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.

ADSORPTION MECHANISM OF SOME BIVALENT HEAVY METAL CATIONS IN SOLUTIONS USING MONTMORILLONITE

The frontier orbital energies of montmorillonite molecule and[Me(H_(2)O)_(6)]^(2+)(Me=Cu^(2+),Zn^(2+),Co^(2+)and Ni^(2+))were calculated by INDO method.Results showed that the chemical interaction between montmorillonite molecule and[Cu(H_(2)O)_(6)]^(2+)or[Zn(H_(2)O)_(6)]^(2+)was possible.The experimental results of powder X-ray diffraction and isothermal adsorption supported the above-mentioned calculation results.

Theoretical Studies on the Interaction between Metal Cations and Cytosine, Guanine

The interaction of tetra- and hexa-coordinated compounds of cytosine(C) and guanine(G) with metal cations Ca(2+), Mg(2+), Mn(2+), Ni(2+), Cu(2+), and Zn(2+) have been calculated by using the B3LYP/6-31G method at the 6-31G(d, p) basis set, while the remaining coordination bonds are saturated by water molecules ((H(2)O)(4)). All geometries were optimized without symmetry restrictions. Comparing the interaction energies we obtained the orders of selectivity of C and G for the above metal ions as follows: (a)Cu(2+)>(a)Ni(2+)>(a)Mg(2+)>(a)Mg(2+)>(b)Cu(2+)>(a)Mn(2+)>(b)Zn(2+)> Ni(2+) and (a)Cu(2+)>(a)Ni(2+> a)Zn(2+)>(a)Mg(2+)>(b)Cu(2+)>(a)Mn(2+)>(b)Zn(2+)>(b)Ni(2+) respectively ((a,b) represent tetra- and hexa-coordinated, respectively), which are in good agreement with the experimental facts. Interaction energies of complexes provide a comparatively reliable quantification of the selectivity of dimethyl phosphate anion for the studied metal ions. In addition, the influence of coordination number and coordination structure on the interaction energy and the variation of ionic energy were discussed sufficiently. After analyzing the interaction energies of two kinds of complexes, the 'mutual selectivity'as well as the nature of the interaction between metal ions and ligands was revealed.

Insight into the Effect of Metal Cations in the Electrolyte on Performance for Electrocatalytic CO_(2)Reduction Reaction

This highlight indicates that the local electrostatic interactions between metal cations and key intermediates facilitate the electrocatalytic CO_(2) reduction reaction.Electrocatalytic CO_(2) reduction reaction(CO_(2)RR)has been considered as a promising strategy to achieve a carbon-neutral cycle and produce valuable fuels and feedstocks.

Effects of metal cations on sorption-desorption of p-nitrophenol onto wheat ash

The mutual effects of metal cations （Cu2＋, Pb2＋, Zn2＋, and Cd2＋） and p-nitrophenol （NP） on their adsorption desorption behavior onto wheat ash were studied. Results suggested that Cu2＋, Pb2＋, and Zn2＋ diminished the adsorption and increased the desorption of NP remarkably, while Cd2＋ had no such effect. In contrast, NP diminished the adsorption of Cu2＋, Pb2＋, and Zn2＋ onto ash, however, this suppression effect depended on the initial concentrations of metal cations. NP had no effect on Cd〉 adsorption on ash. Fourier transform infrared （FT-IR） and X-ray absorption spectroscopic （XAS） studies suggested the following mechanisms responsible for the metal suppression effect on NP adsorption： （1） large hydrated Cu2＋, Pb2＋, and Zn〉 shells occupied the surface of ash and prevent nonspecific adsorption of NP onto ash surface; （2） Cu2＋, Pb2＋, and Zn2＋ may block the micropores of ash, resulting in decreased adsorption of NP; （3） cornplexation of Cu2＋, Pb2＋, and Zn2＋ was likely via carboxyl, hydroxylic and phenolic groups of wheat ash and these same groups may also react with NP during adsorption. As a ＂soft acid＂, Cd2＋ is less efficient in the complexation of oxygencontaining acid groups than Cu2＋, Pb2＋, and Zn2＋. Thus, Cd2＋ had no effect on the adsorption of NP on wheat ash.

