D072型树脂脱除过氧化氢中金属阳离子的工艺研究

实验考察D072型阳离子交换树脂在交换柱中脱除过氧化氢中微量金属阳离子的动态行为．通过改变料液流速、高径比、料液中交换离子浓度及料液组成等参数，绘制不同条件下的透过曲线，以此考察D072型树脂对过氧化氢中金属阳离子的动态交换性能，从而确定适宜的工艺条件，为工业化生产提供科学依据．     

Studies on 16-Membered Azothia- and Azoxythiacrown Ethers as Ion Carriers in Ion Selective Membranes

16-Membered azothia- and azoxythiacrown ethers have been studied as ion carriers in ion-selective membranes. Their selectivities towards alkali, alkaline earth, transition and heavy metal cations were evaluated. The complex formation constants for these compounds with chosen cations have been determined using segmented sandwich membranes method.     

Formation Constants of Complexes of Monovalent Cations with Benzocrown Ethers in Nitromethane

The complexation reactions between the macrocyclic polyethers dibenzo-18-crown-6, benzo-18-crown-6, benzo-15-crown-5 and polyethers bearing a stilbene unit with alkali metal and silver cations have been studied conductometrically in nitromethane. The formation constants of 1 : 1 and 1 : 2 (metal : ligand) complexes were determined and found to decrease with increasing cation diameter. The stability of the stilbene crown – metal cation complexes is lower than for complexes of other investigated crown ethers with analogous cations. There seem to be some effects of double bond-silver ion interactions.     

Effect of multiply charged paramagnetic metal cations on J-aggregation of thiacyanine dyes

J-Aggregation of thiacyanine dyes with a different length of the polymethine chain has been studied in aqueous solutions in the presence of paramagnetic metal cations. The introduction of multiply charged metal cations stimulates J-aggregation. The number of molecules involved in the composition of J-aggregates has been calculated to be four on the basis of analysis of the absorption spectra. The equilibrium constants and the thermodynamic parameters of J-aggregation have been determined. The effect of the dye structure and the metal cation nature on J-aggregation has been revealed.     

Application of a Cation-Exchange Membrane to Determine Cations of Trace Metals in River Water

Donnan-membrane-equilibrium graphite-furnace atomic-absorption spectrophotometry (DME-GFAAS) has been developed to determine cations of trace metals in river water. The method employs a cation-exchange membrane to separate metal cations from their complexes; both total and cationic forms of metals were determined by means of GFAAS. The sensitivity of the method for the measurement of trace metal cations is determined by the detection limits of GFAAS for the metals of interest. Comparable concentrations of metal cations in water from NBS and from the Erhjen river were obtained between the DME-GFAAS and calculated (WATEQ4F) methods, indicating that the developed method is promising for natural fresh waters. The effect of pH on the distribution of metal cation in the NBS river water is significant for Cu and Pb; concentrations of these cations increase with decreasing pH. However, the concentrations of Cd and Zn cations do not vary with pH except that the concentration of the Zn cation decreases significantly as the pH value increases beyond 9. The method was applied to measure the capacity of complexing Cu in Chung-Lu river water, which was estimated to be 2.3 μM.     

Side-chain alkylation of toluene with methanol over zeolite catalysts

Catalytic properties of NaX-type zeolites modified by alkali metal cations under hydrothermal conditions have been studied. The highest process efficiency is obtained for CsNaX catalysts. The effect of operation conditions on the process results was examined.     

Proton ionizable crown compounds. 18. Comparison of alkali metal transport in a H2O-CH2Cl2-H2O liquid membrane system by four proton-ionizable macrocycles containing the dialkylhydrogenphosphate moiety

The macrocycle-mediated fluxes of alkali, alkaline earth, and several transition metal cations have been determined and compared in a H₂O-CH₂Cl₂-H₂O liquid membrane system using four water-insoluble macrocycles containing a dialkylhydrogenphosphate moiety. Transport of alkali metal cations by these ligands was greatest from a source phase pH = 12 or above into an acid receiving phase (pH = 1.5). Very low fluxes were observed for the transport of the alkaline earth cations and all transition metal ions studied except Ag⁺ and Pb²⁺ which were transported reasonably well by these new macrocycles.Deceased: September 5, 1987.     

Separation of metal cations in acidic solution by capillary electrophoresis with direct and indirect UV detection

Methods for the detectionn of metal cations under acidic conditions, near PH 2, in capillary electrophoresis (CE) were investigatged. Conditions for direct UV detection of UV absorbing metal cations such as Cr³⁺, Cu²⁺, Fe³⁺, UO₂²⁺, VO²⁺, and VO²⁺ were established With aqueous HCl or HClO₄ as the electroyte carrier. The speciation of vanadium(IV) and vanadium(V) at PH 2.3 by CE was achieved with direct detection at 185 nm. With the strong absorbance at 185 nm, no complexation was needed to detect the metal cations. An indirect UV detrection scheme for acidic conditions was also investigated. Several background carrier electolytes (BCES) were studied including 4-methylbenzylamince, nicontinamide, pyridazine, guanidine, 3-picoline, and chromium (III) to determine their effectivencess under very acidic conditions. The efect of ioni c surfactants and the nonionic surfactant, Trition X-100, on the peak heights and N Values was also studied.     

