Removal of 60Co and 137Cs from simulated NPP trap waters

The possibility of removing ⁶⁰Co and ¹³⁷Cs from simulated NPP trap waters by sorption and precipitation methods was examined. The use of layered double hydroxides (LDHs) of Mg and Nd, containing CO ₃ ^2? in the interlayer space, for removing ⁶⁰Co from NPP trap waters is inefficient, especially in the presence of EDTA. After 2 h of contact of the solid and liquid phases, the degree of ⁶⁰Co sorption does not exceed 12% at V/m = 500 mL g^?1. Coprecipitation of ⁶⁰Co with a complex precipitate of Fe³⁺ and triethylenediamine (CH₂-CH₂)₃N₂ from simulated NPP trap waters containing 0.03 M Co²⁺ allows ～85% removal of the radionuclide. The ⁶⁰CO coprecipitation with KFe[Fe(CN)₆] from simulated NPP trap waters does not ensure its efficient removal. The degree of coprecipitation of ⁶⁰CO with KFe[Fe(CN)₆] varies from ～55 to ～85%. A procedure was suggested for removing ⁶⁰Co and ¹³⁷Cs from aqueous solutions by coprecipitation of the radionuclides with the solid phase of K⁺, Fe³⁺, and Ni²⁺ ferrocyanides formed by adding K₄[Fe(CN)₆], Fe(NO₃)₃, and Ni(NO₃)₂ in succession to the solution. The procedure ensures almost 100% removal of both radionuclides from simulated NPP trap waters.     

Removal of Pb2+, Ag+, Cs+ and Sr2+ from aqueous solution by brewery's waste biomass

Heavy metal pollution is becoming a more and more serious environmental problem, posing threat to biota life. Biosorption is an alternative technology for the treatment of wastewater containing metal ions. In this paper, the removal of four metal ions, i.e., Pb2+, Ag+, Sr2+ and Cs+ by waste biomass of brewery was studied. The experimental results showed that metal uptake is a rapid process, which can be described by pseudosecond order kinetic model. The Langmuir adsorption isotherm was applied to correlate the equilibrium data and fitted quite well. The maximum biosorption capacities for four metal ions were 0.413 mmol Pb2+/g, 0.396 mmol Ag+/g, 0.091 mmol Sr2+/g and 0.076 mmol Cs+/g, respectively. The binding of metals was also discussed in term of several factors. The order of accumulated metal ions at equilibrium state on the molar basis was as follows: Pb2+>Ag+>Sr2+>Cs+, which positively correlated with their covalent index and electronegative and reversely correlated with dissociation constant.     

Diffusion mechanism of Co2+, Cu2+, Cd2+, Cs+, and Pb2+ ions in the particles of polyaniline silicotitanate

ABSTRACT

The kinetic behavior of Co²⁺, Cu²⁺, Cd²⁺, Cs⁺, and Pb²⁺ in the H-form of polyaniline silicotitanate composite as cation exchanger was studied as a function of particle size, concentration of the exchanging ions, reaction temperature, and drying temperature. The exchange rate was controlled by particle diffusion mechanism as a limited batch technique and is confirmed from the straight lines of B versus 1/r² plots. The values of diffusion coefficients, activation energy, and entropy of activation were calculated and their significance was discussed. The data obtained have been compared with that reported for other organic and inorganic exchangers.     

Ni、Co、Mn、Cu掺杂对K4 Nb6 O17光催化活性的影响

通过高温固相反应合成了铌酸盐K4Nb6O17及Ni2 、Co3 、Mn4 、Cu2 (5.0%mol)掺杂的K4Nb6O17并采用X射线衍射、紫外可见漫反射光谱、扫描电镜、比表面积分析等对其进行了结构和形貌表征.在甲醇为电子给体、Pt为助催化剂的情况下,研究了K4Nb6O17及Ni2 、Co3 、Mn4 、Cu2 掺杂的K4Nb6O17作为催化剂在约400nm紫外辐射下分解水产氢的光催化活性,并讨论了引起催化剂活性差异的原因.     

