Lead Hydroxide Research Articles

Infrared Spectra of M(OH)1,2,4 (M = Pb, Sn) in Solid Argon

Infrared absorptions for the matrix-isolated lead and tin hydroxides M(OH), M(OH)2 and M(OH)4 (M = Pb, Sn) were observed in laser-ablated metal atom reactions with H2O2 during condensation in excess argon. The major M(OH)2 product was also observed with H2 and O2 mixtures, which allowed the substitution of 18O2. The band assignments were confirmed by appropriate D2O2, D2, 16O18O, and 18O2 isotopic shifts. MP2 and B3LYP calculations were performed to obtain molecular structures and to reproduce the infrared spectra. The minimum energy structure found for M(OH)2 has C(s) symmetry and a weak intramolecular hydrogen bond. In experiments with Sn, HD, and O2, the internal D bond is favored over the H bond for Sn(OH)(OD). The Pb(OH)4 and Sn(OH)4 molecules are calculated to have S4 symmetry and substantial covalent character.

Application of some recently synthesized 9, 10-anthraquinone derivatives as new class of ionophores responsive to lead (II) ion

Lead-selective solvent polymeric membrane electrodes, based on some recently synthesized 9, 10-anthraquinone derivatives, are described. The electrode exhibits a good Nernstian response for Pb (II) ions over a wide concentration range of 1.0/spl times/10/sup -6/-1.0/spl times/10/sup -2/ M with a slope of 28.9 mV decade/sup -1/. The potential-pH profile of membrane based on 1-hydroxy-2-({2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}methyl)anthra-9, 10-quinone (A/sub 3/) demonstrated a lack of H/sup +/ interference within a wide pH range (1.5-6.8). The detection limit is 6.7/spl times/10/sup -7/ M. The developed sensor has a very short response time (2.0 s), and it can be used as a working electrode in a flow injection system. The lifetime of the proposed sensor is 120 days (without any considerable divergence in potentials) with good reproducibility (SD=/spl plusmn/0.1 mV). The proposed sensor revealed good selectivity for Pb (II) over a wide variety of other metal ions. It can be used as an indicator electrode in the potentiometric titration of lead ions, with EDTA, oxalate, chromate, and hydroxide ions, and in direct determination of lead in a wastewater sample.

Lead removal in fixed-bed columns by zeolite and sepiolite

The removal efficiency of zeolite (clinoptilolite) and sepiolite from lead containing aqueous solutions was investigated. A series of experiments were conducted in batch-wise and fixed-bed columns. Synthetic wastewaters containing lead (50 mg l −1) and acetic acid (0.001 N) along with untreated and regenerated clinoptilolites and sepiolites were used in the adsorption studies. Batch tests were mainly conducted to isolate the magnitude of lead precipitation from real adsorption. Adsorption isotherms for both abstraction and adsorption were constructed. The removal of lead is found to be a sum of adsorption induced by ion exchange and precipitation of lead hydroxide. The breakthrough curves were obtained under different conditions by plotting the normalized effluent lead concentration ( C/ C 0) versus bed volume (BV). The ion exchange capacity of sepiolite and clinoptilolite for lead removal showed good performance up to approximately 100 and 120 BV where the C/ C 0 remained below 0.1, respectively. The lead removal capacity of clinoptilolite bed from wastewater containing only lead yielded 45% higher performance compared to that of acetic acid partly due to a decrease in the effluent pH and consequently in precipitation. Also, the presence of acetic acid in the sepiolite column decreased the bed volumes treated by about 40%. Removal efficiency of lead–acetic system both in untreated clinoptilolite and sepiolite columns was found higher than that in regenerated columns.

As(V) 希薄含有廃水におけるFe(III)，AlおよびPb塩によるAs(V) 除去および迅速固液分離

The removal of As(V) from wastewater containing low concentration of As(V) was investigated by addition of Fe(III), Al or Pb salts. Results show wastewater that contains 5 mg/dm3 As(V) is reduced below the regulated concentration of Japanese effluent standard (0.1 mg/dm3) when treated at pH 4.5∼7.5 with the addition of 50 mg/dm3 Fe(III) salts and at pH 6∼8 with the addition of 20 mg/dm3 Al salts. Successful removal of 3.75 mg/dm3 As(V) in wastewater is also possible when treated at pH 7∼11 with the addition of 20.7 mg/dm3 Pb salts, subsequently reducing Pb concentration below the regulated concentration of Japanese effluent standard (0.1 mg/dm3).Chemical equilibrium calculation which considering the formation of arsenic salts with Fe(III), Al or Pb hardly explains the experimental results. Furthermore, as the concentration of As(V) increases, the isoelectric point (IEP) of precipitations after the removal of As(V) by Fe(III), Al or Pb shifted to acidic pH. It is surmised that As(V) is removed by adsorption on the surface of ferric, aluminum or lead hydroxide.Solid/liquid separation from these As(V) removal experiments using a column bed method packed with fibrous ferro-nickel slag was also investigated. Ferric, aluminum or lead hydroxide particles adsorbing dilute As(V) that have several hundred nm in sizes, are thinly dispersed and can perform rapid solid/liquid separation (2.5mm/sec).

