No description available.

No description available.

No description available.

No description available.

The primary objective of this research was to investigate multicomponent transport of five major cations, Ca2+, Mg2+, NH4+, K+ and Na+, in laboratory soil columns. The soil columns were packed with soils from two different sites and were equilibrated with fresh groundwater from each respective site. Experimental data was obtained by flushing a simulated contaminant through the soil columns. The soil columns were then flushed with fresh groundwater to simulate decommissioning activities. The breakthrough data and soil exchange capacities obtained from both tests were used to identify key processes affecting the transport of the geochemical species. During the simulated contaminant flushing stage, NH4+ and K+ replaced Ca2+ and Mg2+ on the soil exchange sites. Breakthrough of NH4+ was attenuated by factors of 3.2 and 6 for Sites 1 and 2 soils, respectively. Breakthrough of K+ was attenuated by factors of 3.2 and 5.4 for Sites 1 and 2 soils, respectively. Generally, ions with higher valency will exchange for those of lower valency, but in this case the majority of the ions (NH4+ and K+) in the solution has a lower valency and will exchange with those of higher valency by mass action. Ca2+ was the first to be replaced, followed by Mg2+ once the ionic strength of the solution increased. The displacement of calcium and magnesium created a concentration pulse of these cations that coincides with the chloride breakthrough curve. Calcium and magnesium concentrations reached up to approximately 275% and 2000%, respectively, higher than the freshwater originally in the column. During the freshwater flushing stage, freshwater infiltrated the soil columns to assess the permanency of contaminant attenuation and to identify the geochemical mechanisms of contaminant release. Concentrations of NH4+ and K+ declined quickly. Ninety-five percent of attenuated NH4+ was released by the soil. Therefore, the attenuation of NH4+ is reversible but this occurs over several pore volumes at concentrations lower than those in the simulated contaminant and therefore would not result in a mass loading to the environment. Cation exchange was identified as the mechanism responsible for the release of the adsorbed ammonium and potassium into the soil pore water.

The primary objective of this research was to investigate multicomponent transport of five major cations, Ca2+, Mg2+, NH4+, K+ and Na+, in laboratory soil columns. The soil columns were packed with soils from two different sites and were equilibrated with fresh groundwater from each respective site. Experimental data was obtained by flushing a simulated contaminant through the soil columns. The soil columns were then flushed with fresh groundwater to simulate decommissioning activities. The breakthrough data and soil exchange capacities obtained from both tests were used to identify key processes affecting the transport of the geochemical species. During the simulated contaminant flushing stage, NH4+ and K+ replaced Ca2+ and Mg2+ on the soil exchange sites. Breakthrough of NH4+ was attenuated by factors of 3.2 and 6 for Sites 1 and 2 soils, respectively. Breakthrough of K+ was attenuated by factors of 3.2 and 5.4 for Sites 1 and 2 soils, respectively. Generally, ions with higher valency will exchange for those of lower valency, but in this case the majority of the ions (NH4+ and K+) in the solution has a lower valency and will exchange with those of higher valency by mass action. Ca2+ was the first to be replaced, followed by Mg2+ once the ionic strength of the solution increased. The displacement of calcium and magnesium created a concentration pulse of these cations that coincides with the chloride breakthrough curve. Calcium and magnesium concentrations reached up to approximately 275% and 2000%, respectively, higher than the freshwater originally in the column. During the freshwater flushing stage, freshwater infiltrated the soil columns to assess the permanency of contaminant attenuation and to identify the geochemical mechanisms of contaminant release. Concentrations of NH4+ and K+ declined quickly. Ninety-five percent of attenuated NH4+ was released by the soil. Therefore, the attenuation of NH4+ is reversible but this occurs over several pore volumes at concentrations lower than those in the simulated contaminant and therefore would not result in a mass loading to the environment. Cation exchange was identified as the mechanism responsible for the release of the adsorbed ammonium and potassium into the soil pore water.

No description available.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Abraham M. Lenhoff, Dept. of Chemical Engineering. Includes bibliographical references.

This thesis is concerned with a process which has become commonly used. Producing radical cations specifically for observation at reduced temperatures within the X-band electron spin resonance spectrometer cavity. Gamma irradiation is used to cause electron addition and electron loss centres in a CCl3F matrix. These damage centres can be passed to solutes by the processes outlined below:- [equation] Various functional groups have been investigated. A variety of groups have been chosen to attempt to show a great many of the effects, which cause a molecule to produce interesting e.s.r. spectra. Effects ranging from the 'solvent adducts' investigated in Chapter 2, to the Breit-Rabi distortions encountered by the cations of dialkyl mercurials. Attempts have also been made to clarify one or two areas of radical cation chemistry which have caused contention in the current literature. Such areas are those outlined in Chapters 3, 4 and 5 with ester groupings and Chapter 7 with oxirane cations.

Thermodynamic parameters of solution (DeltaG°s, DeltaH°s, and DeltaS°s) of some haptens [ortho-, meta-, para-, 5-chloro-2-, 6-chloro-2-, 2-chloro-4- and 4-chloro-3- (parahydroxyphenylazo) sodium benzoate] and three cyclodextrins (Delta, Delta and Delta) were carried out in different reaction media. Thermodynamic parameters for the transfer (DeltaG°t, DeltaH°t, DeltaS°t) of haptens and their anions from water to methanol and from water to N,N'-Dimethylformamide were derived. In addition, transfer free energy, enthalpy and entropy of cyclodextrins from water to N,N'-Dimethylformamide are reported. Thermodynamic parameters of complexation between haptenic anions and cyclodextrins were investigated in water and in N,N'-Dimethylformamide and their transfer quantities from water to N,N'-Dimethylformamide are also given. It was found that the selected haptens (anions) are better solvated in methanol than in water than in N,N'-Dimethylformamide. The transfer enthalpies of the anions (data based on the Ph4AsPh4B convention) from water to methanol and from water to N,N'-Dimethylformamide [DeltaH°t (X-)] are largely compensated by their transfer entropies [DeltaS°t (X-)]. As far as solution thermodynamic data of cyclodextrins in water and N,N'-Dimethylformamide are concerned, it was noticed that a compensation effect between the DeltaHs and DeltaS°s values is taking place in water and in N,N'-Dimethylformamide. Only three anions complex with alpha, and gamma-cyclodextrins in water, whereas four haptens form complexes with alpha, beta and gamma-cyclodextrin in N,N'-Dimethylformamide. Again a compensation effect for cyclodextrin-anion complexes was observed in water and in N,N'-Dimethylformamide. A cavity size effect was shown during the formation of cyclodextrin-hapten complexes. Anion-cyclodextrin interaction becomes weaker with an increase in the cavity of cyclodextrin. Inclusion complexes (axial) are found to take place in water and lid-type (equatorial) complexes are found between these haptenic anions and cyclodextrins in N,N'-Dimethylformamide. The transfer parameters for the cyclodextrin-anion complexes were calculated using a thermodynamic cycle. This is the first set of data ever reported on the transfer of cyclodextrin adducts among solvents.