Anionic homopolymers efficiently target zerovalent iron particles to hydrophobic contaminants in sand columns

Elizabeth J. Bishop, Daniel E. Fowler, Joanna M. Skluzacek, Elizabeth Seibel, Thomas E. Mallouk

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The transport of microscale carbonyl iron powder suspensions modified with anionic homopolymers was studied in water-saturated sand columns containing well-dispersed hydrophobic sand grains. Sand grains functionalized with hexadecyltrimethoxysilane were coated with a eutectic mixture of dichlorobenzenes that was solid at -10 °C and was mixed by grinding with unmodified sand grains. The dichlorobenzene coating liquefied at the temperature of the transport experiments, and the coated grains were thus mimetic of uniform droplets of dense nonaqueous phase liquid (DNAPL) contaminants. By comparing iron particle transport in uncontaminated columns with those that contained a small fraction of DNAPL-coated sand grains, sticking coefficients for both types of grains could be estimated. The anionic polyelectrolytes tested (polyacrylate, carboxymethylcellulose, alginate, and metasilicate) all gave low particle sticking coefficients (0.004-0.05) to unmodified sand, as expected from earlier studies. However, iron particles modified with the two moderately hydrophobic polymers (carboxymethylcellulose and polyacrylate) had 30-fold higher sticking coefficients (0.40 and 0.13, respectively) to the model DNAPL surface than they did to the sand surface. In contrast, no significant difference between the two kinds of collector grains was found with the more polar polymers (metasilicate and alginate). The trend in sticking coefficients was correlated with the surface energy of the polymer-modified iron surface as measured by the static contact angle method. From these data one can conclude that the hydrophobicity of the polymer dispersant is a key factor in targeting zerovalent iron to DNAPL source zones in soil and groundwater.

Original languageEnglish (US)
Pages (from-to)9069-9074
Number of pages6
JournalEnvironmental Science and Technology
Volume44
Issue number23
DOIs
StatePublished - Dec 1 2010

Fingerprint

Homopolymerization
Sand
Iron
Impurities
nonaqueous phase liquid
iron
sand
pollutant
Polymers
polymer
Carboxymethylcellulose Sodium
alginate
Liquids
Polyacrylates
Iron powder
dispersant
hydrophobicity
Hydrophobicity
surface energy
particle

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

Cite this

Bishop, Elizabeth J. ; Fowler, Daniel E. ; Skluzacek, Joanna M. ; Seibel, Elizabeth ; Mallouk, Thomas E. / Anionic homopolymers efficiently target zerovalent iron particles to hydrophobic contaminants in sand columns. In: Environmental Science and Technology. 2010 ; Vol. 44, No. 23. pp. 9069-9074.
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Anionic homopolymers efficiently target zerovalent iron particles to hydrophobic contaminants in sand columns. / Bishop, Elizabeth J.; Fowler, Daniel E.; Skluzacek, Joanna M.; Seibel, Elizabeth; Mallouk, Thomas E.

In: Environmental Science and Technology, Vol. 44, No. 23, 01.12.2010, p. 9069-9074.

Research output: Contribution to journalArticle

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AB - The transport of microscale carbonyl iron powder suspensions modified with anionic homopolymers was studied in water-saturated sand columns containing well-dispersed hydrophobic sand grains. Sand grains functionalized with hexadecyltrimethoxysilane were coated with a eutectic mixture of dichlorobenzenes that was solid at -10 °C and was mixed by grinding with unmodified sand grains. The dichlorobenzene coating liquefied at the temperature of the transport experiments, and the coated grains were thus mimetic of uniform droplets of dense nonaqueous phase liquid (DNAPL) contaminants. By comparing iron particle transport in uncontaminated columns with those that contained a small fraction of DNAPL-coated sand grains, sticking coefficients for both types of grains could be estimated. The anionic polyelectrolytes tested (polyacrylate, carboxymethylcellulose, alginate, and metasilicate) all gave low particle sticking coefficients (0.004-0.05) to unmodified sand, as expected from earlier studies. However, iron particles modified with the two moderately hydrophobic polymers (carboxymethylcellulose and polyacrylate) had 30-fold higher sticking coefficients (0.40 and 0.13, respectively) to the model DNAPL surface than they did to the sand surface. In contrast, no significant difference between the two kinds of collector grains was found with the more polar polymers (metasilicate and alginate). The trend in sticking coefficients was correlated with the surface energy of the polymer-modified iron surface as measured by the static contact angle method. From these data one can conclude that the hydrophobicity of the polymer dispersant is a key factor in targeting zerovalent iron to DNAPL source zones in soil and groundwater.

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