India imports large quantities of potash to meet the demand of potassium-based fertilisers. Studies have shown that minerals from the mica family are alternate sources of potassium. India has plenty of mica reserves that can be used for the purpose. Scientists have tried mineral chlorides such as calcium chloride and sodium chloride to recover potassium out from mica. But this method of extracting potassium is so expensive and has yet not been established commercially
Recently, researchers from the Institute of Minerals and Materials Technology, Bhubaneshwar reported a tweak that could make this method economically viable. Instead of relying on mineral chlorides, they used lime mud as additive during leaching. Lime mud, a solid-waste from paper industries, is also a rich source of calcium carbonate.
The researchers collected mica scrap samples from sheet mica manufacturers in Jharkhand and the grey-coloured lime mud waste from a paper mill in Choudwar, Odisha. Replacing calcium chloride with lime mud, they experimented with the standard roast-leach method using a muffle furnace.
The scientists roasted ten grams of the mica sample mixed with different amounts of lime mud and sodium chloride at different temperatures and leached the roasted product using water to extract potash as per routine procedure. They also characterized the products processed at different stages to understand the phase transformations during roasting.
“We could recover ninety-nine percent of potash by roasting for thirty minutes at nine hundred and fifty degrees celsius. Further increase in temperature reduced recovery,” says Sandeep K Jena, CSIR-IMMT.
“When we decreased roasting temperature by sixty-eight degrees, the yield was nearly eighty-five percent potash. But sodium chloride consumption also reduced by 12 per cent. This is economically advantageous,” says Nilima Dash, his colleague.
“Since less heat and sodium chloride are consumed, combining lime mud and sodium chloride is a less costly method for potash extraction. Moreover, this process is value addition to the lime mud, which is regarded as a solid waste and till date not reported to be used in any commercial application”, adds Swagat S Rath, CSIR-IMMT.
The method can help scale up the recovery of potash from scrap mica and reduce the outflow of money for importing potash, say the scientists.
Freelance writer, Cuttack
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