Ion exchange properties of zirconium phosphate phosphite with alkaline earth metal ions.

The ion exchange properties of zirconium phosphate phosphite, a layered compound with asymmetrical layers, towards alkaline earth cations were investigated and compared with those of a-zirconium hydrogenphosphate.

It was found that these cations were easily taken up in the phosphate regionsof_ a-Zr(HPO₄)_{0 7}(HPO₃),.O.5H₂O whereas only Ca²⁺ and Sr²⁺ are directly exchanged from a-Zr(HP0₄)₂.H₂O. The ion exchange mechanism involves a single pnase transition and the solubility of the exchanging cations in the already formed phases. A wide solubility range was found for barium exchange. The interlayer distances and water content of the exchanged forms of zirconium phosphate-phosphite and those of the corresponding phases of zirconium phosphate were compared and discussed on the basis of the structural features of the two hosts.

Zirconium phosphate-phosphite has a relatively low ion exchange capacity (2.5 meq/g) compared to that of the zirconium phosphate (6.64 meq/g)but it is a more facile exchanger for large and hydrated cations.     

The effect of chelation on the selective transport of alkaline earth metal ions in asymmetric cellulose acetate hyperfiltration membranes. II

The effects of chelation on the transport of calcium and magnesium, both separately and in a variety of admixtures, in a controlled series of asymmetric cellulose acetate membranes were characterized. Ethylenediaminetetraacetic acid (EDTA) and ethylenebis(oxyethylenenitrilo)tetraacetic acid (EGTA) were used as chelating agents for the alkaline earth metal ions. Asymmetric cellulose acetate membranes annealed at 70°, 75°, and 85°C were studied. Chelation of each of these alkaline earth metals ions in aqueous solutions at pH 6, by either EDTA or EGTA, significantly increased the overall hyperfiltration rejections of these metals by all the membranes studied. The increase in rejection varied montonically with the fraction of metal ion complexed. The higher rejection of metal chelates, compared to the rejection of unbound metal ions, was considered to be the result of the significantly larger size of the chelated species. Calculations suggested that selective (or competitive) chelation took place at pH 6 in a mixture of calcium and magnesium ions in the presence of a stoichiometrically limiting amount of chelating agent. Calcium successfully competed for most of the available chelating agent in equimolar aqueous solutions of chelating agent, calcium, and magnesium. The calcium rejection was explained primarily in terms of the effects of chelation per se on the effective size of the formed complex even in feeds comprised of these ternary solute mixtures. The complexation reaction between magnesium and EGTA is, however, so unfavorable at pH 6 that the Mg²⁺ ion remains uncomplexed even in the presence of an equivalent amount of EGTA. The observed increased rejection of magnesium ions, therefore, in ternary systems was explained by electroneutrality criteria and by solute–membrane interactions involving the various calcium species and the membranes.     

杯[8]芳烃萃取稀土金属离子的研究

合成了对叔丁基杯[8]芳烃,研究了其对稀土金属钕、铕、镨离子(Nd^3 、Eu^3 、Pr^3 )在溶液中的萃取。测定了在25℃,离子强度I=0．1g／mol时Nd^3 、Eu^3 、Pr^3 的萃取平衡常数。探讨了杯[8]芳烃萃取分离这3种稀土金属离子的条件、萃取反应机理及其规律性。     

Separation of heavy metal ions by complexation on poly (N-vinyl imidazole) hydrogels

Summary Poly (N-vinyl imidazole) (PVIm) hydrogels were prepared by -irradiating binary mixtures of N-vinyl imidazole-water in a ⁶⁰Co- source having 4.5 kGy/h dose rate. These hydrogels were characterized with gravimetric and spectrophotometric studies. Hydrogels with equilibrium swelling ratio of 600% in distilled water were used in the metal ion adsorption studies. The effects of pH, equilibration time, and initial metal ion concentration were considered in batch equilibrium study on the chelation of Cu²⁺, Co²⁺, Cd²⁺, and Pb²⁺ ions. Maximum metal ion adsorption were observed at pH=6.0. It has also been observed that the amount of adsorbed metal ions decreased at lower pHs because of protonation of PVIm ring.     

