Team:HUST-China/project/background
「Background」
The rare earth elements
The rare earth elements (REE) are a group of metals comprised of yttrium and fourteen lanthanide elements: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The REE are important in a growing number of critical technologies due to their unique physical and chemical properties[1]. Therefore, the REE are called “the Vitamin of Industry”. Besides, the output of REE varies from country to country.
In China, especially in Jiangxi province, there’s a huge amount of mining and smelting plants. Because of the waste water from these factories cannot be treated well, the content of REE in the surrounding soils and crops increased at a high rate [2].
The environmental problems
The rare earth elements (REE) may have an impact on soil、water and organism.
When rare earth elements enters the soil, most of them will be absorbed by the soil, a small fraction of the remaining REEs exist in the soil as organic 、inorganic complexes and ionic state which can be absorbed and recycled directly. In this way, the rare earth elements will affect the amount of microorganism、the activity of the enzyme and the nutrients in the soil.
There are two main kinds of rare earth elements in the water, one is being sucked by the organism, the other is transferred to the depositional phase. The rare earth elements in the water is mainly present in the suspended state, so they can’t migrate easily. Finally, they will exist in the deposited state which can be moved easily.
A certain amount of rare earth elements can inhibit the growth of animals and cause the pathological changes of the spleen 、liver and other visceral tissues. Besides, it can also affect the amount of rare earth elements in the internal organs.
Existing recovery technology
While research on methods for recycling and recovering REEs from as early as 1984 was identified during our literature review, it is not until recently that more attention within industry and the literature has been given to the topic of REE recycling. The primary drivers for this renewed focus include the increased demand for REEs, concern about REE supplies, increasing cost of REEs, and new policies implemented by some countries mandating REE recycling for selected items.
Rare Earth Enrichment By Optimised Tools
This year we are going to design a bacteria—the REEBOT to gather REE from the wasted water from the factories. As we know that most of the REE are lanthanide, so we decide to use the most successful lanthanide binders that can selectively bind lanthanide ions with high affinities[3]. We try to make the bacteria express the LBTs intelligently to bind the lanthanide ions in the wasted water.
The present in-situ leaching technology will destroy vegetation, and the electrolyte solution will be poured into the environment[4]. The bacteria we designed will bind the REE in the wasted water and then gather on the surface of the silicon—the si-tag we used in iGEM-HUST 2015—so it limited the bacteria’s expansion to keep safe. We can use this REE-bot to clear up the REE in the wasted water and recycle them and then reuse it in the industrial products.
Through our work, we can reduce the pollution of rare earth elements to the water and meet the high demand of them in the market..We believe that it will be used well in the future.
