Comportement electrochimique de la galene (PbS) dans les conditions de pH proches de celles de la flottation

The electrochemical behaviour of lead sulphide mineral (galena) has been investigated by cyclic voltammetry and controlled potential electrolyses. In the pH range 5–9, the oxidation leads—at + 0.5 V vs sce—to the formation of elemental sulphur and lead species: Pb²⁺, Pb(OH)₂ or Pb(OH)Cl depending on the pH, and on the nature of the electrolyte.

The reactions involved in the overall anodic/cathodic cycle have been interpreted; at pH 9, galena is reduced at − 1.3 V, to lead metal and HS⁻ ions.     

Electrochemical beaviour of the solid ionic conductor Ag7I4PO4

Electrochemical investigation of the solid superionic conductor Ag₇I₄PO₄ (0.8 AgI + 0.2 Ag₃PO₄) at room temperature and at 40°C were performed by means of cyclic voltammetry, cyclic chronoamperometry and cyclic chronocoulometry, normal pulse polarography and ac polarography. It was shown that the Ag⁺ ↔ Ag redox process on Pt and Ag working electrode occurs with a certain overvoltage, ie that for Ag⁺ → Ag⁺ oxidation and the return of Ag⁺ ions into the electrolyte a certain overvoltage is necessary. From the determined values of the exchange current one estimates the redox process as a rather fast one. The silver working electrode is electrochemically inactive, while only cathodically deposited silver is electrochemically active and can be oxidized to Ag⁺ ions. Chronoamperometry and chronocoulometry show that there is a certain difference in the behaviour of Pt and Ag working electrodes due to uneven passivating anodic processes. On the basis of measurements of faradaic and capacitance currents and their dependence on frequency, diagrams of complex impedance of the Pt/Ag₇I₄PO₄ interface at various anodic and cathodic polarizations of the Pt electrode were plotted. The dependence of the serial capacity of the interface on the dc potential and temperature are discussed.     

Solvation of ions—XX. The ferrocene—ferricinium couple and its role in the estimation of free energies of transfer of single ions

The ferrocene-ferricinium electrode (Pt/Foc, Fic⁺) was investigated in water, acetonitrile, ethanol, DMSO and DMF using single scan cyclic voltammetry and phase sensitive ac polarography. The oxidation-reduction is pseudo-reversible in all five solvents with an electrochemical rate constant of approximately 10⁻² cm/s. In all solvents a slow irreversible chemical step involving the ferricinium cation follows electron transfer, so that slow cyclic voltammetry or polarography rather than potentiometry is preferred if ferrocene is to be used as a reference electrode in non-aqueous solvents.

The Strehlow assumption, ΔG_tr(Foc) = ΔG_tr(Fic⁺ gives very different free energies of transfer of single ions from non-aqueous solvents to water when compared with the TATB assumption that ΔG_tr(Ph₄As⁺) = ΔG_tr(Ph₄B⁻). This discrepancy is likely to be because ferricinium is only a moderately large cation, so that ΔG_tr(Fic⁺) is less positive than ΔG_tr(Foc) for transfer to water. The discrepancy is not because of abnormal electrochemical behavior of the Pt/Foc, Fic⁺ electrode in water or other solvents. Values of E° vs nhe, H₂O in a variety of solvents based on the TATB assumption are presented.     

Electrochemical behaviour of the cell Pb/PEO40. Pb(ClO4)2/Pb

The electrochemical behaviour of the polymer-based cell Pb/(PEO)₄₀. Pb(ClO₄)₂/Pb has been investigated over the temperature range 20–160°C by means of impedance spectroscopy and dc polarization methods. The bulk resistance and the charge transfer resistance display a linear trend in an Arrhenius plot. The transference numbers have been evaluated by an electrochemical method, and compared with those obtained from a preliminary experiment with Tubandt's method. These measurements indicate that both cations and anions are mobile, with a transference number for Pb²⁺ lower than 0.1 between 70 and 130°C.     

