Carbonised red mud can treat water cheaply

Carbonised red mud can help in water treatment, say scientists. Copyright: Dany Caron

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[SRINAGAR] Red mud, a by-product of alumina industries, can be ‘carbonised’for safe handling and the resulting material can be used to treat water contaminated with heavy metals, say scientists.

Red mud, so called for its reddish iron content, turns into ‘carbonised’ red mud (CRM) that is enriched with carbon when it is used as a catalyst for ‘cracking’ methane and other hydrocarbons into different products.

Carbonisation occurs when a complex substance is converted into carbon-containing residue through heat during burning; or chemical treatment.  

Research findings on CRM by Ian D. Pulford, senior lecturer at the University of Glasgow — and his associates from The Energy and Resources Institute (TERI) in New Delhi — have been accepted by the Journal of Environment Management – Elsevier for its June 2012 issue.

According to their findings, after carbonisation, the capacity of red mud to remove metal contaminants, particularly lead and copper, from water improves ten-fold as compared to red mud that has been acidified — an existing method to improve the waste material.  

CRM can be separated easily because it is magnetic. Also, being far less caustic than untreated red mud, CRM is safe to handle, Pulford told SciDev.Net. "The caustic nature of a substance means it causes burns to skin and eyes upon handling," he explained. 

An estimated 120 metric tonnes of red mud are produced in the world annually, and a typical plant making alumina may produce up to two times more red mud.

Alumina is extracted from bauxite ore and forms the basic material from which aluminium metal is smelted. It is also widely used in the making of ceramic products and in chemical processes.

Red mud waste poses a huge disposal problem as the land where it is dumped can neither be farmed nor built over.

Accidental release of around one million cubic metres of red mud from an alumina plant in Hungary in October 2010 killed at least nine people and contaminated a large land area. Such incidents have been reported from elsewhere.  

Pulford said further research was needed before the new method of handling red mud can be applied for practical use. 

"We were producing CRM in a small-scale reactor (gram amounts), " Pulford said. "But in order for it to be viable as a water cleanup material, we need to see what happens at a larger scale."

Pulford said more information was needed on production at an industrial scale. "The CRMs produced by cracking different hydrocarbons may have slightly different properties. We are looking at this aspect."

“This is very promising research, but we are still at an early stage,” Rajiv Chibber, information officer at TERI, told SciDev.Net.

Link to the abstract in the Journal of Environment Management