Ann N. Clarke

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 Darcys 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 Henrys law or more complex isotherms for this equilibrium. A method is developed for calculating Henrys constant from field analytical data, and it is noted that use of Henrys 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.

Preparation of Hair for Lead Analysis

A comparison of the washing procedures for hair samples for lead analyses was made. An ethylenediaminetetraacetic acid (EDTA) washing procedure proved best to eliminate the surface lead contamination of hair; neither the detergent nor hot ether washing procedures performed as well. Absorption of surface- bound lead into the hair shaft was not observed.

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...

SOIL CLEAN UP BY IN-SITU SURFACTANT FLUSHING. IV: A TWO-COMPONENT MATHEMATICAL MODEL

Abstract A two-dimensional mathematical model is developed for in-situ surfactant flushing of contaminants from an aquifer by means of injection and recovery wells. The model tracks both surfactant concentration and contaminant concentration, and permits the use of the Langmuir, Freundlich, BET, or other adsorption isotherms for the contaminant-soil binding. The permeability of the aquifer is assumed to be constant and isotropic, and local equilibrium is assumed between adsorbed and solubilized contaminant.

Groundwater cleanup by in-situ sparging. I. Mathematical modeling

The technique of in-situ sparging may provide a cheaper and more rapid method for removal of volatile organic compounds (VOCs) from groundwater than conventional pump and treat operations. A local ...

Electrical Aspects of Adsorbing Colloid Flotation. VIII. Specific Adsorption of Ions by Flocs

Abstract A Gouy-Chapman model of the solid-water interface with specific adsorption of ions is used to calculate surface and zeta potentials. The effects of sign and magnitude of ionic charge and surface charge density, ionic strength, specific binding energy, and temperature are examined. Experimental data on foam flotation of ferric hydroxide with sodium lauryl sulfate in the presence of a variety of anions support the model.

Electrical Aspects of Adsorbing Colloid Flotation. X. Pretreatments, Multiple Removals, Interferences, and Specific Adsorption

Abstract The compatibility of the adsorbing colloid flotation of Cu(II) with Fe(OH)3 and sodium lauryl sulfate with a variety of precipitation pretreatment techniques was studied. Procedures were developed which permitted precipitation pretreatment and effective foam flotation polishing. The interferences of glycerol, ClO4 −, NO3 −, C1−, CN−, CNS−, F−, SO44 2−, HPO4 2−, HAsO4 2−, C2O4 2−, (PO3)6 6−, and EDTA with the precipitate flotation of ferric hydroxide by sodium lauryl sulfate were studied. The simultaneous adsorbing colloid flotation of Cu(II), Pb(II), and Zn(II) with Fe(OH)3 and sodium lauryl sulfate was found to be effective in the pH range 6 to 7 at ionic strengths below 0.1 mole/l. A model was analyzed for calculating surface potentials for floe surfaces having the charge distributed at discrete sites in the presence of electrolytes. Plots of surface potential versus adsorbable ion concentration were calculated for various values of the model parameters.

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

Abstract A pilot-scale system for recycle and reuse of spent surfactant solution from organic-contaminated soil washing was successfully tested. The surfactant recycle system is comprised of an air-stripping column to remove volatile contaminants, a solvent-extraction column to remove nonvolatile contaminants, and a solvent-recovery system to remove and concentrate nonvolatile contaminants from the solvent. The pilot-scale recycle system was operated in conjunction with a soil test bed which was spiked with biphenyl as a representative “nonvolatile” contaminant. The individual components, which had each been tested previously, were operated together as an integrated system to produce a recycled surfactant solution which was reused during the test. The operation of this system is discussed and the results from the integrated testing are presented. Not only was 99% biphenyl removal from soil achieved in 7.7 pore volumes of 2.5 wt% sodium dodecyl sulfate surfactant solution, but there was also no decrease in...