An Insoluble Titanium-Lead Anode for Sulfate Electrolytes
The project is devoted to the development of novel insoluble anodes for copper electrowinning and electrolytic manganese dioxide (EMD) production. The anodes are made of titanium-lead composite material produced by techniques of powder metallurgy, compaction of titanium powder, sintering and subsequent lead infiltration. The titanium-lead anode combines beneficial electrochemical behavior of a lead anode with high mechanical properties and corrosion resistance of a titanium anode. In the titanium-lead anode, the titanium stabilizes the lead, preventing it from spalling, and the lead sheathes the titanium, protecting it from passivation. Interconnections between manufacturing process, structure, composition and properties of the titanium-lead composite material were investigated. The material containing 20-30 vol.% of lead had optimal combination of mechanical and electrochemical properties. Optimal process parameters to manufacture the anodes were identified. Prototypes having optimized composition and structure were produced for testing in operating conditions of copper electrowinning and EMD production. Bench-scale, mini-pilot scale and pilot scale tests were performed. The test anodes were of both a plate design and a flow-through cylindrical design. The cylindrical anodes were composed of cylinders containing titanium inner rods and fitting over titanium-lead bushings. The cylindrical design allows the electrolyte to flow through the anode, which enhances diffusion of the electrolyte reactants. The cylindrical anodes demonstrate higher mass transport capabilities and increased electrical efficiency compared to the plate anodes. Copper electrowinning represents the primary target market for the titanium-lead anode. A full-size cylindrical anode performance in copper electrowinning conditions was monitored over a year. The test anode to cathode voltage was stable in the 1.8 to 2.0 volt range. Copper cathode morphology was very smooth and uniform. There was no measurable anode weight loss during this time period. Quantitative chemical analysis of the anode surface showed that the lead content after testing remained at its initial level. No lead dissolution or transfer from the anode to the product occurred.A key benefit of the titanium-lead anode design is that cobalt additions to copper electrolyte should be eliminated. Cobalt is added to the electrolyte to help stabilize the lead oxide surface of conventional lead anodes. The presence of the titanium intimately mixed with the lead should eliminate the need for cobalt stabilization of the lead surface. The anode should last twice as long as the conventional lead anode. Energy savings should be achieved due to minimizing and stabilizing the anode-cathode distance in the electrowinning cells. The anode is easily substitutable into existing tankhouses without a rectifier change.The copper electrowinning test data indicate that the titanium-lead anode is a good candidate for further testing as a possible replacement for a conventional lead anode. A key consideration is the cost. Titanium costs have increased. One of the ways to get the anode cost down is manufacturing the anodes with fewer cylinders. Additional prototypes having different number of cylinders were constructed for a long-term commercial testing in a circuit without cobalt. The objective of the testing is to evaluate the need for cobalt, investigate the effect of decreasing the number of cylinders on the anode performance, and to optimize further the anode design in order to meet the operating requirements, minimize the voltage, maximize the life of the anode, and to balance this against a reasonable cost for the anode. It is anticipated that after testing of the additional prototypes, a whole cell commercial test will be conducted to complete evaluation of the titanium-lead anode costs/benefits.
- Research Organization:
- Electrodes International, Inc. , Buffalo Grove, IL
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EE)
- DOE Contract Number:
- FG36-01GO11061
- OSTI ID:
- 840009
- Report Number(s):
- DOE/GO11061-1; TRN: US200707%%120
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
ANODES
CATHODES
COBALT ADDITIONS
COMPOSITE MATERIALS
CORROSION RESISTANCE
ELECTROLYTES
ELECTROMETALLURGY
LEAD OXIDES
MANGANESE
MECHANICAL PROPERTIES
MORPHOLOGY
POWDER METALLURGY
QUANTITATIVE CHEMICAL ANALYSIS
SINTERING
SULFATES
TITANIUM
Insoluble anode
titanium-lead anode
copper electrowinning
electrolytic manganese dioxide production
flat anode
cylindrical anode
titanium-lead composite material
titanium powder compaction
sintering
lead infiltration
titanium-lead bushing
titanium rod
structural analysis
mechanical testing
electrochemical testing
electrolyte
current density
cell voltage
bench-scale cell test
mini-pilot scale cell test
pilot scale cell test
market assessment
costs/benefits analysis.