Extraction of titanium with phenol-formaldehyde resol oligomer Yarresin B from peroxide solutions

Extraction of titanium by nitrogen-containing phenol-formaldehyde oligomer Yarresin B from peroxide sulfate solutions was studied. Molecular dynamic (MD), molecular mechanic (MM), ZINDO/1 semiempirical (single-point calculations; program package HyperChem, Release 7.52, Hypercube Inc.) calculations, and the Cambridge Structure Database (ConQuest 1.8) were used to solve the structure of the extracted complex [Ti(O)₂OR(OH)₂]₂SO₄.     

Extraction of niobium from hydrochloric solutions with tertiary amines in aprotic diluents

Extractive recovery of niobium from concentrated hydrochloric acid solutions with tertiary amines in alkylbenzene diluents in the absence of modifiers was studied.     

On the synthesis and structure of resol phenol-formaldehyde resins

Chemical structure of the SFZh-3013 standard resol phenol-formaldehyde resin was studied by the method of quantitative ¹³C NMR spectroscopy.     

Synthesis of phenol-formaldehyde resol resins using organosolv pine lignins

Lignin was extracted from white pine sawdust by organosolv-extraction using hot-compressed ethanol-water co-solvent. The optimum conditions for extracting lignin from the pine sawdust were found to be at 180 °C with ethanol-water solvent (1:1 wt/wt), where the lignin yield attained ca. 26% with a purity of ca. 83%. The lignin under such conditions was oligomers with a broad molecular weights distribution: M_n of 537, M_w of 1150 and polydispersity of 2.14. Bio-based phenol-formaldehyde resol resins were synthesized using the resultant lignin as the replacement of petroleum-based phenol at varying ratios from 25 to 75 wt.% by condensation polymerization catalyzed by sodium hydroxide. Upon heating the lignin-phenol-formaldehyde resols could solidify with a main exothermic peak at around 150-175 °C, typical of the conventional phenolic resol resins, and a secondary peak at 135-145 °C, likely due to the exothermic reactions between the free formaldehyde with phenol or lignin to form methylophenols. The replacement of phenol with lignin at a large ratio deferred the curing process, and the introduction of lignin in the resin formula decreased the thermal stability of the resin, leading to a lowered decomposition temperature and a reduced amount of carbon residue at elevated temperatures. For practical applications, it is suggested that the replacement ratio of phenol with lignin be less than 50 wt.%. The thermal stability can however be improved by purifying the lignin feedstock before the resin synthesis.     

Effect of alkylresorcinols on curing behaviour of phenol-formaldehyde resol resin

Thermal behaviour of cure-accelerated phenol-formaldehyde (PF) resins was studied using the addition of commercial mixture of water soluble oil shale alkylresorcinols (AR) to PF resin, 5-MR being as model compound. The acceleration effect of AR is based on the promotion of condensation of resin methylol groups and subsequent reaction of released formaldehyde with AR. Commercial PF resins SFŽ-3013VL and SFŽ-3014 from the Estonian factory VKG Resins have been used. The chemical structure of resins was characterised by ¹³C NMR spectroscopy. TG-DTA analysis was carried out using labsys^TM instrument Setaram. By TG-DTA measurements, the shift of exothermic and endothermic peaks and the changes of mass loss rate in the ranges of 1.5–10 g AR/100 g PF resin were studied. The effect of AR on the curing behaviour of PF resins was also followed by gel time. Testing of the plywood when using PF resin with 5 mass% of AR shows that the press time could be reduced by about 15%.     

Stability of phenol-formaldehyde ion-exchange sorbents in aqueous solutions

It is shown that ion-exchange sorbents based on phenol-formaldehyde resins can be used for a long time for isolating and separating rare alkali metals without any significant changes in the ion-exchange selectivity and capacity. When the phenol sorbents were used in alkaline solutions at elevated temperatures, carboxyl groups gradually accumulated in them as a result of the oxidation of methylol groups with oxygen dissolved in the solution. This led to a considerable increase in the ion-exchange capacity of the sorbents and a simultaneous decrease in the selectivity with respect to Cs⁺-Rb⁺ and Rb⁺-K⁺ ions (it is desirable to avoid the drying of phenol ionites in air by storing them in a swelled state in closed vessels).     

