Synthesis,characterization and adsorption behaviour of TX-100 based Sn(IV) phosphate,a new hybrid ion exchanger

A new hybrid ion exchanger, Triton X-100 based tin(IV) phosphate (TX-100SnP) has been synthesized and characterized by ion exchange and physico-chemical methods such as ion exchange capacity, elution and concentration behaviour, IR, X-ray, TG/DTA and elemental analysis. Its adsorption behaviour has also been studied for some alkaline earths and heavy metal ions in different acidic media. It has been found generally more selective for metal ions as compared to tin(IV) phosphate prepared earlier. For Pb(II), Hg(II) and Fe(III) its selectivity has been found to be exceptionally good. On this basis, some binary separations have been performed involving these metal ions. Thermal studies show a high thermal stability of the material. It retains 54.54% of its i.e.c. at 200°C and 27.27% at 300°C.     

Use of tetracyanoplatinate (ii) for the luminescent detection of metalions

The tetracyanoplatinate(II) (TCP) ion forms insoluble fluorescent compounds with many metal ions. This property has not hitherto been exploited for analytical use. The soluble sodium TCP salt has been applied as a reagent for metal ion detection. Fluorescent precipitates useful for detection of the metal ions were obtained with Y(III), Zr(IV), Ag(I), Zn(II), Cd(II), Hg(I), Hg(II), A1(III), Pb(II), La(III) and Th(IV). Limits of detection ranged from 5 to 200 ppm. With ammonium acetate as a masking agent, selective detection of 10 ppm of silver was achieved in the presence of the other metal ions. As little as 20 ppm of zirconium can be detected in the presence of hafnium, which yields a non-fluorescent precipitate.     

Determination of Ge(IV), Sn(II), Pb(II) and Zn(II), Cd(II), Hg(II) by ring colorimetry after separation by thin-layer chromatography

Summary Clean and rapid analytical separation of microgram quantities of Ge(IV), Sn(II), Pb(II) and Zn(II), Cd(II), Hg(II) from their mixed solution has been made possible by ascending thin-layer chromatography using the solvent systems: (a)Isobutyl alcohol: Conc. HCl: Et-Me ketone and (b) Isobutyl alcohol: CH₃COOH. For the evaluation of different metal ions, the resulting delineated spots as viewed in U.V. light were scooped out with the help of micro-vacuum cleaner and the collected material transferred to the paper set on the ring oven. Separate rings were obtained for individual metal ions and the computation of results having been made by ring colorimetry, using PTC and other chromogenic reagents.

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Bestimmung von Ge(IV), Sn(II), Pb(II) und Zn(II), Cd(II), Hg(II) durch Ring-Colorimetrie nach Trennung durch Dünnschicht-Chromatographie

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Détermination de Ge(IV), Sn(II), Pb(II) et de Zn(II), Cd(II), Hg(II) par colorimétrie annulaire après séparation par chromatographie sur couche mince

     

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.     

Titanium(IV) tungstosilicate and titanium(IV) tungstophosphate: two new inorganic ion exchangers

Crystalline phases of Ti(IV) tungstosilicate and Ti(IV) tungstophosphate have been synthesised. The ion-exchange capacities of Ti(IV) tungstosilicate and Ti(IV) tungstophosphate have been reported as 0.44 and 0.80 mequiv./g, respectively. Both materials show monofunctional ion-exchange characteristic and are stable in 0.1 M solutions of HNO3, HCl, H2SO4 and acetone and benzene. Ti(IV) tungstosilicate is found to be more stable thermally than Ti(IV) tungstophosphate (loss in ion-exchange capacity was found as 58 and 80%, respectively for samples heated at 200 degrees C). The Kd values for heavy metals such as Pb, Hg, Cd, Sb, Co, Zn, Ni, Fe, Cr etc. have been reported in demineralised water and two surfactant media by batch processes. Cr3+, Fe3+ and Sn4+ are totally adsorbed on both the materials in demineralised water while a decrease in Kd value with increase in concentration of two surfactants is reported. On the basis of Kd values for metal ions, thirteen binary separations and five ternary separations on Ti(IV) tungstosilicate and thirteen different binary separations and four different ternary separations on Ti(IV) tungstophosphate have been achieved. Separation of methylamine from ethylamine has been done by GC on a column packed with Ti(IV) tungstophosphate.     

