Pyridine based zirconium(IV) and tin(IV) phosphates as new and novel intercalated ion exchangers

Pyridine based zirconium(IV) phosphate (PyZrP) and tin(IV) phosphate (PySnP) have been synthesized as new and novel intercalated ion exchangers. These materials have been characterized using X-ray, IR spectra, TG, DTG and DTA studies in addition to their ion exchange capacity, elution, pH titration, concentration and distribution behaviour. The distribution studies towards several metal ions in different media/concentrations have suggested that PyZrP and PySnP are selective for Hg(II) and Pb(II), respectively. As a consequence some binary separations of metal ions involving Hg(II) and Pb(II) ions have been performed on a column of these materials, demonstrating their analytical and environmental potential.     

A Comparative Study of the Synthesis and Ion Exchange Properties of Iodophosphates of Tin(IV), Zirconium(IV) and Iron(III): Separations of Metal Ions on Tin(IV)-iodophosphate Columns

Abstract

Iodates and iodophosphates of tin(IV), zirconium(IV) and iron(III) have been synthesized under varying conditions and studied their ion exchange behaviour. Among the various ion exchangers synthesized, tin(IV)-iodophosphate is chosen for detailed study owing to its highest ion exchange capacity and highest chemical stability. The most stable sample is prepared by mixing 0.1M stannic chloride, 0.1M potassium iodate and 0.1M potassium dihydrogen orthophosphate solutions in the volume ratio 1:1:2 respectively at pH 0–1. It is a monofunctional weak cation exchanger. Its ion exchange capacity for K⁺ is 1.6 meq/dry g. The thermal and chemical stabilities of this material have been determined and compared with Zr(IV)-phosphoiodate. Effect of heating on the properties of tin(IV)-iodophosphate has been determined. To explore the separation potential of tin(IV)-iodophosphate Kd values of different metal ions have been determined in organic solvents. A number of important separations of metal ions of industrial utility have been successfully achieved on the columns of tin(IV)-iodophosphate.     

Sorption Studies in DMSO-NITRIC Acid and DMSO-Acetic Acid Systems and Separation of Metal Ions on TIN(IV)-Iodophosphate

Abstract

Some new samples of tin(IV)-iodophosphate have been synthesized and their ion exchange properties have been studied. Adsorption behaviour of different metal ions on tin(IV)-iodophosphate (TIP₅), in H⁺ form, in different solvent systems have been examined. Kd values of few metal ions, in 4M DMSO medium, have also been determined on the same ion-exchanger in NH⁺ ₄ form. Effect of particle size of tin(IV)-iodophosphate (TIP₅), in H⁺ form, on the Kd values of metal ions has been studied. Separations of a number of metal ions have been achieved on tin(IV)-iodophosphate (TIP₅) columns.     

Determination of Sn(II) and Sn(IV) after mixed micelle-mediated cloud point extraction using alpha-polyoxometalate as a complexing agent by flame atomic absorption spectrometry

The cloud point extraction behavior of Sn(II) and Sn(IV) using alpha-polyoxometalate and mixed surfactants solution was investigated. The mixture of a nonionic surfactant (Triton X-100) and a cationic surfactant (CTAB) was utilized as a suitable micellar medium for preconcentration and extraction of tin complexes. Sn(II) in the presence of Sn(IV) was extracted with alpha-polyoxometalate, 0.3% (w/v) Triton X-100 and 3.5x10(-5) mol L(-1) CTAB at pH 1.2. Whereas the pH value of 3.7 were used for the individual determination of Sn(II) and Sn(IV) and also for total tin determination at the same conditions. Enrichment factors of 100 were obtained for the preconcentration of both metal ions. Under the optimal conditions, linearity was obeyed in the ranges of 55-670 microg L(-1) of Sn(II) and 46-750 microg L(-1) of Sn(IV) ion concentration. The detection limit of the method was also found to be 12.6 microg L(-1) for Sn(IV) and 8.4 microg L(-1) for Sn(II). The relative standard deviation of seven replicate determination of 100 microg L(-1) both metal ions were obtained about 2.4%. The diverse ion effect of some anions and cations on the extraction efficiency of target ions were tested. Finally, the optimized conditions developed were successfully utilized for the determination of each metal ion in various alloy, juice fruit, tape and waste water samples with satisfactory results.     

Radiochemical investigation of the electron exchange reaction between tin(II) and tin(IV) in hydrochloric acid solutions

This paper is concerned with the study of isotope exchange reaction between Sn(II) and Sn(IV) in hydrochloric acid solutions. The kinetics of the exchange reaction of tin in these solutions were studied by extraction of Sn(IV)-hydroxyquinolate into chloroform.¹¹³Sn tracer, initially in the Sn(IV) state, was used. The rate of exchange reaction was determined at 22°C in a wide range of hydrochloric acid concentrations (2.8–12M). The dependence of the exchange rate on the concentration of chloride and hydrogen ions in these solutions (ionic strength: I∼8 and I∼12) are given. The activation energy dependence on chloride ion concentration at I∼12 was determined. The possible mechanism of the exchange reaction between tin(II) and tin(IV) is discussed on the basis of these data.     

