Lead Dioxides Research Articles

Recovery of lead from smelting fly ash of waste lead-acid battery by leaching and electrowinning

Fly ash that was enriched with lead (Pb), formed as an intermediate in waste lead-acid battery (WLAB) smelting, was recycled by the hydro-electrometallurgy. Characterization of fly ash thereof indicated that the Pb was in the forms of PbSO4 (anglesite) and Pb2OSO4 (lanarkite). Nitric acid and sodium hydroxide were firstly used to study the leaching of the fly ash sample, which was affected by leachant dosage and solid-to-liquid ratio (S/L). At an S/L of 60gL−1, the leachability of Pb was 43% and 67% in 2M acidic and basic solutions, respectively, based on an average 70wt% of Pb in the original fly ash. Anglesite was completely soluble in NaOH and lanarkite was mildly soluble in HNO3. Pb was recovered from the pregnant leach solution within an electrolytic cell constructed with graphite or RuO2/IrO2-coated titanium (Ti-DSA) anodes and a stainless steel cathode. Properties of anodes deposited with lead dioxides were analyzed by cyclic voltammetry. The optimized parameters of electrowinning were 2M NaOH leachant, a current density of 0.75Adm−2 and an electrolytic process duration of 120min, which yielded a Pb removal of higher than 99% and a specific energy consumption of 0.57Whg−1. This process constitutes an eco-friendly and economic alternative to the presently utilized secondary pyrometallurgy for treating lead-containing fly ash.

Oxygen evolution reaction on lead–bismuth alloys in sulfuric acid solution

Lead–bismuth alloys with bismuth from 0 to 8 wt.% were prepared. Oxygen evolution reaction on the alloys with lead dioxides was investigated by using linear voltammetry, electrochemical impedance spectroscopy, scanning electron spectroscopy, electron diffraction spectroscopy, oxygen collection experiments. The oxygen evolution reaction on the alloys with bismuth content <0.1% is not affected by the bismuth in the alloys. However, the rate of oxygen evolution reaction increases with increasing the bismuth content in the alloys. This is related to the dissolution of bismuth from the alloys to solution and the adsorption of bismuth ions from solution onto the surface of lead dioxide. Unlike lead, bismuth can dissolve into solution under anodic polarization. At the potentials where there is no oxygen evolution, lead–bismuth alloys are well passivated by lead sulfate or lead dioxide. The lead dioxide on the alloys becomes porous when oxygen evolution takes place on it, thus bismuth in the alloys dissolves. The amount of dissolved bismuth increases with the bismuth content in the alloys and the adsorption of bismuth ions onto lead dioxide takes place when bismuth ion concentration near the oxide surface is high enough. The lead dioxide with adsorbed bismuth ions can accelerates oxygen evolution reaction and oxygen evolution increases with increasing the amount of adsorbed bismuth ions.

Electrochemical properties of lead dioxides formed on various lead alloy substrates

Electrochemical properties of lead dioxides, formed on various lead alloy substrates (Pb–In, Pb–Sn, Pb–Sb, Pb–Tl and Pb–Bi), were investigated using electrochemical techniques with X-ray diffraction (XRD) and electron probe micro analyzer (EPMA). Additive elements, selected by applying Hume-Rothery rules, have similar atomic radius and electronegativity to lead. The reduction capacity of lead dioxides that were formed on Pb–Sb and Pb–Sn alloy substrates decreased, whereas the reduction capacity of lead dioxides formed on Pb–In, Pb–Tl and Pb–Bi alloy substrate increased, compared with those formed on the pure lead substrate. The change of the lattice constant of β-lead dioxides and the existence of additive elements in the lead dioxide layer were confirmed from the analysis results of XRD and EPMA. We concluded that the substitution of additive elements for lead in the β-lead dioxide caused the change of its lattice constant to affect the reduction capacity.