Some ion exchange properties of amorphous titanium (IV) phosphate

An amorphous titanium (IV) phosphate exchanger has been synthesised and characterized through elemental analysis, infrared, and thermogravimetric techniques. Divalent cations Mn, Co, Ni, Cu, Zn, Cd, Hg and Pb in bidistilled water have been exchanged with the proton of the exchanger matrix using a batch method. From these results the thermodynamic selectivity constants and distribution coefficients were calculated, whose values indicate a high selectivity for Pb and Hg. Both cations were successfully separated from a mixture containing all cations studied through column separation experiments.     

Ion-exchange studies on poly-o-anisidine Sn(IV) phosphate nano composite and its application as Cd(II) ion-selective membrane electrode

An organic-inorganic composite, poly-o-anisidine Sn(IV) phosphate, was chemically synthesized by mixing ortho-anisidine into gels of Sn(IV) phosphate with different mixing volume ratios. Studies on the effect of eluant concentration, elution behavior and separation of metal ions were carried out to understand the ion-exchange capabilities. Due to Cd(II) selective nature of composite, revealed by distribution studies, Cd(II) ion selective membrane electrode was fabricated. The analytical utility of the electrode was established by employing it as an indicator electrode in electrometric titrations having fast response time, 3–5s, and long life span of six months. Some physical parameters like self-diffusion coefficient (D₀), activation energy (E_a) and entropy of activation (ΔS₀) have been evaluated under conditions favoring a particle diffusion-controlled mechanism by studying ion-exchange kinetics.      

Adsorption of heavy metal ions onto dithizone-anchored poly (EGDMA-HEMA) microbeads

The dithizone-anchored poly (EGDMA-HEMA) microbeads were prepared for the removal of heavy metal ions (i.e. cadmium, mercury, chromium and lead) from aqueous media containing different amounts of these ions (25-500 ppm) and at different pH values (2.0-8.0). The maximum adsorptions of heavy metal ions onto the dithizone-anchored microbeads from their solutions was 18.3, Cd(II); 43.1, Hg(II); 62.2, Cr(III) and 155.2 mg g(-1) for Pb(II). Competition between heavy metal ions (in the case of adsorption from mixture) yielded adsorption capacities of 9.7, Cd(II); 28.7, Hg(II); 17.6, Cr(III) and 38.3 mg g(-1) for Pb(II). The same affinity order was observed under non-competitive and competitive adsorption, i.e. Cr(III)>Pb(II)>Hg(II)>Cd(II). The adsorption of heavy metal ions increased with increasing pH and reached a plateaue value at around pH 5.0. Heavy metal ion adsorption from artificial wastewater was also studied. The adsorption capacities are 4.3, Cd(II); 13.2, Hg(II); 7.2, Cr(III) and 16.4 mg g(-1) for Pb(II). Desorption of heavy metal ions was achieved using 0.1 M HNO(3). The dithizone-anchored microbeads are suitable for repeated use (for more than five cycles) without noticeable loss of capacity.     