The crystal structure of anthropogenic Pb2(OH)3(NO3), and a review of Pb-(O,OH) clusters and lead nitrates

The previously unknown crystal structure of the basic lead nitrate Pb 2 (OH) 3 (NO 3 ) has been determined using single-crystal X-ray diffraction data (Mo- K α radiation, CCD area detector). The compound is orthorhombic, space group Immm , with a = 8.314(2), b = 8.545(2), c = 17.210(3) A( R 1 = 2.78% for 940 ‘observed’ reflections with F o > 4σ( F o )). The layered structure contains a previously unknown cuboid [Pb 8 (OH) 12 ] 4+ cluster and NO 3 groups. The study used crystals formed by anthropogenic processes on a medieval mine dump, probably involving black gunpowder used in the blasting of ore. Pb 2 (OH) 3 (NO 3 ) is associated with a second nitrate, Pb 13 O 8 (OH) 6 (NO 3 ) 4 , which was previously designated as “Pb 6 O 3 (OH) 4 (NO 3 ) 2 ” or “Pb 3 (OH) 5 (NO 3 )”. It is rhombohedral, space group R 3, with a = 10.263(1), c = 25.454(5) A, and a structure solution is in complete agreement with an independent single-crystal study by Li et al. (2001). Probable hydrogen bonds in Pb 2 (OH) 3 (NO 3 ) are indicated. Reported data on [Pb x 2+ (O, OH) y ] n + clusters and lead hydroxide and oxide nitrates are summarized and discussed critically. The probable conditions of formation of the studied samples are evaluated.

In Situ FTIR−Spectroelectrochemical Study of the Anodic Processes on a Galena (PbS) Electrode under Open-Air Conditions in the Absence and Presence of n-Butyl Xanthate

Anodic reactions on a galena (PbS) electrode were studied in situ using attenuated total reflection/Fourier transform infrared spectroscopy within the −0.5 to +0.7 V (standard hydrogen electrode) potential range in air-saturated borate buffer (pH 9.2) in the absence and presence of n-butyl xanthate. Compared to the deaerated conditions, the anodic decomposition of galena is increased by 2−3 times, being accompanied by the enhanced precipitation of Pb(OH)2 both in the absence and presence of xanthate at low concentrations. The increased precipitation rate of Pb(OH)2 is explained by acceleration of the incongruent dissolution of galena (PbS + H2O + 2h+ ⇒ S° + H+ + Pb(OH)+ ) which is caused by an increase in the potential drop in the Helmholtz layer due to the oxygen adsorption. As in the case of the deaerated xanthate solutions, the formation of bulk lead xanthate is preceded by chemisorption of xanthate, and dixanthogen is formed with no overpotential. However, at low concentrations of the reagent, lead xanthate is formed by the precipitation mechanism against the anodic decomposition of galena. At more anodic potentials, this species is substituted by lead hydroxide. At high concentrations of xanthate, xanthate chemisorption inhibits the electrochemical dissolution of galena and the decomposition of adsorbed lead xanthate mediating the formation of lead xanthate and, at higher potentials, that of both lead xanthate and dixanthogen.

Synthetic hydrocerussite, 2PbCO(3) x Pb(OH)(2), by X-ray powder diffraction.

Synthetic hydrocerussite [trilead dihydroxide dicarbonate, Pb(3)(CO(3))(2)(OH)(2)] can be easily obtained, as a white powder, by the action of carbon dioxide and water on either lead or litharge at pH 4-5. This compound is also found in lead corrosion technological products as a fine-grained phase. Ab initio crystal structure determination was carried out on X-ray powder diffraction data. The heavy-atom method and the Patterson function helped determine the crystallographic model and the atom locations. The Rietveld fitting procedure was used for the final refinement. The atomic arrangement is closely related to the structures of other lead hydroxide carbonates. The hydrocerussite structure can be viewed as a sequence of two types of layers stacked along [001]. Layer A is composed of Pb and CO(3), and layer B is composed of Pb and OH. The stacking sequence is ...BAABAA...

