The rare earth

The rare earth elements (REE) is 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 is important in a growing number of critical technologies due to its unique physical and chemical properties^[1]. Therefore, the REE is 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 sewage 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,some of them exist in the soil as organic,inorganic complexes and ionic state which can be absorbed and recycled directly. In this way, the rare 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 absorbed by the organism, the other is being transferred to the depositional phase.For the former one,it can influence the growth of the organism. For the latter one, the ingredient of the water may be changed.

A certain amount of rare earth elements can have negative impact on animals living 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.

Recovery technology

While research on methods for recycling and recovering REE 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 REE, and new policies implemented by some countries mandating REE recycling for selected items.

Figure 3. REE recycling steps and waste emissions.

Rare Earth Enrichment By Optimised Tools

This year we are going to design bacteria—the REEBOT to gather REE from the sewage 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 sewage.

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 sewage 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 sewage 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.