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May 2018

Baking Bauxite Rocks to Solve A Global Health Crisis

A team of Foundry users has further developed a simple, inexpensive solution to a major global health crisis. Their work was recently published in the journal, Environmental Science & Technology.

Skeletal fluorosis, a condition leading to severe bone deformities and irreversible crippling, is caused by childhood consumption of groundwater naturally contaminated by extremely high concentrations of fluoride (4X -10X higher than the World Health Organization’s permissible limit of 1.5 ppm). Hundreds of millions of people in rural India and other regions of the world rely on groundwater sources that contain toxic levels of fluoride, but cannot afford the common treatment to remove this excess fluoride. The most common method of removing excess fluoride relies on the use of activated alumina, an industrially refined adsorbent material that is prohibitively expensive and inaccessible to impoverished populations. 

In earlier published work, the researchers demonstrated that powdered bauxite, a commonly found aluminum-rich ore, could serve as a cheap material for adsorbing fluoride effectively. However, they found that some bauxite samples sourced from India performed very poorly in fluoride-removal adsorption experiments compared to bauxite samples sourced from other countries (e.g., Ghana, Guinea, and the U.S.). 

For this recent publication, the researchers conducted in-depth studies on different samples of bauxite ore sourced from different parts of the world.  Ironically, some of these bauxite-rich areas were not far from other areas with populations suffering from high-fluoride groundwater. The researchers then used characterization techniques at the Molecular Foundry to determine how and why Indian-sourced bauxite performed poorly in adsorbing fluoride. They discovered that a small trace content of an alkaline mineral (calcite, a form of calcium carbonate) hindered its performance. They also found water molecules chemically bound to, and blocking, some of the active sites in bauxite that would normally bind fluoride.

The team then developed a low-cost approach for increasing the effectiveness of the adsorbent. By simply baking the Indian bauxite at 300˚C, the chemically bound water on bauxite active sites could be driven away. It increased the surface area by an order of magnitude, thereby enabling the bauxite to efficiently absorb the fluoride. The effect of the trace alkali mineral could be countered with a small measured dose of acidic material.  The authors suggest that these low-cost strategies might provide the basis for an effective and affordable approach to fluoride mitigation for about 66 million people in India that suffer from fluoride’s adverse effects.  

Read the paper here.