Developing better methods for extracting materials – from everyday elements like copper, to rare earth elements like cerium, to essential nutrients like potassium — keeps MIT professor Antoine Allanore moving forward.
Allanore, the Thomas B. King Assistant Professor of Metallurgy at MIT, is investigating separating metals such as copper from sulfur compounds using electrolysis, which promises purer metals and less sulfur oxide pollution. "The challenge for us currently is to predict the thermodynamic and physical properties of multi-component sulfides, down the road with the objective to conduct electrolysis, which works very well if you don't have any electronic conductivity," Allanore says.
His lab also developed a new process to extract potassium, a vital agricultural fertilizer, from a mineral rock called feldspar, which is common and available in places like Brazil that rely on imports of potassium from potash salts mined in the Northern Hemisphere. "We work with a rock which contains 15 percent potash. Now we know what we need to do to control the rate of dissolution, and the amount of the original potassium you can gain access to, in a given amount of time; we have actually been very successful," Allanore explains.
Earlier work in the steel industry led to electrochemical processes to make iron without greenhouse gas emissions. One effort, with Donald R. Sadoway, John F. Elliott Professor of Materials Chemistry at MIT, led to breakthroughs in inert anode materials for oxygen evolution.
For current projects in copper sulfide and potassium feldspar, a team of postdoc associates is making headway on individual parts of these materials extraction processes:
• Taisiya Skorina has developed a process based on crushing and chemically altering feldspar to produce a new compound — coined "hydrosyenite" — with a popcorn-like texture in which potassium is contained in water-rich layers that make it more readily available. The chemical process is based on an alkaline treatment that does not lead to waste generation, a critical criteria for sustainable processes. (See related article.)
• Davide Ciceri is using microfluidic techniques to study how potassium leaches from feldspar under exposure to acidic solutions. (See related article.)
• Sang-Kwon Lee is characterizing electric flows in high temperature molten sulfide systems for better electrolysis processes. Postdoc associate Guillaume Lambotte has also been involved in the high temperature electrolysis research. (See related article.)
Allanore presented “Direct Sulfides Electrolysis: A Sustainable Process for Copper Recovery,” at the Copper International Conference in Santiago, Chile, on Dec. 4, 2013. His team will present their potassium feldspar research at the World Soil Science Congress in Korea June 8-13.
Building on success of the earlier steel work, Allanore also is addressing extraction of rare earth elements, such as lanthanum and cerium, with a focus on designing better electrolytes. "We have an ongoing research effort to find new oxide-based systems that allow us to process these very reactive metals. As you change metal feed and product, you have to change your electrolyte," Allanore says.
Allanore also is teaching a class in sustainable chemical metallurgy (3.19) for junior and seniors — the only class at MIT that teaches the principles and modern realities of metal extraction.