Enhancing upconversion emission and temperature sensing modulation of the La2(MoO4)3: Er3+, Yb3+ phosphor by adding alkali metal ions

Trivalent Er³⁺-doped La₂(MoO₄)₃ upconversion phosphors with intense green emmision were synthesized at 800 °C by the solid-state reaction route, promoting the development of novel optical thermometry. The color emitted from the samples was minorly affected by the excitation power and doping concentration. Yb³⁺ is a better sensitizer for the La₂(MoO₄)₃: Er³⁺ phosphor and it can enhance the emission intensity when a certain amount is co-doping in the system. The up-conversion luminescent mechanism was investigated using the pump power-dependent UC emission spectra. Alkali metal doping increased the up-conversion emission intensities drastically, and Li⁺ ions can enhance the luminous intensity by more than 20 times. The fluorescence intensity ratio of the transition emission ²H_11/2-⁴I_15/2 and ⁴S_3/2-⁴I_15/2 was used to study upconversion optical temperature sensing. The sensitivity changes from doping with diverse alkali metal ions and their effects on the optimal temperature range are discussed in detail. Alkali metal ions doping extended the temperature range, indicating that this phosphor is a potential candidate for temperature-sensing probes.     

Fluorescent spongy carbon nanoglobules derived from pineapple juice: A potential sensing probe for specific and selective detection of chromium (VI) ions

Herein, we report, for the first time, the facile, green and one step hydrothermal synthesis of fluorescent spongy carbon nanoglobules (CNG) derived from pineapple juice as a sole carbon source without involving any strong acid treatment. The synthesized CNG not only exhibits hydrophilicity and can remain stable for several weeks but also demonstrates prominent blue color fluorescence under UV light (λ=365 nm). These CNG showed wide range of emission spectra in the visible region depending upon the different excitation wavelengths. The synthesized CNG were characterized in detail in terms of their morphological, structural, optical, compositional and thermal properties using numerous analytical and spectroscopic techniques. For application point of view, the perspective to utilize CNG as fluorescent sensing probe has also been explored with the introduction of various highly toxic metal ions and interestingly, it was observed that the fluorescence intensity of CNG was drastically quenched by chromium (VI) ions with high selectivity over the linear range of concentrations 0–18 µM with stern volmer constant 2.29×10⁴ M⁻¹. Such encouraging results revealed that simply prepared CNG are potential scaffold to fabricate highly sensitive and selective fluorescent sensors for the detection of highly hazardous and life threatening metal ions.     

Extraction of lanthanide ions from aqueous solution by bis(2-ethylhexyl)phosphoric acid with room-temperature ionic liquids

Extractions of five kinds of lanthanide metal ions by bis(2-ethylhexyl)phosphoric acid (DEHPA) with [1-Cn-3-methylimidazolium][PF₆](Cn = C₂, C₄) or [1-butyl-4-methylpyridinium][PF₆] were carried out under various DEHPA and HNO₃ concentrations from 0 to 1 M and under different temperature conditions from 298 to 333 K. These results were compared with those using the conventional organic solvent, hexane, in terms of their distribution coefficient values. Under all of the conditions in this study, the ionic liquid system shows more than three times greater extractability for lanthanide compared to when hexane was used. The distribution coefficient of lanthanide ions decreased as the length of the alkyl chain increased from the ethyl to the butyl. In addition, the imidazolium cation generally shows a higher distribution coefficient compared to the pyridinium cation in an ionic liquid. The concentration ratio of lanthanides and DEHPA resulted in an extraction affinity transition for lanthanides. Also evaluated in this study were issues related to the selectivity associated with the lanthanide mixture and the dependency of the ionic radius during lanthanide extraction.     

Dehydrogenative oligomerization reactivity of transition metal sulfides derived from their tris or bis(o-aminobenzenethiolato)metal complexes

Several tris or bis(o-aminobenzenethiolato)metal complexes, where metals include ruthenium, rhodium, rhenium, molybdenum, platinum, and palladium, were synthesized. They were used as precursors to active metal sulfide catalysts for dehydrogenative oligomerization of 1,2,3,4-tetrahydroquinoline (THQ). The conversion of metal complex precursors to the corresponding metal sulfides was carried outin situ in the THQ solution at 210–270 °C. These metal sulfides polymerized THQ to quinoline oligomers in 71–95% yield. We also observed a periodic trend on the activity of these catalysts showing a maximum oligomer yield with ruthenium sulfide.     

Miscibility of chitosan/poly(ethylene oxide) blends and effect of doping alkali and alkali earth metal ions on chitosan/PEO interaction

The miscibility of Chitosan (CS) and poly(ethylene oxide) (PEO) in their blends and the effect of K⁺ and Ca²⁺ doping on the CS/PEO interaction have been investigated in this work. CS and PEO appeared to be miscible and the DSC analysis suggested the Flory-Huggins interaction parameter χ_AB to be −0.21. Doping of K⁺ and Ca²⁺ into the CS/PEO blend matrix enhanced the cooperative interaction between CS and PEO and this enhancement was larger for Ca²⁺ than for K⁺. The difference between Ca²⁺ and K⁺ possibly reflects a stronger multi-valence interaction of Ca²⁺ with the amino and hydroxyl groups of CS as well as the ether groups of PEO to form a stable CS/Ca²⁺/PEO complex and a less significant interaction of K⁺, as suggested by DSC, WAXD and FTIR results. MD simulations clearly indicated the correlation between the dynamic behavior and the interaction of K⁺ and Ca²⁺ in the CS/PEO blend matrix.     

