skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Slow Desorption of Phenanthrene from Silica Particles: Influence of Pore Size, Pore Water, and Aging Time

Abstract

When micro-porous and meso-porous silica particles were exposed to aqueous phenanthrene solutions for various durations it was observed that sorbed-phase phenanthrene concentrations increased with aging time only for meso-porous but not micro-porous silicas. Desorption equilibrium was reached almost instantaneously for the micro-porous particles while both the rate and extent of desorption decreased with increasing aging time for the meso-porous silicas. These findings indicate that phenanthrene can be sequestered within the internal pore-space of meso-porous silicas while the internal surfaces of micro-porous silicas are not accessible to phenanthrene sorption, possibly due to the presence of physi- or chemi-sorbed water that may sterically hinder the diffusion of phenanthrene inside water-filled micro-pores. By contrast, the internal surfaces of these micro-porous silicas are accessible to phenanthrene when aging methods are employed which assure that pores are devoid of physi-sorbed water. Consequently, when phenanthrene was incorporated into these particles using either supercritical CO2 or via solvent soaking, the aqueous desorption kinetics were extremely slow indicating effective sequestration of phenanthrene inside micro-porous particles. Finally, a two-compartment conceptual model is used to interpret the experimental findings.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
881324
Report Number(s):
PNNL-SA-48083
KP1301010; TRN: US200612%%806
DOE Contract Number:
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: 20th Annual International Conference on Soils, Sediments, and Water: Successes and Challenges published in CONTAMINATED SOILS SEDIMENTS AND WATER, 2006, 10(1-24
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; AGING; DESORPTION; DIFFUSION; KINETICS; PHENANTHRENE; SEDIMENTS; SILICA; SOILS; SOLVENTS; SORPTION; WATER; Aging; Sequestration; Phenanthrene; Sorption

