Abstract: The development of chemical routes for the recovery and separation of rare earth elements (REE) is seen as a priority and strategic action by several countries demanding these elements. Among the possibilities of alternative routes, the biosorption process has been evaluated in our laboratory. In this theme, the present work attempts to assess and fit the solution equilibrium data in Langmuir, Freundlich and DKR isothermal models, based on the biosorption results of the lanthanum and samarium elements by Bacillus subtilis immobilized on calcium alginate gel. It was observed that the preference of adsorption of REE by the immobilized biomass followed the order Sm (III)> La (III). It can be concluded that among the studied isotherms models, the Langmuir model presented better mathematical results than the Freundlich and DKR models.
Abstract: The Jalovchat intrusive is built up of hornblende gabbros, gabbro-norites and norites. Within the intrusive hornblende-bearing gabbro-pegmatites are widespread. That is a coarse-grained rock with gigantic hornblende crystals. By its unusual composition, the Jalovchat intrusive has no analogue in the Caucasus. However, petrologically and geochemically, the intrusive rocks were studied insufficiently. For comprehensive investigations, the authors applied appropriate methodologies: Microscopic study of thin sections, petro- and geochemical analyses of the samples and also different petrogenic, rare and rare earth elements diagrams and spidergrams. Analytical study established that the Jalovchat intrusive by its composition corresponds mainly to the mid-ocean ridge basalts and according to geodynamic type belongs to the subduction type. In general, it is an anomalous phenomenon, as in the rocks of such composition crystallization of hornblende and especially of its gigantic crystals is atypical. The authors believe that the water-rich magma reservoir, which was necessary for the crystallization of gigantic hornblende crystals, appeared as a result of melting of water-rich mid-ocean ridge basaltic rocks during the subduction process in Bajocian time.
Abstract: Dysprosium is a rare earth element which is essential for many growing high-technology applications. Dysprosium along with neodymium plays a significant role in different applications such as metal halide lamps, permanent magnets, and nuclear reactor control rods preparation. The purification and separation of rare earth elements are challenging because of their similar chemical and physical properties. Among the various methods, membrane processes provide many advantages over the conventional separation processes such as ion exchange and solvent extraction. In this work, selective extraction and separation of dysprosium from aqueous solutions containing an equimolar mixture of dysprosium and neodymium by emulsion liquid membrane (ELM) was investigated. The organic membrane phase of the ELM was a nanofluid consisting of multiwalled carbon nanotubes (MWCNT), Span80 as surfactant, Cyanex 272 as carrier, kerosene as base fluid, and nitric acid solution as internal aqueous phase. Factors affecting separation of dysprosium such as carrier concentration, MWCNT concentration, feed phase pH and stripping phase concentration were analyzed using Taguchi method. Optimal experimental condition was obtained using analysis of variance (ANOVA) after 10 min extraction. Based on the results, using MWCNT nanofluid in ELM process leads to increase the extraction due to higher stability of membrane and mass transfer enhancement and separation factor of 6 for dysprosium over neodymium can be achieved under the optimum conditions. Additionally, demulsification process was successfully performed and the membrane phase reused effectively in the optimum condition.
Abstract: The high purity rare earth elements (REEs) have been vastly used in the field of chemical engineering, metallurgy, nuclear energy, optical, magnetic, luminescence and laser materials, superconductors, ceramics, alloys, catalysts, and etc. Neodymium is one of the most abundant rare earths. By development of a neodymium–iron–boron (Nd–Fe–B) permanent magnet, the importance of neodymium has dramatically increased. Solvent extraction processes have many operational limitations such as large inventory of extractants, loss of solvent due to the organic solubility in aqueous solutions, volatilization of diluents, etc. One of the promising methods of liquid membrane processes is emulsion liquid membrane (ELM) which offers an alternative method to the solvent extraction processes. In this work, a study on Nd extraction through multi-walled carbon nanotubes (MWCNTs) assisted ELM using response surface methodology (RSM) has been performed. The ELM composed of diisooctylphosphinic acid (CYANEX 272) as carrier, MWCNTs as nanoparticles, Span-85 (sorbitan triooleate) as surfactant, kerosene as organic diluent and nitric acid as internal phase. The effects of important operating variables namely, surfactant concentration, MWCNTs concentration, and treatment ratio were investigated. Results were optimized using a central composite design (CCD) and a regression model for extraction percentage was developed. The 3D response surfaces of Nd(III) extraction efficiency were achieved and significance of three important variables and their interactions on the Nd extraction efficiency were found out. Results indicated that introducing the MWCNTs to the ELM process led to increasing the Nd extraction due to higher stability of membrane and mass transfer enhancement. MWCNTs concentration of 407 ppm, Span-85 concentration of 2.1 (%v/v) and treatment ratio of 10 were achieved as the optimum conditions. At the optimum condition, the extraction of Nd(III) reached the maximum of 99.03%.