Study of the Complexation Behavior of Calixarene with Transition Metal Cations by UV-vis and Fluorescent Spectra

A new fluorescent compound based on calixarene skeleton was synthesized. Its complexation ability with transition metal ions, such as Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ and Ag +, was investigated by UV vis and fluorescent spectra.

Effect of Metal Cations on Corrosion Behavior and Surface Structure of Carbon Steel in Chloride Ion Atmosphere

In order to better understand why the corrosion behavior of carbon steel exposed in Nansha atmospheric environment is very serious, the effect of sodium, potassium and magnesium chlorides deposited on carbon steel surface has been studied under atmosphere conditions by wet/dry accelerated test. The difference of corrosion behavior and surface structure in Na+, K+, and Mg2+ containing atmosphere has been investigated by thickness loss, scanning electron microscope, X-ray diffraction and electrochemical techniques. The results indicate that the thickness loss of carbon steel exposed in different metal cations containing atmospheric environment increases in the order of Na+, K+, Mg2+. The hard metal cation can promote the dissolution of the steel to a certain extent. In Mg2+ containing atmosphere, the relative content of β-FeOOH is rather higher and the protective ability index α */γ * decreases in the order of Na+, K+, Mg2+. The corrosion current density of both bare carbon steel and the rusted carbon steel increases in the order of Na+, K+, Mg2+. The polarization resistance and the charge transfer resistance decreases in the order of Na+, K+, Mg2+.

Influence of Metal Cations and Cholesterol on Lipid-amphotericin Membrane

Amphotericin B（AmB） has been widely used in antifungal therapy. AraB molecules combine with cholesterol to form pores that can be toxic to human cells, thus greatly limiting its clinical application. The interaction between Arab and the cell membrane may be influenced by potassimn, sodium and calcium ions. Lq this study, the bilayer in large unilamellar lipid-drug liposomes with or without cholesterol was employed as a model membrane. N-（7-Nitrobenz-2-oxa-1,3-diazol-4-yl）-1,2-dipalmitoyl-sn-glycero-3-phosphoetheanolamine（N-BD-PE） and 1-palmi-toyl-2-[6（7-nitrobenz-2-oxa-1,3-diazol-4-yl）aminodoclecanoyl]-sn-glysero-3-phosphocholine（6-NBD-PC） are two kinds of fluorescent lipid probes, and the NBD group is attached to the polar lipid headgroup in the former, but to the sn-2 fatty acyl chain in the latter. The effect of these metal cations on the lipid-drug membrane was monitored by red edge excitation shift（REES）, fluorescence polarization, and the fluorescence lifetime of lipid probes in hydrophilic and hydrophobic areas of the membrane. These ions have different effects on the lipid-AraB membrane. Cholesterol can strengthen the packing ability of the membrane, which is influenced differently by potassium, sodium and calcium ions. Moreover, the influence of these ions on the membrane may be relative to the method of ion transportation through the membrane. This study is significant to understand the reduction of AraB＇s cellular toxicity.

Infrared Spectroscopy of CO2 Transformation by Group Ⅲ Metal Monoxide Cations

Infrared photodissociation spectroscopy of mass-selected[MO(CO2)n]^+(M=Sc,Y,La)complexes indicates that the conversion from the solvated structure into carbonate one can be achieved by the ScO^+ cation at n=5 and by the YO^+ cation at n=4,while only the solvated structures are observed for the LaO^+ cation.These findings suggest that both the ScO^+ and YO^+cations are able to fix CO2 into carbonate.Quantum chemical calculations are performed on[MO(CO2)n]^+ to identify the structures of the low-lying isomers and to assign the observed spectral features.Theoretical analyses show that the[YO(CO2)n]^+ complex has the smallest barrier for the conversion from the solvated structure into carbonate one,while[LaO(CO2)n]^+ exhibits the largest conversion barrier among the three metal oxide cations.The present system affords a model in clarifying the effect of different metals in catalytic CO2 transformation at the molecular level.