Isosteric heats of n-hexane sorption in ion-exchanged NaX containing Co2+, Ni2+, Zn2+, and Cd2+

Sorption—desorption isotherms of n-hexane have been measured at 288 and 298 K in zeolites M_xNa_87-2xX (M = Co, Ni, Zn, Cd) and the corresponding isosteric heats have been obtained. The effect of cations on isosteric heats is highly pronounced at low cowerage, being different for each particular cation. An attempt is made to explain the large differences in those heats in terms of cationic size, charge, electronic configuration, and location in the lattice.     

Speciation of artificial radionuclides 60Co, 137Cs, 152Eu, and 241Am in bottom sediments of the Yenisei river

The speciation of artificial radionuclides ⁶⁰Co, ¹³⁷Cs, ¹⁵²Eu, and ²⁴¹Am in surface layers of bottom sediments of the Yenisei river, collected within the near zone of impact of the Mining and Chemical Combine (Rosatom), was studied. In these samples the radionuclides ⁶⁰Co, ¹⁵²Eu, and ²⁴¹Am are mainly associated with fractions of humic and fulvic acids. The fraction of ¹⁵²Eu associated with nonsilicate iron is approximately 92%. The migration capability of radionuclides collected near the Atamanovo settlement decreases in the order ¹⁵²Eu > ²⁴¹Am > ⁶⁰Co > ¹³⁷Cs. For samples collected near Bol’shoi Balchug settlement, this order is as follows: ¹⁵²Eu ≈ ²⁴¹Am > ⁶⁰Co > ¹³⁷Cs. The presence of radionuclide-bearing micro-particles in bottom sediments considerably complicates the distribution of radionuclides, in particular, of ²⁴¹Am and ¹³⁷Cs, among migration forms.     

Adsorption and kinetic performance of Cs+, Co2+, and Ce4+ radionuclides on zirconium vanadate as a cation exchanger

Amorphous zirconium vanadate samples with different molar ratios have been prepared under optimum conditions. The experimental parameters such as the order of mixing and mixing ratios were established. The ion-exchange powders were characterized by X-ray diffraction, IR spectroscopy, and differential thermal analysis. The materials are thermally and chemically stable. The sorption behavior of Cs⁺, Co²⁺, and Ce⁴⁺ radionuclides was studied at varied values of Zr: V molar ratio, pH, and temperature. The thermodynamic equilibrium constants and the values of ΔG ₀, ΔH ₀, and ΔS ₀ for the exchange of Cs⁺, Co²⁺ and Ce⁴⁺ radionuclides at Zr: V = 1: 6 were calculated from the exchange isotherms. At Zr: V = 1: 6, the capability of the material to sorb Cs⁺, Co²⁺, and Ce⁴⁺ ions is the highest. The process kinetics can be descirbed by first- or second-order equations.     

腐植酸树脂对电镀废水中重金属离子的吸附

利用泥炭为原料制备出腐植酸树脂。在动态条件下 ,研究了腐植酸树脂对重金属离子Pb2 +、Cu2 +、Zn2 +、Ni2 +、Cr3+的吸附效果及条件。同时探讨了腐植酸树脂对Pb2 +、Cu2 +、Zn2 +、Ni2 +、Cr3+的吸附与解吸再生机理。含Pb2 +、Cu2 +、Zn2 +、Ni2 +、Cr3+的电镀废水经腐植酸树脂吸附后 ,废水中重金属离子的含量低于国家排放标准     

A solid phase extraction procedure for Fe3+, Cu2+ and Zn2+ ions on 2-phenyl-1H-benzo[d] imidazole loaded on Triton X-100-coated polyvinyl chloride

A new and efficient solid phase extraction method is described for the preconcentration of trace heavy metal ions. The method is based on the adsorption of Fe(3+), Cu(2+) and Zn(2+) on 2-phenyl-1H-benzo[d] imidazole (PHBI) loaded on Triton X-100-coated polyvinyl chloride (PVC). The influences of the analytical parameters including pH and sample volume were investigated. Common coexisting ions did not interfere on the separation and determination of analytes under study. The adsorbed analytes were desorbed by using 5 mL of 4 mol L(-1) nitric acid. The preconcentration factor is 90. The detection limits (3 sigma) were in the range of 0.95-1 microg L(-1). The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be more than 2.7 mg of ions per gram of sorbent. The recoveries of analytes were generally higher than 95%. The relative standard deviations (R.S.D.s) were generally lower than 4%. The method has been successfully applied to some real samples.     

