Gallium recovery from Bayer's liquor using hydroxamic acid resin

Gallium, which is extensively used in the production of semiconductor materials, is present at the parts per million level in Bayer's liquor. The low concentration of gallium in the liquor, along with the high concentration of aluminum, prompted the use of chelating ion exchangers as an alternative separation process. A chelating ion exchange resin with hydroxamic groups attached to the copolymer of acrylonitrile‐divinylbenzene has been prepared by suspension polymerization followed by hydrolysis and chelation with hydroxylamine hydrochloride. Adsorption studies of gallium, using the above hydroxamic acid resin, were carried out. Adsorption was dependent on particle size of the resin and optimum conditions are determined for obtaining 0.3‐ to 0.5‐mm particles by varying the composition of the emulsion, using a secondary polymerization technique, and adding of diluents. Acrylic acid, as a diluent in the copolymer matrix, was found to increase the particle size and stability of the resin. IR studies, carried out for the products obtained at various stages, confirmed the conversion of polymer to resin with a hydroxamic acid group and its complex formation with gallium. Both batch and column studies were carried out for the determination of the capacity of the resin with synthetic Bayer's liquor containing gallium and commercial Bayer's liquor. Scaled‐up column studies were carried out with commercial Bayer's liquor to test the cyclability and stability of the resin. It was observed that chelated ion exchange resin could be recycled up to 30 times. The optimal liquid to solid phase ratio was found to be 1:12. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 847–855, 2004     

钒铬还原渣碱浸提钒工艺及其动力学

采用常压下空气氧化-碱浸工艺,对钒冶炼的钒铬还原渣进行提钒. 通过正交实验考察了碱浓度、浸出温度、液固比对钒浸出率的影响,研究了钒的浸出动力学. 结果表明,最佳条件为碱浓度100 g/L、浸出温度100℃、液固比4 mL/g、浸出时间1 h. 该条件下钒浸出率最高达98%. 钒的浸出过程符合核收缩模型,受扩散步骤控制,表观活化能为11.04 kJ/mol.     

钒渣焙烧-碱浸提钒工艺焙烧过程机理

对钒渣空白焙烧-碱浸提钒,研究了钒渣中钒的转化和溶出规律. 结果表明,焙烧过程中渣中钒铁尖晶石FeV2O4中的钒逐步氧化成VO2和V2O5,并优先与Ca, Mn和Mg等形成钒酸盐;浸出分为低温浸出和高温浸出,低于180℃只能浸出钒酸盐和钒氧化物,高于180℃可浸出固溶在硅酸钙中的钒,钒浸出率达97.63%.     

Extraction of protactinium from acid media using Aliquat 336

Solvent extraction studies on protactinium were carried out from hydrofluoric acid, hydrochloric acid, and a mixture of hydrochloric and hydrofluoric acids using Aliquat 336 and ²³¹Pa. The extraction of protactinium from hydrofluoric acid (0.025–10 M) decreased with increasing acid concentration and was less than 10% above 5 M. The extraction from hydrochloric acid (0.5–8 M) started only above 4 M and increased with increasing acid concentration. The extraction of protactinium from a mixture containing hydrochloric acid (0.5–8 M) and 0.03 M hydrofluoric acid decreased with increasing acid concentration reached to a minimum at about 2 M and then increased with increasing acid concentration. At low acidity, extraction of protactinium from hydrofluoric acid was higher compared to hydrochloric acid and the mixture of hydrochloric and hydrofluoric acids. Nitric acid (10 M) and hydrofluoric acid (10 M) were suitable for quantitative recovery of protactinium from organic phase. The extraction of ²³¹Pa from real thorium lean raffinate of thorium–uranium extraction process was studied using optimized extraction conditions.     