Voltammetry of nanoparticle-coupled imine linkage-based receptors for sensing of Al(III) and Co(II) ions

Zinc oxide nanoparticle-coupled imine linkage-based receptors (T4, T5 and T6) were studied for their voltammetric characteristics. T4 and T5 having electron withdrawing and electron donating substituents at meta position of the imine linkage showed prominent cathodic (reduction of imine group) peaks at ?0.930 and ?1.850 V, respectively, while T6 (without any substituent) showed a cathodic peak at ?1.220 V. Voltammograms of the receptors indicated that T4 and T5 responded quantitatively for aluminium ions, while T6 responded for cobalt ions. All the three receptors exhibited linear dynamic concentration ranges between 0.1 and 0.42 µM with regression coefficients ≥0.98. Calibration curves for the determination of aluminium and cobalt ions based on DPV data are reported and supported with potentiometric studies. Energy minimization studies using Gaussian 03W software also supported stability of the complexes. The proposed analytical method has been validated with complexometric method for metal detection in real-time samples.     

Kinetics of copolycondensation of bis(4-hydroxybutyl) terephthalate and bis(2-hydroxyethyl) terephthalate by ester-interchange reaction

The kinetics of polycondensation and copolycondensation reactions were investigated using bis(4-hydroxybutyl) terephthalate (BHBT) and bis (2-hydroxyethyl) terephthalate (BHET) as monomers. BHBT was prepared by ester interchange reaction of dimethyl terephthalate and 1,4-butanediol. BHBT and BHET were polymerized at 270°C in the presence of titanium tetrabutoxide (TBT) as a catalyst. Applying second-order kinetics for polycondensation, the rate constants of polycondensation of BHBT and BHET, k₁₁ and k₂₂, were calculated as 3.872 min⁻¹ and 2.238 min⁻¹, respectively. BHBT and BHET were also copolymerized at 270°C using TBT. The rate constants of crossreactions in the copolycondensation of BHBT and BHET, k₁₂ and k₂₁, were obtained by using the results obtained from a proton nuclear magnetic resonance (¹H-NMR) spectroscopy and a high-performance liquid chromatography (HPLC). It was found that the rate constants during the copolycondensation of BHBT and BHET at 270°C decreased in the order k₂₁ > k₁₁> k₂₂ > k₁₂ and the monomer reactivity ratio of BHBT was four or five times larger than that of BHET. In calculating the crossreactions, the method by the ¹H-NMR spectroscopy gave more accurate results than that by the HPLC. © 1996 John Wiley & Sons, Inc.     

Interaction of metal ions with clays: I. A case study with Pb(II)

Pb(II) adsorption was studied under different conditions (pH, time, metal ion concentration, clay amount, temperature) on kaolinite, montmorillonite, and their poly(hydroxo)zirconium (ZrO–kaolinite, ZrO–montmorillonite) and tetrabutylammonium (TBA–kaolinite, TBA–montmorillonite) derivatives. All samples were calcined (ZrO-derivatives at 773 K, TBA-derivatives at 973 K) before using as adsorbents. The data were interpreted assuming first- and second-order kinetics. The rate constants including the pore diffusion rate constant are reported. The adsorption data could be fitted with Freundlich and Langmuir isotherms, and the coefficients indicated favorable adsorption of Pb(II) on the clays. Determination of the thermodynamic parameters, ΔH, ΔS, and ΔG showed the adsorption to be exothermic accompanied by decrease in entropy and Gibbs energy.     