Ion-exchange isolation of chromate from alkaline peroxide solutions

The interference by excess of peroxide seriously affects the reliability of chromium determination procedures involving prior oxidation of the element with sodium or hydrogen peroxide. Some of the methods used to overcome this problem are either cumbersome or unreliable. A method for quantitative and rapid isolation of chromate from alkaline peroxide solutions is now presented. This involves sorption of chromate on a strongly basic anion-exchange resin. The interfering peroxide is washed away with 2% aqueous sodium hydroxide solution.     

A two-temperature concentration of alkali solutions on phenol-formaldehyde sorbents

The new phenomenon of a two-temperature non-reagent concentration of alkali solutions on sorbents based on the phenol-formaldehyde resin Amberlit XAD 761, PFR-1.4/0.7, and sulfonated phenol-formaldehyde ionite KU-1 was investigated. It was found that during an alkali solution’s passage through a column with a sorbent and a periodical change in temperature in the “cold” stage, the concentration of alkali in the filtrate appeared to decrease, while in the “hot” stage, the alkali concentration appeared to increase. It was shown that the increase in alkali concentration in a solution in contact with phenol-formaldehyde resin is determined by the ion-exchange properties of the phenol groups, and is associated with an increase in water dissociation upon a rise in temperature.     

Extraction of cobalt from thiocyanate solutions with polyurethane foam

The extraction of cobalt (II) from aqueous thiocyanate solutions with polyurethane foam has been extensively investigated. The extraction is enhanced by high thiocyanate concentration, high ionic strength and low temperature. A pH of 1.0-9.0 can be used for efficient extraction. Cobalt can be extracted at low concentration and the distribution coefficient is independent of foam weight. Several foam types and foam pretreatments have been examined. The effect of various substances added to the cobalt thiocyanate solutions has been investigated. Some of these substances caused either enhanced or decreased extractions by interacting with the polyurethane foam or by changing the solution chemistry.     

Preparation of pure hydrogen peroxide and anhydrous peroxide solutions from crystalline serine perhydrate

Hydrogen peroxide is one of the most versatile oxidation reagents, still it has not fully been exploited by synthetic chemists since anhydrous (let alone pure) hydrogen peroxide requires hazardous preparation protocols. We have recently reported on the crystallization of serine and other amino acid perhydrates, thus paving the way for a new method for laboratory-scale production of anhydrous hydrogen peroxide solutions. Serine is insoluble in most organic solvents (e.g., methanol, ethyl acetate, and methyl acetate) that readily dissolve hydrogen peroxide. Moreover, since the adduct of hydrogen peroxide and serine is unstable in these organic solvents, crystalline serine perhydrate readily decomposes to give anhydrous solutions of hydrogen peroxide and crystalline precipitate of the amino acid. This procedure can then yield an anhydrous hydrogen peroxide solution in a single step. Moreover, filtration of the amino acid, and room temperature evaporation of the volatile solvent (e.g., methyl acetate), yields over 99% hydrogen peroxide.     

Extraction spectrophotometric determination of niobium in rocks with sulfochlorophenol S

After acid decomposition and potassium pyrosulfate fusion, niobium (1—26 ppm) is separated from interfering elements by extraction into methyl isobutyl ketone from 6 M H₂SO₄—2 M HF and back-extracted into water. The niobium—sulfochloro-phenol S complex is extracted into amyl alcohol.     

Extraction of f-elements from nitric acid solutions with phosphoryl ketones

The extraction ability and selectivity of a series of phosphoryl ketones Ph₂P(O)CH₂C(O)Me, and Ph₂P(O)CRR’CH₂C(O)Me (R = H, Me; R’ = H, Me, n-C₅H₁₁, Ph, 2-thienyl, 2-furyl) towards trivalent lanthanides (La^III, Nd^III, Ho^III, Yb^III) and actinides (U^VI, Th^IV) were studied. The efficiency and selectivity of the new ligands in the extraction of f-elements from nitric acid solutions into chloroform were compared to those of model phosphine oxide Ph₂P(O)Bu and known extractants: tributyl phosphate (BuO)₃P(O), trioctylphosphine oxide (C₈H₁₇)₃P(O), and carbamoylmethyl phosphine oxide Ph₂P(O)CH₂C(O)NBu₂.     