Citation Formats

Huesemann, Michael H., Fortman, Timothy J., Riley, Robert G., Thompson, Christopher J., Wang, Zheming, Truex, Michael J., and Peyton, Brent M. Slow Desorption of Phenanthrene from Silica Particles: Influence of Pore Size, Pore Water, and Aging Time. United States: N. p., 2006. Web.
Huesemann, Michael H., Fortman, Timothy J., Riley, Robert G., Thompson, Christopher J., Wang, Zheming, Truex, Michael J., & Peyton, Brent M. Slow Desorption of Phenanthrene from Silica Particles: Influence of Pore Size, Pore Water, and Aging Time. United States.
Huesemann, Michael H., Fortman, Timothy J., Riley, Robert G., Thompson, Christopher J., Wang, Zheming, Truex, Michael J., and Peyton, Brent M. Mon . "Slow Desorption of Phenanthrene from Silica Particles: Influence of Pore Size, Pore Water, and Aging Time". United States. doi:.
@article{osti_881324,
title = {Slow Desorption of Phenanthrene from Silica Particles: Influence of Pore Size, Pore Water, and Aging Time},
author = {Huesemann, Michael H. and Fortman, Timothy J. and Riley, Robert G. and Thompson, Christopher J. and Wang, Zheming and Truex, Michael J. and Peyton, Brent M.},
abstractNote = {When micro-porous and meso-porous silica particles were exposed to aqueous phenanthrene solutions for various durations it was observed that sorbed-phase phenanthrene concentrations increased with aging time only for meso-porous but not micro-porous silicas. Desorption equilibrium was reached almost instantaneously for the micro-porous particles while both the rate and extent of desorption decreased with increasing aging time for the meso-porous silicas. These findings indicate that phenanthrene can be sequestered within the internal pore-space of meso-porous silicas while the internal surfaces of micro-porous silicas are not accessible to phenanthrene sorption, possibly due to the presence of physi- or chemi-sorbed water that may sterically hinder the diffusion of phenanthrene inside water-filled micro-pores. By contrast, the internal surfaces of these micro-porous silicas are accessible to phenanthrene when aging methods are employed which assure that pores are devoid of physi-sorbed water. Consequently, when phenanthrene was incorporated into these particles using either supercritical CO2 or via solvent soaking, the aqueous desorption kinetics were extremely slow indicating effective sequestration of phenanthrene inside micro-porous particles. Finally, a two-compartment conceptual model is used to interpret the experimental findings.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 16 00:00:00 EST 2006},
month = {Mon Jan 16 00:00:00 EST 2006}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • Studies of Joule-discharge heating of packed beds of chemically modified silica gel address the influence of pore diameter, particle size, and chemical modification on the heating kinetics of the silica gel. The results reveal that surface modification and pore diameter affect the connectivity of the intraparticle pore network. Heating of packed beds consisting of 60-, 100-, and 147-[angstrom] pore-diameter silica gels modified with n-triacontyldimethylsilyl (C30), dimethyloctadecylsilyl (C18), or trimethylsilyl (C1) ligands are monitored by observing the temperature-dependent fluorescence of NBD-hexanoic acid in MeOH/H[sub 2]O solvents. A decrease in the silica pore diameter, an increase in the length of surface ligands,more » or an increase in bonding density of the ligands causes a reduction in the rate of the energy dissipation in the temperature-jump cell. The temperature equilibration time or minimum heating time, [tau][sub h,min], depends on particle size with 5-, 10-, and 40-63-[mu]m octadecylsilica exhibiting [tau][sub h,min] values of ca. 5, 10, and 250 [mu]s, respectively. Joule heating at a discharge rate of 2 X 10[sup 5] s[sup [minus]1] of 5- and 10-[mu]m silicas is uniform, as indicated by a single-exponential response of the fluorescence thermometer, while a biexponential response for larger particle silica shows evidence of nonuniform heating. The rate and uniformity of heating depend upon the particle size and length of the alkyl ligands attached to the surface. 18 refs., 4 figs., 8 tabs.« less
  • The pore size r{sub p} in a gel is determined by the extent of shrinkage of the gel network during drying. Shrinkage is driven by the collapse of the gel network in response to the capillary pressure P{sub c} exerted by the pore fluid. The extent of shrinkage depends on the balance between the capillary pressure P{sub c} in the pore fluid and the bulk modulus K{sub p} of the gel. The hydraulic pore radius, r{sub H} = 2V{sub p}/S{sub a}, where V{sub p} is the pore volume and S{sub a} is the apparent N{sub 2} BET surface area, ismore » often used to characterize the pore size of a gel. A series of acid catalyzed silica gels dried in pore fluids with different {gamma}{sub lv}, showed that there is a limit to the minimum apparent r{sub H} obtainable in a gel, and when the volume fraction of porosity {phi} {le} 0.37, r{sub H} becomes constant and {approximately}0.8 nm. In contrast, experimental data show that the true pore size r{sub p} of gels continues to decrease when {phi} {le} 0.37. Analysis of their adsorption isotherms show that while r{sub H} apparently stays constant: (a) the BET C constant continues to increase, (b) the width and average of their pore size distributions continue to decrease, and (c) as shrinkage continues the gels eventually become non-porous to N{sub 2} at 77K but are still porous to CO{sub 2} at 273K. This paper reviews these results and addresses micropore formation in silica gels with the goal of determining how P{sub c} influences the final r{sub p}, and why r{sub p} and r{sub H} diverge when {phi} {le} 0.37.« less
  • Controlled porosity materials are currently the focus of many research groups. Inorganic thin films typically have porosity with long tortuous paths leading to low flux. To attain high selectivity and high flux the ideal film would have short one-dimensional pores. Potential applications of such inorganic membranes are in gas separation for oxygen enrichment, purification of natural gases, and sensor materials. In this study mixed monolayers of octadecyltrimethoxysilane (OTMS) and a template amphiphile were prepared and deposited on silicon substrates as Langmuir-Blodgett films. The template amphiphiles were homogeneously dispersed within the thin silica matrix on the water surface and following pyrolizationmore » formed micro-porous membranes. Controlled pore-size patterning has been attempted by varying the mole fraction of siloxane to template amphiphile. The resultant molecularly thick silica films were characterized by ellipsometry, scanning force microscopy, and impedance measurement. Our results on pore-size patterning and our attempt to engineer micro-porous silica thin films by pyrolysis will be presented.« less
  • The authors present an apparatus capable of detecting micron sized particles traveling at speeds up to 10{sup 6} cm/sec. The apparatus uses light scattering methods with automated data processing. Data generated by this apparatus should be extremely useful in radiation damage studies of components in contamination sensitive optical systems.