Precipitation and Determination of Zirconium Using Some Unusual Alpha-Hydroxyacids

Abstract

Zirconium forms stable, insoluble, chelate compounds with many organic alpha-hydroxyacids (substituted glycolic acids) and a number of them have been investigated for the gravimetric determination of zirconium. Four new reagents were studied: hexahydromandelic acid, atrolactic acid, p-phenylene diglycolic acid and 2-hydroxy-4-phenyl-3-buteonic acid. Quantitative precipitation of zirconium was achived with all the above acids but most precipitates are of indefinite composition and must be ignited to the oxide for weighing. These studies lead to a better understanding of the nature of alpha-hydroxyacid complexes of zirconium.     

The determination of trace amounts of zirconium,hafnium, thorium and cerium in silicate rocks

A method is described for the determination of traces of zirconium, hafnium, cerium and thorium in rocks. After the sample has been opened up, these elements are separated from the major component elements by extraction from 10 N nitric acid with a 40% solution of tri-n-butyl phosphate, cerium being oxidised with bro-mate. After back-extraction the elements are separated from each other and from other extracted elements by cation exchange. Zirconium is determined photometrically with quinalizarin sulphonic acid which gives about twice the sensitivity of alizarin red S. Thorium is determined photometrically with thorin, and cerium by utilizing its bleaching action on iron(II) phenanthroline. Hf is determined spectro-graphically.     

Determination of zirconium in zirconium metal and zirconium powder by use of mandelic acid

An accurate gravimetric method is proposed for the determination of zirconium in zirconium metal and zirconium powder by use of mandelic acid. The sample is dissolved in a mixture of hydrofluoric, nitric, perchloric and sulfuric acids, the solution is evaporated to dryness, and the salts are dissolved in dilute hydrochloric acid. Zirconium mandelate is precipitated at 80°. The residual zirconium in the filtrate is recovered by heating at 80° overnight and the combined precipitates are ignited to Zirconium dioxide. An investigation was made of the factors involved in the dissolution of the sample, precipitation with mandelic acid, ignition of the precipitate, and size of sample. The effect of hafnium is discussed.     

Solvent Extraction Separation of Zirconium (iv) With Anberlite LA - 1 From Citrate Solutions

Abstract

Zirconium was quantitatively extracted with 8 × 10^?2 M of Amberlite LA-1 or LA-2 xylene from 0.001 M citric acid at pH 3.5 and it was stripped from the organic phase with 2 M hydrochloric acid and was determined spectrophotometrically at 665 nm as its complex with arsenazo III. Zirconium was separated from binary as well as tertiary mixtures by exploiting the difference in the distribution coefficient or by selective extraction or selective stripping. The method was applied for the analysis of zircon.

Zirconium was extracted as its anionic complex with various mineral acids by liquid anion exchanger. The chlorocomplex of zirconium was extracted from 6–10 M hydrochloric acid with trioctylamine^1–5, triisooctylamine⁶ or Aliquat 3365⁷. The sulphotocomplex of zirconium was extracted with Aliquat 3365⁸, Primine JMT⁹, Alamine 336¹⁰. The nitratocomplex was less extensively utilised for the extractive separation of zirconium^{11, 12}.

Zirconium was extracted quantitatively from oxalate^{13, 14} and malonate media¹⁵. These extractions were carried out at low pH and separated zirconium from large number of associated elements. The ion exchange chromatographic behaviour of zirconium on column with cation exchange^16–17 or with anion exchange¹⁸ resin with citric acid as eluent were utilised but extraction studies from citrate solutions were never attempted.

From the critical study of existing methods it was observed that zirconium was extracted at narrow pH range; with high concentration of complexing ligand for extraction with liquid anion exchangers and long period of equilibration for extraction as well as stripping. So also such extractions were possible mostly at milligram concentrations involving use of hazardous diluents like benzene. In order to circumvent these difficulties an attempt was made to develop a better method for the solvent extraction separation of zirconium by ion pair formation.

Therefore this paper presents systematic investigations on the solvent extraction separation of zirconium from citrate media with liquid anion exchangers. From the study of various factors. The optimum conditions for the extraction and the separation of zirconium from associated elements are evaluated. The method has been extended for the analysis of zirconium from zircon.     

Syntheses of amino alkyl sulphonic acids and their peptide analogues

New amino alkyl sulphonic acids have been synthesized, including some substituted derivatives and several peptide analogues containing the ---CO·NH--- group formed from amino acid and amino alkyl sulphonic acid components. Peptide-like compounds containing the ---SO₂·NH--- group were prepared from N-substituted taurine and esters of amino acids. Theoretical aspects underlying the reactions involved are discussed.     

