Electron Transfer Studies of TIN(IV)/TIN(II) in Acid Media

Abstract

Cyclic voltammaetry of mixed tin(II)/tin(IV) solutions was investigated in 6M HCl on gold and mercury electrodes. It was found that the reduction of tin(II) to tin(iv) proceeded irreversibly while tin(II) to tin(IV) was reversible. Two forms of tin(IV) are postulated. The peak potential for the reduction of tin(IV) was a function of both tin(II) and tin(IV) while that for the oxidation of tin(II) was a function only of tin(II) concentration Potentials for all oxidations and reductions were a function of potential scan rate.     

Electrochromatography of Metal Ions on Zirconium(IV) Phosphoantimonate Papers: Quantitative Separation of Platinum(IV) from Platinum Group and Other Metal Ions

Abstract

Zirconium (IV) phosphoantimonate impregnated papers have been used to study the electrochromatographic behaviour of 29 metal ions in buffers of weak organic acids with their corresponding ammonium salts as background electrolytes at fixed voltage and time intervals. As a result of these investigations, the variation in the average mobility of metal ions with the ionisation constants of the organic acids used in buffers and other parameters such as atomic numbers and charge on the metal ions has been studied. On the basis of the differential mobilites of the metal ions, which depends on the ion exchange properties of Zr(IV) phosphoantimonate and the nature of the complexes formed with the electrolytes, some binary, ternary and quarternary separation have been achieved. Besides microgram separations (25 μg-100 μg) of Pt(TV) from Pt group and other metal ions have also been achieved.     

Cation Exchange and Sorption Properties of TIN(IV) Phosphate

The ion exchange and sorption properties of crystalline Tin bis(monohydrogen orthophosphate) monohydrate of composition Sn(HPO(4))(2).H(2)O were studied in an aqueous solution of KCl over the temperature range 300-320 K, varying the pH and metal ion concentration in the solution. The data were explained on the basis of the law of chemical equilibrium. The metal ion sorption data were fitted to the Langmuir adsorption equation to evaluate the Langmuir parameters. The extent of adsorption was found to increase with an increase in temperature and metal ion concentration in the selectivity order Cu(2+)>Co(2+)>Ni(2+). The Langmuir parameters were used to calculate the thermodynamic functions like standard entropy, enthalpy, and free energy changes during the process of sorption. Copyright 2000 Academic Press.     

Sorption of Some Metal Ions on Inorganic Electron and Ion Exchangers Based on Zirconium(IV)

Conditions of sorption of nonferrous metal ions on inorganic electron and ion exchangers based on zirconium(IV) were analyzed. The sorption capacity was evaluated as influenced by pH, concentration, and temperature of the contacting solutions and nature and chemical composition of the ion exchanger.     

Quantitative Separation of Pd(II) by TLC of Metal Ions on Cerium (IV) Antimonate

Abstract

A quantitative TLC separation of metal ions using cerium (IV) antimonate as the solid phase are described. Using an acetonitrile- HNO₃ solvent Pb²⁺ can be separated quantitatively (2–10 μg) from several other ions. A quantitative spectrophotometric assay using p-nitroso-dimethylaniline is proposed.     

Quantitative Separation of Hg(11) From Several Metal Ions on Zr(IV) Antimonate Papers

Abstract

The chromatographic behaviour of 32 metal ions has been studied on paper Impregnated with Zirconium(IV) antimonate in aqueous HCI and mixed solvent system containing dimethyisul phoxide and dioxane. Several Important binary and ternary separations have been achieved. Quantitative separation of Hg(ll) from Ni²⁺, Pb²⁺, Pd²⁺, Ru³⁺, Rh³⁺, Bi³⁺, Co²⁺, Cd²⁺ and Gd³⁺ is described.     

Sorption of Metal Ions on Clay Minerals

The mechanism of Co uptake from aqueous solution onto hectorite (a magnesian smectite) and its impact on the stability of this clay mineral were investigated as a function of Co concentration (TotCo = 20 to 200 μM, 0.3 M NaNO(3)) and ionic strength (0.3 and 0.01 M NaNO(3), TotCo = 100 μM) by combining kinetics measurements and Co K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The morphology of the sorbent phase was characterized by atomic force microscopy (AFM) and consists of lath-type particles bounded by large basal planes and layer edges. At low ionic strength (0.01 M NaNO(3)), important Co uptake occurred within the first 5 min of reaction, consistent with Co adsorption on exchange sites of hectorite basal planes. Thereafter, the sorption rate dramatically decreased. In contrast, at high ionic strength (0.3 M NaNO(3)), Co uptake rate was much slower within the first 5 min and afterward higher than at 0.01 M NaNO(3), consistent with Co adsorption on specific surface sites located on the edges of hectorite. Time-dependent isotherms for Co uptake at high ionic strength indicated the existence of several sorption mechanisms having distinct equilibration times. The dissolution of hectorite was monitored before and after Co addition. A congruent dissolution regime was observed prior to Co addition. Just after Co addition, an excess release of Mg relatively to congruent dissolution rates occurred at both high and low ionic strengths. At high ionic strength, this excess release nearly equaled the amount of sorbed Co. The dissolution rate of hectorite then decreased at longer Co sorption times. EXAFS spectra of hectorite reacted with Co at high and low ionic strengths and for reaction times longer than 6 h, exhibited similar features, suggesting that the local structural environments of Co atoms are similar. Spectral simulations revealed the occurrence of approximately 2 Mg and approximately 2 Si neighboring cations at interatomic distances characteristic of edge-sharing linkages between Co and Mg octahedra and corner-sharing linkages between Co octahedra and Si tetrahedra, respectively. This local structure is characteristic of inner sphere mononuclear surface complexes at layer edges of hectorite platelets. The occurrence of these complexes even at low ionic strength apparently conflicts with kinetics results, as exchangeable divalent cations are known to form outer sphere surface complexes. To clarify this issue, the amount of Co adsorbed on exchange sites was calculated from the solute Co concentration, assuming that cation exchange was always at equilibrium. These calculations showed that sorbed Co was transferred within 48 h from exchange sites to edge sorption sites. Copyright 1999 Academic Press.     