Third-Order Nonlinear Optical Responses of Bis(15-crown-5)-stilbenes Binding to One-or Two-Alkali Metal Cation(Li^(+),Na^(+)and K^(+))

Bis(15-crown-5)-stilbenes containing crown ether parts have been widely used in a variety of chemical applications,such as cation detectors,because of their ability to selectively bind to alkali metal cations,Bis(15-crown-5)-stilbenes and its derivatives with complexation of one-or two-alkali metal cation(Li^(+),Na^(+)and K^(+))have been theoretically investigat-ed by quantum chemistry methods.The coordination of alkali cations results in partial shrinkage of crown ethers,which directly affected natural distribution analysis charges and molecular orbital energy levels.The number of alkali metal ions has significant effects on absorption spectra and mean second hyperpolarizability.When one alkali metal ion was added to the anticonformer of bis(15-crown-5)-stilbene,the absorption spectra were obvious-ly redshifted and the mean second hyperpolarizability values were slightly increased;while two alkali metal ions were added to bis(15-crown-5)-stilbene,the absorption spectra were ob-viously blue shifted and the mean second hyperpolarizability values decreased.On the other hand,as the radius of the alkali ions increased,the mean second hyperpolarizability values of the compounds increased gradually.It is indicated that the mean second hyperpolarizability value is sensitive to the number and radius of the alkali metal cations,thus the third order nonlinear optical response can be used as a signal to detect the number and type of alkali met-al ions.

Effect of co-doped metal caions on the properties of Y_2O_3:Eu^(3+) phosphors synthesized by gel-combustion method

Y2O3：Eu3＋ phosphors co-doped with different metal cations （Li＋, Na＋, K＋, Mg2＋, Ca2＋） are prepared by the gel- combustion method with Y2O3：Eu3＋, and R（NO3）x （R = Li, Na, K, Mg, Ca） serving as raw materials and glycine as fuel, calcined at 1000 ℃ for 2 h. The synthesized Y203 ：Eu3＋ phosphors doped with different metal cations and doping ratios are characterized by x-ray diffractometry （XRD）, fluorescence and phosphorescent spectrophotometer. The co-doping metal cations are advantageous to the development of Y203：Eu3＋ lattice. All the samples can emit red light peaked at 611 nm under 254-nm excited. The luminescence intensities of co-doping samples are increased because the cations increase the electron transition probability of Eu3＋ from 5D0 level to 7F level. The fluorescence lifetime of Eu3＋ （SD0 --＋7F2） is increased by doping metal cations.

Metal cation exchanged silica gel for identification of cationic and nonionic surfactants with preliminary separation by thin layer chromatography

Silica gel impregnated with 1% aqueous solutions of different metal cations （Li^＋, Mg^2＋, Zn^2＋, Cu^2＋, Co^2＋, Ni^2＋, Ba^2＋and Th^4＋） has been used for the analysis of nonionic and cationic surfaetants using simple aqueous acetone as mobile phase system. Co^2＋ was found the most suitable impregnant for the mutual separation of nonionic surfactants （Brij-35 and Brij-57） and cationic from nonionic surfactants （tetmdecyltrimethylammonium bromide and Cween-20）. Zinc sulphate impregnation （Zn^2＋-silica gel） shows identical chromatographic behavior and these layers are useful to separate nonionic surfactant （Brij-35） from cationic surfaetant （cetylpyridinium chloride）. The mutual separation of B J-35 and B J-57 is not influenced by the presence of optical brightener in the sample.

