Grantee Research Project Results
Final Report: Spouted Bed Electrolytic Recovery of Metals for Source Reduction and Waste Minimization
EPA Grant Number: R826165Title: Spouted Bed Electrolytic Recovery of Metals for Source Reduction and Waste Minimization
Investigators: Calo, Joseph M.
Institution: Brown University
EPA Project Officer: Hahn, Intaek
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: Safer Chemicals , Land and Waste Management
Objective:
The objective of this research project focused on the development of a robust pollution prevention technology for "point source" recovery and recycling of metals from aqueous waste streams generated in a wide variety of large and small-scale industries. The process concept is based on the use of spouted beds of metallized or metallic particles as cathodes for electrolytic recovery. These systems have significant potential for providing superior performance in terms of current efficiency and current density, down to very low metal concentrations, with high recovery rates in comparison to other current technologies, as well as providing for facile recovery of metal in a high-quality form for recycling. The resultant devices are simple and inexpensive, with low maintenance costs. These devices also are quite scaleable for large-scale applications via the use of various configurations and staging strategies.
Summary/Accomplishments (Outputs/Outcomes):
In the cylindrical spouted bed electrolytic reactor (SBER), metal ions are reduced to metal on the surfaces of circulating particles when they are in contact with the cathodic connection located at the conical bottom of the vessel. The electrolyte liquid is introduced as a high-velocity jet at the center of the bottom of the vessel, which entrains particles rolling down the conical bottom from the periphery towards the center. This jet carries the particles through a draft duct to the top of the bed, where they disengage from the liquid in a region known as the "fountain," and then fall on the inverted conical distributor that directs them to the bed periphery where they fall on the moving bed cathodic, completing the toroidal particle circulation circuit.
Considerable progress in the development of this technology has been achieved over the course of this project. Laboratory-scale, prototype SBERs (12, 7.5, and 4 inches in diameter) were constructed. These reactors were used under a variety of conditions to recover metals on metallized glass spheres from metal ion-containing solutions selected to simulate those that may be found in a number of industries. In particular:
· Silver was successfully recovered in high-quality metallic form from cyanide solutions at high rates and high current efficiencies. In addition, silver was recovered from actual spent photographic fixer solution down to levels less than 1 ppm.
· Copper was successfully recovered from copper sulfate solutions. Significant backdissolution of metallic copper was noted because of both the spontaneous oxidation (attributed to low pH and dissolved oxygen) and the creation of anodic zones on the bottom conical cathode during electrowinning. These problems were circumvented via a combination of modification of operating conditions and SBER design modifications. In spite of this effect, copper still was recovered at high rates and current efficiencies. An electrochemical kinetic model was developed that explained the observed electrolytic recovery curves reasonably well.
· The recovery of nickel from nickel sulfate solutions was more difficult because it was more sensitive to pH and backdissolution effects than the copper sulfate system. However, these problems were resolved, and nickel recovery was quite successful.
· A two-dimensional spouted vessel was constructed to investigate SBER hydrodynamics. Experimental data on the velocity field, pressure distribution, and particle circulation rates were obtained under a variety of conditions. The hydrodynamic mechanism of particle entrainment in the draft tube was investigated, as well as the phenomenon of "choking" of the particle circulation under certain conditions of solids loading and liquid flow rate.
· A two-dimensional hydrodynamic model was developed to correlate the experimental data. This model represents the first generation of a predictive/design model for SBER-type systems. In summary, it was found that the SBER approach was quite successful in recovering metal in a high-quality form from all the solutions investigated to date, at high current densities and current efficiencies. Observations indicate that different optimal operating conditions exist for each type of solution, depending on its particular chemistry. This technology now is at the point where it could be commercialized for various metals recovery applications and strategies. Future work is planned for adapting this approach to the sequential/simultaneous recovery of multiple metals from complex solutions, as well as scaling up to larger-scale applications.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
| Other project views: | All 15 publications | 2 publications in selected types | All 2 journal articles |
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Shirvanian PA, Calo JM. Hydrodynamic scaling of a rectangular spouted vessel with a draft duct. Chemical Engineering Science. 2004;103(1-3):29-34. |
R826165 (Final) |
not available |
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Shirvanian PA, Calo JM. Copper recovery in a spouted vessel electrolytic reactor (SBER). Journal Of Applied Electrochemistry. 2005;35(1):101-111. |
R826165 (Final) |
not available |
Supplemental Keywords:
water, metals, heavy metals, pollution prevention, innovative technology, renewable, waste reduction, waste minimization, treatment, remediation, cleanup, engineering, analytical, modeling, metal finishing, metal waste, metalworking, electroplating, semiconductor manufacturing, aircraft manufacturing, machine tools, communications., Sustainable Industry/Business, Scientific Discipline, Industry Sectors, Manufacturing - NAIC 31-33, Chemical Engineering, Engineering, Environmental Chemistry, cleaner production/pollution prevention, chemical use efficiency, source reduction, waste minimization, chemical precipitation processes, cyanide solutions, pollution prevention, green technology, metal recovery , waste streams, circuit board manufacturing, waste reduction, cleaner production, spouted bed electrolytic recoveryProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.