Synthesis, characterization and ion-exchange properties of a new and novel ‘organic-inorganic’ hybrid cation-exchanger: Nylon-6,6, Zr(IV) phosphate

Organic-inorganic hybrid materials enable the integration of useful organic and inorganic characteristics within a single molecular-scale composite. Unique ion-exchange properties of these types of materials have been observed, and many others can be envisioned for this promising class of materials. In this paper, we describe the ion-exchange and physico-chemical properties of one family of self-assembling organic-inorganic hybrid based on nylon-6,6, framework with Zr(IV) phosphate an inorganic ion-exchanger. The physico-chemical properties of this hybrid material were determined using atomic absorption spectrophotometry (AAS), CHN elemental analysis, ICP-MS, UV-vis spectrophotometry, FTIR, TGA-DTA and scanning electron microscope (SEM) studies. Ion-exchange capacity (IEC), thermal stability and distribution behavior, etc. were also carried out to understand the cation-exchange behavior of the material. On the basis of distribution studies, the material was found to be highly selective for Hg(II), a highly toxic environmental pollutant. Its selectivity was examined by achieving some important binary separations like Hg(II)-Mg(II), Hg(II)-Zn(II), Hg(II)-Fe(III), Hg(II)-Bi(III), etc. Thus, the relatively new field of “organic-inorganic” hybrids offers a variety of exciting technological opportunities to decrease the environmental pollution.     

Synthesis and characterization of nano-composite ion-exchanger; its adsorption behavior

A novel organic-inorganic nanocomposite cation-exchanger has been synthesized via sol-gel method. It was characterized on the basis of FTIR, XRD, SEM, TEM, AFM and Raman studies. The structural studies reveal semi-crystalline nature of the material with the particle size ranging from 1-5 nm. Physiochemical properties such as ion-exchange capacity, chemical and thermal stability of composite material have also been determined. Bifunctional behavior of the material has been indicated by its pH titrations curves. The nanocomposite material exhibits improved thermal stability, higher ion-exchange capacity and better selectivity for toxic heavy metals. The ion-exchange material shows an ion-exchange capacity of 1.8 meq g(-1) for Na(+) ions. Sorption behavior of metal ions on the material was studied in different solvents. The cation exchanger was found to be selective for Pb(II), Hg(II) and Zr(IV) ions. The limit of detection (LOD) and the limit of quantification (LOQ) for Pb(II) ion was found to be 0.85 and 2.85 μg L(-1). Analytically important separations of heavy metal ions in synthetic mixtures as well as industrial effluents and natural water were achieved with the exchanger. The practical utility of polyanilineZr(IV)sulphosalicylate cation exchanger has been established for the analysis and recovery of heavy metal ions in environmental samples.     

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.     

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.     

Enhanced metal ion selectivity of 2,9-di-(pyrid-2-yl)-1,10-phenanthroline and its use as a fluorescent sensor for cadmium(II)