Reactivity studies of 2,3,5,6-Tetra(2-pyridyl) pyrazine (tppz) with first-row transition metal ions

Reactions of 2,3,5,6-tetra(2-pyridyl) pyrazine (tppz) with [ML₆][X]₂ (L = CH₃CN, H₂O;X = [BF₄]⁻, [ClO₄]⁻, [NO₃]⁻ [BArF]⁻(BArF - B[3,5-C₆H₃(CF₃)₂]₄) lead to the high-yield formation of mononuclear [M(tppz)₂]²⁺, (M = Mn^II, Fe^II, Co^II, and Ni^II) and dinuclear [Ni₂(tppz)(CH₃CN)₆]⁴⁺ species. The new compounds were fully characterized by X-ray crystallographic, spectroscopic, and magnetic susceptibility measurements. Surprisingly, the 2:1 M:tppz reactions did not lead to isolation of the dinuclear species except in the case of Ni(II). It was further noted that even in the case of the Ni reactions, the nuclearity of the product depends on the choice of anions and the reaction conditions. Magnetic measurements of the mononuclear species [Co(tppz)₂]²⁺ revealed thermally induced spin-crossover behavior from a high-spin S = 3/2 at higher temperatures to a low-spin S = 1/2 complex at lower temperatures. The dinuclear compound [Ni₂(tppz)(CH₃CN)₆]⁴⁺ exhibits a weak anti-ferromagnetic interaction through the bridging tppz ligand.     

Temperature-swing adsorption of precious metal ions onto poly(2-(dimethylamino)ethyl methacrylate) gel

The temperature-swing adsorption (TSA) of heavy metal ions onto 2-(dimethylamino)ethyl methacrylate (DMAEMA) gel has been examined. The DMAEMA gel adsorbs precious metal ions (Pt(IV), Au(III), and Pd(II)) in HCl aqueous media as a result of the electrostatic interactions between the protonated amino groups in the gel and the anionic chloro complexes, while it is inactive against Cu(II) and Ni(II) cations. The amount of Pt(IV) ions adsorbed onto the DMAEMA gel decreases linearly with an increase in temperature. The TSA operation was successfully carried out; the DMAEMA gel repeatedly adsorbed and desorbed Pt(IV) ions in the temperature-swing operation between 20 °C and 60 °C. The TSA technique using the DMAEMA gel is simple, environment-friendly, and potentially applicable in various separation processes for precious metals in industries.     

Synthesis,characterization, thermal study,and crystal structure of a new layered alkaline earth metal sulfonate: Sr[C2H4(SO3)2]

A rare two-dimensional layered inorganic–organic hybrid material, strontium sulfonate Sr[C₂H₄(SO₃)₂] was synthesized by hydrothermal reaction of strontium chloride hexahydrate and ethane disulfonic acid at 160 °C. Single-crystal X-ray diffraction was utilized for structural determination. Data showed that the compound, crystallized in the monoclinic system and space group of C2/c. With cell parameters a = 8.3183(7) Å, b = 5.4416(5) Å and c = 14.9784(13) Å. The new material was extensively studied by DRIFT-infrared spectroscopy, thermogravimetric analysis, SEM and powder X-ray diffraction. Results show that the compound is thermally stable.     

Adsorption of heavy metal ions in ternary systems onto Fe(OH)3

The adsorption behavior of amorphous Fe(OH)₃ has been studied in multicomponent metal system. The metal ions uptake in the ternary system is lower than in the single system, suggesting that certain sites on the surface of the solid are blocked due to competition. The selectivity trend in the ternary system is observed to be Ni²⁺>Zn²⁺>Cd²⁺ which is, however, lost with increase in the temperature of the aqueous solution. Further, the observed selectivity trend is neither related to electronegativity of the metal ions nor to the pH of the hydrolysis, but has been found dependent on charge to radius ratio. The metal ions adsorption is found to increase with pH, while the converse is true with the rise in temperature. The uptake of metal ions data has been interpreted in terms of stoichiometry, binding constants and adsorption capacities. The negative values of ΔG show that uptake of metal ions is favored at lower temperatures, indicating that the adsorption mechanism essentially remains ion exchange in nature.     

Adsorption properties of poly(acrylaminophosphonic-carboxyl-hydrazide)type chelating fiber for heavy metal ions

In this article, the adsorption properties of poly(acrylaminophosphonic-carboxyl-hydrazide) chelating fibers for Cu(II), Cd(II), Co(II), Mn(II), Pb(II), Zn(II), Ni(II), and Cr(III) are investigated by a batch technique. Based on the research results of binding capacity, adsorption isotherm, effect of pH value on sorption, and adsorption kinetics experiments, it is shown that the poly(acrylaminophosphonic-carboxyl-hydrazide) chelating fibers have higher binding capacities and good adsorption kinetic properties for heavy metal ions. The sorption of the metal ions on the chelating fibers is strongly dependent on the equilibrium pH value of the solution. The adsorption isotherms of Cu(II) and Cd(II) on the chelating fiber exhibit a Langmuir-type equation. The adsorbed Cu(II), Cd(II), Zn(II), and Pb(II) could be eluted by diluted nitric acid. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 7–14, 1998