Increase In Rare Earth Elements Research Articles

Mycoremediation of Flotation Tailings with Agaricus bisporus.

Due to their enzymatic and bioaccumulation faculties the use of macromycetes for the decontamination of polluted matrices seems reasonable for bioremediation. For this reason, the aim of our study was to evaluate the mycoremediation ability of Agaricus bisporus cultivated on compost mixed with flotation tailings in different quantities (1, 5, 10, 15, and 20% addition). The biomass of the fruit bodies and the content of 51 major and trace elements were determined. Cultivation of A. bisporus in compost moderately polluted with flotation tailings yielded significantly lower (the first flush) and higher (the second flush) biomass of fruit bodies, compared with the control treatment. The presence of toxic trace elements did not cause any visible adverse symptoms for A. bisporus. Increasing the addition of flotation tailings to the compost induced an elevated level of most determined elements. A significant increase in rare earth elements (both flushes) and platinum group elements (first flush only) was observed. The opposite situation was recorded for major essential elements, except for Na and Mg in A. bisporus from the second flush under the most enriched compost (20%). Nevertheless, calculated bioaccumulation factor values showed a selective accumulation capacity—limited for toxic elements (except for Ag, As, and Cd) and the effective accumulation of B, Cu, K, and Se. The obtained results confirmed that A. bisporus can be used for practical application in mycoremediation in the industry although this must be preceded by larger-scale tests. This application seems to be the most favorable for media contaminated with selected elements, whose absorption by fruiting bodies is the most efficient.

Geochemical and spectroscopic investigation of apatite in the Siilinjärvi carbonatite complex: Keys to understanding apatite forming processes and assessing potential for rare earth elements

The Siilinjärvi phosphate deposit (Finland) is hosted by an Archean carbonatite complex. The main body is composed of glimmerite, carbonatite and combinations thereof. It is surrounded by a well-developed fenitization zone. Almost all the rocks pertaining to the glimmerite-carbonatite series are considered for exploitation of phosphate. New petrological and in-situ geochemical as well as spectroscopic data obtained by cathodoluminescence, Raman and laser-induced breakdown spectroscopy make it possible to constrain the genesis and evolution of apatite through time. Apatite in the glimmerite-carbonatite series formed by igneous processes. An increase in rare earth elements (REE) content during apatite deposition can be explained by re-equilibration of early apatite (via sub-solidus diffusion at the magmatic stage) with a fresh carbonatitic magma enriched in these elements. This late carbonatite emplacement has been known as a major contributor to the overall P and REE endowment of the system and is likely connected to fenitization and alkali-rich fluids. These fluids - enriched in REE - would have interacted with apatite in the fenite, resulting in an increase in REE content through coupled dissolution–reprecipitation processes. Finally, a marked decrease in LREE is observed in apatite hosted by fenite. It highlights the alteration of apatite by a REE-poor fluid during a late-magmatic/hydrothermal stage. Regarding the potential for REE exploitation, geochemical data combined with an estimation of the reserves indicate a sub-economic potential of REE to be exploited as by-products of phosphate mining. Spectroscopic analyses further provide helpful data for exploration, by determining the P and REE distribution and the enrichment in carbonatite and within apatite.

Coercivity enhancement of hot-deformed Ce-Fe-B magnets by grain boundary infiltration of Nd-Cu eutectic alloy

The coercivity of hot-deformed Ce-Fe-B magnet was substantially improved from ∼8 × 10−4 to ∼0.7 T by the grain boundary infiltration of Nd-Cu eutectic alloy. Transmission electron microscopy have shown the formation of (NdxCe1-x)2Fe14B shell in Ce2Fe14B grains and the increase of rare earth elements in the intergranular phases after the process. The former enhances the anisotropy field of the shell region and the latter weakens intergranular exchange coupling. Micromagnetic simulations showed that the increase of the Nd content in the (NdxCe1-x)2Fe14B shell results in only a slight increase in coercivity for ferromagnetic intergranular phase. This explains the minor increment of coercivity of only ∼0.2 T for the increased amount of the Nd-Cu infiltration from 10 wt% to 40 wt%. For further increase of the coercivity, exchange decoupling by increasing the rare earth content in the intergranular phase is predicted to be effective.

An in vitro study on the biocompatibility of WE magnesium alloys

Magnesium alloys are being actively studied for intravascular stent applications because of their good mechanical strength and biocompatibility. To rule out the high allergenicity of nickel and neurotoxicity of aluminum element, four kinds of WE magnesium alloys (where "W" represents the metallic element Y and "E" represents mixed rare earth (RE) elements; Y: 2.5, 5.0, 6.5, and 7.5 wt %; Nd: 1.0, 2.6, 2.5, and 4.2 wt %; Zr: 0.8 wt %) were chosen for in vitro investigation of their biocompatibility using cell culture. The results showed that, with the increase of rare earth elements in WE magnesium alloys, fibrinogen adsorption decreased and coagulation function was improved. It was also found that WE magnesium alloys promoted the adhesion of endothelial cells. With the increase of adhesion time, adhered cell numbers increased gradually. With 25% extracts, all the WE alloys promoted cell migration, while 100% extracts were not conducive to cell migration. Based on the above results, WE magnesium alloys 5.0WE (5.0Y-2.6Nd-0.8Zr) and 6.5WE (6.5Y-2.5Nd-0.8Zr) have better biocompatibility as compared with that with 2.5WE (2.5Y-1.0Nd-0.8Zr) and 7.5WE (7.5Y-4.2Nd-0.8Zr), and could be as the promising candidate materials for medical stent applications.

Comparison of speciation and bioavailability of rare earth elements between wet rhizosphere soil and air-dried bulk soil

A comparison was made between the speciation and bioavailability of rare earth elements in rhizosphere and nonrhizosphere soils and between wet and air-dried soils under greenhouse conditions by using a homemade rhizobox. The speciation of rare earth elements in soils is experimentally defined as water soluble, exchangeable and carbonate bound (B1), Fe–Mn oxide bound (B2) and organic matter and sulfide bound (B3). The air-drying process of the wet soils resulted in an increase in rare earth elements in fractions B1 and B2, and a decrease in B3. Generally, a better correlation was obtained between the speciation and bioavailability by using wet soils than that by using air-dried soils, and as the conditions in the former are close to the realistic conditions of plant growth in the environment better plant availability is also achieved between the speciation of rare earth elements in the rhizosphere soils than that in the nonrhizosphere soils. Application of the rhizosphere wet soils is be strongly recommended in the future study on the speciation analysis and bioavailability of trace elements in soils.