The metal ion complexing properties of the ligand DPP (2,9-di-(pyrid-2-yl)-1,10-phenanthroline) were studied by crystallography, fluorimetry, and UV-visible spectroscopy. Because DPP forms five-membered chelate rings, it will favor complexation with metal ions of an ionic radius close to 1.0 A. Metal ion complexation and accompanying selectivity of DPP is enhanced by the rigidity of the aromatic backbone of the ligand. Cd2+, with an ionic radius of 0.96 A, exhibits a strong CHEF (chelation enhanced fluorescence) effect with 10(-8) M DPP, and Cd2+ concentrations down to 10(-9) M can be detected. Other metal ions that cause a significant CHEF effect with DPP are Ca2+ (10(-3) M) and Na+ (1.0 M), whereas metal ions such as Zn2+, Pb2+, and Hg2+ cause no CHEF effect with DPP. The lack of a CHEF effect for Zn2+ relates to the inability of this small ion to contact all four donor atoms of DPP. The structures of [Cd(DPP)2](ClO4)2 (1), [Pb(DPP)(ClO4)2H2O] (2), and [Hg(DPP)(ClO4)2] (3) are reported. The Cd(II) in 1 is 8-coordinate with the Cd-N bonds to the outer pyridyl groups stretched by steric clashes between the o-hydrogens on these outer pyridyl groups and the central aromatic ring of the second DPP ligand. The 8-coordinate Pb(II) in 2 has two short Pb-N bonds to the two central nitrogens of DPP, with longer bonds to the outer N-donors. The coordination sphere around the Pb(II) is completed by a coordinated water molecule, and two coordinated ClO4(-) ions, with long Pb-O bonds to ClO4(-) oxygens, typical of a sterically active lone pair on Pb(II). The Hg(II) in 3 shows an 8-coordinate structure with the Hg(II) forming short Hg-N bonds to the outer pyridyl groups of DPP, whereas the other Hg-N and Hg-O bonds are rather long. The structures are discussed in terms of the fit of large metal ions to DPP with minimal steric strain. The UV-visible studies of the equilibria involving DPP and metal ions gave formation constants that show that DPP has a higher affinity for metal ions with an ionic radius close to 1.0 A, particularly Cd(II), Gd(III), and Bi(III), and low affinity for small metal ions such as Ni(II) and Zn(II). The complexes of several metal ions, such as Cd(II), Gd(III), and Pb(II), showed an equilibrium involving deprotonation of the complex at remarkably low pH values, which was attributed to deprotonation of coordinated water molecules according to: [M(DPP)(H2O)]n+ <==> [M(DPP)(OH)](n-1)+ + H+. The tendency to deprotonation of these DPP complexes at low pH is discussed in terms of the large hydrophobic surface of the coordinated DPP ligand destabilizing the hydration of coordinated water molecules and the build-up of charge on the metal ion in its DPP complex because of the inability of the coordinated DPP ligand to hydrogen bond with the solvent.     

A new pyridine-based 12-membered macrocycle functionalised with different fluorescent subunits; coordination chemistry towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II)

The coordination chemistry of the new pyridine-based, N2S2-donating 12-membered macrocycle 2,8-dithia-5-aza-2,6-pyridinophane (L1) towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) has been investigated both in aqueous solution and in the solid state. The protonation constants for L1 and stability constants with the aforementioned metal ions have been determined potentiometrically and compared with those of ligand L2, which contains a N-aminopropyl side arm. The measured values show that Hg(II) in water has the highest affinity for both ligands followed by Cu(II), Cd(II), Pb(II), and Zn(II). For each metal ion considered, 1:1 complexes with L1 have also been isolated in the solid state, those of Cu(II) and Zn(II) having also been characterised by X-ray crystallography. In both complexes L1 adopts a folded conformation and the coordination environments around the two metal centres are very similar: four positions of a distorted octahedral coordination sphere are occupied by the donor atoms of the macrocyclic ligand, and the two mutually cis-positions unoccupied by L1 accommodate monodentate NO3- ligands. The macrocycle L1 has then been functionalised with different fluorogenic subunits. In particular, the N-dansylamidopropyl (L3), N-(9-anthracenyl)methyl (L4), and N-(8-hydroxy-2-quinolinyl)methyl (L5) pendant arm derivatives of L1 have been synthesised and their optical response to the above mentioned metal ions investigated in MeCN/H2O (4:1 v/v) solutions.     

Removal of heavy metal ions from water by using poly(ethyleneglycol dimethacrylate-co-acrylamide) beads

Poly(ethyleneglycol dimethacrylate-co-acrylamide) (poly(EDGMA-co-AAm)) copolymer beads have been prepared for use in the separation Pb(II), Hg(II), and Cd(II), metal ions in aqueous solution by a batch equilibration technique. Adsorption capacity were increased with pH for Pb(II), Cd(II) and Hg(II) and then reached almost plateau value around 6.0. The high initial rate of metal ions uptake (<10 min) suggests that the adsorption occurs mainly at the bead surface. The metal uptake results show that poly(EGDMA-co-AAm) can be used for the adsorption of the following metals in the indicated order: Pb(II) > Cd(II) > Hg(II) expressed on a molar basis. However, when the uptake was expressed in terms of the amount of metal removed from solution was as follows: Pb(II) > Hg(II) > Cd(II). The beads still showed preference toward Pb(II) when this metal was in a mixture with Hg(II) and Cd(II). A linearized form of the Freundlich and the Langmuir isotherm model fits the experimental equilibrium concentration data of Hg(II) and Cd(II) better than isotherm type model of Pb(II). The recovery of the metal ions after adsorption and the regeneration of the adsorbent can be carried out by treatment of the loaded beads with either 0.5 M NaCl, or 1 M HNO₃.     