Liquid Emulsion Membrane (LEM) Process for Vanadium (IV) Enrichment: Process Intensification

Abstract

A liquid emulsion membrane (LEM) system for vanadium (IV) transport has been designed using di‐2‐ethylhexyl phosphoric acid (D2EHPA), dissolved in n‐dodecane as carrier. The selection of extractant, D2EHPA, was made on the basis of conventional liquid‐liquid extraction studies. The work has been undertaken by first carrying out liquid‐liquid extraction studies for vanadium (IV) to get stoichiometric constant (n), and equilibrium constant (K_ex), which are important for process design.

Transport experiments were carried out at low vanadium (IV) concentration (ppm level). The studies on liquid emulsion membrane included i) the influence of process parameters i.e. feed phase pH, speed of agitation, treat ratio, residence time and ii) emulsion preparation study i.e., organic solvent, extractant concentration, surfactant concentration, internal strip phase concentration. When the strip phase concentration was 2 mol/dm³ (H₂SO₄) and feed phase pH 3 better extraction of vanadium was obtained. Higher V_m/V₁ gave higher extraction of vanadium (IV). A simplified, design engineer friendly model was developed.     

Cross-linked polyvinyl amidoxime fiber: a highly selective and recyclable adsorbent of gallium from Bayer liquor

Gallium, a scarce metal produced mainly from Bayer liquor, is widely used in semiconductors. Ion-exchange method is currently considered as the most effective method to recover gallium from Bayer liquor. In this article, fibrous amidoxime adsorbents are introduced to recover gallium from Bayer liquor. In addition, hydrazine cross-linked polyvinyl amidoxime (HPAO) fibers have been prepared. The structure of the as-prepared fibers was ascertained by FTIR, elemental analysis and weight gain rate. The adsorption kinetics, adsorption isotherm and recycling performance were investigated by batch method. Cross-linking duration was studied and it turned out to be an important factor to optimize the adsorption capacity and recycling performance. After 1.5 h cross-linking time, the fiber showed the highest gallium adsorption capacity of 14.83 mg/g in Bayer liquor. After 3 h cross-linking time, the fiber showed the best recycling performance, which retained 82.9% of the initial adsorption ability after four cycles. Adsorption capacity of vanadium was lower than 1 mg/g for all samples. HPAO displayed very fast adsorption kinetics with an equilibrium at 60 min. The EDS results confirmed the low extraction of aluminum and vanadium provided by HPAO fibers. The gallium-loaded fiber could be effectively eluted by acidified thiourea. With proper control of the cross-linking duration by hydrazine, HPAO fiber with high selectivity towards gallium, high adsorption capacity and good recycle performance could be obtained, which is promising for recovering gallium needed for industrial applications.     

Deep oxidation of light alkanes over titania-supported palladium/vanadium catalysts

The total oxidation of short-chain hydrocarbons has been studied using a titania-supported palladium catalyst modified with vanadium. A range of catalysts has been prepared by coimpregnation of the titania support with palladium (II) chloride and ammonium metavanadate. The addition of vanadium promoted the rates of oxidation at lower temperatures. Vanadium loadings between 0.5 and 3.0 wt% were investigated and the most active catalyst was 0.5% Pd1.5% V/TiO₂. The addition of vanadium decreased the palladium dispersion and the number of surface palladium sites. Microlaser Raman characterisation identified the supported vanadium species and the vanadium loading influenced these. The addition of palladium modified the vanadium species. In particular the presence of palladium increased the concentration of polymeric vanadium species. Temperature-programmed reduction studies showed that the addition of palladium to V/TiO₂ significantly increased the ease of catalyst reduction. Characterisation using electron paramagnetic resonance spectroscopy showed that the presence of palladium significantly increased the concentration of V⁴⁺ species. It is proposed that the increased catalyst activity is related to the modified redox properties of the catalysts.     