Ion-exchange of Pb2+, Cu2+, Zn2+, Cd2+, and Ni2+ ions from aqueous solution by Lewatit CNP 80

Removal of trace amounts of heavy metals can be achieved by means of selective ion-exchange processes. The newly developed resins offered a high resin capacity and faster sorption kinetics for the metal ions such as Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) ions. In the present study, the removal of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) ions from aqueous solutions was investigated. Experimental investigations were undertaken using the ion-exchange resin Lewatit CNP 80 (weakly acidic) and were compared with Lewatit TP 207 (weakly acidic and chelating). The optimum pH range for the ion-exchange of the above mentioned metal ions on Lewatit CNP 80 and Lewatit TP 207 were 7.0-9.0 and 4.5-5.5, respectively. The influence of pH, contact time, metal concentration and amount of ion-exchanger on the removal process was investigated. For investigations of the exchange equilibrium, different amounts of resin were contacted with a fixed volume of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) ion containing solution. The obtained sorption affinity sequence in the presented work was Ni(2+)>Cu(2+)>Cd(2+)>Zn(2+)>Pb(2+). The metal ion concentrations were measured by AAS methods. The distribution coefficient values for metal ions of 10(-3)M initial concentration at 0.1mol/L ionic strength show that the Lewatit CNP 80 was more selective for Ni(2+), Cu(2+) than it was for Cd(2+), Zn(2+) and Pb(2+). Langmuir isotherm was applicable to the ion-exchange process and its contents were calculated. The uptake of metal ions by the ion-exchange resins was reversible and thus has good potential for the removal of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) from aqueous solutions. The amount of sorbed metal ion per gram dry were calculated as 4.1, 4.6, 4.7, 4.8, and 4.7mequiv./g dry resin for Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+), respectively. Selectivity increased in the series: Cd(2+)>Pb(2+)>Cu(2+)>Ni(2+)>Zn(2+). The results obtained showed that Lewatit CNP 80 weakly acidic resin had shown better performance than Lewatit TP 207 resin for the removal of metals. The change of the ionic strength of the solution exerts a slight influence on the removal of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+). The presence of low ionic strength or low concentration of NaNO(3) does not have a significant effect on the ion-exchange of these metals by the resins. We conclude that Lewatit CNP 80 can be used for the efficient removal of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) from aqueous solutions.     

过渡金属离子掺杂对TiO2纳米尺寸及其相结构的影响

利用酸催化的溶胶-凝胶法合成了一系列不同掺杂量的Fe3 /TiO2、Cr3 /TiO2纳米复合微粒.用XRD和TEM研究了Fe3 、Cr3 的掺杂对TiO2纳米粒子尺寸和相结构的影响.结果表明:掺杂离子不同,对TiO2纳米粒子尺寸和相结构的影响不同.在所研究的掺杂量范围内(x:0.0000～0.1000),TiO2纳米粒子的粒径随Cr3 掺杂量的增加呈减小的趋势,但幅度不大;而Fe3 的掺杂则会引起TiO2粒子的团聚和晶粒的长大;由XRD分析可知:在掺杂量范围内,不会发生Fe2O3、Cr2O3等相的偏析,但Fe3 的掺杂引起了TiO2在低温条件下由锐钛矿向金红石的相转变.通过UV-Vis光谱的研究发现:Fe3 、Cr3 的加入,可以使TiO2对光的吸收拓展到可见区,同时随着掺杂量的增加,对可见光的吸收强度显著增强.     