Abstract: Heavy rare earth (HRE) oxalate concentrates were
prepared from the Egyptian crude monazite sand (graded about 47%).
The concentrates were specified quantitatively for their constituents
of individual rare earth elements using ion chromatograph (IC) and
qualitatively by scanning electron microscope (SEM) for the other
major constituents. The 1st concentrate was composed of 10.5%
HREE where 7.25% of them represented yttrium. The 2nd concentrate
contained about 41.7% LREE, 17.5% HREE and 13.6% Th. The
LREE involved 18.3% Ce, 10.5% La and 8% Nd while the HREE
were 8.7% Y, 3.5% Gd and 2.9% Dy. The 3rd concentrate was
containing about 8.0% LREE (3.7% Ce, 2.0% La and 1.5% Nd),
10.2% HREE (6.4% yttrium and 2.0% Dy) and 2.1% uranium. The
final concentrate comprised 0.84% uranium beside iron, chromium
and traces of REE.
Abstract: Single crystals of Magnesium alloys such as Mg-1Al,
Mg-1Zn-0.5Y, Mg-3Li, and AZ31 alloys were successfully fabricated in this study by employing the modified Bridgman method. Single
crystals of pure Mg were also made in this study. To determine the exact orientation of crystals, Laue back-reflection method and pole figure measurement were carried out on each single crystal. Dimensions of single crystals were 10 mm in diameter and 120 mm in
length. Hardness and compression tests were conducted and the results
revealed that hardness and the strength strongly depended on the
orientation. The closer to basal one the orientation was, the higher hardness and compressive strength were. The effect of alloying was
not higher than that of orientation. After compressive deformation of single crystals, the orientation of the crystals was found to rotate and to be parallel to the basal orientation.
Abstract: Studies have shown that the SnAgCu solder family has been widely used as a replacement for conventional Sn-Pb solders. An attractive approach is by introducing alloying additives (rare earth elements (RE), Zn, Co, Fe, Ni, Sb) into the SnAgCu solder, which helps in refining the microstructure also improving the mechanical and wetting properties of the solder. The present work focuses on the effect of additions of 0.5% Ce and Fe into Sn-3.0Ag-0.5Cu solder, in attempt to reduce the intermetallic compound (IMC) growth and reflow properties of the solder on Cu and Ni (P) surface finish, as well as effects thermal aging on the formation of intermetallic compound (IMC) on different surface finish. Excessive intermetallic compound growth may effect the interface and solder joint due to the brittle nature of the intermetallic compounds. Thus, by introducing alloying elements, IMC layer thickness can be decrease, resulting in better joint and solder reliability.
Abstract: Twenty seven tektites from the Wenchang area, Hainan
province (south China) and five tektites from the Khon Kaen area
(northeast Thailand) were analyzed for major and trace element
contents and Rb-Sr isotopic compositions. All the samples studied are
splash-form tektites. Tektites of this study are characterized by high
SiO2 contents ranging from 71.95 to 74.07 wt% which is consistent
with previously published analyses of Australasian tektites. The trace
element ratios Ba/Rb (avg. 3.89), Th/Sm (avg. 2.40), Sm/Sc (avg.