Lead Deposits in Dutch Natural Gas Systems

Summary During the production of natural gas from Dutch Rotliegend and Kupferschiefer sediments that are next to "conventional" carbonate and sulphate scales, lead deposits sometimes also form. These deposits, which vary in composition from galena (lead sulphide) to elemental (metallic) to lead and complex lead (hydr)oxides, may form a serious threat to operations because they tend to block production equipment or injection pumps and tubing. In some cases, radioactive lead (lead-210 with a half-life of 22.3 years) is incorporated into these compounds at levels greater than regulatory concern, which necessitates additional safety measures during operations and maintenance. In sour gas wells, the deposition of galena can be explained by local supersaturation (caused by a sudden temperature or pressure drop) where bisulphide anions react with lead cations in the produced water, in which concentrations of up to 150 mg lead per liter brine have been detected. In the absence of hydrogen sulphide and even in "dry" gas wells, the deposition of metallic lead has been observed locally at rates of 10 g/D or more. An electrochemical mechanism is held responsible for lead deposition on carbon steel tubing: iron from the tube wall is oxidized by lead ions in solution, leading to corrosion of the wall and deposition of lead scales in thicknesses of 10 mm or more. Under unfavourable conditions or during maintenance operations, metallic lead is easily converted into secondary lead minerals. Detailed knowledge on the geological origin, the transport pathways to surface facilities, and the mechanisms of lead scale formation might enable the future development of techniques that can prevent lead deposition.

A multi-parameter titration method for the determination of formation pH for metal hydroxides

pH values of metal hydroxide formation were determined at 23°C using a new multi-parameter scanning instrument employing simultaneous turbidity, conductivity and pH measuring capabilities. Results suggest that a combination of data from several simultaneously measured parameters provides a more reliable basis for the generation of quantitative data regarding formation pH and solubility products of metal hydroxide precipitates than corresponding values obtained from single parameter measurements. The advantage rests in the possibility to compare data from parallel sources as well as in the availability of characteristic information reflecting complementary aspects of the investigated systems. The present results obtained from alkaline titration of metal ion solutions coincide well with those found in literature, in particular when considering the great disparity among published values. Mean pK sp-values determined for 1, 5 and 10mM solutions of lead, cadmium, copper and zinc hydroxide are 18.7, 14.4, 19.7 and 16.0, respectively. The pH IEP values of metal hydroxide precipitates were determined from stoichiometric solutions to be 11.1, 10.0, 8.8 and 10.3 for Pb(OH) 2(s), Cd(OH) 2(s), Cu(OH) 2(s) and Zn(OH) 2(s), respectively, by zeta potential measurements. A dedicated instrument was used to measure the corresponding particle sizes, which corroborated with observations from the formation pH studies.

Influence of condensed silica fume on the properties of cement-based solidified wastes

Influence of condensed silica fume (CSF) addition as cement replacement material on the properties of cement-based solidification products was investigated. Final setting, unconfined compressive strength, and leachability of the synthetic lead and chromium hydroxides were determined. CSF was used at 0, 5, 10, and 20 wt.%. substitution for Portland cement. A water-to-solid ratio (w/s) of 0.45 was used for all mixes. Experimental results showed that the severe retardation effect on ordinary Portland cement (OPC) hydration caused by lead hydroxide has been minimized due to the pozzolanic effect and, as a result, the time to final setting has been significantly reduced. In addition, compressive strength of the solidified wastes was increased to the highest with 10% cement replacement but decreased to lower than the one without CSF at 20% replacement. Leaching of the amphoteric lead and chromium hydroxides is primarily determined by leachate pH and therefore lead was found in the leachates at higher concentration than chromium.

