Electrokinetics laboratory tests

Conductance measurements are useful practically to monitor ionic distribution profiles in electrokinetic laboratory test cells and to characterize the electrical properties of soil samples. 

Applying this soil remediation technology requires special expertise this chapter describes the technology and its applications, indicating the materials and decontamination methods that can be used and how the system should be initiated and controlled. It also specifies the samples that need to be taken in order to monitor the decontamination process. Before remediation can commence, however, it is first necessary to clarify where contamination is present in the area of soil concerned and in what form. It is furthermore necessary to perform electrokinetic laboratory tests with one or preferably more representative soil samples. Finally, it is explained how the data are analyzed and used for carrying out the design of the remediation system. 

The design and dimensions of the ER system to be deployed at a site are based on and derived from the data collected during the preceding investigations and from one or more electrokinetic laboratory tests. If possible, some electrical resistivity soundings should be performed on the site in order to measure the electrical resistance of the ground. 

Laboratory Tests Electrokinetic laboratory tests are done on soil samples from the site, preferably taken at the contamination hot spots, that is, the locations with the highest concentrations of contaminants. The client can choose between two separate or combined test configurations ... 

Test Results The electrokinetic laboratory tests are finalized with a report. This presents relevant data, such as sample preparation, analysis results, concentration decrease, type of electrolyte solutions, electrolyte conditioning, and electrical and electrokinetic parameters. The electrical parameters are voltage (V), drop in potential (V/m), current (A), current density (A/m ), electrical power (kW/m ), and resistivity (Ohmm). Conditioning parameters comprise type of add... 

Fig. 15.31. One-dimensional laboratory test apparatus. (Reprinted from R. J. Gale, Soil Decontamination Using Electrokinetic Processing, in Environmental Oriented Electrochemistry, C. A. C. Sequeira, ed., Fig. 4, p. 362, copyright 1994. Reproduced with kind permission of Elsevier Science-NL, Sara Burgerhartstraat 25, 1055 KV Amsterdam, The Netherlands.)...

Interest in soil decontamination by electrokinetic processing has been increasing steadily, as shown by the volume of scientific studies. There have been two workshop/conferences dedicated to this topic in the U.S. in recent years [86,87] and a number of companies now have offered specialized services in this area. The technology is an emerging one and it is not yet fully mature. There exists a need to conduct further basic and applied studies before it achieves its full potential. In environmental remediation, the site chemistry before and after any application of technical processes need to be fully evaluated. It is recommended that bench scale, laboratory tests be undertaken prior to any site work to help optimize the process parameters. Although the... 

Figures 2.8 and 2.9 present the spatial distribution of the total lead and the pH for 1-day and 35-day runs of the Cao model. Superimposed on the numerical solutions are results from laboratory tests of Pb(N03)-contaminated kaolinite clay subjected to long-term electrokinetic treatments. Although the initial concentrations of the lead used in the numerical simulator and the experiments were different (0.05 M in the numerical and 0.15 M in the experiment), as well as the length of the...

Electrokinetic remediation is limited by the type of contaminant, heterogeneities or anomalies in the soil, extreme pHs, pore water chemistry, lack of pore water, contaminant and noncontaminant ion concentrations, metals precipitation, and reduction-oxidation changes induced by the process electrode reactions. It may be difficult to estimate the time that will be required to remediate a site using this technology. Laboratory treatability testing may provide a false indication of the applicability of electrokinetic remediation at a specific site. Further research is required to determine the technology s limitations and ramifications. 

While electrokinetic treatment of soils looks promising, most of the work performed was bench-scale, under carefully controlled laboratory conditions. For electrokinetic remediation to be a viable alternative for in-situ cleanup of waste sites, a number of factors will have to be investigated. All of the work to date has dealt with uniformly contaminated soil samples. Studies performed on partially saturated soils will yield different results. Further studies on the removal of mixed metal contaminated soils, using different soil types, are needed. The presence of organic compounds in the soil will also influence successful treatment of real contaminated soils. The use of reagents which could increase desorption and/or solubilization (without further contaminating the soil matrix) may also be areas of future investigation. Finally, field tests need to be performed to substantiate studies accomplished on the bench scale. 

W. B. Hambleton, Jr., designed and automated synthesis facility and prepared the coated alumina samples E. E. Carroll, Jr., made the surface area measurements M. L. and M. J. Van Kavelaar performed the TEM measurements B. F. Burgess and the Galbraith Laboratories of Knoxville, TN, made the ICP-AES determinations R. E. Johnson, Jr., and J. V. Hughes, Jr., made the electrokinetic potential measurements D. B. Chase developed the DRIFT spectra and P. E. Bierstedt performed the XPS tests. We are grateful to D. P. Button for encouragement and support to do his work. We dedicate this chapter to the late Ralph K. Iler, who was an invaluable source of inspiration at the early stages of our work with MSA and zeolites. 

Electrochemical Remediation Heavy metals and other contaminants can be removed from the soil and groundwater with the help of electrokinetic phenomena (electroosmosis, electrophoresis, electrolysis). In electrochemical remediation processes, a continuous electrical field is generated with electrodes that are inserted into the contaminated soil (Shapiro etal. 1989 Ottosen etal. 1995 Hansen etal. 1997). Laboratory and pilot tests have been conducted, for example, with acetic acid as cleaning solution (Renaud 1990). With elec-... 

Previous reports have generally described laboratory-scale experiments and there were few field demonstrations or full-scale applications. Kaolin was used as a model soil in most studies. However, recent electrokinetic tests of PAH removal have been conducted with real heterogeneous contaminated soils and have demonstrated the potential of EK. 

Before implementing electrokinetics, it is necessary to find if the site conditions match the requirements necessary for the successful performance of the technology. This can be done by a number of field and laboratory screening tests ... 

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