Alkali metal cation doping of metal-organic framework for enhancing carbon dioxide adsorption capacity

Metal-organic frameworks （MOFs） have attracted much attention as adsorbents for the separation of CO2 from flue gas or natural gas. Here, a typical metal-organic framework HKUST-I（also named Cu-BTC or MOF-199） was chemically reduced by doping it with alkali metals （Li, Na and K） and they were further used to investigate their CO2 adsorption capacities. The structural information, surface chemistry and thermal behavior of the prepared adsorbent samples were characterized by X-ray powder diffraction （XRD）, thermo-gravimetric analysis （TGA） and nitrogen adsorption-desorption isotherm analysis. The results showed that the CO2 storage capacity of HKUST-1 doped with moderate quantities of Li＋, Na＋ and K＋, individually, was greater than that of unmodified HKUST-1. The highest CO2 adsorption uptake of 8.64 mmol/g was obtained with 1K-HKUST-1, and it was ca. 11% increase in adsorption capacity at 298 K and 18 bar as compared with HKUST- 1. Moreover, adsorption tests showed that HKUST-1 and 1K-HKUST-1 displayed much higher adsorption capacities of CO2 than those of N2. Finally, the adsorption/desorption cycle experiment revealed that the adsorption performance of 1K-HKUST-1 was fairly stable, without obvious deterioration in the adsorption capacity of CO2 after 10 cycles.

Alkali metal cation effects on electrocatalytic CO_(2)reduction with iron porphyrins

The electrocatalytic CO_(2)reduction reaction(CO_(2)RR)has attracted increasing attention in recentyears.Practical electrocatalysis of CO_(2)RR must be carried out in aqueous solutions containing electrolytesof alkali metal cations such as sodium and potassium.Although considerable efforts havebeen made to design efficient electrocatalysts for CO_(2)RR and to investigate the structure–activityrelationships using molecular model complexes,only a few studies have been investigated the effectof alkali metal cations on electrocatalytic CO_(2)RR.In this study,we report the effect of alkali metalcations(Na^(+)and K^(+))on electrocatalytic CO_(2)RR with Fe porphyrins.By running CO_(2)RR electrocatalysisin dimethylformamide(DMF),we found that the addition of Na^(+)or K^(+)considerably improves thecatalytic activity of Fe chloride tetrakis(3,4,5‐trimethoxyphenyl)porphyrin(FeP).Based on thisresult,we synthesized an Fe porphyrin^(N)18C6‐FeP bearing a tethered 1‐aza‐18‐crown‐6‐ether(^(N)18C6)group at the second coordination sphere of the Fe site.We showed that with the tethered^(N)18C6 to bind Na^(+)or K^(+),^(N)18C6‐FeP is more active than FeP for electrocatalytic CO_(2)RR.This workdemonstrates the positive effect of alkali metal cations to improve CO_(2)RR electrocatalysis,which isvaluable for the rational design of new efficient catalysts.

New Approach to Synthesis of Silica with Chemically Bound Guanidine Hydrochloride for Preconcentration of Metal Ions

Guanidine hydrochloride was chemically bonded to surface of modified silica by means of condensation with grafted amino groups. Ion-exchanging and complexing properties of the obtained adsorbent have been studied with respect to cations of Zn(II), Cu(II), Pb(II), Cd(II), Co(II) and metal-containing oxoanions of W(VI), Mo(VI), Cr(VI), V(V). Optimum conditions for quantitative extraction of the studied ions were determined. The structure and composition of Co(II) and Cu(II) complexes on the surface of the synthesized adsorbent have been investigated. The possibility of quantitative determination of cobalt(II) and copper(II) trace amounts after their preconcentration by the synthesized adsorbent was demonstrated.

Releasing characteristics of phosphorus and other substances during thermal treatment of excess sludge