TLC Separation of Metal Ions Using Di(n-butyl)dithiophosphoric Acid and Neutral Organophosphorus Ligands

JPC – Journal of Planar Chromatography – Modern TLC - Thin-layer chromatographic separation of U(VI), Th(IV), the lanthanides Ln(III), (La(III), Ce(III), Pr(III), Sm(III), Gd(III),...     

Agar-immobilized Metal Sulfides and Their Sorption Power with Respect to Ag(I) Ions

Russian Journal of General Chemistry -     

Effect of Mn(II) and Ce(IV) Ions on the Oxidation of Lactic Acid by Chromic Acid

The kinetics and mechanism of lactic acid oxidation in the presence of Mn(II) and Ce(IV) ions by chromic acid were studied spectrophotometrically. The oxidation of lactic acid by Cr(VI) was found to proceed in two measurable steps, both of which gave pyruvic acid as the primary product in the absence of Mn(II). 2Cr(VI)+2CH₃CHOHCOOH → 2CH₃COCOOH+Cr(V)+Cr(III) Cr(V)+CH₃CHOHCOOH → Cr(III)+CH₃COCOOHThe observed kinetics was explained due to the catalytic and inhibitory effects of Mn(II) and Ce(IV) on the lactic acid oxidation by Cr(VI). The reactivity of lactic acid depends upon the experimental conditions. It acts as a two-or three-equivalent reducing agent in the absence or presence of Mn(II). It was examined that Cr(III) products resulting from the direct reduction of Cr(VI) by three-equivalent reducing agents. The oxidation of lactic acid follows the complex order kinetics with respect to [lactic acid]. The activation parameters E_a, ΔH^#, and ΔS^# were calculated and discussed.     

Retention of Some Metal Ions and Their Separation on Silica Gel Modified with Acid Red 88

 Acid Red 88 is strongly extracted by chloroform solutions of Aliquat 336 by an ion exchange mechanism and for its reextraction from the ion pair formed, relatively high concentrations of mineral acids are required. By impregnation of silica with the ion pairs between the cation of Aliquat 336 and the anion of the dye a chelating sorbent for metal ions can be obtained. The sorbent prepared may be successfully used for separation of mixtures of various metal ions by the column extraction chromatography technique, additional purification of sodium and potassium salts from ions of heavy metals and for concentration of trace amounts of ions of various metals from aqueous solutions followed by their quantitative determination. The sorbent can be used repeatedly in the process of sorption and desorption of metal ions (especially those forming less stable complexes with the reagent) after regeneration with solutions of perchloric acid. Received January 28, 1998. Revision March 1, 1999.     

Tetrachloro (NN-dimethylformamide) (dimethylsulphoxide) TIN (IV) revisited

The previously reported mixed ligand compound SnCl₄ (DMF) (DMSO) (DMF=NN-Dimethylformamide, DMSO=Dimethylsulphoxide) has been studied by IR, Raman and Mössbauer spectroscopy. Our results confirm its homogeneity with the DMF and DMSO ligands coordinating in cis position through the oxygen atoms. The compound does not isomerize when heated to 135 C, but decomposes giving rise to cis-SnCl₄(DMSO)₂ and trans-SnCl₄ (DMF)₂.     

聚苯胺及其复合物对重金属离子的高效吸附性能

基于国外最新文献,系统总结了近年来聚苯胺及其复合物的制备方法及其重金属离子吸附性能,重点分析了吸附性能特征,指出聚苯胺及其复合物具有吸附下限浓度低、达到吸附平衡快以及解吸附性能优异等特点.填充有聚苯胺颗粒的吸附柱在动态处理初始浓度为83 ng/L的汞离子溶液时,经一次吸附与解吸循环操作后,汞离子的富集倍数可达120倍.应用于冷原子吸收光谱的待测样品的浓缩与富集,可以将汞的测试下限拓展到0.05 ng/L.聚苯胺及其复合物在痕量重金属离子的高效富集与灵敏探测等方面展示了广阔的应用前景.     

