scholarly journals Dissolution kinetics of rare earth metal phosphates in carbonate solutions of alkali metals

2021 ◽  
Vol 251 ◽  
pp. 712-722
Author(s):  
Tatyana Litvinova ◽  
Ivan Oleynik
Keyword(s):  
Rare Earth ◽  
Calcium Carbonate ◽  
Alkali Metal ◽  
Ammonium Sulfate ◽  
Rare Earth Metal ◽  
Ammonium Carbonate ◽  
Rare Earth Metals ◽  
Earth Metal ◽  
Phosphate Dissolution ◽  
Carbonate Complexes

Treatment of apatite raw materials is associated with the formation of large-tonnage waste – phosphogypsum. The content of rare earth metals in such waste reaches 1 %, which makes it possible to consider it a technogenic source for obtaining rare earth metals and their compounds. Up to the present moment, there are neither processing plants, nor an efficient process flow to handle phosphogypsum dumps. It is rational to use a way that involves extraction of valuable components and overall reduction of phosphogypsum dumps. Such process flow is available with carbonate conversion of phosphogypsum to alkali metal or ammonium sulfate and calcium carbonate upon the condition of associated extraction of rare earth metal (REM) compounds. Associated extraction of REM compounds becomes possible since they form strong and stable complexes with hard bases according to Pearson, which among other things include carbonate, phosphate and sulfate anions. Formation of lanthanide complexes with inorganic oxygen-containing anions is facilitated by the formation of high-energy Ln-O bonds. The study focuses on the dissolution of lanthanide phosphates in carbonate media. It was established that formation of REM carbonate complexes from their phosphates is a spontaneous endothermic process and that formation of lanthanide carbonates and hydroxides serves as thermodynamic limitation of dissolution. A shift in equilibrium towards the formation of carbonate complexes is achieved by increasing the temperature to 90-100 °C and providing an excess of carbonate. The limiting stage of REM phosphate dissolution in carbonate media is external diffusion. This is indicated by increasing rate of the process with an intensification of stirring, first order of the reaction and the value of activation energy for phosphate dissolution from 27 to 60 kJ/mol. A combination of physical and chemical parameters of the process allowed to develop an engineering solution for associated REM extraction during carbonate conversion of phosphogypsum, which included a 4-5 h conversion of phosphogypsum at temperature of 90-110 °C by an alkali metal or ammonium carbonate solution with a concentration of 2-3 mol/l. As a result, a solution with alkali metal (ammonium) sulfate is obtained, which contains REMs in the form of carbonate complexes and calcium carbonate. The rate of REM extraction into the solution reaches no less than 93 %. Rare earth metals are separated from the mother liquor by precipitation or sorption on anion exchange resins, while the excess of alkali metal or ammonium carbonate is returned to the start of the process.

Deep-ultraviolet transparent alkali metal-rare earth metal sulfate NaY(SO4)2.H2O as a nonlinear optical crystal: synthesis and characterization

CrystEngComm ◽  
2021 ◽  
Author(s):  
Chao Wu ◽  
Lin Lin ◽  
Tianhui Wu ◽  
Zhipeng Huang ◽  
Chi Zhang
Keyword(s):  
Rare Earth ◽  
Alkali Metal ◽  
Rare Earth Metal ◽  
Earth Metal ◽  
Synthesis And Characterization ◽  
Nonlinear Optical Crystal ◽  
Metal Sulfate ◽  
Deep Ultraviolet ◽  
Crystal Synthesis ◽  
Optical Crystal

A new alkali metal-rare earth metal sulfate with the formula NaY(SO4)2.H2O has been synthesized using a mild hydrothermal method. It crystallizes in the noncentrosymmetric trigonal space group P3121 (No. 152)...

scholarly journals Highly efficient stabilisation of meta-ethynylpyridine polymers with amide side chains in water by coordination of rare-earth metals

2015 ◽  
Vol 13 (6) ◽  
pp. 1700-1707 ◽  
Author(s):  
Hiroki Makida ◽  
Hajime Abe ◽  
Masahiko Inouye
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Earth Metal ◽  
Helical Structure ◽  
Metal Salts ◽  
Side Chains ◽  
Highly Efficient

An amphiphilic meta-ethynylpyridine polymer with chiral amide side chains coordinated with rare-earth metal salts, especially strongly with Sc(iii), to stabilise its helical structure with CD enhancement.

scholarly journals Stability Constant of Rare Earth Metals with Substituted Thiazoles at 298.15K