Recovery of Lead-Loaded Zeolite Particles by Flotation

The solid/liquid separation of zeolite particles from aqueous suspensions by froth flotation was investigated as a function of various experimental parameters and discussed with respect to the selective recovery of lead-loaded zeolites. Two kinds of collectors were studied: two long-chain positively charged nitrogen-containing surfactants and the negatively charged amyl xanthate. Efficient but nonselective recovery was achieved with using stearylammonium or cetylpyridinium because these surfactants were able to bind the surface of both the lead-loaded zeolites and the sodium-containing raw materials. Amyl xanthate (AMX) did not interact with the sodium form of zeolites, preventing recovery by flotation, but it was found to react with the lead-loaded zeolites leading to the formation of an insoluble complex, Pb(AMX)2, out of the zeolite particle. Adjusting pH at an appropriate value, enabling the formation of lead hydroxide on the zeolite surface, led to the autoassembling of a Pb(OH)2/Pb(AMX)2 overlayer onto the zeolite surface. This resulted in the aggregation of the zeolite particles and their subsequent recovery by flotation. This way to recover zeolite particles loaded with heavy metal species looks promising for exploiting pure synthetic zeolite powders in wastewater treatments.

In situStudy of the Oxidation of Galenite (Natural PbS) in Alkaline Media by FTIR Spectroscopy: Anode Processes in the Absence of Oxygen

Surface compounds on a galenite electrode anodically polarized from –0.5 to 0.7 V (NHE) in a sodium tetraborate deoxygenated solution (pH 9.18) are identified in situby the FTIR spectroscopy; a voltammogram is recorded simultaneously. It follows that lead hydroxide forms on galenite by the salt-film mechanism, giving lead thiosulfate and sulfite in the next oxidation step.

Crystal chemistry of basic lead carbonates. III. Crystal structures of Pb3O2(CO3) and NaPb2(OH)(CO3)2

AbstractThe crystal structures of synthetic Pb3O2(CO3) and NaPb2(OH)(CO3)2, have been solved by direct methods and refined to R = 0.062 and 0.024, respectively. Pb3O2(CO3) is orthorhombic, Pnma, a = 22.194(3), b = 9.108(1), c = 5.7405(8) Å, V = 1160.4(3) Å3, Z = 8. There are four symmetrically distinct Pb2+ cations in irregular coordination polyhedra due to the effect of stereoactive s2 lone electron pairs. The structure is based upon double [O2Pb3] chains of [O(1)Pb4] and [O(2)Pb4] oxocentred tetrahedra and CO3 groups. The [O2Pb3] chains are parallel to the c axis, whereas the CO3 groups are parallel to the (010) plane. NaPb2(OH)(CO3)2 is hexagonal, P63mc, a = 5.276(1), c = 13.474(4)Å, V = 324.8(1) Å3, Z = 2 and has been solved by direct methods. There are two symmetrically distinct Pb2+ cations in asymmetric coordination polyhedra due to the effect of stereoactive s2 lone-electron pairs. The single symmetrically unique Na+ cation is in trigonal prismatic coordination. The structure is based on hexagonal sheets of Pb atoms. Within these sheets, Pb atoms are located at vertices of a 36 net, such that each Pb atom has six adjacent Pb atoms that are ~5.3 Å away. Two sheets are stacked in a close-packing arrangement, forming layers that contain the (CO3) groups. The layers are linked by OH groups that are linearly coordinated by two Pb2+ cations. Na+ cations are located between the layers. The structure is closely related to the structures of other lead hydroxide carbonates (leadhillite, macphersonite, susannite, hydrocerussite, ‘plumbonacrite’).

水酸化鉛を用いたゾル‐ゲル法によるチタン酸ジルコン酸鉛の作製

Lead zirconate titanate (PZT) powder was prepared by the sol-gel method. Lead hydroxide, Zr butoxide, and Ti butoxide were used as starting materials. PZT powders were crystallized at about 773K with through out the precursors. Thermo gravimetric and differential thermal analysis (TG-DTA) were used to measure the weight changes of the dried gels to determine the annealing temperature. TG-DTA curve of the dried gels indicated that the thermal decomposition of organics occurred below 873K. The results of X-ray diffraction analyses showed that the pylochlore phase formed below 873K, and the perovskite phase was formed between 873K and 973K. The powder calcinated at 873K was pressed into pellet at 30MPa and additionally pressed by CIP at 100MPa. This sample was sintered at 1273K. The dielectric constant of the pellet was also measured.

