Anionic homopolymers efficiently target zerovalent iron particles to hydrophobic contaminants in sand columns.
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.
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Elizabeth J
EJ
Bishop
Daniel E
DE
Fowler
Joanna M
JM
Skluzacek
Elizabeth
E
Seibel
Thomas E
TE
Mallouk
D000180:Acrylic Resins / Q000737:chemistry; D000464:Alginates / Q000737:chemistry; D000838:Anions / Q000737:chemistry; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry; D052918:Environmental Restoration and Remediation / Q000379:methods; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D007501:Iron / Q000737:chemistry*; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D016062:Porosity; D017640:Silicates / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
D000180:Acrylic Resins; D000464:Alginates; D000838:Anions; D006603:Hexuronic Acids; D011108:Polymers; D017640:Silicates; C006903:carbopol 940; D012822:Silicon Dioxide; D020723:Glucuronic Acid; D007501:Iron; D002266:Carboxymethylcellulose Sodium