The electrodeposition of gallium from synthetic Bayer-process liquors

Gallium was electrodeposited from a synthetic Bayer solution comprising 4.5m NaOH/0.2m Na₂CO₃/0.3m NaCl/1.7m Al(OH)₃. Hydrogen evolution occurred in parallel with gallium deposition, the latter process being in part controlled by mass transfer and in part by the electron transfer step. Combined coulometric and voltammetric measurements allowed estimation of a diffusion coefficient for Ga (III) of 3.6×10^–6 cm² sec^–1 at 40° C. The coulombic efficiency for gallium deposition was a function of current density, deposition time, electrode rotation rate, temperature and gallium concentration. Values of up to 11% were obtained on a copper electrode from a solution containing 3.2×10^–3 m Ga (III). Heavy-metal impurities, such as iron and vanadium, usually found in these liquors, promote the hydrogen evolution reaction, completely inhibiting gallium production if present above certain critical concentrations.     

Separation of Gallium and Aluminum from HCl Solution by Microemulsion

Gallium was separated from aluminum in hydrochloric acid medium by a steady microemulsion. In the cetyltrimethylammonium bromide (CTAB)/n-pentanol/n-heptane/HCl/tributyl phosphate (TBP) system, TBP was introduced as the modifier to avoid emulsification of the microemulsion. The extraction efficiency on gallium was also improved by adding TBP. The factors that influenced the separation efficiency were explored. The results of the experiments showed that the gallium and aluminum were effectively separated within a very short time, and the extraction efficiencies of gallium and aluminum were 92% and 5%, respectively. The maximum back-extraction efficiency of gallium was 92% in HCl solution (4 M).     

Solvent Extraction of Cyclohexanecarboxylic Acid From Waste Fluid by Using a Mixture of Toluene and 1-Octanol

Solvent extraction studies have been carried out for the recovery of cyclohexanecarboxylic acid (CCA) from simulated waste fluid. Influences of various parameters including extractant types, pH of the solution, equilibration time, and initial concentrations of CCA, etc., were studied. A mixture of toluene and 1-octanol (90:10, v/v) was found suitable for the extraction. The results showed that solution pH had a great effect on the distribution ratio, and CCA could be efficiently extracted when the pH was lower than 3.5. The extraction was found quite rapidly. The distribution ratio decreased as the initial concentration of CCA increased. The stripping rate of CCA using sodium hydroxide as stripping agent was found to be increased with the increase of alkali concentration. After back extraction once, more than 98% stripping efficiency was achieved with 0.8 mol/L sodium hydroxide solution at aqueous to organic phase (A/O) ratio 1:1 when CCA concentration was lower than 38.3 g/L. The practical extraction process was carried out for the waste fluid (concentration of CCA 36.5 g/L) discharged in the production of caprolactam from toluene. After four extraction stages at A/O ratio 1:1, the cumulative extraction recovery reached 99.3%. The practical stripping efficiency from loaded organic phase reached 98.2% in one single stage.     

Vanadium doping effects on microstructure and dielectric properties of barium titanate ceramics

V-doped barium titante ceramics were prepared by conventional solid state reaction method. XRD patterns show that V⁵⁺ ions have entered into the tetragonal perovskite structure of solid solution to substitute for Ti⁴⁺ ions on the B sites. Addition of vanadium accelerates grain growth of BTO ceramics and there is abnormal grain growth of barium titanate ceramics with higher vanadium concentration. Vanadium doping can increase the Curie temperature and decrease the dielectric loss of barium titanate ceramics. As vanadium concentration increases, the remnant polarization of V-doped BTO ceramics begins to increase and reaches the maximum and then decreases. The coercive electric field for V-doped barium titanate ceramics decreases with the increasing of vanadium concentration. As temperature rises, the remnant polarization and the coercive electric field of V-doped barium titanate ceramics decrease simultaneously.     