Concentration, separation and determination of scandium, zirconium, hafnium and thorium with a silica-based sulphonic acid cation-exchanger

A study has been made of the dependence of the sorption of scandium, zirconium, hafnium and thorium from aqueous solutions with a silica-based sulphonic cation-exchanger (SCE-SiO(2)) on the concentration and nature of the acid medium, time of contact, concentration of the element, and the ionic strength. The selectivity decreases in the order Zr approximately Hf > Th > Sc > Fe(III). The sorption characteristics of silica gel and SCE-SiO(2) have been compared, and the sorption mechanism is discussed. The SCE-SiO(2) exchanger has been used for 100-fold concentration of scandium, zirconium, hafnium and thorium from their 10(-8)-10(-7) M solutions, and a spectrophotometric method has been developed for their determination with a detection limit of 0.5 ng/ml for Zr and Sc and 0.1 ng/ml for Hf and Th. Zirconium and hafnium have been determined in the solvent phase by X-ray fluorescence and atomic-emission methods.     

Mechanism of the grafting of organosilanes on mineral surfaces

The grafting of organosilyl groups in the interlamellar space of certain crystalline silicic acids, such as H-magadiite, occurs when the interlayer spaces have been expanded previously by intercalation of some polar organic substances. The interlamellar Si-OH groups are then accessible to silylating reagents and Si-O-Si bridges form between the silicic acid surface and the organic groups.The grafting reaction is controlled by a diffusion mechanism: desorption of the polar organic guest molecules has to occur simultaneously with the diffusion of the reacting molecules into the interlayer space.The resulting materials are organosilicic compounds which retain the lamellar structure of the starting crystalline silicic acids. Their surface properties are determined by the grafted groups.Part I: This Journal 256:135 (1978); Part II: This Journal 257:178 (1979).     

Fluorimetric determination of zirconium with morin

Zirconium can be determination fluorimctrically with morin in 2M hydrochloric acid in the presence of such elements as Al, Be, Ga, Sb, Sn, Th and U, which fluorcsce much less strongly under the conditions, by measuring the fluorescence intensity before and after adding ethylenediaminetetraacetic acid. This substance destroys the fluorescence of zirconium only and the difference in fluorescence intensities corresponds to the concentration of zirconium in solution. The determination of zirconium in the presence of aluminum has especially been studied. Satisfactory accuracy can be obtained even when Al/Zr = 10,000, if the proper morin concentration is used. Iron docs not interfere if reduced to the ferrous state with mercap oacetic acid, Zirconium can be determined in silicate rocks without any separations except those made automatically in tlie sodium carbonate decomposition. Niobium and tantalum should not exceed 0.05%.     

Synthesis of highly hindered polyanionic chelating ligands

Practical and efficient protocols to obtain highly hindered polyanionic chelating ligands based on bis-(3,5-di-tert-butyl-2-hydroxybenzamido) compounds are reported here. N-3,5-di-tert-Butylsalicyloyloxysuccinimide was treated with aliphatic diamines to form aliphatic hydrocarbon-linked bis-amides 4a-4g. Aromatic diamines required more powerful electrophile, thus the corresponding benzylated acid chloride was used to form aromatic hydrocarbon-linked bis-amides 8a-8d. The yields ranged from good to very good and showed that choosing the right acylating agent is a key point in this synthesis. All the compounds were characterized by elemental analysis, IR, MS and NMR.     

Determination of zirconium and hafnium with xylenol orange and methylthymol blue

Both Xylenol Orange and Methylthymol Blue are highly selective and sensitive reagents for zirconium and hafnium forming intensely red complexes in an acidic medium. The factors affecting the color formation have been studied. The properties of the complexes have been determined and compared. In general, zirconium forms a more stable complex with the two dyes than hafnium, and Xylenol Orange forms a stronger complex with either zirconium or hafnium than Methylthymol Blue. Hydrogen peroxide can completely mask the zirconium complexes of either dye but only slightly affects the hafnium complex of Xylenol Orange. Zirconium and hafnium can both be determined without separation using peroxide as a masking agent and sulfate as a demasking agent. A bleaching reaction was observed when small amounts of hafnium were added to the red zirconium complex of Methylthymol Blue in 2.4 N perchloric acid or a small amount of zirconium was added to the red hafnium complex of Methylthymol Blue solution at pH 2 to 3.     