0.45), Th/Sc (avg. 0.99) and the rare earth elements (REE) contents of
tektites of this study are similar to the average upper continental crust.
Based on the chemical composition, it is suggested that tektites in this
study are derived from similar parental material and are similar to the
post-Archean upper crustal rocks. The major and trace element
abundances of tektites analyzed indicate that the parental material of
tektites may be a terrestrial sedimentary deposit. The tektites from the
Wenchang area, Hainan Island have high positive εSr(0)
values-ranging from 184.5~196.5 which indicate that the parental
material for these tektites have similar Sr isotopic compositions to old
terrestrial sedimentary rocks and they were not dominantly derived
from recent young sediments (such as soil or loess). Based on Rb-Sr
isotopic data, it has been suggested by Blum (1992) [1]that the
depositional age of sedimentary target materials is close to 170Ma
(Jurassic). According to the model suggested by Ho and Chen
(1996)[2], mixing calculations for various amounts and combinations
of target rocks have been carried out. We consider that the best fit for
tektites from the Wenchang area is a mixture of 47% shale, 23%
sandstone, 25% greywacke and 5% quartzite, and the other tektites
from Khon Kaen area is a mixture of 46% shale, 2% sandstone, 20%
greywacke and 32% quartzite.
Abstract: There are many sources trough which the soil get
enriched and contaminated with REEs. The determination of REEs in
environmental samples has been limited because of the lack of
sensitive analytical techniques. Soil samples were collected from
four sites including open cast coal mine, natural coal burning, coal
washery and control in the coal field located in Dhanbad, India.
Total concentrations of rare earth elements (REEs) were determined
using the inductively coupled plasma atomic absorption spectrometry
in order to assess enrichment status in the coal field. Results showed
that the mean concentrations of La, Pr, Eu, Tb, Ho, and Tm in open
cast mine and natural coal burning sites were elevated compared to
the reference concentrations, while Ce, Nd, Sm, and Gd were
elevated in coal washery site. When compared to reference soil,
heavy REEs (HREEs) were enriched in open cast mines and natural
coal burning affected soils, however, the HREEs were depleted in the
coal washery sites. But, the Chondrite-normalization diagram showed
significant enrichment for light REEs (LREEs) in all the soils. High
concentration of Pr, Eu, Tb, Ho, Tm, and Lu in coal mining and coal
burning sites may pose human health risks. Factor analysis showed
that distribution and relative abundance of REEs of the coal washery
site is comparable with the control. Eventually washing or cleaning
of coal could significantly decrease the emission of REEs from coal
into the environment.
Abstract: Cenozoic basalts found in Jiangsu province of eastern
China include tholeiites and alkali basalts. The present paper analyzed
the major, trace elements, rare earth elements of these Cenozoic
basalts and combined with Sr-Nd isotopic compositions proposed by
Chen et al. (1990)[1] in the literatures to discuss the petrogenesis of
these basalts and the geochemical characteristics of the source mantle.
Based on major, trace elements and fractional crystallization model
established by Brooks and Nielsen (1982)[2] we suggest that the
basaltic magma has experienced olivine + clinopyroxene fractionation
during its evolution. The chemical compositions of basaltic rocks from
Jiangsu province indicate that these basalts may belong to the same
magmatic system. Spidergrams reveal that Cenozoic basalts from
Jiangsu province have geochemical characteristics similar to those of
ocean island basalts(OIB). The slight positive Nb and Ti anomalies
found in basaltic rocks of this study suggest the presence of Ti-bearing
minerals in the mantle source and these Ti-bearing minerals had
contributed to basaltic magma during partial melting, indicating a
metasomatic event might have occurred before the partial melting.
Based on the Sr vs. Nd isotopic ratio plots, we suggest that Jiangsu
basalts may be derived from partial melting of mantle source which
may represent two-end members mixing of DMM and EM-I. Some
Jiangsu basaltic magma may be derived from partial melting of EM-I
heated by the upwelling asthenospheric mantle or asthenospheric
diapirism.