Theoretical oscillator strengths for some transitions in Si(II), Ge(II), Sn(II) and Pb(II) spectra

Calculations are reported of non-relativistic and relativistic oscillator strengths for the principal, sharp and diffuse series as well as some lifetimes in the spectra of singly-ionized silicon, germanium, tin and lead. The radial integrals were computed by employing the wave functions obtained from a semiempirical approach which included exchange effects (the semiempirical X$\text{α}$ method). Good agreement was obtained with available experimental and theoretical data. A comparison between non-relativistic and relativistic oscillator strengths confirms the importance of the spin-orbit interaction of the optical electron, as well as other relativistic effects for the oscillator strengths, even for the spectra of moderately heavy ions. Some systematic trends in the calculated oscillator strengths and line-strength ratios were investigated along the spectral series, as well as along the sequence of homologous ions.     

Zur Frage der Pb(II)-Komplexe in Gemischten KCl-KBr-Kristallen

The absorption and fluorescent spectra of mixed KCl-KBr crystals with lead admixtures were measured. A comparison with the absorption of analogical mixed solutions showed that the displacement of the absorption band of lead towards longer wave-lengths with increasing content of bromide is caused by the creation of mixed complexes. The latter are also responsible for the fluorescence of the crystals.

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Die Verfasser danken herzlich Herrn Dr. A. Bohun für die wertvollen Diskussionen. Sie danken ferner Frau K. Dolealová für die Durchführung der Absorptionsmessungen der Kristalle und Frau M. Kubovská für die Züchtung der Kristalle.     

Zur Frage der Pb(II)-Komplexe in den Alkalibromiden

Zusammenfassung Mittels der polarographischen Methode wurden die Bildungskonstanten der Bleibromokomplexe in Kaliumbromidlösungen berechnet, wobei als höchster der Komplex mit sechs Bromionen ermittelt wurde. Die gemessenen Absorptionsbanden von Blei in verschieden konzentrierten Kaliumbromidlösungen wurden den einzelnen Komplextypen zugeordnet.Auf Grund des Vergleiches des Absorptionsspektrums der mit Blei dotierten Alkali-bromidkristalle und der genügend konzentrierten analogen Lösungen ist man zur Ansicht gelangt, daß in Kristallen die die Gitterstelle des Alkaliions besetzenden zweiwertigen Bleiionen mit sechs benachbarten Bromionen als Liganden einen oktaedrischen Komplex bilden, analog wie dies bei Alkalichloridkristallen der Fall ist.

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On the problem of lead (II) complexes in alkaline bromides

The polarographic method was used to determine the stability constants of complexes of bivalent lead with bromide ions. The absorption bands of lead, measured in solutions of potassium bromide of varying concentration, were ascribed to these complexes. The agreement of the absorption bands of KBr crystals doped with lead and of analogical sufficiently concentrated solutions shows that in alkali bromide crystals lead is bound in the octahedral complex with six neighbouring bromine ions.

     

Zur Frage der Pb(II)-Komplexe im Gemischten System KCl-KJ

The absorption spectra of mixed solutions KCl-KI with lead admixture and of crystals of that system, as far as they make fast solutions were measured. From the absorption spectra it was derived that lead builds up mixed complexes in the mentioned system. With the growing relative abundance of iodide in the system the content of the iodide component in complexes increases faster than that one.

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Der Verfasser dankt herzlich Herrn Dr. A. Bohun für die Unterstützung bei dieser Arbeit und Frau L. Svárová für die Züchtung der Kristalle.     

Infrared Studies on the Complexes of Zn(II), Cd(II), Hg(II), Pb(II), Cu(I) and Ag(I) with 5-Benzylthio-1,2,4.-triazole

Zn(II), Cd(II), Hg(II), Pb(II), Cu(I) and Ag(I) complexes of 5-benzylthio-1,2,4-triazole (BTT) have been prepared and characterised on the basis of analytical and IR data. Hg(II), Cd(II), Zn(II), and Pb(II) complexes are assigned tetrahedral structure with polymeric intermolecular linkages through S and N atoms while Ag(I) and Cu(I) are proposed to have polymeric linear structure     