The releasing characteristics of phosphorus, nitrogen compounds, organics, and some metal cations during thermal treatment of excess sludge were investigated. It was found that during heating not only phosphorus, but also nitrogen compounds, organics, and some metal cations could be released in abundance. The maximum orthophosphate （ortho-P） release of about 90 mg/L in concentration was observed at 50℃ in 1 h. Except for volatile fatty acids （VFAs）, comparatively little total nitrogen （TN）, total organic carbon （TOC）, and metal cations were released at the same time. Such results might favor further process of phosphorus recovery. VFAs were considerably released only at 50℃. Acetic, butyric, and propionic acid were the most abundant components in turn and their releasing profiles exhibited good linear relationship with time （R2 = 0.9977, 0.9624, and 0.8908, respectively）. The concentrations of Mg^2＋ and K^＋ increased with time and temperature during thermal treatment, but Ca^2＋ decreased. The release of Mg^2＋ and K^＋ agreed well with TP release （R^2 = 0.9892 and 0.9476, respectively）. Temperature in the experimental range had very little impact on the linear relationships, especially of Mg^2＋. Moreover, the parameter of mixed liquor suspended solids （MLSS） was found to be an important factor for thermal sludge treatment as the released ortho-P and total phosphorus （TP） at 50℃ increased more than one-fold when MLSS was increased from 4000 to 8000 mg/L.

Retention of clay-solidified grouting curtain to Cd^(2+), Pb^(2+) and Hg^(2+) in landfill of municipal solid waste

The effects of components and their ratio of grouts on anti-seepage capability of clay-solidified grouting curtain and its permeability of heavy metal cations were investigated by permeating experiments, using reactive solute transport model to study the permeation of heavy metals (Cd2+, Pb2+ and Hg2+). The study of permeating for different mixture ratios of cement and clay indicates that hydraulic conductivity of clay-solidified grouting curtain with different ratios of solid to liquid or with the same ratio of solid to liquid but with different ratios of cement to clay is changed. The laboratory simulation test results also show that precipitates produced in heavy metal cation migration process in curtain block up water flowing passage which makes the hydraulic conductivity of the solution-permeated curtain decrease with the leakage time. The permeation velocities for different heavy metal cations vary with ionic concentration, exchange capacity and ion radius etc. The test results indicate that the permeation rapidity order of heavy metals cations in clay-solidified grouting curtain is Hg2+>Pb2+ in the same experimental circumstance. In addition, permeability for different mixture ratios and antisepsis capabilities of clay-solidified grouting curtain were studied in tests.

Leaching behavior of zinc from crude zinc oxide dust in ammonia leaching

Zinc extraction from crude zinc oxide(CZO)is beneficial to the full utilization of secondary resources and environmental protection.In this paper,a systematic investigation was carried out to study the leaching behavior of CZO by using ammonia-ammonium carbonate solution.It was found that the maximum leaching rate of zinc from CZO dust was 95.7%under the conditions of[Zn]T:[NH 3]T:[CO_(3)^(2−)]=1:7.00:1.75,liquid to solid ratio 5:1,leaching temperature 30℃ and leaching time 60 min.Compared with pure zinc oxide(PZO)leaching,the CZO leaching required longer time and more leaching agents,which is caused by the Cd^(2+),Pb^(2+) and other metal cationic impurities in CZO.The metal cationic impurities dissolved in the leaching solution and combined with ammonium to form complexes,consuming leaching agents and affecting zinc leaching.

Theoretical Study on the Dehydrogenation Reaction of H_2S by VS^+ (~3Σ^-)

The dehydrogenation reaction of H2S by the ^3Σ^- ground state of VS^＋： VS^＋ ＋ H2S → VS2^＋ ＋ H2 has been studied by using Density Functional Theory （DPT） at the B3LYP/DZVP level. It is found that the reaction proceeds along two possible pathways （A and B） yielding two isomer dehydrogenation products VS2^＋-1 （^3B2） and VS2^＋-2 （^3A1）, respectively. For both pathways, the reaction has a two-step-reaction mechanism that involves the migration of two hydrogen atoms from S2 to V^＋, respectively. The migration of the second hydrogen via TS3 and that of the first via TS4 are the rate-determining steps for pathways A and B, respectively. The activation energy is 17.4 kcal/mol for pathway A and 22.8 kcal/mol for pathway B relative to the reactants. The calculated reaction heat of 9.9 kcal/mol indicates the endothermicity of pathway A and that of -11.9 kcal/mol suggests the exothermicity of pathway B.