Coordination geometries of selected transition metal ions (Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Hg2+) in metalloproteins

In order to determine preferred coordination geometries of six divalent cations (Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Hg2+), two sources of experimental data were exploited: Protein Data Bank and Cambridge Structural Database. Metal-binding sites of approximately 100 metalloproteins and 3000 smaller transition metal complexes were analyzed and classified. The correlation between the geometries of small-molecule crystal structures and the metal-binding sites in metalloproteins was investigated. The abundance of amino acid residues participating in coordination metal-protein bonds of metalloproteins was evaluated. From the performed analysis it follows that the octahedral arrangement is preferred by Co2+ and Ni2+, tetrahedral by Zn2+, square planar by Cu2+, and linear by Hg2+. Cadmium (II) cation tends to bind in both tetrahedral and octahedral arrangements and single coordination geometry cannot be unambiguously ascribed to it.     

Mg~（2＋）,Ca~（2＋）,Ba~（2＋）离子部分取代对SrAl_2O_4：Eu~（2＋）,Dy~（3＋）晶体结构和发光性能的影响

采用高温固相反应法制备了Sr0.9M0.1Al2O4：Eu2＋,Dy3＋（M=Mg,Ca,Ba）长余辉发光材料,并对其晶体结构、光谱性质、余辉特性进行了分析.X射线衍射测试结果表明,Mg2＋,Ca2＋,Ba2＋离子部分取代SrAl2O4基质中的Sr后,基质晶体结构并没有发生改变.光谱测试结果表明,Mg2＋,Ca2＋,Ba2＋取代后发光材料的激发光谱都是一个从250~450 nm范围内的宽激发带,在266nm,320nm,360nm,416 nm处各有一个激发峰.发射光谱中Mg2＋和Ba2＋的取代使波长出现蓝移,而Ca2＋的取代使波长出现红移.余辉测试结果表明,Ca2＋取代后的余辉时间长于Mg2＋和Ba2＋的取代.     

The effects of Mg2+, Mn2+, Zn2+, and Al3+ on the nickel deposit during electrowinning from sulfate bath

The presence of impurities like Mg²⁺, Mn²⁺, Zn²⁺, and Al³⁺ during electrowinning of nickel shows several effects. The effects include current efficiency, deposit quality, purity, crystallographic orientation, surface morphology, and polarization behavior. Addition of the impurities did not change the current efficiency significantly but did change the quality and purity of the electrodeposited nickel. Based on the quality of the deposits obtained, the tolerance limits of these impurities in nickel bath were obtained. Although no deviation of nickel structure from fee was observed, the peak height values for different orientations changed with all of the impurities and the values varied with impurity concentration. The surface morphologies of electrodeposited nickel in the presence of impurities also showed changes. The potentiodynamic scan curves for nickel deposition showed deviations in the presence of all the impurities studied. Based on the results, an attempt was made to correlate the various effects.     

Ni2+、Cu2+、Zn2+对氧化亚铁硫杆菌氧化 活性影响

为研究金属离子对氧化亚铁硫杆菌（Acidithiobacillus ferrooxidans,At.f）氧化活性的影响,通过测定经初步驯化的At.f菌在不同初始pH下的生长活性,开展不同浓度梯度的Ni2+、Cu2+、Zn2+及三种金属离子共存时对At.f菌的氧化活性影响的试验。结果表明,当初始pH为1.8时,At.f菌生长活性最好,且低浓度的Ni2+、Zn2+对At.f菌氧化活性影响较小,对两种金属离子的耐受浓度均在20 g/L以上;而该细菌对Cu2+比较敏感,当Cu2+浓度为2.5 g/L时,菌株的生长活性明显下降,特别是10 g/L时,对At.f菌的氧化能力有显著的抑制作用。三种金属离子同时存在时对At.f菌氧化活性的影响大于单一金属离子,当三种金属离子的浓度均为2.5 g/L时,在48小时内对At.f菌的氧化能力有显著的抑制作用,当三种金属离子的浓度均为5 g/L时,80小时时菌株对Fe2+的氧化率极低,说明At.f菌需要经过多种金属离子共存驯化培养后才能更好地运用于多金属复杂矿物的处理。     