XAFS研究不同pH下土壤对Pb的吸附

利用X射线吸收精细结构光谱(XAFS)研究了不同初始pH条件下土壤吸附Pb(Ⅱ)的微观结构及吸附机理。表明土壤对Pb(Ⅱ)的吸附以形成Pb4(OH)44+的内圈吸附作用为主,其次为外圈吸附。同时,在吸附Pb(Ⅱ)过程中,Pb(Ⅱ)通过置换作用取代土壤中碳酸钙Ca(Ⅱ)的位置,形成含Pb碳酸钙(PbCaCO3)沉淀。土壤对Pb的吸附随初始pH(6.0~8.5)的增大,第一配位层(Pb—O)半径减小(0.172 7~0.166 6nm),内圈吸附比重加大,表明土壤对Pb(Ⅱ)的吸附机制受初始pH的影响。     

含硫磷酸钙纳米颗粒的制备及对铅离子的高效选择性去除

用一种简易共沉淀法制备了非晶含硫磷酸钙（SCP）材料,实现硫原子原位引入磷酸钙纳米颗粒中,并研究了其对Pb（II）的吸附特性和机理。与羟基磷灰石相比,SCP对Pb（II）的去除性能显著增强,在10 min内能快速将20 ppm的Pb（II）溶液降低至饮用水标准下。由Langmuir吸附等温线模型计算可知,SCP对Pb（II）的最大饱和吸附量高达1720.57 mg/g,这个数值远远超过以往所报道的绝大部分吸附剂材料。在竞争离子Ni（II）,Co（II）,Zn（II）和Cd（II）共存的条件下,SCP还表现出对Pb（II）的选择性去除。研究表明,SCP对Pb（II）超高的去除效率和优异的亲和力归因于其可通过溶解沉淀和离子交换反应在其表面形成棒状的羟基磷酸铅晶体,以及形成沉淀物硫化铅。SCP以其对Pb（II）快速、高效和优异选择性成为在实际铅污染治理中的理想材料.     

Kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain from aqueous solutions

Spent grain, a main by-product of the brewing industry, is available in large quantities, but its main application has been limited to animal feeding. Nevertheless, in this study, spent grain modified with 1 M NaCl solution as a novel adsorbent has been used for the adsorption of Pb(II) in aqueous solutions. Isotherms, kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain were studied. The equilibrium data were well fitted with Langmuir, Freundlich and Dubinin-Radushkevick (D-R) isotherm models. The kinetics of Pb(II) adsorption followed pseudo-second-order model, using the rate constants of pseudo-second-order model, the activation energy (E_a) of Pb(II) adsorption was determined as 12.33 kJ mol⁻¹ according to the Arrhenius equation. Various thermodynamic parameters such as ΔG^ads, ΔH^ads and ΔS^ads were also calculated. Thermodynamic results indicate that Pb(II) adsorption onto modified spent grain is a spontaneous and endothermic process. Therefore, it can be concluded that modified spent grain as a new effective adsorbent has potential for Pb(II) removal from aqueous solutions.     

FAAS法研究顺丁烯二酸-co-苯乙烯微球对铅的吸附性能

采用无皂乳液聚合法以顺丁烯二酸和苯乙烯交联合成顺丁烯二酸-co-苯乙烯微球并采用傅里叶变换红外光谱和电子扫描电镜对微球的结构和表面形貌进行表征。以火焰原子吸收光谱(FAAS)法研究了它对铅的动态吸附性能,考察了影响吸附率和解吸率的相关因素,结果表明:溶液pH为5、上样流速为1.0mL.min-1时,吸附率可达到95%以上。以1mol.L-1 HNO3为解吸剂,洗脱液流速为0.5mL.min-1时,Pb(Ⅱ)的解吸率可达到99%以上。在优化的试验条件下,微球对Pb(Ⅱ)的吸附量可达到26.5mg.g-1,检出限为(3σ11)2.1μg.L-1,相对标准偏差为2.5%;将预富集与火焰原子吸收法联用,用于痕量铅的测定得到令人满意的结果。     

DNAzyme Based Amplified Biosensor on Ultrasensitive Fluorescence Detection of Pb (II) Ions from Aqueous System

A label -free DNAzyme amplified biosensor is found to be highly selective and sensitive towards fluorescent detection of Pb²⁺ ions in aqueous media. The DNAzyme complex has designed by the hybridization of the enzyme and substrate strand. In the presence of Pb²⁺, the DNAzyme activated and cleaved the substrate strand of RNA site (rA) into two oligonucleotide fragments. Further, the free fragment was hybridized with a complementary strand on the surface of MBs. After magnetic separation, SYBER Green I was added and readily intercalate with the dsDNA to gives a bright fluorescence signal with intensity directly proportional to the concentration of Pb²⁺ions. A detection limit of 5 nM in Pb²⁺ the detection range 0 to 500 nM was obtained. This label- free fluorescent biosensor has been successfully applied to the determination of environmental water samples. Then results open up the possibility for real-time quantitative detection of Pb²⁺ with convenient potential applications in the biological and environmental field.

