High Efficiency Electro-Refining for Direct Capture of Saleable Metals
DOE Phase II Contract DE-FG02-05ER84320
Many advances are needed to reduce energy consumption and environmental impact in mineral extraction and metal production. Electrowinning is widely used as a relatively clean and versatile process method for primary mineral extraction and refined metal production, however, conventional technologies have economic and efficiency limitations that leave significant resources unutilized or lost to waste discharge. The major challenges for electrowinning technologies are increasing production efficiency, eliminating waste, and combining separation, refining and production into a single process. Another desirable process synergy made possible with greater efficiency is combining mine waste treatment with metal production.
A unique, high efficiency electrowinning technology has been developed to economically capture metals from aqueous streams, especially low concentration (<500 mg/L), and at the same time selectively produce metals and reduced metal oxides. This technology also has the ability to turn the expense of waste treatment in to an economically profitable endeavor.
During Phase I, a number of process conditions and system configurations were evaluated for removing several different metals from acid solutions without the use of additives while the reactor design was scaled up for future use in a pilot system. Unique capabilities in energy efficiency, waste treatment and material production were demonstrated at low concentration (200 mg/L), the most notable being production of copper or cuprous oxide for about $0.30 per pound and production of iron ferrite directly from solution for less than $0.15 per pound, and removal of arsenic to discharge levels.
During Phase II, process conditions will be optimized for more selective production of specific products (metals and metal oxides) from feed streams relevant to solvent extraction and mine waste using the pilot scale reactor produced in Phase I. A pilot scale system incorporating several reactors will be designed, fabricated, and demonstrated as the vehicle to transition the technology to one of several interested potential end-users and commercial partners.
Commercial applications and market entry will initially focus on the metals recovery and reduced oxide products markets since these are very large (several $ billion each), the economic benefits are clear, and interested companies are numerous. Mine waste and acid mine drainage treatment will be leveraged by the entry applications. Based on current performance cost advantages the internal rate of return (IRR) for a licensing venture is estimated at 152% with a Net Present Value of about $145 million for just the production of cuprous oxide and iron ferrite alone (not including metals recovery) indicating very substantial economic value for this technology.
A high efficiency electrowinning technology is being developed for economic and energy efficient production of metals and metal products directly from liquid streams. This technology provides significant economic advantages for production, processing, and mine waste treatment over conventional technologies.