智能微流控检测芯片的构建及其Pb2+检测性能

通过将具有Pb²⁺响应性的聚（N-异丙基丙烯酰胺-共聚-苯并-18冠-6丙烯酰胺）智能微凝胶与H型微通道相结合，构建了一种能便捷、灵敏、可视化检测水溶液中Pb²⁺浓度的新型智能Pb²⁺检测微流控芯片。该微流控检测芯片主要由软光刻技术构建，并结合紫外光照聚合在H型微通道中原位构建智能微凝胶。基于该微凝胶的Pb²⁺响应性体积相变和H型微通道中的流体流动，该微流控检测芯片能将Pb²⁺浓度信号有效转换为易于检测读取的、可视化的H型微通道中指示液覆盖的指示柱数目的变化信号。通过光学显微镜便捷观察测量指示液覆盖的指示柱数目的变化，实现了对水溶液中痕量Pb²⁺浓度的超灵敏定量检测。该微流控检测芯片为水环境中的痕量Pb²⁺浓度的便捷、灵敏、可视化检测提供了新策略。     

Hydrothermal synthesis of zeolitic material from circulating fluidized bed combustion fly ash for the highly efficient removal of lead from aqueous solution

The utilization of coal fly ash derived from circulating fluidized bed combustion(CFBFA) still faces great challenges because of its unique characteristics. In this study, a zeolitic material with Na-P1 zeolite as the main phase was successfully synthesized via a hydrothermal method by using CFBFA as the raw material.The effects of hydrothermal temperature, time, and added CTAB amount on the characterizations of synthesized materials were investigated by XRD, SEM, and XPS. The properties of the ...     

Structure stabilization and dielectric properties of pzn ferroelectric ceramics

Structure stabilization and dielectric properties of Pb (Zn_1/3 Nb_2/3)O₃ -PbTiO₃ -BaTio₃ (PZN-PT-BT) ferroelectric ceramics have been carefully studied. Around morphotropic phase boundary (MPB) of PZN-PT system, heterovalant substitution of K⁺ for Pb²⁺ stabilizes the pesrovskite Structure, while substitution of La³⁺ for Pb²⁺ goes toward the other end. Nonstoichiometry addition of excess ZnO or BaO can also suppress the formation of pyrochlore phase.     

Reversible electrochemical insertion of anions in poly-p-phenylene from aqueous electrolytes

Poly-p-phenylene (PPP) was synthesized from benzene according to the Kovacic method. Electrodes were made from this electronic insulator by cold- or hot-pressing of the loose, brown powder, under the addition of 7.5 wt. % soot (Corax L^®, Degussa AG). The electrochemical insertion and removal of anions HSO⁻₄, ClO⁻₄ in this material in aqueous solutions of the corresponding acids was investigated by slow cyclic voltammetry.

Initially, only a surface layer of about 0.1 mm thickness takes part in the electrochemical processes, which are reversible. A maximum concentration of anions in the solid of [(−C₆H₄−)⁺₇ A⁻] is attainable. The maximum degree of insertion is equal to 0.14. The insertion potential U_I shifts strongly into the negative direction with increasing concentration c of the acid. A linear U_I/c relationship is observed as in the case of graphite, where the intercalation potential is more positive by 20–200 mV for the same electrolyte. The round trip current efficiency for the insertion/removal cycle increases with increasing acid concentration attaining 100% in 14 M H₂SO₄ or 11.3 M CHlO₄. For a given concentration, increases in the same order as with graphite (H₂SO₄ < HClO₄ < HBF₄), being somewhat lower for a given electrolyte composition. From anodic current limitation (j_lim = 5–10 mA cm⁻²), a diffusion coefficient of about D = 2 × 10⁻⁷ cm² s⁻¹ is derived for the transport of anions in the bulk of PPP. The striking similarity of our results to former findings with graphite is thoroughly discussed. Some general conclusions are derived thereof.     

Electro-optical studies of submonolayers of lead formed on gold electrodes by faradaic adsorption in 1 M HClO4

Current-potential and specular reflectivity-potential curves of a Au electrode have been measured in 1 M CHlO₄ in the presence of 1·0 × 10⁻³ M Pb²⁺. Four peaks were found on a linear sweep voltammogram at potentials more positive than the Nernst reversible potential of Pb⁰/Pb²⁺ couple, which are attributed to the Faradaic adsorption of Pb²⁺.

Specular reflectivity-potential curves recorded simultaneously at varied wavelengths gave a clear indication of the adsorption which increased the reflectivity at shorter wavelengths while decreased at longer wavelengths.