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Graphical Abstract

     

Surface phonons on Pb(111)

We present an ab initio study of the lattice dynamics of the Pb(111) surface. The calculations were carried out within the density-functional theory using a linear response approach in the mixed-basis pseudopotential representation. We observe a rich spectrum of surface localized modes, and make a detailed assignment to measured modes in a recent helium-atom scattering experiment. We find that the inclusion of spin–orbit coupling considerably softens the phonon spectrum of the surface, thereby improving the agreement with experiment significantly.     

Synthesis of thiol-functionalized MCM-41 mesoporous silicas and its application in Cu(II), Pb(II), Ag(I), and Cr(III) removal

Thiol-functionalized MCM-41 mesoporous silicas were synthesized via evaporation-induced self-assembly. The mesoporous silicas obtained were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption analysis, Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The products were used as adsorbents to remove heavy metal ions from water. The mesoporous silicas (adsorbent A) with high pore diameter (centered at 5.27 nm) exhibited the largest adsorption capacity, with a BET surface area of 421.9 m² g^?1 and pore volume of 0.556 cm³ g^?1. Different anions influenced the adsorption of Cu(II) in the order NO₃ ^? < OAc^? < SO₄ ^2? < CO₃ ^2? < Cit^? < Cl^?. Analysis of adsorption isotherms showed that Cu²⁺, Pb²⁺, Ag⁺, and Cr³⁺ adsorption fit the Redlich–Peterson nonlinear model. The mesoporous silicas synthesized in the work can be used as adsorbents to remove heavy metal ions from water effectively. The removal rate was high, and the adsorbent could be regenerated by acid treatment without changing its properties.     

Two-Step Oxidation of Pb（111） Surfaces

We report on a two-step method for oxidation of Pb（111） surfaces, which consists of low temperature （90K） adsorption of 02 and subsequent annealing to room temperature. In situ scanning tunnelling microscopy observation reveals that oxidation of Pb（111） can occur effectively by this method, while direct room temperature adsorption results in no oxidation. Temperature-dependent adsorption behaviour suggests the existence of a precursor state for 02 adsorption on Pb（111） surfaces and can explain the oxidation-resistance of clean Pb（111） surface at room temperature.     

Preparation and properties of binary metal monolayers: II. Pb and Sn on Al(100)

The growth modes, structures and thermal properties of binary monolayers of lead and tin on the (100) face of aluminium have been investigated by LEED and AES. Monolayers of pure lead and pure tin were also examined. Dense binary layers were formed by successive vapour deposition of the two elements. The compositions were accurately determined by AES. For the pure monolayers sharp changes in the sticking probability at half-monolayer coverage (detectable by AES) lead to accurate determinations of the densities of the complete monolayers. The LEED pattern for the pure lead monolayer can be interpreted in terms of a pseudo-hexagonal arrangement while that for tin shows intensity features that favour an arrangement of dense atomic chains. For the binary layers the apparent mesh parameter varies continuously as a function of composition between the values for the pure monolayers. Different variations in parameter are found, depending on which element is deposited first. It is deduced that the binary layers are formed of intimate mixtures of the coincidence meshes of the pure monolayer structures together with disordered regions. Each binary layer is characterized by a temperature for complete thermal desordering T_d. For tin-rich layers there are significant differences between values of T_d for “tin-first” and “lead-first” layers. A sharp minimum in T_d is observed for the composition Sn₄Pb.     

A study of the reactions208Pb(d,d)208Pb and208Pb(d,p)209Pb at energies above and below the Coulomb barrier

The reactions²⁰⁸Pb(d, d)²⁰⁸Pb and²⁰⁸Pb(d, p)²⁰⁹Pb have been studied in the energy region from below to above the Coulomb barrier. An optical-model analysis of the elastic scattering results has been performed to obtain parameters for a DWBA analysis. Distorted wave calculations for the direct transitions leading to single-particle states in²⁰⁹Pb have been used to extract spectroscopic factors. Only two deuteron potential sets give a good account of the stripping data throughout the energy region studied.