Superfund Research Program

Metals Removal via Spouted Bed Electrolytic Reactors (SBER)

Project Leader: Joseph M. Calo
Grant Number: P42ES013660
Funding Period: 2005-2009

Project-Specific Links

Final Progress Reports

Year:   2008 

The goal of this project is the development of new, effective ex-situ remediation technologies for contaminated sites, based on the application of spouted bed particulate electrodes and novel electrochemical techniques to the removal of heavy metal compound mixtures from contaminated aqueous sources. The following are highlights of Dr J.M. Calo’s team’s work.

• During the past project year, the construction of the novel combined Cyclic Electrowinning/Precipitation (CEP) was completed and the test program is ongoing. CEP is a computer-controlled system developed for the remediation of heavy metal mixtures from aqueous solutions down to low concentrations. It combines the large volume reduction capability of heavy metal removal by electrowinning on particulate electrodes, coupled with in-process precipitation/redissolution steps to reduce heavy metal concentrations to very low levels in the final effluent, while also increasing in-process metal concentrations for effective removal via electrowinning. The results thus far look very promising. The experimental program is continuing with binary mixtures of Cu, Ni, and Cd, followed by three-component mixtures of these metals as well.
• In conjunction with the CEP system work, this project partnered with the Research Translation Core by serving as a sponsor/mentor of a student project in the undergraduate course ENGN1930G,H, Entrepreneurship I and II. CHMR Solutions (the mentored the student entrepreneurship team) is based on the CEP system described above to remove heavy metal contamination from Brownfields sites. The CHMR Solutions business plan was first runner-up ($3,500) in the contest run by the local student entrepreneurship club at Brown University, and in the statewide contest it was one of only two runners-up ($5000).
• The research team has demonstrated that arsenic, chromium, and mercury can be co-electrosorbed on granular activated carbon (GAC) in an electric field at µg/l-levels. It was also shown that the presence of chromium increases both the uptake rate of arsenic on the GAC, as well as its capacity. This cooperative effect appears to be due to "electro-assisted precipitation." That is, electrosorbed chromium anions are electrosorbed and then arsenic anions apparently "precipitate" onto the Cr-containing sites. The data suggest that a number of different metals may be used in this fashion as arsenic "getters." This opens up a number of possibilities for engineering sorbents and adsorption systems to specifically take advantage of this effect. Electrodesorption of arsenic by switching the carbon potential from anodic to cathodic was also shown to be effective for removal of electrosorbed arsenic from the GAC. This represents a potentially facile and economical adsorbent regeneration technique.
• The team has also demonstrated "cyclic electrosorption" of arsenic using cyclic voltammetry (CV) with a porous carbon electrode on a quartz crystal microbalance (QCM). Results show that continuous cycling of the potential on the carbon electrode from cathodic to anodic as a sawtooth wave creates new carbon adsorption sites during each cycle, such that the mass increase attributed to arsenic, increases with each cycle. "Cyclic electrosorption" is a new finding that may be developed into a potentially useful remediation technique. It may also be effective for other heavy metals and pollutants as well. It can be used to increase the capacity of sorbents as well as to regenerate them in a cost-effective fashion.
• The team has also developed a technique for the electrodeposition of selenium on porous carbons for enhanced mercury capture from aqueous solutions, while minimizing Se loss. They have now electrodeposited elemental selenium on a few different carbon materials, including: a platinum-supported, carbon ‘paste’ electrode, produced from a granular activated carbon (Darco 12×20); monolithic carbon rods; and a commercially available woven activated carbon fibre cloth (Spectracarb 2225). These materials show promise for the development of “high performance” sorbents for mercury removal from aqueous solutions.