From the analysis of the current-potential curve of four peaks in relation to the reflectivity change, the following results were obtained:

(1) The existence of four peaks on the voltammogram is the indication of four different adsorbed states.

(2) The Pb atoms in a submonolayer on Au electrode have rather similar optical properties to those of metallic Pb except for the adsorbed atoms formed at the most potential region.

(3) The adsorbed Pb formed at the most positive potential region have the shortest distance to the surface Au atom, and accordingly, have the strongest interaction with the surface.     

牛血清白蛋白纳米球接枝杨梅单宁的制备以及吸附去除水体中Pb2+的性能

采用去溶剂法和杨梅单宁-戊二醛固化接枝制备得到杨梅单宁（BT）接枝牛血清白蛋白（BSA）纳米球（BSA-BT-NSs）吸附材料，并系统探讨了其在不同吸附条件下对水体中Pb²⁺的吸附去除性能。研究结果表明：50%用量杨梅单宁（基于BSA-NSs量）接枝固化得到的BSA-BT-NSs具有较好的球形结构和良好的分散性。在吸附实验中，Pb²⁺初始浓度为250mg/L、pH 5.0、温度为298K 条件下吸附20min，BSA-BT-NSs（0.4g/L）对Pb²⁺的吸附效果最佳，最大吸附容量为76mg/g，优于多数同类型吸附材料。BSA-BT-NSs对Pb²⁺吸附过程符合Langmuir方程和准二级吸附动力学模型，且吸附后的BSA-BT-NSs经0.1mol/L 硝酸进行解吸取得了92.04％的良好解吸效果，并可再次重复使用。进一步分析其Pb²⁺吸附机理，表明BSA-BT-NSs中的氨基氮原子、羟基和羧基氧原子作为电子供体参与了与Pb²⁺的空轨道发生配位作用。     

Effect on cathodic reduction of β-PbO2 in sulfuric acid solution of surface concentration of Pb ions formed on β-PbO2

The discharge reaction of positive electrode of lead-acid battery was investigated with the rotating ring-disc electrode. The large supersaturation of Pb²⁺ ion on the electrode surface was obtained during discharge of initial period and the PbSO₄ nuclei was formed. The precipitation of PbSO₄ proceeded smoothly in the presence of PbSO₄ nuclei. In the steady state, the colloidal PbSO₄ film on the electrode surface of which stability depended on the concentrations of sulfuric acids was formed from the dissolving Pb²⁺ ions. Especially its stability in 1.0 M H₂SO₄ was so low that the concentration of Pb²⁺ ions during discharge was the largest of those in any other sulfuric acids, so that the effect of the film on the overpotential during galvanostatic discharge is the smallest, as discussed in a following paper[1].

The particle sizes of PbSO₄ precipitated during discharge were related to the concentration of Pb²⁺ ions on the electrode. These sizes increased with increasing concentration of Pb²⁺ ions. If the discharge capacity is limited by the passivation with PbSO₄ crystal, the use of 1.0 M H₂SO₄ as the electrolyte of lead-acid battery may be favoured.     

Influence of synergistic effect of LiNi0.8Co0.15Al0.05O2@Cr2O5 composite on the electrochemical properties

LiNi_(0.8)Co_(0.15)Al_(0.05)O_2@Cr_2O_5(NCA)@Cr_2 O_5 composite electrode combines the high rate-capability characteristics of NCA with the stability of Cr_2 O_5, playing a synergistic role in improving the cyclic stability, initial discharge capacity and the security of low cut-off voltage(2.0 V). When the mass ratio of Cr_2 O_5 in NCA is 45%(mass), the capacity retention rate increases from 58.5% without Cr_2 O_5 to 69.3% in the range of 2.0–4.3 V.The initial discharge capacity of NCA@Cr_2 O_5 composite material is 211.4 m A·h·g~(-1), its first coulombic efficiency is 94.2%, and the charging capacity remains approximately constant when mixed with 15%(mass)Cr_2 O_5. The reason for the improvement of the initial charge–discharge efficiency(ICDE) was explained.Impedance and cyclic voltammetry analysis reveal more detailed reasons of the observed improvements.Compared with NCA cathode material, the NCA@Cr_2 O_5 composite material can provide not only additional stable sites and channels for Li+insertion/extraction to make up for the loss of active Li+sites and prevent the accumulation of Li+in the circulation process, but also protect the NCA electrode from the corrosion of the electrolyte decomposition by the Cr_2 O_5 nanoparticles adhering to NCA interface.     

