the silica (SiO2) is one of the most used raw materials in the world, among its applications are glasses, Solar cells, refractory ceramics and even toothpaste. In this way, hundreds of thousands of tons are produced every year around the world.
Nonetheless, the traditional way this material is produced is not the most efficient way, both in energy and in economic terms. to make it, silicon metal is heated together with anthracite-type coal to very high temperatures (3500°C) to form silicon compounds.
A Professor of Materials Engineering at the University of Michigan, called Richard Laine, invented a process that, in addition to being more efficient than the traditional, uses waste in the process. According to the professor, with this process it is possible to save six tons of carbon emissions for each ton of material produced and it costs 90% unless. Incredible, not?
And what is the source of material for this new method?
Agricultural waste! Most industrial waste contains silica, such as rice husks, that hundreds of millions of tons are produced annually. And what is done with them? They are often burned and used as an energy source and their ashes (which also contains a lot of silica) are discarded in dumps or landfills.
Obtaining silica from agricultural waste is not that easy, thanks to the strong chemical bond between silicon and oxygen. But Laine managed to break this bond simply and cheaply with the help of ethylene glycol, or antifreeze and ethanol, or grain alcohol.
Ethylene glycol with a small percentage of sodium hydroxide weakens the chemical bond between silica and rice husk ash early in the process, dissolving silica in a liquid solution. Then the solution is heated to 200°C to obtain silica as a silica antifreeze polymer., which can be filtered in order to separate the polymer from the rest of the ash.
Due to the similar structures of ethanol and ethylene glycol, adding ethanol to polymer, it will replace the antifreeze, that can be removed and reused. Thus, the silica can be isolated from alcohol through distillation and a material with high purity is obtained. (99,9%).
The professor is marketing the silica made by this process through the company he formed, to Mayasil. Production is still in testing phase, mainly to know whether or not it will be scalable.
As the teacher says in the video below, they turned the ashes from a negative residue in the world to something valuable.. There's materials engineering changing the world once again!
References:
Video: New ‘green’ method for large-scale silica production gives agricultural waste a purpose
Going green: ACerS member pioneers sustainable approach for high-purity silica production
Rice husks can also be reused to make Ecocements!
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