N. Minkova

Effect of the application of superphosphate on rare earths' content in the soil

Abstract The total rare earth content in superphosphate produced by the sulphuric acid treatment of Kola apatites is ∼ 2.6 mg/g. The amount of rare earths (in forms usable by plants) transferred into the soil solution when 300 kg fertilizer/ha per year is applied has been evaluated to be 30–170 g/ha per year. A long-term use of such a superphosphate leads to a statistically significant increase of the content of the rare earths in the cultivated soils.

Solubility of some lanthanide sulfates in polycomponent systems containing H2SO4

SummaryThe paper presents data on the solubility of La, Ce, Pr, Nd sulfates in the polycomponent system La2(SO4)3·8H2O-Ce2(SO4)3·8H2O-Pr2(SO4)3·8H2O-Nd2(SO4)3· 8H2O-H2SO4-H2O (at 25°C and 64°C) as well as in the same polycomponent system but in the presence of CaSO4·2H2O. The solubility of the sulfates — ocathydrates of Pr at 25°C and 64°C and of La and Ce at 64°C in tricomponent systemLn2(SO4)3·8H2O-H2SO4-H2O are also reported.ZusammenfassungDie Arbeit präsentiert Daten für die Löslichkeit von La-, Ce-, Pr- und Nd-Sulfaten in den Vielkomponenten-Systemen La2(SO4)3·8H2O-Ce2(SO4)3·8H2O-Pr2(SO4)3·8H2O-Nd2(SO4)3· 8H2O-H2SO4-H2O (bei 25°C und 64°C) sowie in den gleichen Systemen, jedoch in Anwesenheit von CaSO4·2H2O. Über die Löslichkeit von Sulfatoctahydraten von Pr bei 25°C und 64°C und von La und Ce bei 64°C in den Dreikomponenten-SystemenLn2(SO4)3·8H2O-H2SO4-H2O wird auch berichtet.

The Possibility for Separation of Lanthanum by Solid-State Complexes with 2-Ethylhexyl Phosphoric Acids

Abstract The elemental composition, molecule, and crystal structure of precipitates obtained from an acetone solution of Ln(NO3)3 (Ln = Pr + Er or La + Nd) with a mixture of bis- and mono-(2-ethylhexyl) phosphoric acids and their sodium salts were studied. In this study we found enrichment of the precipitate with the heavier lanthanide. The separation factor for the La-Nd couple is much greater than for the Er-Pr couple, and decreases with increasing rare-earth yield in the precipitate. We discuss the significant role of the stability of LnA3 against HNO3, especially the formation of La complexes with mono-(2-ethylhexyl) phosphoric acid during enrichment.

Purification of rare earth oxide mixtures from a concentrate obtained during the processing of apatite

Abstract The possibility of purifying the rare earth concentrates produced as a by-product of sulphuric acid processing of apatite was investigated. Special attention was paid to the elimination of silicon. The precipitation of hydroxides and oxalates gave rare earth oxide mixtures with a rare earth content of about 99.6%.

The sulfuric acid processing of rare earth concentrate with high calcium content: an attempted simplified mathematical description

Abstract The sulfuric acid treatment of a rare earth concentrate with a high calcium content (produced from phosphogypsum) was studied. A simplified model of both the sulfatization process and the treatment of the sulfate precipitate produced is proposed to evaluate the material balance of the process.

Influence of complexation on the composition of equilibrium phases in the system of Ce2(SO4)3-La2(SO4)3

The cocrystallization of Ce2(SO4)3 and La2(SO4)3 is studied in aqueous and H2SO4 (150 g/dm3) solutions at 25 °C and 64 °C. The effect of the formation of inner sphere sulfate complexes of the type LnSO4+ in determining the composition of the equilibrium phases is revealed.

Changes of yttrium-aluminium garnet by thermal and mechanochemical treatment

Abstract The influence of thermal or mechanochemical treatment on the structural state of yttrium-aluminium garnet (YAG) is studied. The formation of tetragonal form of Y 3 AL 5 O 12 is assumed by X-ray diffractometry. The effects of the temperature, pressure and cooling rate are discussed and a scheme explaining the transformation is proposed. The thermally and mechanically activated samples show an increased reactivity towards some mineral acids.

Conversion of yttrium-aluminum garnet to soluble forms as a result of mechanochemical treatment

SummaryThe changes in the solubility and in the phase composition of yttrium-aluminum garnet (YAG) as a result of its mechanochemical treatment for 2 h in a planetary ball mill together with H3BO3 and Na2CO3 (mole ratio H2BO3/Na2CO3=4) in ratios (H3BO3+Na2CO3)/YAG=2,4, and 9 are studied. At a ratio of 9, the yield of yttrium in the water solution obtained upon treatment of the activated mixture at 90 °C (50 cm3 water/g sample) reaches 85%. Its content in the same solution is above 93% relatively to the sum Y+Al.ZusammenfassungDie Änderungen bezüglich Löslichkeit und Phasenzusammensetzung von Yttrium-Aluminium-Granat (YAG) als Ergebnis einer zweistündigen mechanochemischen Behandlung in einer Kugelmühle zusammen mit H3BO3 und Na2CO3 (Molverhältnis H3BO3/Na2CO3=4) bei (H3BO3+Na2CO3)/YAG-Verhältnissen von 2, 4 und 9 wurden untersucht. Bei einem Verhältnis von 9 erreicht die Ausbeute an Yttrium in der wäßrigen Lösung nach Behandlung der aktivierten Mischung bei 90 °C (50 cm3 H2O pro Gramm) 85%. Relativ zur Summe Y+Al beträgt der Yttriumgehalt 93%.