Liquid – liquid extraction behavior of V(IV) using phosphinic acids as extractants

The extraction behavior of V(IV) in the presence of Mo(VI), W(VI), U(VI), V(V), Ti(IV), Al(III), Cr(III), Fe(III), Mn(II), Zn(II) and Pb(II) has been studied using two alkylphosphinic acid extractants, Cyanex 272 and 301. The effect of various parameters, such as the nature of diluent, the type of mineral acid and the concentration of the acid, and metal ions has been investigated. The loading and recycling capacity of the extractants has been assessed. Based on the distribution data some binary separations from V(IV) were achieved. Received: 24 October 1996 / Revised: 2 July 1997 / Accepted: 5 July 1997     

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.     

Liquid-liquid extraction study of tellurium(IV) with N-n-octylaniline in halide medium and its separation from real samples

N-n-Octylaniline in xylene is used for extractive separation of tellurium(IV) from hydrochloric acid media. Tellurium(IV) is extracted quantitatively with the 3% reagent in xylene from 5.5 to 7.5 M hydrochloric acid. It is stripped from organic phase with 1:1 ammonia and estimated spectrophotometrically with pyrimidine-2-thiol (4'-bromoPTPT). The effects of metal ion, acids, reagent concentration, diluents and various foreign ions have been investigated. The log-log plots of distribution ratio (D(Te(IV))) versus N-n-octylaniline concentration indicate that the nature of extracted species is [(RR'NH(2)(+))(2) TeCl(6)(2-)](org). The method affords binary separation of tellurium(IV) from gold(III), selenium(IV), bismuth(III), copper(II), lead(II), antimony(III), germanium(IV) and is applicable to the analyses of synthetic mixture containing associated metal ions and alloy samples. The method is simple, selective, rapid and accurate.     

Synthesis and characterisation of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) Zr(IV) monothiophosphate composite cation exchanger: analytical application in the selective separation of lead metal ions

In this study, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) zirconium(IV) monothiophosphate composite cation exchanger was prepared by sol–gel precipitation method. The presence of sulphur in the cation exchanger enhances affinity towards the heavy metal ions which can improve the selectivity of the material. The selectivity studies showed that the material is selective towards Pb(II) ions. To characterise the material, several physicochemical properties were also studied which includes X-ray, scanning electron microscopy and transmission electron microscopy studies. The ion-exchange behaviour of this cation exchanger was studied by using some of the selected properties like ion-exhange capacity for various metal ions, elution, effect of eluent concentration, thermal effect on ion-exchange capacity (IEC). The results of IEC and physicochemical properties revealed that the material is nanocomposite, crystalline, chemically, mechanically and thermally stable. The analytical ability of this cation exchanger was demonstrated in binary separation of Pb(II) ions from a mixture of other metal ions. The recovery is qualitative and the separations are reproducible.     

The manganese(IV) oxide electrode as a manganese(II) sensor

Manganese(IV) oxide electrodes formed with a graphite/PTFE substrate are shown to have near-theoretical response to manganese(II) ions in pH-4 acetate medium and a sub-Nernstian response in 0.1M nitric acid medium. Lead and iron(III) ions interfere, and iron(II) ions even more so, but other bivalent transition metal ions have little effect. The main drawback of this type of electrode is its long response time (~ 20 min). Some attempts to use manganese(IV) oxide electrodes as the basis for phosphate electrodes by use of MnHPO(4).3H(2)O and MnNH(4)PO(4).H(2)O are also described.