聚丙烯酸钠包覆Fe3O4磁性交联聚合物的制备及其对Pb(Ⅱ)和Cd(Ⅱ)的吸附性能

采用溶液分散聚合和Ca²⁺表面交联制备了聚丙烯酸钠包覆Fe₃O₄的磁性交联聚合物（CPAANa@Fe₃O₄）,对其进行了XRD、FT-IR、SEM和TGA等表征。以CPAANa@Fe₃O₄为吸附剂研究了CPAANa@Fe₃O₄对水溶液中Pb²⁺、Cd²⁺的静态吸附,考察了溶液pH、吸附剂投加量、金属离子初始浓度对吸附的影响。结果表明：CPAANa@Fe₃O₄在pH 2～6范围内均具有较好的吸附性能,当吸附剂投加量分别为1.0 g·L^-1和1.6 g·L^-1时对初始浓度分别为200 mg·L^-1的Pb²⁺和100 mg·L^-1的Cd²⁺的去除率达到最大,可使Pb²⁺实现达标排放（GB 8978-1996）;CPAANa@Fe₃O₄对Pb²⁺和Cd²⁺的吸附动力学符合准二级模型,吸附等温线符合Langmuir模型,对Pb²⁺和Cd²⁺的最大吸附量分别为454.55 mg·g^-1和275.48 mg·g^-1。将CPAANa@Fe₃O₄用于处理实际电解矿浆废水,发现能有效吸附其中的Pb²⁺和Cd²⁺,具有潜在实用价值。     

Radiotracer study of the underpotential formation of a silver sulfide monolayer on silver electrodes in alkaline medium

The formation of Ag₂S monolayer has been studied in 0.1 mol dm⁻³ NaOH supporting electrolyte by a radiotracer method in the potential range from −400 to +200 mV (on rhe scale) using ³⁵S labelled Na₂S. Comparison of the results obtained with the radiotracer method and cyclic voltammetric measurements leads to the conclusion that the formation of the Ag₂S monolayer takes place at least in two separate steps in two different potential ranges.     

生物除磷颗粒污泥去除Pb2+的效能机制

以好氧颗粒污泥的吸附作用和磷酸盐对重金属的螯合作用为基础,采用富含磷酸盐的生物除磷颗粒污泥作为吸附剂来处理含铅废水,考察了不同吸附条件（pH、Pb²⁺的初始浓度、吸附反应时间）下,颗粒污泥对Pb²⁺的去除效果。结果表明,除磷颗粒污泥在pH为4,初始Pb²⁺浓度为150 mg·L^-1时,对铅的去除率最高（为99.9%）;在吸附反应20 min时即可达到吸附平衡。生物除磷颗粒污泥对Pb²⁺的吸附可以用Langmuir模型拟合（R²=0.993）,最大吸附量为49.5 mg·g^-1。其中离子交换和磷酸盐与Pb²⁺的螯合作用对除磷颗粒污泥去除Pb²⁺起到重要作用;傅里叶变换红外光谱（FTIR）测定表明-COOH、-OH、磷酰基等多种官能团也参与了除磷颗粒污泥除Pb²⁺过程。     

Electroextraction of Pb ions from diluted solutions by a process combining ion-exchange textiles and membranes

The extraction of Pb²⁺ ions from diluted solutions was achieved using a hybrid process combining cation exchange textiles, ion-exchange membranes and electric current. Two methods were investigated: an electroextraction process in two steps where the fixation of Pb²⁺ ions was followed by electroregeneration of the cation-exchange textiles; the second one a continuous electroextraction process where the ion exchange and regeneration take place simultaneously. For these electroextraction processes, the cation-exchange textile is introduced into an electrodialysis cell and compressed between two cation-exchange membranes. Under an applied current, the Pb²⁺ ions are substituted by regenerating ions coming from the anodic compartment and are transferred into a receiver compartment at the cathodic side where they are concentrated. Cation-exchange textiles having strong or weak acid functional groups, sulfonic (SCET) and carboxylic (CCET), respectively, were used. Different regenerating ions, H⁺, Na⁺, K⁺ and NH₄⁺ were investigated under various current densities. Electroregeneration ratios between 85% and 100% were obtained with sulfonic and carboxylic textiles previously loaded with Pb²⁺ ions. In the continuous electroextraction, removal efficiencies higher than 95% were obtained with a 10 ppm Pb²⁺ feed solution giving an outlet concentration of less than 1 ppm. The efficiency of the two textiles was compared in terms of mass transfer and energy consumption.     