2016 ◽  
Vol 64 ◽  
pp. 106-109
Author(s):  
A.B. Naik ◽  
M.S. Poharkar
Keyword(s):  
Rare Earth ◽  
Ionic Strength ◽  
Stability Constant ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Sodium Perchlorate ◽  
Earth Metal ◽  
Water Mixture ◽  
Dissociation Process ◽  
The Stability

The stability constant on complexation of rare earth metal ions Eu (III), Gd (III), Nd (III) and Tb (III) with substituted thiazole in 70% Dioxane (Dx)-water mixture have been determined by a pH and spectrophotometric method at 298.15K and ionic strength 0.1mol.dm-3(sodium perchlorate). At constant temperature, the stability constant of the formed complexes decreases in the order Tb (III), Gd (III), Eu (III), Nd (III). The dissociation process is non-spontaneous, endothermic and entrophically unfavorable while formation of metal complexes has been found to be spontaneous, endothermic and entrophically favorable.

Azopyridine-based chiral oxazolines with rare-earth metals for photoswitchable catalysis

2021 ◽  
Author(s):  
Kento Nakamura ◽  
Masaru Kondo ◽  
Chandu G Krishnan ◽  
Shinobu Takizawa ◽  
Hiroaki Sasai
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Earth Metal ◽  
Group Coordination ◽  
Azo Group ◽  
Re Catalyst

An azopyridine-based oxazoline was developed for utilizing azo group coordination and isomerization as a photoswitchable ligand. The ligand coordinated to rare-earth metal (RE) catalyst underwent efficient E/Z photoisomerization, suggesting tri-...

ChemInform Abstract: Synthetic Study of Some Rare-Earth-Metal Monohalide Hydrides MXHx and Their Alkali-Metal Intercalates.

ChemInform ◽  
1987 ◽  
Vol 18 (15) ◽  
Author(s):  
G. MEYER ◽  
S.-J. HWU ◽  
S. WIJEYESEKERA ◽  
J. D. CORBETT
Keyword(s):  
Rare Earth ◽  
Alkali Metal ◽  
Rare Earth Metal ◽  
Earth Metal

Synthetic study of some rare-earth-metal monohalide hydrides MXHx and their alkali-metal intercalates

1986 ◽  
Vol 25 (27) ◽  
pp. 4811-4818 ◽  
Author(s):  
Gerd Meyer ◽  
Shiou Jyh Hwu ◽  
Sunil Wijeyesekera ◽  
John D. Corbett
Keyword(s):  
Rare Earth ◽  
Alkali Metal ◽  
Rare Earth Metal ◽  
Earth Metal

scholarly journals Biotechnical toxicity assessment system of rare earth metals compounds

2020 ◽  
pp. 56-67
Author(s):  
M. I. Semenova ◽  
◽  
A. V. Smirnov ◽  
A. Sokolov ◽  
A. S. Kovalevskaya ◽  
...  
Keyword(s):  
Rare Earth ◽  
Human Health ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Safety Data ◽  
Earth Metal ◽  
Toxicity Assessment ◽  
Hazardous Substances ◽  
Metal Compounds ◽  
Modern Methods

Introduction. Expanding the scope of application of rare-earth metal compounds that are unique in their properties increases the interest of many researchers in studying the impact of rare-earth metals and their compounds on human health and the environment. One of the most relevant and modern methods for assessing the safety of the studied media for a biological test object is bioassay. Problem Statement. The objective necessity of determining the combined effect of rare earth metals and their compounds on human health and the environment involves the use of biological systems. Modern methods of bioassay are extremely sensitive, which is sufficient to determine sub-threshold concentrations of hazardous substances in accordance with international standards. Thus, the use of these methods can make it possible to determine the index and the degree of toxicity of rare earth metal compounds with high accuracy in order to prepare a package of necessary documentation on industrial safety of products. Theoretical Part. Based on the studied toxicological effects of rare earth metals, the authors proposed to conduct a toxicity assessment based on the concept of biotechnical systems. The object of research was oxides and carbonates of rare earth metals. The results of the study to determine the index and the degree of toxicity of rare earth metal compounds, as well as to assess the lethal concentration of LC50 (24 h) by biotesting using test organisms Paramecium Caudatum were used to write a safety data sheet for cerium oxide and carbonate. Conclusion. The studies have shown that a certain modification of the technical solutions embedded in the devices of the Biotester series makes it possible to correctly solve the problem of assessing the toxicity of rare earth metals and their compounds. Based on the research results, the safety data sheets were developed.

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