Solubility of uranoarsenates MAsUO6·nH2O in water and aqueous HClO4 (M = H+, Li+, Na+, K+, Rb+, Cs+, NH 4 + )

The solubility of poorly soluble uranoarsenates MAsUO₆·H₂O in water and aqueous HClO₄ was determined. The solubility products and Gibbs energies of formation of these compounds were evaluated from the experimental data using the principles of equilibrium thermodynamics. The state of uranoarsenates in aqueous solutions in the range not studied experimentally was estimated.     

The study of various parameters affecting the ion exchange of Cu2+, Zn2+, Ni2+, Cd2+, and Pb2+ from aqueous solution on Dowex 50W synthetic resin

A gel resin containing sulfonate groups (Dowex 50W) was investigated for its sorption properties towards copper, zinc, nickel, cadmium and lead metal ions. The use of selective ion exchange to recover metals from aqueous solution has been studied. The ion exchange behavior of five metals on Dowex 50W, depending on pH, temperature, and contact time and adsorbate amount was studied. Experimental measurements have been made on the batch sorption of toxic metals from aqueous solutions using cation exchanger Dowex 50W. The maximum recoveries (about 97%) Cu(2+), Zn(2+), Ni(2+), Cd(2+) and (about 80%) Pb(2+) were found at pH ranges 8-9. The amount of sorbed metal ion was calculated as 4.1, 4.6, 4.7, 4.8, and 4.7mequiv./gram dry resin for Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+), respectively. The precision of the method was examined at under optimum conditions. Selectivity increased in the series: Pb>Cd>Cu>Zn>Ni. It has been observed that, selectivity of the -SO(3)H group of the resin increases with atomic number, valance, degree of ionization of the exchanged metals. The equilibrium ion exchange capacity of resin for metal ions was measured and explored by using Freundlich and Langmuir isotherms. Langmuir type sorption isotherm was suitable for equilibrium studies.     

Electronic and spin configurations of Co3+ and Ni3+ ions in oxides of K2NiF4 structure: A magnetic susceptibility study

In La₄LiCoO₈, Li⁺ and Co³⁺ ions are ordered in two dimensions and Co³⁺ ions undergo transitions from the low-spin to the intermediate as well as the high-spin states. Both Sr₄TaCoO₈ and Sr₄NbCoO₈ exhibit low to intermediate-spin state transitions of Co³⁺ ions. In the system LaSr_1?xBa_xNiO₄, the e_g electrons are essentially in extended states forming a band. With increase in x, the band width decreases accompanying an increase in unit cell volume; high-spin Ni³⁺ ions are formed to a small extent with increasing x, but there is no spin-state transition. In LaSrAl_1?xNi_xO₄, at small x, there is a small proportion of high-spin Ni³⁺; when x ≈ 0.6, there is an abrupt decrease in the $\text{c}$/$\text{a}$ ratio, signalling the formation of the band. In LnSrNiO₄, the $\text{c}$/$\text{a}$ ratio decreases sharply between Ln = La and Nd; this is likely to be accompanied by a broadening of the band.     

铁离子对二氧化钛晶型转变的影响

通过共沉淀法制得纳米掺铁TiO2粒子，并利用TEM、DSC-TG和XRD测试手段研究了铁离子TiO2晶型转变过程中的作用，以及铁离子掺杂浓度对TiO2晶型转变的影响。     

Modeling the long-term leaching behavior of (137)Cs, (60)Co, and (152,154)Eu radionuclides from cement-clay matrices

Leaching characteristics of some radionuclides that are commonly encountered in radioactive waste streams from immobilized waste matrices in different cement-clay grouts have been assessed to investigate the influence of the clay additives on the leaching behavior of the solid waste matrices. The International Atomic Energy's Agency (IAEA) standard leach method has been employed to study the leach pattern of (137)Cs, (60)Co, and (152,154)Eu radionuclides immobilized in ordinary Portland cement (OPC), OPC-bentonite, and OPC-red clay grouts. The examination of the leaching data revealed that adding clays to OPC reduces the leach pattern as OPC-bentonite相似文献   

The formation of disilicides from bilayers of Ni/Co and Co/Ni on silicon: Phase separation and solid solution