用HBL110从硫酸锌溶液中直接萃取分离铜镉钴的试验研究

研究了采用新型萃取剂HBL110从硫酸锌溶液中直接萃取分离Cu~(2+)、Cd~(2+)、Co~(2+),考察了萃取剂体积分数、有机相皂化度、萃取时间、相比对Cu~(2+)、Cd~(2+)、Co~(2+)、Zn~(2+)萃取率的影响。结果表明:在萃取剂体积分数45.6%、有机相皂化度100%、萃取时间10min、萃取相比2/1条件下,Cu~(2+)萃取率为96.41%,Cd~(2+)萃取率为85.54%,Co~(2+)萃取率为65.07%,Zn萃取率仅为6.64%,β(Cu/Zn)=331,β(Cd/Zn)=73.09,β(Co/Zn)=23.09,实现了硫酸锌与杂质Cu~(2+)、Cd~(2+)、Co~(2+)的有效分离。     

Preparation and Long Persistence Red Luminescence of M0.2Ca0.8TiO3∶Pr3+(M=Mg2+,Sr2+,Ba2+,Zn2+)

M0.2Ca0.8TiO3∶Pr3 (M=Mg2 , Sr2 , Ba2 , Zn2 ) long persistence red phosphors were prepared by solid state reaction. The influence of the partially replacing Ca2 in CaTiO3 with Mg2 , Sr2 , Ba2 , Zn2 on the excitation spectra, the emission spectra and the long persistence properties were studied. The results suggest that certain quantity of Mg2 , Sr2 , Ba2 , Zn2 which partially replace Ca2 can enhance the luminescent intensity and prolong the afterglow persistence of the samples. The intensity of Mg0.2Ca0.8TiO3∶Pr3 is above all of the samples. Take Mg0.2Ca0.8TiO3∶Pr3 as the basic sample, the influence of Pr3 concentrations(C(Pr3 )) on the long afterglow properties were also studied. The results suggest that when the C(Pr3 ) is 0.10%(mol fraction) the intensity of the sample is the highest. The excitation spectra of all these samples show broad band spectra ranging from 300～500 nm peaking at about 342 nm. The emission spectra also exhibit a broad band peaking at 613 nm(CaTiO3∶Pr3 is 612 nm). XRD research indicates that the crystalline phases change due to the replacement of divalent metal ions.The research on the thermoluminescence spectra of Mg0.2Ca0.8TiO3∶Pr3 indicates that the peak is at 107.35 ℃ and the depth of the trap energy is about 0.852 eV.     

Preparation of Orange-Red Long Afterglow Phosphors Y2O2S:Sm3+, Mg2+, Ti4+

The orange-red long afterglow phosphors Y₂O₂S:Sm³⁺, Mg²⁺, Ti⁴⁺ was prepared by high temperature solid-state method. By XRD analysis, the crystal phase of the sample was Y₂O₂S, belonging to hexagonal system, and no new crystal phase arose when doping Sm³⁺, Mg²⁺, Ti⁴⁺. The characteristic peaks of excitation spectrum were located at 373, 388, 417, 430, 475 and 491 nm, and the characteristic peaks of emission spectrum were located at 571, 609 and 657 nm. The content of Sm³⁺ and doped ions Mg²⁺, Ti⁴⁺ affected the luminescent properties obviously, and Sm³⁺ affected the luminescent brightness mainly. Mg²⁺ and Ti⁴⁺ could deepen properly trap energy of Y₂O₂S crystal and strengthen its afterglow properties, the brightness and afterglow properties of sample were better when the mole ratio of Sm/Y, Mg/Y and Ti/Y is 1.4%, 1.25% and 0.9%, respectively.     

Sorption of Pb2+, Cd2+, and Sr2+ Ions on Calcium Hydroxyapatite Powder Obtained by the Hydrothermal Method

The sorption of Pb2+, Cd2+, and Sr2+ ions from aqueous solutions by carbonate-substituted calcium hydroxyapatite (HAP) obtained by the hydrothermal decomposition of urea and calcium–ethylenediaminetetraacetic acid chelates was investigated. The shift of the point of zero charge (pHpzc) of HAP toward lower pH values in solutions of Pb2+ and Cd2+ ions, which was more pronounced for Pb2+ ions than for Cd2+ ions, indicates that specific adsorption of these cations on HAP had occurred. There was no shift of the pHpzc in the solution containing Sr2+ ions, suggesting that specific adsorption of this cation on HAP had not occurred. The sorption isotherms suggest that the sequence of the efficiency of sorption by HAP is Pb2+>Cd2+>Sr2+. Ion exchange is the main mechanism of removal of Sr2+ ions from aqueous solution by apatite, whereas during the sorption of Cd2+ ions, this mechanism occurs simultaneously with the process of specific adsorption. The interaction of the apatite with Pb2+ ions includes the previously mentioned mechanisms and dissolution of the apatite, followed by the precipitation of lead hydroxyapatite.     

