosolvency-induced model on organic acid sorption onto humic substance from methanol mixture

AU - Kim, Minhee

AU - Kim, Juhee

AU - Kim, Jeong-Gyu

AU - Hyun, Seunghun

PY - 2015/6/2

Y1 - 2015/6/2

N2 - Applicability of cosolvency model for describing the sorption of organic acids to humic substance was investigated by analyzing dataset of sorption (Km) and solubility (Sm) of selected solutes (benzoic acid, 1-naphthoic acid, 2,4-dichlorophenoxyacetic acid, and 2,4,6-trichlorophenol (2,4,6-TCP)) as a function of pHappCME (apparent pH of liquid phase) and fc (methanol volume fractions). For all solutes, the Km decreased with fc with the Km reduction being less than the Sm-based prediction. The slope of log Km-fc plot in the three organic carboxylic acids was well correlated with their cosolvency power, whereas the data of organic phenolic acid (2,4,6-TCP) was placed above the trend, indicating the different actions of functional groups. The occurrence of Ca2+ bridge between carboxylate and negatively charged humic surface may explain this phenomenon. Normalizing the Km to the corresponding Sm (α′ = Km/Sm) was not in unity over the pHapp-fc range but decreased with fc, indicating a possible structural modification of sorption domain favoring extra sorption. For a given solute, the α′ of neutral species was always greater than that of anionic species, showing that extra interaction will be likely at pHapp a − 2 when both solute and sorbent are uncharged. In short, the knowledge of cosolvent-enhanced solubility is incapable of describing sorption of organic acids by humic substance in methanol/water mixtures. Modification of humic structure and hydrophilic interaction (such as Ca2+ bridge and same-charge repulsion) is considered a relevant process that possibly restricts the applicability of the cosolvency model.

AB - Applicability of cosolvency model for describing the sorption of organic acids to humic substance was investigated by analyzing dataset of sorption (Km) and solubility (Sm) of selected solutes (benzoic acid, 1-naphthoic acid, 2,4-dichlorophenoxyacetic acid, and 2,4,6-trichlorophenol (2,4,6-TCP)) as a function of pHappCME (apparent pH of liquid phase) and fc (methanol volume fractions). For all solutes, the Km decreased with fc with the Km reduction being less than the Sm-based prediction. The slope of log Km-fc plot in the three organic carboxylic acids was well correlated with their cosolvency power, whereas the data of organic phenolic acid (2,4,6-TCP) was placed above the trend, indicating the different actions of functional groups. The occurrence of Ca2+ bridge between carboxylate and negatively charged humic surface may explain this phenomenon. Normalizing the Km to the corresponding Sm (α′ = Km/Sm) was not in unity over the pHapp-fc range but decreased with fc, indicating a possible structural modification of sorption domain favoring extra sorption. For a given solute, the α′ of neutral species was always greater than that of anionic species, showing that extra interaction will be likely at pHapp a − 2 when both solute and sorbent are uncharged. In short, the knowledge of cosolvent-enhanced solubility is incapable of describing sorption of organic acids by humic substance in methanol/water mixtures. Modification of humic structure and hydrophilic interaction (such as Ca2+ bridge and same-charge repulsion) is considered a relevant process that possibly restricts the applicability of the cosolvency model.

KW - Cosolvency

KW - Humic substance

KW - Hydrophobic organic acid

KW - Sorption

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