Synthesis,Ion Exchange Properties and Applications of Thermally Stable Stannic Selenophosphate: Comparison With Other TIN(IV) Based Ion Exchangers

Abstract

Samples of stannic selenophospnate have been synthesized by mixing 0.05m aquous solutions of stannic chloride, sodium selenite and sodium dihydrogen phosphate in different volume ratios at pH = 1. The chemical compositions have been determined. The Tin, Selenium and Phosphorous contents of all these samples have been found to be in the ratio of 1:1:1. Sample with a high ion exchange capacity (1.63 meq/ dry gm) has been studied in detail. pH titrations, IR and X-ray analysis, distribution coefficients of metal ions in different systems were performed. The differential selectivity of metal ions on stannic selenophosphate has been utilized for the important separations. Fourteen quantitative separations of industrial and analytical-importance have been achieved on its column. A comparison of the important properties of stannic selenophosphate have been made with stannic tungsto-arsenate, stannic molybdoarsenate, stannic arsenophosphate, stannic vanadophosphate, stannic phosphate and stannic selenite. It peak due to inter stitial water (1600cm^?1) persists upto 500°C. However, the peak vanishes completely when the drying temperature is increased to 800°C.     

Synthesis and ion exchange behaviour of polyaniline Sn(IV) arsenophosphate: a polymeric inorganic ion exchanger

Incorporation of a polymer material into an inorganic ion exchanger provides a class of hybrid ion exchangers with a good ion exchange capacity, high stability, reproducibility and selectivity for heavy metals. Such a type of ion exchanger ‘polyaniline Sn(IV) arsenophosphate’ has been synthesized by mixing polyaniline into inorganic material. This material is characterized using X-ray, IR, TGA studies in addition to ion exchange capacity, pH-titration, elution and distribution behaviour. On the basis of distribution studies, the material has been found to be highly selective for Pb(II). Kinetic study of exchange for the metal ions has been performed and some physical parameters such as self diffusion coefficient D₀, energy E_a and entropy ΔS* of activation have been determined.     

Rapid Solvent Extraction of Tin(IV) with High Molecular Weight Amine from Hydrochloric Acid Solution

A novel method has been developed for the solvent extraction of tin(IV) from 8 M hydrochloric acid with 4% N‐n‐octylaniline. Tin(IV) from the organic phase was determined spectrophotometrically with pyrocatechol violet at 550 nm. Extraction was found to be quantitative in the range of 7–10 M hydrochloric acid. When the concentration of N‐n‐octylaniline was varied from 0.05–20% in xylene, it showed that optimum concentration was > 3%. Amongst diluents like benzene and xylene, toluene was found to be an effective diluent. Effect of shaking time, concentration of metal ion, and salting out agents was studied. Tolerance limits of various diverse ions were determined by masking interfering cations. Tin(IV) was separated from associated elements in its binary mixture with Se(IV), Sb(III), Bi(III), Pb(II), Au(III), Cu(II) and Zn(II) and from its ternary mixtures with Sb(III), Bi(III) and Cu(II), Au(III). The proposed method was applied for separation and determination of tin(IV) in tin bearing alloys and foodstuffs.     

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.     

The importance of cerium substituted phosphates as cation exchanger-some unique properties and related application potentials

Seven different samples of an inorganic ion exchanger, cerium phosphate, suitable for column use have been prepared under varying conditions. The property of these exchangers has been characterized by Inductively Coupled Plasma Spectroscopy. These exchangers are stable in water, dilute mineral acids, ethanol, methanol, acetone and ether. However, in concentrated HCl and HNO(3) they decompose. They retain about 50% of their exchange value after drying at 80 degrees C, and can be regenerated twice without any decrease in exchange capacity. The distribution coefficient measurements for alkaline earth metals, tellurium, iodine and molybdenum using these seven ion exchangers were studied. This revealed the relative affinity for each exchanger, where the sorption in general was most effective at pH 6-8. The titration curves of cerium phosphate (disodium) with alkaline earth metals showed that the selectivity sequence Ba(2+)>Sr(2+)>Ca(2+)>Mg(2+) is observed. Furthermore, it could be deduced that the adsorption of alkaline earth metal cations greatly depends on the cation. These studies have also shown that cerium phosphates with divalent ions are strongly preferred to monovalent ones. Therefore, as for the cerium phosphates with large monovalent ions, the lack of exchange for Ba(2+), Mg(2+) or other alkali earth metal ions should be essentially due to steric hindrance and this could include any one of the following: the large crystalline radius of metal ions or large hydrated ionic radius and high energy of hydration for other divalent ions. Three binary separations of Te(IV)-Mo(VI), Te(IV)-I(I) and Mo(VI)-I(I) has been developed and the recovery ranging from 90 to 100% has been achieved on cerium phosphate (disodium) columns.     