Wurster''s crownophanes: an alternate topology for para-phenylenediamine-based macrocycles

Six redox-active cyclophane/crown hybrid molecules (crownophanes) were prepared via cyclization reactions involving N,N′-dimethyl-p-phenylenediamine and tosylated oligoethylene glycols of varying length. These new host molecules differ from other phenylenediamine-containing crown ethers in that the electron-rich π face is designed to be part of the ligating group. Their electrochemical properties were determined by cyclic voltammetry with a correlation found between macrocyclic architecture and ease of oxidation. The affinity of the smaller crownophanes for cations was studied by cyclic voltammetry with the result that these hosts show no electrochemical response to alkali metal cations, but, dependent on macrocycle size, modest selectivity for alkaline earth metal cations. This stands in contrast to previously reported phenylenediamine-containing crown ethers in which the redox centers are linked to guest ions through a macrocyclic amino group.     

Trace metal analysis of rocks by flameless atomic-absorption spectrometry with a metal micro-tube atomizer

Flameless atomic-absorption spectrometry with a metal micro-tube atomizer has been studied. The element to be determined was atomized by electrical heating of the micro-tube in an inert atmosphere within a glass chamber. A detailed study of the atomic-absorption characteristics of the micro-tube atomizer is presented. The absolute sensitivities were 2.6 x 10(-12), 2.9 x 10(-11), 2.5 x 10(-10), 1.1 x 10(-10) and 1.4 x 10(-10)g for copper, cobalt, aluminium, palladium and selenium, respectively. The interferences of cations were studied for determination of cobalt and copper. Cobalt and copper in rock samples were determined in order to evaluate the metal micro- tube atomizer.     

Solvent extraction and self-assembly of nanosized aggregates of p-tert-butyl thiacalix[4]arenes tetrasubstituted at the lower rim by tertiary amide groups and monocharged metal cations in the organic phase

New p-tert-butyl thiacalix[4]arenes functionalized with morpholide and pyrrolidide groups at the lower rim in cone, partial cone, and 1,3-alternate conformations were synthesized, and their receptor properties for monocharged cations (alkali metal and silver ions) were studied using the picrate extraction method and dynamic light scattering (DLS). To evaluate the ability of the p-tert-butyl thiacalix[4]arene derivatives to recognize metal ions, liquid-liquid extraction of their picrate salts has been carried out in a mutually saturated water-dichloromethane system. The degrees of extraction and the extraction constants for monocharged metal cations (Li⁺, Na⁺, K⁺, Cs⁺) have been determined. The ability of the systems, consisting of host and guest molecules, to self-assembly was proved by DLS using a Zetasizer Nano ZS particle size analyzer. It was shown that all the investigated thiacalix[4]arenes are able to form nanoscale particles with silver cations under the experimental conditions. The pyrrolidide derivative in the cone conformation showed both self-association and aggregation processes with lithium cations. The degree of extraction for all the investigated systems that formed nanoscale aggregates in the organic phase was more than 67% and the extraction constants, log K_ex determined by the picrate extraction method, more than 6.     

Extraction of triply charged metal cations in aqueous phase-separating system antipyrine–sulfosalicylic acid–water

Extraction of macro amounts of triply charged metal cations (0.01–0.05 mol L^?1) in aqueous phase-separating system antipyrine–sulfosalicylic acid–water containing no organic solvent is studied. Optimum conditions for phase separation are established and the influence of the concentrations of the major components, inorganic acids (H₂SO₄, HCl), salting-out agents, and the volume of the aqueous phase on the process in question is determined. It was found that the optimum antipyrine/sulfosalicylic acid ratio in the system was (1.5–2.0): 1.0. The introduction of inorganic salting-out agents causes the volume of the organic phase (0.8–1.8 mL) to increase to 2 mL and more. The extractability series of triply charged metal ions is as follows: Tl > Fe > Sc > In > Ga. It was shown that inorganic salts and hexamine influence the degree of extraction of metal cations and that inorganic acids and water affect the distribution mechanism and the composition of the complexes. The half-extraction pH values (pH₁/₂) of the cations are calculated and correlations between the pH₁/₂ values, the ionic radii of the cations, and the polarization ability of the metal ions are established.

     

MODIFICATION OF TRANSITION METAL CATIONS TO POLYMER-STABILIZED PLATINUM COLLOIDAL CLUSTERS IN ENANTIOSELECTIVE HYDROGENATION OF METHYL PYRUVATE

Modification of transition metal cations to polymer-stabilized Pt colloidal clusters modified with cinchonidine was studied in enantioselective hydrogenation of methyl pyruvate. Compared to the enantiomeric excess (e.e.) value (71.4%) obtained without the presence of metal cations, obvious e.e. enhancement (up to 82.5%) was resulted from the addition of Zn^2 but with a certain decrease in activity. The reaction parameters in the presence of Zn^2 were also studied. It was found that the Pt colloidal catalysts in the presence of metal cations performed very differently from that in the absence of metal cations.     

