Monday, 24 March 2014 15:08

A New Source for Potassium Fertilizer

    Allanore lab chemically alters feldspar, an ore closer to home for countries like Brazil, as an alternative to reliance on imports.
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    Bananas we eat for obtaining potassium, an essential nutrient for life, are often grown in places like Brazil, in the Southern Hemisphere, but they require potassium fertilizer obtained from mining potash in the Northern Hemisphere. That makes a country like Brazil dependent on imports for 90 percent of its potassium and India, 100 percent. 

    Hydrosyenite powders developed from potassium feldspar rock by Antoine Allanore, the Thomas B. King Assistant Professor of Metallurgy at MIT, and Postdoctoral Associate Taisiya Skorina promises to provide potassium fertilizer for places like Brazil from locally abundant natural ore deposits. The newly developed compound has a popcorn-like texture. Photo courtesy of the researchers.

    Antoine Allanore, the Thomas B. King Assistant Professor of Metallurgy at MIT, is leading a research effort with globally important implications to produce potassium fertilizer from feldspar, a rock abundant in places like Brazil but which naturally releases potassium at too slow a rate for commercial farming.

    The Canadian province of Saskatchewan is home to a third of global output, making Saskatchewan the world's second largest potash producer, with annual revenues of about $5.3 billion, according to recent research report from Rockstone Research Ltd. Rising corn and wheat consumption for animal feed as well as growing world population drove potash demand up by 83 percent since 1970 to about 62.8 million tons in 2012, mainly attributable to increased demand from China, India, and Brazil. China's largest state-owned fertilizer producer, China Blue Chemical, last year made an investment in Vancouver-based Western Potash Corp. that will guarantee it a supply of potash for 20 years.

    MIT research, funded by Brazilian mining company Terrativa, may have a solution, beginning with Brazil. The research funds are managed through the Materials Processing Center. In the Allanore lab, several Postdoctoral Associates are exploring different aspects of producing potassium from feldspar.

    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.)

    David Ciceri is using microfluidic techniques to study how potassium leaches from feldspar under exposure to acidic solutions. Ciceri is in the process of writing a review article, which will include a historical perspective, of the potash problem. (See related article.)

    "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. Allanore and colleagues have a provisional patent. When the provisional patent in converted, Allanore will disclose his findings; Skorina will be a co-author their paper. Allanore and Ciceri plan to present their potassium feldspar research at the World Soil Science Congress in Korea June 8-13, 2014.

    A field study is underway in Brazil, to see how plants such as sugar cane and oranges react to the new potassium material. Field studies are needed because laboratory studies don't replicate natural conditions where release of potassium into the soil and its uptake by plants are affected by bacteria, fungi and other material in the soil. "It's a pretty intricate system, where we don't have a benchtop experiment to replicate that," Allanore says. Microfluidic devices may be better able to mimic actual field conditions.

    "It was pretty significant funding, and we've accomplished both goals. One was to develop a process to make the material perform better, in a controlled manner, and at the same time we are developing the tools that can allow someone to validate the performance of the material in more real conditions," Allanore says. "This is extremely exciting for us because we've been doing a lot of work on that, and finally our results have a direct impact."

    The new material could also reduce waste in agricultural fertilizers because farmers typically only get the benefit of about three-quarters of the potassium fertilizer they apply. About 30 percent is lost to run-off from rainfall and other factors, so farmers need to apply 30 percent extra. Another potential benefit is eliminating the harmful salt build up that can be caused by potassium chloride-based fertilizer from potash because in feldspar-based fertilizer, potassium is released from silicon and oxygen compounds and doesn't include chloride.

    Written by Denis Paiste, Materials Processing Center

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    Last modified on Wednesday, 21 May 2014 17:21