Preparation of Dense Non-aqueous Phase Nano Zero-valent Iron Suspension for Environmental Restoration
Date Issued
2010
Date
2010
Author(s)
Liu, Pei-Ge
Abstract
The remediation for dense non-aqueous phase liquids (DNAPLs) in soils and aquifers is the most difficult problem at present. Because of the complex nature of the transport of DNAPL and its special physical and chemical properties, it is particularly difficult to detect and characterize these kind of pollution sources. Most of the technologies are applicable only to contaminants in the dissolved phase. Treatment technologies currently being applied to the remediation of the residual zones and DNAPL pools are limited.
In this study, octadecyl dihydrogen phosphate (ODP) was synthesized and applied as surface modifier to produce hydrophobic zero-valent iron (HZVI). The properties of the HZVI and its capability of degradation of DNAPL were examined. The HZVI retained the surface properties of zero-valent iron which was verified by X-ray powder diffraction (XRD). ODP can bond to the particle surfaces or the particle surfaces covered by carboxylic acid group of polyacrylic acid (PAA). Hydrogen bonds as well as anhydride formed between ODP and PAA make the particles well covered by ODP and kept hydrophobic. The contact angle of HZVI in the test of wettability is over 100 degrees. The maximum contact angle was 133 degrees when the dosage of modifier was 5 % wt. The hydrophobic nano zero-valent iron can well be dispersed and stabilized in non-aqueous solvents. The stable dense non-aqueous zero-valent iron suspension contain 300 g-Fe/L in 1-octanol with viscosity at 280 cp.
The reactivity of the dense non-aqueous phase nano zero-valent iron suspension with 8.7 mg of TCE in amber serum bottle was investigated. Two milliliters of dense non-aqueous phase nano zero-valent iron suspension with concentration of 300 g-Fe L-1 in 1-octanol as a solvent was injected into the bottle. TCE concentrations decreased 23 % in 90 minutes, and the total removal rate of TCE was 54 % in 267 hours.
Only slight penetration of a blob of dense non-aqueous zero-valent iron suspension into saturated sand column occurred due to very small difference between hydraulic heads of water column and the tested liquid, high surface tension and high viscosity of the tested liquid.
Subjects
zero-valent iron
surface modifier
hydrophobic nano particles
dense non-aqueous zero valentiron suspension
trchloroethylene
Type
thesis
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