Synergistic Extraction of Gallium from Sulfate Solution

A novel extractant mixture, di-2-ethylhexyl phosphate (DEHPA) plus HX, was proposed and tested for recovering gallium from sulfate solution. It was found that the extraction capacity of DEPHA for gallium from sulfate solution could be enhanced significantly due to the synergistic effect of acidic extractant HX. Gallium extraction is negligible below pH 0 and highly sensitive to pH of aqueous phase in the range from 0 to 1, and satisfactory extraction can be gained at pH>1. More than 96% Ga extraction was obtained using 15% DEHPA plus 2% HX. Although Fe (Ⅲ) was found to be extracted preferentially to Ga (Ⅲ), effective extraction of Ga (Ⅲ) was possible by reducing ferric to the ferrous state prior to extraction. A loaded organic phase containing 0.48g L-1 Ga could be produced from solution of 0.12g L-1 Ga at A/O ratio of 4 : 1 via three mixer-settler operation stages. Gallium was stripped quantitatively from the loaded organic phase with l,5mol L-1 of sulfuric acid.     

Solvent Extraction Behavior of Trivalent Metals with Liquid Ion Exchangers

Abstract

A systematic liquid-liquid extraction behavior of some trivalent metals has been carried out with the high-molecular-weight synthetic carboxylie acid SRS-100 with benzene as diluent. In most cases extraction was quantitative; but in the casss of gallium and antimony the maximum extraction was 97.2 and 65%, respectively. Using pure solvent (without benzene diluent), quantitative extraction (> 99%) of gallium was possible with SRS-100 at pH 4.6. Gradual neutralization techniques have been adopted to study the extraction behavior of antimony in the pH range 2.0–6.5. The effect of metal ion concentration, solvent concentration, salting-out agents, diluents, and finally the interferences of associated elements were critically examined. The percentage extraction at various ranges of pH has also been studied. Some important separations have been carried out by exchange reactions. The proposed methods are very simple, rapid, and fairly selective. They can be carried out both at micro and macro levels.     

The direct adsorption of low concentration gallium from fly ash

This study is mainly focused on the direct adsorption of low concentration gallium from the feed solution in pre-desilication soda-lime sintering process from coal fly ash. The adsorption kinetics, mechanism, and the influence of impurities, cyclic times, and eluant content are systematically researched. Results showed that the adsorption capacity was 2.89 mg/g resin with gallium concentration of 50 mg/L. The adsorption mechanism could be explained by the interaction between the oxygen atoms and nitrogen atoms of amidoxime group. Gallium was eluted efficiently by NaOH and Na₂S mixed solution and the concentration could be reached to 2400 mg/L.     

E.s.r. of Alberta tar sand bitumen and thermally hydrocracked products

A study of the vanadium and free radical species present in Athabasca bitumen and thermally upgraded products from a hydrocracking pilot plant was carried out. The samples were separated into asphaltene, chloroform resin, tetrahydrofuran resin and oil components, and the fractions studied by electron spin resonance. All samples except the oil fraction contained vanadyl (VO²⁺) ions and free radicals. It was found that even mild thermal treatment of bitumen produced considerable redistribution of vanadyl groups among the fractions, whereas at the severest hydrocracking conditions 94 wt% of all vanadyl groups were associated with the asphaltene fractions compared with only 58.5 wt% in the original bitumen. As the hydrocracking severity increased, the asphaltene vanadyl concentration initially increased above the value for unreacted bitumen and then decreased to a lower value. On the other hand, the resin vanadyl concentration decreased continuously and more rapidly than asphaltene vanadyl concentration. This indicates that vanadyl groups associated with the resin fractions are less stable than those associated with the asphaltenes and also suggests that transfer of vanadyl groups from the resin fractions to asphaltene predominates at low severity while removal of vanadyl groups predominates at high severity. The average spin Hamiltonian parameters showed that the chemical environment of vanadyl ions in the THF resins was significantly different from the vanadyl environment in the other two fractions.     

Solvent Extraction and Separation of Gallium(III) using Hexaacetato Calix(6)Arene

Gallium(III) was extracted at pH 3.5 by equilibrating eight min with 10 mL of 0.0001 M acetyl derivative of calix(6)arene in xylene. Gallium(III) was stripped quantitatively with 0.1 N hydrochloric acid and determined spectrophotometrically with 0.01% PAR at 510 nm. The nature of the extracted species was determined from the log-log plots and its stoichiometry was confirmed by numerical treatment to experimental data. The IR analysis of Ga(III) loaded organic phase was also studied. The conformational change of reagent during complex formation was studied from the ¹H NMR treatment. The temperature dependence of the extraction equilibrium and metal loading capacity of the reagent was also evaluated. The proposed method was successfully applied for the extraction and separation of multicomponent mixtures, synthetic mixtures, and binary and ternary separation of gallium from the associated elements. The results obtained were reproducible and accurate.     