Interaction of Clofazimine with Divalent Metal Ions: A Fluorescence Quenching Study

The interaction of clofazimine (CFZ) with divalent metal cations was studied by measuring fluorescence quenching spectra, synchronous fluorescence spectra and ultraviolet spectra. The fluorescence quenching spectra of CFZ in the presence of metal ions showed that metal ions quenched the fluorescence of CFZ. The quenching constants were determined using the Stern–Volmer equation. The binding constants (log K) and binding site were obtained. The thermodynamic parameters obtained in this study revealed that the interaction between CFZ and metal ions was mainly driven by a hydrophobic force. The conformational changes of CFZ were investigated by synchronous spectrum studies.     

Copper removal by carbon nanomaterials bearing cyclam-functionalized silica

The synthesis of metal (Fe, Co, Ni)-encapsulated carbon nanomaterials coated with cyclam-bonded silica has been described. The organic layer was identified by Fourier transform infrared spectroscopy and elemental analysis. The functionalized magnetic nanomaterials were employed to extract the divalent cations: copper, calcium, cobalt, manganese and nickel from aqueous solutions. Their adsorption capacities were studied by the batch procedure. The concentration of cations extracted was determined by inductively coupled plasma mass spectrometry. Influence of different parameters viz. pH, amount of the compound studied, contact time, on the cation extraction was investigated. Under optimum conditions copper extraction was significantly more efficient when compared with other coexisting ions.      

丙烯酸乙酯/甲基丙烯酸缩水甘油酯乳液共聚过程中凝胶的形成及控制

通过不同金属离子对环氧型丙烯酸橡胶凝胶含量的影响，得出几种金属离子催化开环的顺序，探讨了高价金属离子对环氧基的催化开环机理；依据交联点单体对共聚物凝胶含量的影响数据，通过近似计算得到共聚物的凝胶含量超过１％时的环氧基开环数的临界值．     

冠硫醚化学Ⅵ: 生色冠硫醚的合成及其配合机理的研究

本文报道了四个新的含7-氮杂-1,4,10,13-四硫杂环十六烷单元的生色冠硫醚的合成, 测定了其中3,4的电离常数分别为: pK~α=8.63(3); pK~a~1=8.49,pK~a~2=12.12(4)。通过光谱方法研究了它们与过渡金属离子的配合机理。     

Effect of Alkali Metal Cations on Length and Strength of Hydrogen Bonds in DNA Base Pairs

For many years, non-covalently bonded complexes of nucleobases have attracted considerable interest. However, there is a lack of information about the nature of hydrogen bonding between nucleobases when the bonding is affected by metal coordination to one of the nucleobases, and how the individual hydrogen bonds and aromaticity of nucleobases respond to the presence of the metal cation. Here we report a DFT computational study of nucleobase pairs interacting with alkali metal cations. The metal cations contribute to the stabilization of the base pairs to varying degrees depending on their position. The energy decomposition analysis revealed that the nature of bonding between nucleobases does not change much upon metal coordination. The effect of the cations on individual hydrogen bonds were described by changes in VDD charges on frontier atoms, H-bond length, bond energy from NBO analysis, and the delocalization index from QTAIM calculations. The aromaticity changes were determined by a HOMA index.     

Adsorption of radiocobalt on lead dioxide from aqueous solution

Adsorption of cobalt on lead dioxide from aqueous solutions has been studied in relation to shaking time, amount of adsorbent, pH, and concentration of the adsorbate. The data fitted very well Langmuir, Freundlich, and Dubinin-Radushkevich isotherms and their corresponding constants were calculated. In another set of experiments the influence of different anions and cations on the adsorption of cobalt under the optimum experimental conditions have been determined. EDTA, tartrate, citrate, thiocyanate, oxalate, U(VI), Al(III), Fe(III), Cr(III), and Th(IV), drastically reduced adsorption of cobalt. Therefore these anions and cations should be removed before adsorption of cobalt on lead dioxide. Adsorption of other metal ions on the oxide were measured under identical conditions. TheK _D values indicate that cobalt can be separated successfully from Hg(II), Ag(I), Ta(V), In(III) and Tc(VII).     

Selectivity of bacterial ionophore monensin for monovalent metal cations. Solvent effects in methanol and biphasic water-organic systems

Interactions of ionophore monensin with heavy metal monovalent cations, Ag⁺, Tl⁺, Hg ₂ ²⁺ , were studied in methanol and in various biphasic waterorganic solvent systems to supplement previous data on alkali-metal cations. The species formed were identified and the corresponding formation constants determined. Enthalpies of formation were also obtained in methanol for Ag⁺ and Tl⁺ from calorimetric measurements. The results for monovalent cations in general are discussed in terms of cation size and solvation, and structure of the ionophore anion.