Thermolysis of the phenyltin chlorides,PhxSnCl4–x, (x=1−3): Products and pathways

The thermal degradation of triphenyltin chloride, diphenyltin dichloride and phenyltin trichloride has been studied by pyrolysis at 375°C in sealed tubes for various time periods. In all cases, biphenyl and tin(II) chloride are produced. For both phenyltin trichloride and diphenyltin dichloride, ter- and poly-phenyls are also obtained. In some cases tin(IV) chloride or elemental tin are obtained. Pathways that account for all observed products are presented.     

Synthesis of organically templated nanoporous Tin(II/IV) phosphate for radionuclide and metal sequestration

Nanoporous tin(II/IV) phosphate materials, with spherical morphology, have been synthesized using cetyltrimethylammonium chloride [CH3(CH2)15N(CH3)3Cl] as the surfactant. The structure of the material is stable at 500 degrees C; however, partial oxidation of the material occurs with redox conversion of Sn2+ to Sn4+, resulting in a mixed Sn(II)/Sn(IV) material. Preliminary batch contact studies were conducted to assess the effectiveness of nanoporous tin phosphate, NP-SnPO, in sequestering redox-sensitive metals and radionuclides, technetium(VII), neptunium(V), thorium(IV), and a toxic metal, chromium(VI), from aqueous matrixes. Results indicate that tin(II) phosphate removed >95% of all contaminants investigated from solution.     

The study of the Cd(NH3) 4 2+ /Cd*(NH3) 4 2+ exchange reaction in hydrous oxides of zirconium(IV), silicon(IV) and tin(IV)

Kinetics of the exchange reaction of cadmium(II)-ammine complex ion using radio-active isotope¹¹⁵Cd in the same chemical form in hydrous oxides of zirconium(IV), silicon(IV) and tin(IV) has been studied. It has been found that the major contribution in the overall exchange process is from the surface of the exchanger particles. It has also been found that the rate of exchange follows the order: hydrous ZrO₂>hydrous SnO₂>hydrous SiO₂     

Studies on Liquid‐Liquid Extraction and Recovery of Bismuth(III) from Succinate Media Using 2‐Octylaminopyridine in Chloroform

A procedure is described for the liquid‐liquid extraction and recovery of bismuth(III) from succinate solution using 2‐octylaminopyridine (2‐OAP) as an extractant. The quantitative extraction of bismuth(III) occurs from 0.004 to 0.007 M sodium succinate solution of pH 2.5‐10 using 0.036 M 2‐OAP in chloroform. The extracted metal ion has been recovered by stripping with (3 × 10 mL) 0.5 M nitric acid. The log‐log plot of distribution ratio versus succinate concentration and distribution ratio versus 2‐OAP concentration gave slopes of 2.0 and 0.9, respectively, indicating a metal‐succinate ratio of 1:2 and a metal: 2‐OAP ratio of 1:1. The ion pair complex has a high distribution ratio in chloroform, while other solvents are poor. The extractants are stable towards prolonged acid contacts and there is no loss in its extraction efficiency even after recycling ten times. The extraction behaviour of some commonly associated metal ions, namely Ga(III), Cd(II), Zn(II), Cr(VI), Cu(II), Ba(II), Sb(III), Sn(IV), Tl(I) and Pb(II), has also been investigated. Based on partition data, conditions have been identified for attaining some separations of bismuth(III) from other metal ions; these conditions are extended for the recovery of pure bismuth from ore and alloys. Thermodynamic quantities for the extraction process were calculated.     

Synthesis,characterization, and antimicrobial activity of heterobimetallic complexes of Sn(IV) and Zn(II) with 4-aminophenylacetic acid

A series of new heterobimetallic complexes of zinc and tin with 4-aminophenylacetic acid has been prepared. Their composition and structure in solid state and in solution have been elucidated by elemental analysis, IR, ¹H NMR, and ¹³C NMR spectroscopy. IR spectroscopy results have confirmed the bidentate nature of the ligand, its molecules being arranged in planar square [Zn(II)] and trigonal bipyramid [Sn(IV)] around the metal ions. NMR studies have revealed four-coordinated geometry in the solution. The complexes containing both Sn(IV) and Zn(II) are better antimicrobial agents as compared to the Zn-only analog.     

