17 research outputs found
Track D Social Science, Human Rights and Political Science
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138414/1/jia218442.pd
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Manipulating subsurface colloids to enhance cleanups of DOE waste sites. 1998 annual progress report
'This project seeks to increase the effectiveness of pump and treat systems for removal of pollutants from sandy aquifers. Pollutants which sorb strongly to aquifer solids are not efficiently remediated using pump and treat technologies. However, if the sorbents most active in immobilizing pollutants (e.g., clays, humics, and iron oxides) were dispersed into colloidal size particles (colloid mobilization), these colloids and their associated pollutants might be pumped from aquifers. At a chromium contaminated sandy aquifer, this project seeks to: (1) understand the forces which stabilize colloidal particles in the aquifer, (2) devise solutions which will disrupt these colloid stabilizing forces, and (3) demonstrate the effectiveness of colloid mobilization as a remediation technique for removing sorbed chromium from the aquifer. This progress report summarizes work completed after 1 1/2 years of a three-year project. The efforts have focused on remediation of a chromium contaminated aquifer located on the property of National Chromium in northeastern Connecticut. Work to date may be divided into three areas: (1) site characterization; (2) identification of colloid binding forces and development of an effective colloid dispersion treatment; and (3) field testing of the aquifer remediation strategy.
Adsorption coefficients of organic compounds to activated carbon from water: Can we understand the sorption isotherms and estimate these via linear solvation energy relationships?
Evaluating Activated Carbon-Water Sorption Coefficients of Organic Compounds Using a Linear Solvation Energy Relationship Approach and Sorbate Chemical Activities
A linear solvation energy relationship (LSER) approach was used to investigate the evolving contributions of intermolecular interactions controlling organic compound sorption by granular activated carbon (GAC) from water as a function of sorbate chemical activities. Using a particular GAC (20-40 mesh Darco), 14 sorption isotherms were measured using sorbates with diverse functional groups to represert the range of possible surface interactions, and the data for each sorbate were fit with the Freundlich equation. Using interpolated adsorption :coefficients, K(d) values (L/kg), LSERs for specific sorbate activities (0-1, 0.01, and 0.001 saturation) were deduced. These expressions revealed that the intermolecular interactions controlling sorption to our particular GAC from water evolved with sorbate activities, such that a global correlation dependent on sorbate activity was found: log K(d) (L/kg) = [(3.76 +/- 0.28) - (0.20 +/- 0.10) log a(i)]V + [(-0.80 +/- 0.14) - (0.48 +/- 0.05) log a(i)]S + [(-4.47 +/- 0.20) + (0.16 +/- 0.06) log a(i)]B + (0.73 +/- 0.28) - (0.24 +/- 0.09) log a(i) (N = 176, R(2) = 0.96), where log ai is the activity of sorbate i, V is McGowan's characteristic volume for the sorbate, S reflects the compound's polarity/polarizability, and B reflects the compound's electron-donation basicity. Hence, sorption was promoted by dispersive forces and was diminished for sorbates capable of proton acceptance/electron donation, although both of these became less important at higher sorbate activities. Other intermolecular interactions were only weakly contributing (e.g., the "S" term) or were not significant at all for this GAC (i.e., the "R" and "A" terms). This result implies the Freundlich coefficients, K(f), for sorbates are given by (3.76V - 0.80S - 4.47B + 0.73) + (0.20V + 0.48S - 0.16B + 0.24) log C(i,W)(satn), and their exponents, 1/n, are equal to -0.20V - 0.48S+ 0.16B + 0.76. The data set could also be used to deduce a sorbate concentration-dependent LSER which would be useful for estimating equilibrium sorption coefficients for new sorbates of interest: log K(d) (L/kg) = [(1.89 +/- 0.07) - (0.22 +/- 0.06) log C(iW)]V + [(0.90 +/- 0.05) - (0.48 +/- 0.03) log C(iw)]S + [(-2.36 +/- 0.07) + (0.30 +/- 0.05) log C(i,w)]B + (2.98 +/- 0.07) - (0.26 +/- 0.06) log C(iw) (N = 176, R(2) = 0.98), where log C(i,W) is the concentration in water of each sorbate (mg/L)