An Electrolytic Technique to Study the Mobility of Inorganic Constituents in Soils and Waste Materials

Abstract

Leaching tests are important laboratory tools that provide a method to determine the leachability and mobility of contaminants in the environment. Although a wide variety of leaching tests are available in the literature, few address the effect of oxidation/reduction reactions on contaminant release. In the laboratory, reducing conditions have been studied using biological methods, chemical reducing agents, and electrolytic techniques. Electrolytic techniques involve applying an electrolytic potential in order to change the redox of the system and were chosen for this research in order to eliminate the use of chemical reducing agents and microorganisms. The specific objectives of the research presented here were to: 1) develop an apparatus based on electrolytic techniques and 2) use the apparatus to determine the effect of time and varying potentials on changes in suspension pH, Eh, and constituent solubility. These objectives were met through two sets of studies: 1) preliminary studies using sampled-current voltammetry experiments consisting of cyclic potential sweeps and 2) electrolytic oxidation/reduction studies. Three different systems were used: 1) an iron(III) nitrate solution (test system), 2) an arsenic contaminated soil suspension (naturally oxidized system), and 3) a furnace slag suspension (naturally reduced system). The electrolysis technique was shown to be capable of changing the bulk solution Eh, pH, and constituents concentrations. However, further research must be completed in order to further explore the capability of this method.