Bauxite For Defluorination

By Milica Krstovic

Chinnasaidulu Arpula, 32, who was left crippled by fluorosis by his early 20s, stands with the aid of a walking stick after a successful operation on his spine, CREDIT: Catherine Davison, SOURCE: The Telegraph, UK


Over 200 million people around the world are at risk of exposure to geogenic fluoride in the drinking water which results in century-old problems of dental or skeletal fluorosis development in children. Still, there exists no technology that addresses this issue properly, but Katya Cherkumilli has a simple and innovative idea for its potential solution.


Universal and equitable access

Having a glass of pure water does not sound like a privilege until one realizes that over a fourth of the world's population does not have access to safely managed drinking water. UNICEF has set a goal to achieve “universal and equitable access to safe and affordable drinking water for all” by 2030. However, investigating the current integration state of available water treatment technologies reveals that this goal may be a bit too ambitious. We will focus here on the issue of fluoride contamination and options for its remediation.


Do we need to ‘invent the wheel’?

Having a closer look at already existing technologies for defluorination may give a hint for creating the one that will be a breakthrough. Affordability, simplicity of maintenance, scalability, and cultural acceptability are the main qualities we are looking for. Nonetheless, there were some great ideas that did not reach the scale-up because they were missing some additional reconsiderations.


Turned into the storage for eggs

One great example of this case was the supply of alumina tanks with active alumina filters to Indian villages. Women were asked to maintain the filter by scraping the top layer off for its unplugging from time to time. However, alumina tanks soon turned into storage places for eggs and other agricultural means. People simply decided to use it for ‘higher priority’ needs. So, this technology, although practical, relied heavily on the behavioral change and overburden of women, who are usually responsible for collecting and treating the water.


Can we make it simpler?

Using activated alumina as a filter media for fluoride removal is already scaled-up technology, however with a very complex global supply chain and high cost. It is produced through high temperature (1000 °C) calcination and processing treatment of bauxite, widely spread alumina-rich ore. While searching for the optimal technology, Katya Cherkumilli came to the thought: What if we skip the expensive high-temperature treatment phase, and instead use bauxite directly for the adsorption of fluoride? Resources of bauxite are often positioned near regions with endemic fluorosis and the cost reduction would be enormous (from $1500 to $30 per ton of bauxite), which would enable its easy incorporation with lower logistical complexity.


Bauxite, SOURCE: Bauxite Mining and Aluminum Processing, Bruker


Increasing Efficiency

In some regions, the presence of limestone in bauxite ores reduces the fluoride affinity for adsorption, so additional treatments were considered to be taken into account to improve the bauxite adsorption efficiency. The required bauxite dose can be reduced by 73-90%  by performing the heating treatment at 200-300°C and acidifying the solution with bauxite using CO_2 or some acid.


Getting out of the lab to the real industry world

Several challenges need to be faced when stepping out of the lab zone. Firstly, while just milligrams of bauxite are needed to be milled in the lab for its performance testing, the story significantly differs when the main objective is the utilization of the large mills for industrial purposes. Also, the additional technology for bauxite filtering is unavoidable, since its particles remain suspended in water (with fluoride adsorbed on them), introducing additional chemical contaminants in the water from the ore. Nevertheless, already-performed tests show that bauxite can become a remarkably cheaper alternative to the active alumina treatment.


However, the incorporation of the treatment technology in places where the water quality assessment is inapplicable makes no sense. Thus, quality monitoring is the area that needs to advance parallel to the water treatment field in order to reach scalable, affordable, and equitable solutions for the defluorination of drinking water.


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