Bilayers of Ni/Co and Co/Ni were deposited onto silicon by means of electron beam evaporation. The annealing behavior was investigated as a function of time in the temperature range 475–550 °C by Rutherford backscattering spectrometry, Auger electron spectroscopy, scanning electron microscopy and X-ray analysis. In this temperature range it is observed that the disilicide (solid solution) nucleates and grows from a film containing both the monosilicide of cobalt and that of nickel. These nearly insoluble monosilicides are separated into layers; the disilicide grows from the interface between the NiSi and the CoSi phase. If there are equal amounts of the two metals this interface is located approximately midway between the upper surface and the silicon substrate. The disilicide grows simultaneously both toward the free surface and toward the silicon substrate. The growth kinetics of the disilicide have been analyzed and are found to be complex. The general behavior of the disilicide formation is found to be similar to that found for Co-Ni alloy films and as for the latter case indicates the primacy of nucleation over diffusion as the controlling mechanism in the disilicide formation. The site of nucleation of the disilicide at the NiSi-CoSi interface is explained by a model based on (a) the phase separation of the two monosilicides and (b) the high entropy of mixing of the mixed disilicide. In agreement with this model the nucleation of the mixed disilicides is shown to occur at temperatures much lower than those for either CoSi₂ or NiSi₂. Given the common crystal structure and the almost identical lattice parameters, the mutual solubilities of CoSi₂ and NiSi₂ follow from elementary concepts of alloy phase theory. However, the behavior of the monosilicides is more unexpected. The limited solubilities of the monosilicides, CoSi and NiSi, in each other are shown to result from specific features of the electronic band structure of these two compounds, features which are not found for example in the isomorphous disilicides CoSi₂ and NiSi₂.     

Barium–Strontium and Nickel–Cobalt Solid-State Interdiffusion between the Hexagonal Z-Ferrites Ba3Co2Fe24O41, Sr3Co2Fe24O41, and Ba3Ni2Fe24O41

The Ni, Co, Ba, and Sr profiles in the diffusion zones produced between hexagonal Z-ferrites (Sr₃Co₂Fe₂₄O₄₁/Ba₃Co₂Fe₂₄O₄₁, Ba₃Co₂Fe₂₄O₄₁/Ba₃Ni₂Fe₂₄O₄₁, and Sr₃Co₂Fe₂₄O₄₁/Ba₃Ni₂Fe₂₄O₄₁) by annealing at 1420–1520 K were used to evaluate the cation interdiffusion coefficients by the Boltzmann–Matano method over the whole composition range.     

La3+掺杂Co0.5Ni0.5(Fe0.5Cr0.5)2O4尖晶石红外辐射材料的研究

用固相合成法制备La3+掺杂Co0.5Ni0.5(Fe0.5 Cr0.5)2O4尖晶石体系红外辐射材料,并通过DTA-TG、XRD和IRE-2型红外辐射测试等方法研究了材料的结构特征与红外辐射性能的关系,结果表明:随着La3+含量的增加,La3+以不同的形式进入Co0.5Ni0.5(Fe0.5 Cr0.5)2O4体系中,当La2O3掺杂浓度为5%(质量分数)时,样品的法向全波段辐射率达到0.91.     

Dielectric behaviour and magnetoelectric effect in Ni0.5Co0.5Fe2O4+Ba0.8Pb0.2TiO3 ME composites

Magnetoelectric composites with compositions xBa_0.8Pb_0.2TiO₃+(1−x)Ni_0.5Co_0.5Fe₂O₄ in which x varies as 0, 0.55, 0.70, 0.85 and 1.0 were prepared by double sintering method. The presence of single phase in x=0 and x=1 as well as two phases in x=0.55, 0.70 and 0.85 composites has been confirmed by XRD. The dielectric constant and loss tangent were studied as a function of frequency and temperature. The static value of the magnetoelectric conversion factor, i.e. d.c. (ME)_H was studied as a function of the magnetic field. The maximum value of ME coefficient was observed for x=0.85 composite, whereas minimum for x=0.55 composite.