Experimental evaluation of electrode‐based technologies for in situ sediment remediation and industrial brine treatment

Sediment caps that degrade contaminants can improve their ability to contain contaminants relative to sand and sorbent‐amended caps, but few methods to enhance contaminant degradation in sediment caps are available. The objective of this study was to determine if powered carbon electrodes emplaced within a sediment cap could create a redox gradient and provide electron donor for the potential degradation of contaminants. In a simulated sand cap overlying the sediment from the Anacostia River (Washington, DC), electrochemically induced redox gradients were developed within 3 days and maintained over the period of the test (~100 days). Hydrogen and oxygen were produced by water electrolysis at the electrode surfaces and may serve as electron donor and acceptor for contaminant degradation. Electrochemical and geochemical factors that may influence hydrogen production were studied. Hydrogen production displayed zero order kinetics with ~75% current efficiency. The production rate was proportional to the applied voltage between 2.5V to 5V, and not greatly affected by pH or presence of divalent metal ions. Hydrogen production was promoted by increasing 1 This chapter was published in Environmental Science & Technology in 2010 under the title “Redox control and hydrogen production in sediment caps using carbon cloth electrodes”.