Spouted Bed Electrolytic Recovery of Metals for Source Reduction and Waste MinimizationEPA Grant Number: R826165
Title: Spouted Bed Electrolytic Recovery of Metals for Source Reduction and Waste Minimization
Investigators: Calo, Joseph M.
Institution: Brown University
EPA Project Officer: Shapiro, Paul
Project Period: January 14, 1998 through January 13, 2001 (Extended to January 13, 2002)
Project Amount: $291,499
RFA: Exploratory Research - Environmental Engineering (1997) RFA Text | Recipients Lists
Research Category: Engineering and Environmental Chemistry , Land and Waste Management
Description:This project is focused on establishing a sound technical basis for the development of a novel, spouted bed electrolytic recovery (SBER) technology for metals from dilute process waste streams such as are commonly encountered in the metal finishing, aircraft, machinery, and circuit board manufacturing industries.
In SBER, the cathode is a moving bed of conductive particles upon which the metal deposits. The treated liquid is introduced into the bed of particles as an upward flowing, high velocity jet at the center of the bottom of a small conical vessel. This jet penetrates to the free surface at the top of the bed, producing a concentric cavity known as the spout. The spout entrains particles which disengage above the bed surface, which then "rain down" on the downward moving, annular bed to be re-entrained, producing continuous toroidal circulation of particles. The spouted bed electrolytic reactor incorporates advantages of both fluidized and fixed bed particulate cathodes, while avoiding most of their important shortcomings.
Scoping data demonstrate that these systems can exhibit superior performance in comparison to other current technologies, with high metal recovery rates at high current densities and efficiencies. This means that these devices can be made quite small (capable of being mounted near individual rinse and drag-out tanks, for example). They have been demonstrated for point source recovery of silver from simulated cyanide (plating) solutions and thiosulfate (photographic) solutions, and also copper from cyanide and sulfate, nickel from sulfate, and gold from cyanide solutions. These systems also exhibit stable operation for long periods of time, unattended. Moreover, the use of metal shot or metallized glass spheres, allows for facile recovery of the deposited metal, in a high quality form which eliminates the production of objectionable byproduct pollutants such as sludges resulting from chemical precipitation processes. All of these characteristics strongly suggest that these devices can be inexpensive, with low operating and maintenance costs, which would be quite attractive both to large industrial concerns, as well as small businesses for which electrolytic recovery has heretofore been an expensive option.