On the question of electrochemical activity of differently formed lead dioxides

Electrochemically and chemically formed lead dioxides show varying electrochemical properties, which has often been discussed in terms of hydrogen content and amorphous phases. These differences in electrochemical activity have always interested research related to their behaviour as the positive active material (PAM) in the lead–acid battery. In this work, the crystallinity and composition of different lead dioxide samples were examined with respect to preparation method. Two electrochemically oxidised samples, one originating from a pure lead foil and the other one from tetra basic lead sulphates (TBLS), were investigated and compared with a commercial chemically prepared lead dioxide. The samples were investigated by X-ray diffraction (XRD) and thermogravimetric analysis (TGA) as a function of temperature in the range of 25–600°C. The experimental results show that only surface bound water is present in the different lead dioxide phases investigated. However, a clear difference between chemically and electrochemically formed oxide is revealed from high temperature XRD (HT-XRD). At high temperatures, a lead oxide sulphate phase is formed in the electrochemically prepared samples, showing the existence of sulphate ions bound to internal surfaces. These ions are believed to facilitate the reduction process of lead dioxide and hence contribute to the electrochemical activity.

Structure influence on electrocatalysis and adsorption of intermediates in the anodic O 2 evolution at dimorphic α- and β-PbO 2

Studies of the kinetics of anodic O 2 evolution and of the adsorption behaviour of the kinetically involved intermediates, OH and O, in this process at the α and β forms of PbO 2 offers the possibility of examining how electrocatalysis in this reaction depends on the structure, and in particular the exposed surface structure, of these materials which otherwise have chemically identical compositions. Potential relaxation transients, following anodic current interruptions, and a.c. frequency response measurements have been used to derive information on the adsorption behaviour of the intermediates in relation to the steady-state polarization behaviour of the two “allotropic” forms of PbO 2. Significant differences in the kinetic behaviour of O 2 evolution and of the adsorbed intermediate species are found. The characterization of O 2 evolution behaviour on lead dioxides is of practical relevance to the anodic processes that take place during overcharge of the positive plates of lead —acid batteries.

Compression Studies of Single-Crystal SnO2 and PbO2 in a Diamond Cell

Compression behaviors of two single-crystal rutile-structure dioxides, SnO2 (cassiterite) and PbO2 (plattnerite), were studied in a Merrill-Bassett type diamond cell at room temperature. The samples were compressed in a mixture of 4:1 methanolethenol solution with pressure measurements by the ruby scale. A four-circle diffractometer was used to obtain the diffraction patterns of these crystals at high pressures. Compression results on Sn02 did not show significant lattice distortion, with a slight increase in c/a up to 35 kbar. The compression data are in excellent agreement with Hazen and Finger (1981) and in reasonable agreement with Ming and Manghnani (1982). Fitting these data to the Birch-Murnaghan equation gives a bulk modulus (K。) of 2.24±0.08 Mbar with K。' =6.3. On the other hand, the rutile-type PbO2 was found to transform from a tetragonal to an orthorhombic phase above 5 kbar. The cell parameters a, b and c of this phase have different linear compressibility. This phase is different from the reported orthorhombic phases of lead dioxides (α-PbO2). It could represent an intermediate distorted phase which occurs during the transformation from the β-PbO2 to the α-PbO2 phase. The bulk modulus of Pb02 was determined to be 1.34±0.06 Mbar by fitting the data to the Birch-Murnaghan equation. A linear relationship was found to exist between the bulk sound velocity and mean atomic weight of the rutile-type dioxides.

Oxidative alkoxylation of 4H-imidazole N-oxides as a new method of synthesis of stable nitroxyl radicals of the 2- and 3-imidazoline series with alkoxy groups at the ?-carbon atom of the radical center

1. Oxidation of 5-R1-2R2-4H-imidazole 1,3-dioxides in methanol with lead dioxide leads to the formation of stable nitroxyl and nitronylnitroxyl radicals with methoxy groups at the α-carbon atom of the radical center. The ratio between these radicals is determined by the electronic character of the substituents at the 2- and 5-positions of the heterocyclic ring. 2. Oxidation of 4H-imidazole 1-oxides and 4H-imidazole 3-oxides in methanol with lead dioxide leads to the formation of iminonitroxyl radicals. 3. Oxidation of 2-unsubstituted 4H-imidazole 1,3-dioxides and 4H-imidazole 3-oxides in alcohols by lead or manganese dioxides leads to 2,2-dialkoxy-substituted stable nitroxyl radicals, which are derivatives of 3-imidazoline 3-oxide and 3-imidazoline.

