E. P. Lokshin

Preparation of LiTaO3 , LiNbO3 , and NaNbO3 from Peroxide Solutions

A procedure is described for preparing peroxide solutions of LiTaO3 and LiNbO3 . It is shown that the use of peroxide solutions makes it possible to obtain stoichiometric LiTaO3 , LiNbO3 , and NaNbO3 and LixNa1 – xNbО3 solid solutions.

Sol-gel synthesis of Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

A modified sol-gel process was studied as applied to synthesize a lithium-conducting solid electrolyte of composition Li1.3Al0.3Ti1.7(PO4)3 (LATP) using water-soluble salts Al(NO3)3 · 9H2O, LiNO3 · 3H2O, and (NH4)2HPO4 and a titanium(IV) citrate complex. As-synthesized samples were characterized using X-ray powder diffraction, DSC/TG, SEM, and impedance spectroscopy. Sintering of as-synthesized amorphous powders at 700°C was found to yield LATP with crystallite sizes of 42–48 nm. Ionic conductivity of the electrolyte measured in the frequency range 25–106 Hz in disks having 86–90% density that were sintered at 1000°C was (3–4) × 10−4 S/cm. Temperature-dependent ionic conductivity was studied in the range 25–200°C. The activation energy of conduction was determined for LATP.

Water Purification with Titanium Compounds To Remove Fluoride Ions

Sorption of fluoride ions from water by titanium compounds was studied. The possibility of deep purification of fluorine-containing wastewater with water-soluble oxotitanium(IV) sulfates was analyzed and the optimal conditions of this process were determined.

Recovery of lanthanides from extraction phosphoric acid produced by the dihydrate process

Variant of precipitation of a concentrate of lanthanides from the extraction phosphoric acid formed in the dihydrate processing of the Khibiny apatite concentrate by introduction of sulfuric acid and sodium compounds into the acid is suggested. The main components of the concentrate are double sulfides of lanthanides with sodium, calcium sulfate dihydrate, and sodium hexafluorosilicate. The efficiency of recovery of lanthanides into the concentrate was studied in relation to a sodium compound used.

On integrated processing of phosphogypsum

It is shown that phosphogypsums obtained from the Khibiny apatite concentrate can be purified by percolation leaching with low-concentration sulfuric acid solutions to remove admixtures of fluorides, phosphates, and water-soluble compounds of sodium, with simultaneous transfer of rare-earth element sulfides into solution. The achievable degree of impurity extraction enables use of the purified material as a gypsum raw material for manufacture of gypsum binders and cement. The method is applicable to processing of both currently produced phosphodihydrate, phosphohemihydrate, and mixtures of these and those long stored in dumps.

Processing of phosphodihydrate to separate rare-earth elements and obtain gypsum free from phosphates and fluorides

Geotechnological complex processing of phosphodihydrate, including sulfuric acid leaching, sorption extraction of rare-earth elements, recovery of leaching solutions to obtain rare-earth products and gypsum material, which in the radioactivity and concentration of impurity fluorides and phosphates is suitable for use in building and cement industries, is outlined.

Leaching of Lanthanides from Phosphohemihydrate with Nitric Acid

Factors were examined that determine passing of lanthanides into solution during nitric acid leaching of phosphohemihydrate obtained in the course of production of wet-process phosphoric acid from Khibiny apatite concentrate by the hemihydrate technique. The data obtained were compared to the results of sulfuric acid leaching.

A study of the solubility of yttrium, praseodymium, neodymium, and gadolinium sulfates in the presence of sodium and potassium in sulfuric-phosphoric acid solutions at 20°C

Solubility of yttrium, praseodymium, neodymium, and gadolinium sulfates in the presence of sodium and potassium ions and the composition of solid phases were studied at 20°C in relation to the concentration of acids in sulfuric acid, phosphoric acid, and sulfuric-phosphoric acid solutions containing up to 36 wt % H2SO4 and 33.12 g 1−1 H3PO4.

TiO2- and Nb2O5-based photocatalytic composites

We have studied the influence of Nb content (0.35–60 wt %) and heat treatment on the phase composition, texture, and photocatalytic activity (PCA) of composites based on titanium(IV) and niobium(V) oxides and obtained materials that possess PCA under illumination at λ ≥ 900 nm.

Synthesis and conductivity studies of Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte

This paper describes the preparation of a lithium ion conducting solid electrolyte with the composition Li1.5Al0.5Ge1.5(PO4)3 by a new liquid-phase method with the use of the water-soluble salts Al(NO3)3 · 9H2O, LiNO3 · 3H2O, and (NH4)2HPO4 and the germano-oxalic acid H2[Ge(C2O4)3]. The synthesized materials have been characterized by X-ray diffraction, differential scanning calorimetry, thermogravimetry, and impedance spectroscopy. The results demonstrate that sintering of the synthesized amorphous powders at a temperature of 650°C leads to the formation of phase-pure Li1.5Al0.5Ge1.5(PO4)3. The ionic conductivity of the electrolyte measured at frequencies from 10 Hz to 2 MHz using pellets with an 86% relative density was 4.2 × 10–4 S/cm.