Homogeneous isotopic exchange between nickel(II) and bis(resacetophenone oxime) nickel(II) complex

Isotopic exchange behaviour of bis(resacetophenone oxime) nickel(II) complex with nickel(II) in tri-n-butyl phosphate (TBP) and ethanol medium has been studied. The studies were carried out at different temperatures by varying the concentrations of both metal ion and the complex. Experimental observations showed that the complex is kinetically labile. Increase in temperature increases the isotopic exchange rate. Increase in concentration of either metal ion or complex results in significant increase of the reaction rate.     

Thermal decomposition of some linear trinuclear schiff base complexes with acetate bridges

Ni(II)–M(II)–Ni(II) nuclear structured complexes were prepared from N,N’-bis(salicylidene)-1,3-propanediamine (LH2) and its derivatives N,N’-bis(salicylidene)-2,2’-dimethyl-1,3-propanediamine (LDMH₂) and N,N’-bis(salicylidene)-2-hydroxy-1,3-propanediamine (LOH3), where M represents one of the following metal ions; Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II). Two different μ-bridges are found between the metal nucleus of the complexes. The phenolic oxygens and acetate ions tend to form μ-bridges between the terminal Ni(II) ions and central metal(II) ion. The coordinatively bonded DMF molecules, in the complexes, were observed to abandon the structure between 160–180°C. Further heating resulted primarily in the thermal decomposition of the complexes above 310°C, whereas metal oxide residue mixtures were observed above 650°C.     

Oxidation of cyclohexane catalyzed by metal-ion-exchanged zeolites

The ion-exchange rates and capacities of the zeolite NaY for the Cu(II), Co(II), and Pb(II) metal ions were investigated. Ion-exchange equilibria were achieved in approximately 72 h for all the metal ions. The maximum ion exchange of metal ions into the zeolite was found to be 120 mg Pb(II), 110 mg Cu(II), and 100 mg Co(II) per gram of zeolite NaY. It is observed that the exchange capacity of a zeolite varies with the exchanged metal ion and the amount of metal ions exchanged into zeolite decreases in the sequence Pb(II) > Cu(II) > Co(II). Application of the metal-ion-exchanged zeolites in oxidation of cyclohexane in liquid phase with visible light was examined and it is observed that the order of reactivity of the zeolites for the conversion of cyclohexane to cyclohexanone and cyclohexanol is CuY > CoY > PbY. It is found that conversion increases by increase of the empty active sites of a zeolite and the formation of cyclohexanol is favored initially, but the cyclohexanol is subsequently converted to cyclohexanone.     

Pyrolysis of N-doped organic aerogels with relation to sorption properties

Resorcinol–formaldehyde aerogels (five samples, three of them with addition of nitrogen containing precursors—3-hydroxypyridine, 3-aminophenol and melamine) have been prepared by sol–gel polycondensation, subcritical drying and pyrolysis. The pyrolysis of prepared organic aerogels has been studied by non-isothermal TG at constant heating rate. The process of pyrolysis has been found to consist of three steps with the total mass loss 40.2–61.7% (room temperature—1,000 °C). The resulted carbon aerogels have been tested as sorbents of Ni(II), Pb(II) and Cu(II) ions from aqueous solutions. Various relations have been found among the results obtained from the pyrolysis experiments and properties affecting adsorption. Besides the expected correlation between the mass loss gained from TG (isothermal step at 500 °C was applied) and from heating in the laboratory oven, the relationship between the mass loss during pyrolysis and sorption capacities for all three metal ions has been found. Other relations among pyrolysis behaviour, surface area and content of nitrogen have been also examined. Batch adsorption experiments show (with an exception of one sample) that N-doped samples have higher adsorption capacity for metal ions. In addition, changing of nitrogen functionalities during the pyrolysis has been considered and pyridinic-N (N-6) functionality has been contemplated as a suitable structure for the adsorption process.     

Separation of transition metal ions and preconcentration of platinum (IV) and chromium (III) on alumina-immobilized diethylenetriaminepentaacetic acid by ligand exchange

Summary Basic alumina-bonded diethylenetriaminepentaacetic acid (DTPA) has been utilized for the separation and preconcentration of some transition metal ions on the basis of ligand exchange. Breakthrough capacity and rate of sorption have been studied. The distribution coefficients of 16 transition metal ions have been determined in demineralized water, 0.01 M sodium citrate and in four different pH systems. On the basis of differences in Kd values some quantitative separations of metal ions have been achieved. The greater selectivity behaviour (higher Kd values) of the adsorbent for Pt(IV)and Cr(III) has been utilized for their preconcentration in the presence of other metal ions. The method has been employed for the recovery of Pt(IV) and Cr(III) from tapwater and sea-water samples.