NMR spectra of cyclic nitrones. 4. Synthesis and 13C NMR spectra of 4H-imidazole N-oxides and N,N-dioxides

4H-Imidazole 1,3-dioxides and 4H-imidazole 3-oxides were obtained by oxidation of 1-hydroxy-3-imidazoline 3-oxides and 1-hydroxy-3-imidazolines with lead and manganese dioxides or the stable nitroxyl radical, while 4H-imidazole 1-oxides were obtained by thermal decomposition of 1-acetoxy-3-imidazoline 3-oxides. Facile oxidation of the ethyl group in 5-ethyl-4H-imidazole 1,3-dioxide and the formation of 5-acetyl-4H-imidazole 1,3-dioxide and 5-acetyl-4H-imidazole 3-oxide were observed. It is shown that a strictly determined region of chemical shifts of the C(2), C(5), and C(4) atoms is characteristic for each group of 4H-imidazole N-oxides in the 13C NMR spectra; this makes it possible to clearly establish the position of the N-oxide oxygen atom.

The crystal structures of lead dioxides from the positive plate of the lead/acid battery

Full profile neutron powder diffraction structure refinements have been performed on electrolytically- and chemically-prepared varieties of the dimorphs of lead dioxide, the primary constituents in the charged positive plate of the lead/acid battery. Electrolytic samples of α-PbO 2 (columbite related structure) contain significant amounts of noncrystalline material, have severe cation disorder, and display evidence of severe lattice strain and unit cell incoherency in the [010] direction. On the other hand, chemically-prepared varieties of α-PbO 2 are more highly crystalline, are essentially stoichiometric, and are well ordered. Electrolytic samples of β-PbO 2 (rutile structure) from both new and used battery plates also contain more noncrystalline material than chemically-prepared forms, but all varieties are near-stoichiometric, well ordered, and structurally indistinguishable insofar as coherent neutron diffraction is concerned. Given that positive plates cycled under normal conditions for long periods of time consist primarily of the beta form of lead dioxide, the onset of battery failure is therefore not manifest in the long range crystal structure of this dioxide. In view of the high proportion of noncrystalline material present in electrolytic samples of PbO 2, property changes previously associated with loss of crystalline dioxide activity may relate instead to the “amorphous” component of the positive plate mass.

Quantitative determination of lead dioxide polymorphs by X-ray powder diffractometry

The X-ray diffractometric methods used by previous workers to analyse positive plate material from lead-acid batteries for α-, β- and amorphous lead dioxides are critically appraised. In addition two alternative approaches, not previously applied to this problem, are assessed. An internal standard method is considered to be the best.

Electronic spectra of the oxides of lead and of some ternary lead oxide compounds

Electronic spectra have been measured by diffuse reflectance techniques of PbO 2-I, PbO 2-II, Pb 12O 19, Pb 2O 3, Pb 3O 4, PbO-M, SrPbO 3, Sr 2PbO 4, Cd 2PbO 4, and CdPb 2O 5. The lead dioxides and compounds of cadmium, which have a high electrical conductivity, have an intense absorption feature in the near infrared. The other compounds, semiconducting or insulating, exhibit only an absorption edge in the visible or near ultraviolet. There is a linear relationship between the optical absorption edge of the lead oxides and the average number of valence electrons per lead ion.

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Colorimetric determination of sulfur oxides in atmosphere by lead dioxides cylinder methods

二酸化鉛法による大気中イオウ酸化物の定量法として,クロラニル酸バリウムを用いる比色法について検討した.定量操作において,アルカリ中和のpH調整に指示薬として2,5-ジニトロフェノールを用い,塩酸で行なったところよい結果が得られた.またこの際生ずる塩化ナトリウムの影響があり,これをできるだけ除くため,硫酸鉛から硫酸イオンとして浸出に必要な炭酸ナトリウムの所要量を求めた.これらの結果により,比色法の操作条件を明らかにし,実際試料について行ない,重量法による定量値と比較したが,相対誤差は最高-6.9%で,ほぼ満足した結果が得られた.