Studies of Hydrous Zirconium Oxide. I. Thin-Layer Chromatography of Some Metal Ions on Hydrous Zirconium Oxide: Quantitative Separation of Bi(III) from Several other Metal Ions

Abstract

The analytical potentiality of hydrous zirconium oxide as an ionexchanger has been investigated by thin-layer chromatographic (TLC technique. Binder-free thin-layers of hydrous zirconium oxide are useful for 25 ternary and 12 quaternary separations. Quantitative separation of Bi (III) from some ternary and quaternary mixtures of metal ions has been achieved.     

Separation of Selected Transition Metal Ions and Divalent Metal Ions by HPLC Using UV-VIS Detection

Abstract

The use of ethylenediaminetetraacetic acid, disodium salt, (pH 3-5) has been investigated as an eluant for the separation and detection of nanogram levels of selected divalent and trivalent metal ions. The effect of pH and eluant concentration upon the retention times and resolution of the system are given and the ability to alter the eluant characteristics to optimize the chromatographic results in different situations will be discussed. The method is less complicated than the method frequently used for transition metal ion determinations which uses a post-column derivitization reagent. This method is applicable to a wider range of metal ions and provides detection limits which are generally within two orders of magnitude of the post-column derivitization method.     

Separation of Pd(II) and Tl (III) from Various Metal Ions on Hydrous Zirconium Oxide Column

Abstract

The utility of hydrous zirconium oxide for the separation of metal ions has been explored. The Kd-values from different concentrations of chloride ions(pH-2) have been determined. On the basis of the sorption data Pd (II) and Tl (III) have been quantitatively separated from a number of metal ions. The representative elution curves are given and the recovery of the metal ions is reported.     

Sorption Purification of Scandium(III) To Remove Zirconium(IV) Impurity in Hydrochloric Acid Solutions

A study was made on separation of the Zr(IV) impurity from scandium(III) in hydrochloric acid solutions by sorption with KRF-20t-60 cation exchanger, including sorption kinetics and sorption under dynamic conditions. The sorbent regeneration with 5% ammonium fluoride or 10% potassium carbonate at 22°C was considered.     

Separation Studies of Metal Ions in Sodium Thioglycolate Medium by Thin Layer Partition Chromatography

Abstract

A thin layer partition chromatographic method has been developed for separation of Fe(III), Ni(II), Zn(II), Cu(II), Pb(II) and Mn(II) on thin layers of silica gel-G as an adsorbent. The R_f values were determined using 0.01–0.2 aqueous solution of sodium thioglycolate as a mobile phase. The dependence of R_f values on the migration time, pH and concentration of mobile phase has been studied. The optimum conditions for possible 3-component separation have been determined. Metal ions have been separated, detected, eluted and quantitatively determined by atomic absorption spectroscopy. The present method was applied to the separation and determination of zinc in forensic samples.     

离子相互作用色谱法分离金属离子的研究

离子相互作用色谱在无机离子的分离和分析中潜力很大。它通过离子相互作用试剂,能容易控制或改变柱交换容量或分析物的保留值,分离效率高,可快速完成多组分的同时分离。 在ODS固定相上涂敷阳离子型的十六烷基吡啶(CPI),使金属离子成为阴离子型的氨羧络合物,因不同金属氨羧络合物与CPI的作用程度不同从而可使金属离子分离。金属氨羧络合物亲水性很强,在键合相上的吸附作用可忽略,流动相中不需加入有机溶剂,因此络合物     

Recovery of Metal Ions by Chitosan: Sorption Mechanisms and Influence of Metal Speciation

Chitosan is characterized by a high affinity for metal ions due to its high content of amine groups. The sorption mechanism depends on both the protonation of these amine groups and the speciation of metal ions. Metal cations may be adsorbed at pH close to neutrality by chelation mechanism while metal anions can be adsorbed in acidic solutions through ionic interactions with protonated amine groups. Several examples are considered. The first example focuses on Cd sorption, which proceeds by a chelation mechanism on free non‐protonated amine groups in neutral media. In acidic solutions the protonation of amine groups limits the ability of amine groups to complex Cd. The cross‐linking of chitosan with glutaraldehyde also results in a dramatic decrease of sorption properties due to the decrease in the density of complexation sites available for sorption. The sorption of vanadium(V) and molybdenum(VI) illustrates the high capacity of chitosan for the sorption of oxo‐anions. They are very efficiently sorbed in acidic solutions by ionic interactions. The correlation of sorption capacities with the distribution of metal species shows that the sorbent has a greater affinity for highly charged anionic species. The sorption of complex anionic species such as chloro‐complexes of Pd and Pt; and that of copper complexed with organic ligands have also been studied. The optimum conditions for sorption are obtained when anionic complexes predominate in the solution. The chemical modification of chitosan, obtained by grafting of sulfur compounds, allows modifying the sorption mechanism: the ion‐exchange polymer is transformed to a dual ion‐exchange and chelating polymer.

Copper sorption isotherm in presence of sodium citrate (0.004 M ) (? RNH: fraction of protonated amine groups; ACuC: total fraction of anionic copper complexes; Cu‐FAL: total fraction of copper‐free anionic ligands).