Thermoreversible polyaniline gels

Polyaniline (PANI) forms thermoreversible gels in different sulphonic acids e.g. dinonyl napthalene sulphonic acid (DNNSA), dinonylnapthalene disulphonic acid (DNNDSA), ± camphor ‐ 10 ‐ sulphonic acid (CSA) and dodecyl sulphonic acid (DSA) when processed from the formic acid medium. The surfactant concentration has been varied from weight fraction of PANI (W_PANI)=0.05−0.60. In most cases at W_PANI=0.05−0.40 compositions fibrillar network structures are observed from SEM study. They also exhibit reversible first order phase transition during both heating and cooling in DSC. The melting temperature and the gelation temperature increases with increase in surfactant concentration of the gel. From the WAXS pattern it is concluded that crystallization of the surfactant tails anchored from the nitrogen atom of PANI through its SO₃ H head group is responsible for gelation. The conductivity of all the gels with increase in PANI concentration showed a maximum with composition. The maximum conductivity is ∼0.01 S/cm, for W_PANI=0.22. The conductivity variation has been explained by considering it as a function of both interchain and intrachain contributions.     

Zirconium meta-sulfonphenyl phosphonic acid-incorporated Nafion membranes for reduction of methanol permeability

Zirconium meta-sulfonphenyl phosphonic acid (Zr-msPPA)/Nafion^® composite membranes were prepared to reduce methanol permeability of the Nafion^® 117 membrane in direct methanol fuel cell (DMFC) applications. Zr-msPPA crystalline nano proton conductors were synthesized inside the membranes via the reaction of zirconium chloride octahydrate and meta-sulfonphenyl phosphonic acid that had been soaked prior. Synthesis of the Zr-msPPA in the membranes was identified from a series of chemical and physical structure characterizations using FTIR, NMR, EDS, and XRD spectroscopy. The thermal stability of the composite membranes was enhanced by addition of the Zr-msPPA, with considerable reduction in methanol permeability with increasing Zr-msPPA content, as the Zr-msPPA nano conductors acted as crystalline barriers to methanol permeation. The ion conductivity also decreased with increasing Zr-msPPA content, but its effect was not as strong as with methanol permeation given the innate, high conductivity of Zr-msPPA.     

Mandelic acid and halogen-substituted mandelic acids as reagents for the determination of zirconium

o-, m-, and p-Fluoro- and -trifluoromethylmandelic acids have been prepared and an assessment made of their value as précipitants for zirconium. Though the p-derivatives are satisfactory there are no obvious advantages in their use. Direct weighings of zirconium mandelate and p-bromomandelate, about which there have been conflicting reports in the literature, have been investigated also. P-Bromomandelic acid has been used successfully for the determination of amounts of zirconium oxide between 3 and 50 mg per 100 ml but ignition of the precipitate to zirconium oxide is necessary. Of the acids examined, mandelic itself gives the only precipitate which is almost constant and stoichiometric in composition. The composition of this compound, however, varies slightly with the amount of zirconium present in the solution under test, and though an overall empirical factor can be applied its use is recommended only if a high order of accuracy is not required. If a series of determinations in a narrow range is to be carried out by direct weighing of zirconium mandelate, more accurate results might be obtained by determination of the appropriate factor for that range.     

Hydrolysis of oligosaccharides by sulphonic ion exchangers

The hydrolysis of oligosaccharides by sulphonic ion exchangers has been performed in batch and in column experiments. The rate constants and selectivity are compared with the values obtained in homogeneous phase with H₂SO₄ and polystyrene sulphonic acid. The rate constants are lower in the presence of ion exchangers for dimers and the efficiency decreases as the degree of polymerization of the oligosaccharides increases, because of control by intraparticle diffusion. It is concluded that the ion exchanger process is rather inefficient for higher molecular weight solutes when compared with the corresponding polyelectrolyte or low molecular weight acid.     

