Among the 275 substances on the 2007 CERCLA Priority List of Hazardous Substances are included all the heavy metals. Thus, the effective remediation of contaminated sites must invariably address the effective removal of heavy metals from contaminated water and aqueous leachates. The goal of this project is the development of new heavy metal removal/remediation/recovery technologies based on electrochemical techniques. Work has included the use of spouted particulate electrodes with circulating conductive particles for electrowinning (i.e., direct metal reduction) of heavy metals from solution. This has been applied to the development of the Cyclic Electrowinning/Precipitation (CEP) System that combines electrowinning with precipitation/redissolution to remove heavy metals from aqueous mixtures onto solid particles in a cyclic process, producing no precipitate sludges external to the process. The spouted particulate electrode is also being used as a contacting device for electrosorption/electrodesorption (ES/ED) processes on adsorbents in an electric field (SBED). Laboratory-scale electrochemical cell results have demonstrated effective performance of ES/ED methods on the removal of As, Cr, and their mixtures at ug/L levels. The SBED approach will also be used for the enhancement of zerovalent iron (ZVI) techniques for the removal of heavy metals, both with and without applied potentials. Work on this project has also identified other heavy metal contamination, purification, and analysis problems that can be effectively addressed using novel electrochemical techniques. The project goal will be achieved by fulfilling the following Specific Aims:
Specific Aim 1 : Electrowinning.
This Aim i s focused primarily on the development of the CEP System, as noted above. This system has been constructed, is operational, and is currently in the test phase.
Specific Aim 2 : Electrosorption/Electrodesorption.
This Aim i s focused on the development of ES/ED techniques, including electrochemical cycling, to enhance the uptake of heavy metals from complex mixtures onto adsorbents, and their subsequent regeneration in the SBED system. The latter will also be used for the enhancement of zero-valent iron (ZVI) techniques for the removal of heavy metals, both with and without an applied potential. In both Aims 1 and 2, data are being obtained on the removal of heavy metals from complex synthetic mixtures, and then on mixtures derived from contaminated field samples identified in collaboration with RIDEM.
Specific Aim 3 : Electrochemical Methods for Other Heavy Metals Contamination Problems.
This Aim i s focused on the development and application of electrochemical techniques, such as c/c//c electrosorption, electrochemical potential cycling for purification of heavy metal-contaminated materials, electro-deposition of modifiers for the improvement of electrosorption/adsorption performance on adsorbent materials, and the development of electrochemical methods, such as anodic stripping voltammetry (ASV), for more rapid and facile heavy metal analyses. This work will be pursued in collaboration with R. Hurt and Project 6.
The over-arching goal of this Superfund Basic Research Program is to address health concerns, and to design novel remediation techniques, related to mixed exposures arising from contaminated lands and buildings, using Rhode Island as a model for appropriate research, educational, and training interventions. This particular project is focused on the development of more effective remediation methods, based on novel electrochemical techniques, for the removal/recovery of heavy metals from complex aqueous mixtures derived from Superfund and Brownfields sites, as well as other sources of contaminated water.
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