Pb2+识别响应型智能高分子功能材料的研究进展

发酵生物甲烷的菌群可以吸附Pb²⁺等重金属而在沼液和沼渣中富集;因此,在生物甲烷系统研究过程中,Pb²⁺等重金属离子的检测和处理是沼液和沼渣处理的关键问题之一。18-冠-6具有选择性络合Pb²⁺的能力,研究者们将18-冠-6的Pb²⁺识别特性与聚N-异丙基丙烯酰胺的相变行为特性相结合制备了一系列Pb²⁺识别响应型智能高分子功能材料。本文综述了基于18-冠-6和聚N-异丙基丙烯酰胺的离子识别响应型智能高分子材料在检测和去除Pb²⁺等方面的研究进展。     

基于18-冠-6的铅离子检测技术研究进展

铅是一种对环境和人体有严重危害的重金属污染物,研究铅离子（Pb²⁺）检测技术具有重要的实用意义。近年来,利用18-冠-6的Pb²⁺特异识别性能,研究者们设计构建了一系列智能高分子材料系统,为Pb²⁺检测提供了新的策略和途径。本文综述了近年来基于18-冠-6的Pb²⁺检测技术研究进展,重点介绍了基于智能膜、智能光学元件、智能微芯片、智能微胶囊等智能材料系统的Pb²⁺检测技术,讨论了这些Pb²⁺检测技术在实际应用中需要重点关注和解决的问题,以期为这类基于18-冠-6的Pb²⁺检测技术的进一步开发和应用提供参考。     

REMOVAL OF TOXIC Pb2+ IONS BY SYNTHETIC HYDROXYAPATITES

The removal behavior of toxic Pb²⁺ ions from aqueous and nonaqueous solutions by two synthetic hydroxyapatites (S-1 and S-2) has been investigated by using both batch and column methods.

It was found that Pb²⁺ ions in the both solutions were easily removed to the apatite samples mainly by cation-exchange reactions between the Pb²⁺ ions in the solutions and Ca²⁺ ions of the samples at room temperature. Further, in the system of aqueous PbF₂ solutions, anion-exchange reactions between F^- ions in the solutions and OH ^- ions of the samples occurred simultaneously and the liberated OH ^- and Ca²⁺ ions influenced removal behavior of Pb²⁺ and F^- ions. The maximum removal amount of Pb²⁺ ions from the aqueous solutions was 400 mg per g of S-1. Pb^- ions in the waste water from lead plating factories were completely removed to the apatite samples. In this manner, it was found that the apatites, especially S-1 can be employed as a new removal agent for the treatment of poisonous Pb²⁺ ions in waste water.     

原位构建富氟SEI的凝胶电解质用于金属锂二次电池

以六氟磷酸锂（LiPF₆）为四氢呋喃的聚合引发剂制备凝胶电解质,同时作为氟源在金属锂负极表面原位构建富含LiF的固态电解质界面层（solid electrolyte interface,SEI）来抑制锂枝晶的生长以及金属锂/电解液之间的副反应。所制备的凝胶电解质具有较高的室温离子电导率（1.33 mS·cm^-1）和较宽的电化学稳定窗口（4.5 V）。原位聚合方式组装金属锂对称电池循环后,锂负极表面没有明显的锂枝晶和被损毁的形貌出现;XPS结果表明锂负极表面生成了富含LiF的SEI。组装的LiFePO₄全电池在1 C的电流密度下,稳定循环400周后仍保持118.7 mAh·g^-1的放电比容量。得益于四氢呋喃在开环聚合反应过程中,促进了LiPF₆分解反应平衡的正向移动,在锂负极表面形成稳定的富含LiF的SEI,能够抑制锂枝晶的生长并防止其被持续性的腐蚀破坏。