Ann N. Clarke

Bio: Ann N. Clarke is an academic researcher from Vanderbilt University. The author has contributed to research in topics: Sparging & Stripping (chemistry). The author has an hindex of 14, co-authored 41 publications receiving 646 citations.

Soil Clean Up by in-situ Aeration. I. Mathematical Modeling

Abstract: Mathematical models are developed suitable for use in evaluating the feasibility of in-situ vapor stripping approaches for selected chemicals and site-specific environments. These models simulate the operation of both laboratory soil stripping columns and field-scale vacuum extraction wells (vent pipes). The effect of an anisotropic Darcy's constant is examined and the compressibility of the extracting gas is taken into account. The models incorporate the assumption of local equilibrium for the volatile compounds between the condensed and vapor phases. These models may use Henry's law or more complex isotherms for this equilibrium. A method is developed for calculating Henry's constant from field analytical data, and it is noted that use of Henry's constants calculated from laboratory data on solutions of volatile solutes in pure water can lead to very serious errors. It is shown that evacuation wells should be screened only down near the impermeable layer beneath the zone of stripping (unsaturat...

Separation by Flotation

Abstract: There has been much recent activity in the theory and application of separation by flotation, both in the United. States and abroad. This review primarily addresses new developments in foam flotation, colloid flotation and precipitate flotation. The work in ore flotation represents a major effort and would itself require a lengthy article. Work from ore flotation which significantly impacts on the areas of interest listed above is included here, however. Foam separation of biological materials and the microflotation of bacteria are not routinely discussed in this review. A few recent review articles on these areas are included at the end of the Review Articles and Books Section to afford the interested reader a start on that literature. The development and use of flotation separation techniques for waste treatment and water reuse over the last few years are included in this article.

Soil Clean-Up by Surfactant Washing. I. Laboratory Results and Mathematical Modeling

Abstract: The removal of weathered-in PCBs from clayey soil by surfactant washing is demonstrated at bench scale. Spent surfactant solution was treated for recycle at bench scale by countercurrent liquid-liquid extraction for the removal of nonvolatile contaminants, and by thin film aeration in packed columns for removal of volatile organics. A correlation of micelle/water partition coefficients with octanol/ water partition coefficients reported earlier by Valsaraj et al. is extended to several additional compounds. Mathematical models for batch–batch, batch–continuous flow, and countercurrent flow surfactant soil washing are described, and the effects of the model parameters are discussed.

Soil Clean-Up by Surfactant Washing. II. Design and Evaluation of the Components of the Pilot-Scale Surfactant Recycle System

Abstract: The components of a pilot-scale system to recycle and reuse a surfactant solution containing contaminants from remediated soil were designed, fabricated and successfully tested. Use of surfactants in soil washing or flushing can expedite remediation manyfold as the aqueous solubility of hydrophobic compounds is increased. The process is of even greater utility when the contaminants are also nonvolatile and nonbiodegradable. Biphenyl was used to represent nonvolatile contaminants. Not only was 99% biphenyl removal (initial concentration 1000 mg/ kg) from soil achieved in 7 pore volumes of 2.5 wt% sodium dodecyl sulfate (SDS) solution, but there was no decrease in the effectiveness of the recycled solution in removing the biphenyl compared to the virgin solution. Approximately 1 ppm biphenyl remained in the SDS solution after recycle. Toluene was used to represent volatile contaminants. Toluene removal from the soil test bed was 98% when using the same SDS solution. There was approximately 3 ppm to...

Mechanisms of Slow Sorption of Organic Chemicals to Natural Particles

Abstract: The use of equilibrium expressions for sorption to natural particles in fate and transport models is often invalid due to slow kinetics. This paper reviews recent research into the causes of slow sorption and desorption rates at the intraparticle level and how this phenomenon relates to contaminant transport, bioavailability, and remediation. Sorption kinetics are complex and poorly predictable at present. Diffusion limitations appear to play a major role. Contending mechanisms include diffusion through natural organic matter matrices and diffusion through intraparticle nanopores. These mechanisms probably operate simultaneously, but the relative importance of each in a given system is indeterminate. Sorption shows anomalous behaviors that are presently not well explained by the simple diffusion models, including concentration dependence of the slow fraction, distributed rate constants, and kinetic hysteresis. Research is needed to determine whether adsorption/desorption bond energies may play a role alon...

Possible health effects of high manganese concentration in drinking water.

Abstract: Three areas in the same region of northwest Peloponnesos, Greece, that had varying concentrations of manganese (Mn) in drinking water were selected for study. The Mn concentrations in areas A, B, and C were 3.6–14.6 μg/I, 81.6–252.6 μg/I, and 1 800–2 300 μg/I, respectively. A random sample (62 in area A, 49 in area B, and 77 in area C) of males and females who were at least 50 y of age were submitted to a thorough neurological examination and their whole-blood Mn and hair Mn concentrations were determined. Although all areas were similar with respect to social and dietary characteristics, significant differences were observed for prevalence of chronic manganese poisoning (CMnP) symptoms and hair Mn concentration. The means (both sexes) of neurological scores were 2.7, 3.9, and 5.2, respectively, for areas A, B, and C (Kruskal-Wallis, X 2 = 6.44, 2 df, p < .05 for males; X 2 = 7.78, 2 df, p < .05 for females). Hair Mn concentrations were also significantly different, the means for which were 3.51,...