Cryoscopic studies in fluoride-Oxide-Silica systems: Part II. systems containing Mg2+, Ca2+, Ba2+ and Pb2+

The depressions of the freezing temperatures of MgF₂, CaF₂, and BaF₂ by adding 2MO · SiO₂, 3MO · 2SiO₂, MO · SiO₂, 2MO · 3SiO₂, and MO · 2SiO₂ where M = Mg, Ca and Ba, have been measured, as have the depressions of the freezing temperature of PbF₂ resulting from additions of 2Pb · SiO₂, 3PbO · 2SiO₂ and PbO · SiO₂. The variations of the activities of the fluorides with liquidus composition have been calculated. These are shown to be in good agreement with a proposed theoretical model of the constitutions of these melts. In the alkaline earth systems with MO/SiO₂ > 1.5 linear chain silicate ions and free F⁻ ions are postulated and in melts of MO/SiO₂ < 1.5 reaction between F⁻ and silicate ions to form polyfluorosilicate anions is postulated. These conclusions are in agreement with those drawn from infrared absorption studies of CaF₂-CaO-SiO₂ glasses. The activity behavior in the reciprocal systems MF₂-M′O · SiO₂ and M′F₂-MO · SiO₂ is explained in terms of polymerization and preferred ionic association effects within the melts. In the lead fluoride-silicate systems fluorination of the silicate ions occurs at PbO/SiO₂ = 2 and, in contrast with the alkali and alkaline earth systems, it appears that polyfluorosilicate anions and free O²⁻ anions can coexist in lead fluorosilicate melts.     

Characterization of Y2O2S:Eu3+, Mg2+, Ti4+ Long-Lasting Phosphor Synthesized by Flux Method

Long-lasting phosphor Y2O2S∶Eu3 , Mg2 , Ti4 was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu2O3 content in Y2O2S∶Eu3 x(0.01≤x≤0.10). On the other hand, the change of unit cell parameter a is not linear dependence. In the Y2O2S∶ Eu3 crystal structure, Eu3 ions only replaced Y3 ions′ places in which it posited center position of c axis. With the increase of Eu2O3 content, the position of the strongest emission peak changed from 540 nm (5D1→7F2 transition) to 626 nm (5D0→7F2 transition), and the maximum intensity was obtained when x=0.09 in Y2O2S∶Eu3 x(0.01≤x≤0.10). This is due to the environment of trivalent europium in the crystal structure of Y2O2S. Doping with Mg2 or Ti4 ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg2 and Ti4 ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence (LLP) was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye (0.32 mcd*m-2). Thus the LLP mechanism was analyzed.     

Complexes of carboxymethylcellulose in water. Part 2. Co2+ and Al3+ remediation studies of wastewaters with Co2+, Al3+, Cu2+, VO2+ and Mo6+

The properties of carboxymethylcellulose (CMC) complexes and Co²⁺ and Al³⁺ are reported in this work. The complexing power of CMC was greater to Al³⁺ than to Co²⁺, although it was not possible to determine some of the equilibrium constants. The infrared (IR) spectroscopy and thermal analysis helped in showing the existence of these complexes in the solid state. The films observed by scanning electron microscopy (SEM) provided a certainty that the chains of the biopolymer were not extensively broken by the use of strong mineral acid employed in some of the experimental steps of this study.Two water solutions — bidistilled and deionized water and an Iraí River, Curitiba, PR (Brazil) sample — were obtained by adding metal salts of Al³⁺, Co²⁺, Cu²⁺, Mo⁶⁺(initially in the form of molybdate) and VO²⁺ to which CMC was later added as a remediation agent. At different times, aliquots of those water samples were analyzed for their metal contents and showed ability to sequester different percentages of each of the metal ions, therefore, rendering the water samples within the Brazilian and Spanish standards for potable water (varying from < 0.3 to 5 mg/L depending on toxicity). The CMC complexes could be recovered by mechanical removal at the pH where these complexes are not very soluble. This process can be applied to municipal wasterwater treatment plants as CMC is a more cost-effective and non toxic alternative material than commercial employed alum. The metals can be recycled after the decomplexing process from the recovered solid complexes and with the additional benefit of using CMC that it will leave no trace of Al³⁺ ions in the water rising from the use of alum.