D001树脂吸附铁离子后的脱附研究

通过脱附试验,选用HCl对D001树脂进行再生,考察了脱附剂浓度、脱附时间、脱附温度对树脂脱附效果的影响;通过吸附试验,考察了D001树脂在不同HCl浓度下对铁离子的吸附.试验结果表明,25℃时,质量分数为20%的HCl在对吸附铁离子的D001树脂(吸附量为11.729mg/g)进行脱附,60min时可达到较大的脱附量...     

Microwave Synthesized Mesoporous Vanadium-MFI Catalysts for Epoxidation of Styrene Using Molecular Oxygen

Carbon templated mesoporous vanadium MFI catalysts with different Si/V ratios were successfully synthesized using microwave irradiation. X-ray diffraction studies revealed the formation of more crystalline MFI structures. SEM and TEM imaging also showed well ordered zeolite single crystals having mesoporosity. The N₂ sorption isotherm showed the formation of bimodal mesoporous zeolites. FT-IR studies showed absorbance around 970 cm^?1 corresponding to Si–O–V stretching vibration and the UV–Vis studies revealed strong peaks in the range of 230–340 nm which is related to the presence of tetrahedral V⁵⁺ state. The catalytic activity of the microwave synthesized catalysts was evaluated for epoxidation of styrene using molecular oxygen. The catalysts exhibited 20–40% styrene conversion with 60–75% epoxide selectivity. With increasing Vanadium content, the conversion as well as the selectivity was observed to increase. The catalyst could be recycled for three cycles without a loss in activity.     

Introduction of alkali soaking and microwave drying processes to improve agar quality of <Emphasis Type="Italic">Gracilaria verrucosa</Emphasis>

Gracilaria species produce agars with low quality due to their high sulfate concentrations. For this reason, the gel properties of many Gracilaria agars must be improved by appropriate processes. In this study, we developed an improved agar extraction process for Gracilaria verrucosa by alkali soaking extraction and microwave thawing and drying. Variables such as the seaweed to alkali volume ratio, extraction time, and alkali concentration were adjusted to optimize the yield and agar quality. The yield of the agar was maximized (34.5±0.6%) using 3% alkali concentration; the lowest yield (17.0±1.7%) was obtained with 1% alkali concentration. Agar gel strengths ranged from 462.0±7 to 627.3±11 g·cm^?2. We have developed a process for quickly producing an agar gel through thawing and drying using microwave radiation. This study shows the possibility of producing a high-value agar using alkali soaking extraction methods for nonedible G. verrucosa.     

钒渣钠化焙烧熟料浸出液除磷工艺研究

以钒渣钠化焙烧熟料浸出后得到的含钒溶液为原料,分析了二水硫酸钙在碱性条件下对含钒溶液中磷的去除机制,研究了二水硫酸钙用量、溶液pH、反应时间、反应温度等因素对磷去除率、钒损失率以及溶液中五氧化二钒与磷质量浓度比的影响。研究结果表明：在弱碱性条件下,二水硫酸钙可有效去除含钒溶液中的磷,磷去除率达到70%以上、钒损失率小于1%、五氧化二钒与磷质量浓度比大于2 300,满足后续沉钒的要求。确定的除磷工艺条件：二水硫酸钙与磷物质的量比为5.3,溶液pH为9.0,反应时间为30 min,反应温度为25 ℃。除磷后的含钒溶液经沉钒、洗涤、煅烧得到五氧化二钒产品,沉钒率大于99%,五氧化二钒产品质量满足YB/T 5304—2011《五氧化二钒》中99级的要求。