General
- The rare earth
elements comprise fifteen lanthanide elements (atomic number, Z = 57–71)
as well as yttrium (Z = 39) and scandium (Z = 21), although promethium
(Z = 61) does not appear in nature due to its radioactive
instability.They are an extremely coherent group in terms of chemical
behavior and have recently been subjected to intense investigation sin
the field of marine geochemistry.
- All of the rare earth
metals are found in group 3 of the periodic table, and the 6th and 7th
periods. The Rare Earth Elements are made up of two series of elements,
the Lanthanide and Actinide Series.
Processing
- Monazite, one of
the major sources of rare earths, is normally opened by digestion
with hot concentrated caustic soda solution. Caustic digestion
dissolves phosphate and leaves a hydrated mixed metal oxides cake
containing thorium, uranium and rare earths. By leaching this cake
with hydrochloric acid at pH 3.0 to 3.2 bulk of the rare earths are
preferentially removed and separated.
- The individual
extraction of rare-earth elements (from terbium to ytterbium, plus
yttrium) was systematically investigated in hydrochloric acid
aqueous solution, where the metals concentration ranging from
0.05mol/L to 0.5mol/L, using a solvent mixture containing 1.0M of
the extracting organic know as Ionquest-801, diluted in an aliphatic
organic compound, and an acidic range of 0.001mol/L to 0.7mol/L,
aiming at identifying suitable conditions to the fractioning of
liquors with similar chemical composition to those obtained during
the processing of a Brazilian xenotime concentrate, using lower
acidity levels than those usually practiced.
Technology
- The inductively
coupled plasma atomic emission spectroscopy (ICP-AES) for the
determination of individual rare-earth elements (REE) was evaluated
by comparison with instrumental neutron activation analysis (INAA)
and x-ray fluorescence spectrometry (XRF) .
- As rare earth
elements are widely used in many fields, we deem it worthwhile to
add rare earth elements to the thermal
sprayed cored wires and observe their effect on the coatings.
Therefore, this research is an effort to develop the Fe-Cr-Ni
austenitic stainless steel thermal sprayed cored wires with rare
earth elements added and study the effect of the rare earth
elements on the coating’s corrosion-resistance.
Functions
- Differences in
behavior among the chlorides of seven rare earth elements (REEs)—yttrium
(Y), cerium (Ce), and praseodymium (Pr) (light REEs); europium (Eu)
and dysprosium (Dy) (medium REEs); ytterbium (Yb) and lutetium (Lu)
(heavy REEs)—were investigated through intravenous administration of
the REEs to rats.
- The validity of
using rare earth elements as flow markers of undigested residues was
evaluated by comparing mean gastrointestinal residence time (GMRT)
of rare earths specifically applied to cottonseed hulls (CSH) to
that of the indigestible fiber of CSH. Feces were collected from
five lambs fed a mineral supplemented diet of CSH containing 52 g
CP/kg DM and five lambs fed a CSH plus cottonseed meal diet
(CSH+CSM) containing 123 g CP/kg DM.
Market
- Due to the wide
fields in end use of rare earth elements, the market trend of rare
earth products is closely linked to the whole economic environment.
The slump of global economy beginning from the year of 2000
certainly made great impact on rare earth industry. In this article,
a brief comment is made on the impact of global economic background
to Chinese rare earth industry
- The annual growth
rate of over 9% in Chinese rare earth industry in 90s of 20th mostly
benefited from end uses of New economy‚ industry. Gue-Consilium has
announced the discovery of many economic-grade samples of rare earth
elements in the Grevet Twp, Lebel-sur-Quevillon area of northwestern
Quebec, Canada. This area may become the first rare earths mine in
Canada and eastern North America.
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