Application of zirconium-modified silica gel as a stationary phase in the ion-exclusion chromatography of carboxylic acids II. Separation of aliphatic carboxylic acids with pyromellitic acid as eluent and with suppressed conductimetric detection

The application of zirconium-modified silica gels (Zr-Silica) as stationary phases for ion-exclusion chromatography with conductimetric detection (IEC–CD) for C₁–C₈ aliphatic carboxylic acids (formic, acetic, propionic, butyric, valeric, caproic, heptanoic and caprylic acids) was carried out using pyromellitic acid as the eluent. Zr-Silicas were prepared by the reaction of the silanol group on the surface of silica gel with zirconium tetrabutoxide [Zr(OCH₂CH₂CH₂CH₃)₄] in ethanol solution. An ASRS-Ultra anion self-regenerating suppressor in the K⁺ form was used for the enhancement of conductimetric detector response of these aliphatic carboxylic acids. A Zr-Silica adsorbed on 10 mg zirconium g⁻¹ silica gel was the most suitable stationary phase in IEC–CD for the separation of these aliphatic carboxylic acids. Excellently simultaneous separation and highly sensitive detection for these aliphatic carboxylic acids were achieved in 25 min by IEC–CD with the Zr-Silica column (250×4.6 mm I.D.) and a 0.2 mM pyromellitic acid containing 0.15% heptanol as the eluent.     

Anion exchange studies of zirconium(iv) in citrate solution separation from mixtures

The anion exchange behaviour of zirconium(IV) in a citrate system is described. Nitric acid, hydrochloric acid, perchloric acid and ammonium chloride were tested as eluants on Dowex ₂₁K column. Zirconium is separated from fission product elements e.g., barium, strontium, cadmium, caesium, molybdate and also from lead.     

Sur la thermogravimétrie des précipités analytiques : Dosage du zirconium

With the help of the chevenard thermobalance, the authors have traced and examined the thermolysis curves of the precipitates proposed for the determination of zirconium. The methods in which picric acid, potassium iodate, ammonium arsenate and oxine are used, have been rejected; those in which ammonia, aniline, diethylaniline and in particular mandelic acid are used, are recommended for the automatic determination of zirconium. Zirconium hydroxide can be prepared in a pure state by means of aniline, while various other reagents smoothly afford zirconyl hydroxide. The problem of reduction of zirconium by pyrolysis of its arsenic(V) derivatives has been posed but not solved.     

Solvolytic behaviour and the solubilities of various inorganic compounds, lewis acids and bases in fused monobromo acetic acid solvent system—II

Solubilities and the solvolytic behaviour of various inorganic compounds, Lewis acids and bases in fused monobromoacetic acid at 60 ± 0.5°C are discussed. Ionic compounds are fairly soluble, iodides and thiocyanates being comparatively more soluble than chlorides and bromides. Tetraalkyl ammonium halides are highly soluble in this solvent. Conductometric and spectroscopic studies of various Lewis acids and bases in fused monobromoacetic acid indicate their solvolytic behaviour and their subsequent ionization. The solvolyses products BBr₃·CH₂BrCOOH and SbCl₅·CH₂BrCOOH have been observed to be the strongest Bronsted acids. Auto-ionization of this solvent has been supported by acid/base titrations.     

Comparison of silica-based and polymer-based cation exchangers for the ion chromatographic separation of transition metals

Silica gel- and polymer-based exchangers differ not only in the substrate but usually also in the structure of their sulphonic acid exchange group. The performance and chromatographic behaviour of modern macroporous poly(styrene-divinylbenzene) polymers of 5-μm particle size after surface sulphonation were examined. Further, two commercially available silica gel cation exchangers were investigated as references for what is now possible and how the chromatographic performance is influenced by the substrate and the structure of the exchange site. The influence of the capacity of surface-sulphonated exchangers for acid and complexing eluents, which are necessary when transition metals are to be separated, was studied. The interaction of polarizable metal cations with the π-system of the polymer depends on the resin capacity, and a comparable dependence for H⁺ and complexing eluents was found. The distance of the functional group from the core influences the adsorption effects dramatically. Lowering the non-specific interaction increases the chromatographic efficiency rapidly. The performance of silica gel-based exchangers is nearly one order of magnitude better than that of surface-sulphonated exchangers. The selectivity of the exchangers investigated is strongly dependent on the structure of the exchange site and on the resin capacity.     

Use of organic reagents in inorganic analysis

Summary Seven anilic acids obtained from phthalic anhydride and aromatic amines were studied for their quantitative precipitating action on zirconium. The anilic acids from p-toluidine, m- and p-nitranilines and -naphthylamine were only found effective for the quantitative determination of zirconium. Zirconium is completely precipitated at a little lowerph value with these reagents, than thorium. Compositions of the zirconium salts of these acids are not definite, so ignition of the precipitates to zirconia is necessary. Separation of zirconium from common elements like Cu, Al, Cr, Mg, Zn, Ti etc. may be done with ease. But for iron, uranium, cobalt and nickel double precipitation is essential. A considerable amount of thorium has been separated from zirconium, by extraction with amylacetate.