Selective precipitation of rare earth orthophosphates with hydrogen peroxide from phosphoric acid solutions

It has been shown for the first time that the use of hydrogen peroxide allows precipitation of rare earth orthophosphates (La–Tb) from phosphoric acid solutions at temperatures below 100°C. Either anhydrous or hydrated orthophosphates with monazite or rhabdophane structure, respectively, can be obtained depending on rare earth element position in lanthanide series and precipitation conditions (orthophosphoric acid and hydrogen peroxide concentration). Hydrated orthophosphates with rhabdophane structure can be prepared by precipitation with hydrogen peroxide for all studied rare earth elements.     

Studies on precipitation and co-precipitation of tantalum and niobium from potassium fluoride solutions

Summary Precipitation and co-precipitation of tantalum and niobium from KF solution were investigated under various experimental conditions. Results obtained indicate that variations of HF concentration do not influence the K₂TaF₇ precipitation yield, but variations in KF concentration do. Niobium co-precipitation is mainly due to adsorption onto the surface of the solid phase. Chemical composition of the potassium tantalum fluoride was checked by neutron-activation analysis.

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Zusammenfassung Die Fällung und Mitfällung von Tantal und Niob aus Kaliumfluorid-lösungen wurde unter verschiedenen Versuchsbedingungen untersucht. Veränderungen der Flußsäurekonzentration beeinflussen die Fällungsausbeute an K₂TaF₇ zwar nicht, im Gegensatz dazu aber wird diese Ausbeute durch Veränderungen der Kaliumfluoridkonzentration beeinflußt. Die Niob-Mitfällung erfolgt hauptsächlich auf Grund der Adsorption an der Oberfläche der festen Phase. Die chemische Zusammensetzung des Kaliumtantalfluorids wurde durch Neutronenaktivierungsanalyse überprüft.

     

Extraction of ethylene glycol from aqueous salt solutions

A method is proposed for extracting ethylene glycol from aqueous salt solutions by dialysis through ion-exchange membranes, based on the Donnan exclusion of the electrolyte. Dialysis is performed in the continuous and batch modes. It is found that the batch mode of dialysis is more effective for extracting ethylene glycol from its aqueous salt solutions. The effect of the ionic form of the membrane on ethylene glycol fluxes is explained through computer simulation.     

Extraction of rhodium(III) with sulfoxides from hydrochloric acid solutions

Extraction of rhodium(III) from hydrochloric acid solutions with dihexyl sulfoxide (DHSO) and with petroleum sulfoxides (PSOs) was studied, and the optimal conditions for its recovery were found. At a phase contact time of up to 0.5 h, the extraction of rhodium(III) with sulfoxides occurred mainly by an ionassociation scenario. If the phase contact time exceeds 0.5 h, a mixed extraction scenario predominated to form the extracted complexes (L · H⁺) · [RhCl₄L₂]-(DHSO)_o and PSO (LH⁺) · [RhCl₄(H₂O) · L]⁻. The protonation of the extraction agents occurred at the donor oxygen atoms of the sulfoxide group. When rhodium was extracted with PSOs, the coordination of the extractant molecule in the inner coordination sphere of the acido complex to the metal ion occurred through the donor sulfur atom of the sulfoxide group, while with the use of DHSO, through the donor atoms of sulfur and oxygen of the sulfoxide group. Electronic, ¹H NMR, and IR spectroscopy and elemental analysis were used to determine the composition of the extracted compounds and suggest their structure.     

Extraction of rhenium(VII) with aliphatic alcohols from acid solutions

Extraction of rhenium(VII) with C₇–C₁₀ aliphatic alcohols from HCl and H₂SO₄ solutions was examined. The rhenium(VII) distribution coefficients were examined in relation to the acidity and temperature. The composition of the extracted complexes and the thermodynamic parameters of extraction were determined. The extraction method of recovery and preconcentration of rhenium(VII) from H₂SO₄ solutions with secondary octyl alcohol was tested in the counterflow mode.     

Extraction of Ce(III) with naphthenic acid from nitrate solutions

Extraction of Ce(III) with naphthenic acid from nitrate solutions was studied. The composition of solvation complexes, extraction constants, and Gibbs energies of extraction were found from the dependences of the distribution coefficients on pH and compositions of the aqueous and organic phases.     

Extraction and preconcentration of anthocyan dye from aqueous solutions with water-soluble poly-N-vinylamides

Extraction of an anthocyan dye with poly-N-vinylpyrrolidone (PVP) and poly-N-vinylcaprolactam (PVC) under the conditions of separation of aqueous solutions of this polymer into two phases in the presence of salting-out agents (sodium chloride and sodium or ammonium sulfate) was studied.