Recovery of metal values from zinc solder dross

Zinc solder dross containing 14.8% Sn, 16.3% Pb, 0.41% Al and 64.5% Zn was leached with 3% H 2SO 4 at 45°C for 1 h. Zinc and aluminum went into solution, whereas lead and tin remained with the residue. Aluminum was selectively precipitated as calcium aluminum carbonate by treating the sulphate leachate with limestone at pH 4.8. Zinc sulphate solution was either evaporated to obtain zinc sulphate crystals or precipitated as basic zinc carbonate at pH 6.8. The undissolved lead and tin were leached with 5 M hot hydrochloric acid. The major part of lead chloride (≌ 73%) was separated by cooling the leached products down to room temperature. From the soluble fraction, tin was recovered as hydrated tin oxide by alkylation with caustic soda at pH 2.4, while the remaining lead was separated at pH 8.5 as lead hydroxide. A process flowsheet had been suggested which involved two-stage hydrometallurgical treatment. Parameters affecting the recovery efficiency of the suggested method such as temperature, time, pH and acid: solid stoichiometric ratio were investigated. Results obtained revealed that the optimum leaching conditions were achieved by using 20 ml of 3% H 2SO 4 acid/g dross for 1 h at 45°C. Recovery efficiency of the metal salts was 99.1, 99.4, 99.6 and 99.5% for Zn, Al, Pb and Sn respectively. Recovery efficiency was related to the solubility of the concerned salts under the given experimental conditions.

Lead metal removal by recycled alum sludge

In this study, alum sludge was recycled using a chemical precipitation process to promote the removal of lead metal in wastewater. To make the process more cost-effective, two different pH ranges were suggested for daily operation, depending on the involvement or otherwise of an aluminum regeneration process at a later stage. If aluminum regeneration was expected, an elevated pH (11.6) was suggested to optimize both the aluminum regeneration and lead removal. Lead hydroxide coprecipitated with alum sludge in alkaline conditions, where the high pH would also facilitate the alkaline regeneration of alum at a later stage. With the use of recycled alum sludge (RAS) in the coagulation process, lead removal rates increased from 79% to 96–98% with 100–180 mg/l of RAS, while the required fresh alum dosage was reduced from 175 mg/l to 50–12.5 mg/l only. If no fresh alum is added to the system, the RAS can still remove up to 94% of lead at low recycling doses (75–100 mg/l), which suggests that the sweep-floc mechanism is crucial to the sludge reuse process. However, if the regeneration of aluminum is not required, a lower initial pH (10.5) should be used to decrease chemical costs.

Effect of calcium chloride on the hydration and leaching of lead-retarded cement

The effect of adding CaCl 2 to ordinary portland cement containing 10% (by weight) of a synthetic lead hydroxide waste has been investigated using differential thermal analysis, conduction calorimetry, and by analysing solutions extracted from mixes during the early stages of hydration. Lead wastes are known to retard initial cement hydration reactions, and for the waste loading used in these experiments the peak in the heat of hydration curve was delayed from 8.7 to 172 h. The addition of CaCl 2 reduced this retarding effect but was associated with a decrease in the overall extent of cement hydration, particularly at high CaCl 2 concentrations. The acceleration induced is associated with lower concentrations of hydroxyl ions in solution. This reduces dissolution and subsequent adsorption of Pb(OH) 3 − ions onto C-S-H surfaces forming around hydrating cement particles. Samples containing CaCl 2 show significantly higher weight loss during leaching in 0.05 N acetic acid solutions. This observation, combined with the overall reduced level of hydration, suggests that addition of CaCl 2 does not produce improved materials for disposal.

The structure of lead stabilizers. 2: Basic salts of inorganic acids

AbstractFTIR and NMR measurements were used to infer structural formulas for the heat stabilizers dibasic lead phosphite, tribasic and tetrabasic lead sulfates, and basic lead carbonate. These compounds are not the customarily written double salts of lead oxide or hydroxide, but distinct species capable of rapid HCI neutralization.

Leachability of lead from lead tailings

Laboratory column studies were used to predict the effect on the leachability of lead when using fly ash or a fly ash/sludge mixture as a cover for a lead tailings site. A high pH fly ash cover produced a leachate with a pH 12. This was sufficiently high to allow for the formation of lead hydroxide complexes which are slightly soluble. Therefore, the leachate had an average lead concentration of about 5 mg L-1, while the pH in the leachate from the column with only tailings was 7.8 and a lead concentration below the detection limit (≤0.1 mg L-1). The fly ash cover changed the availability of the remaining lead, making it less available. Rainfall rate did not affect the fly ash cover, but did have an effect on the fly ash/sludge cover.

Sulphite modification of galena surfaces and its effect on flotation and xanthate adsorption

The effect of sulphite interaction with galena on the mechanism of ethyl xanthate adsorption onto galena surfaces has been studied in situ using UV spectroscopy. The influence of sulphite on galena flotation has been studied. X-ray photoelectron spectroscopic (XPS) and dissolution studies have been used to identify the mechanism of interaction between sulphite and galena surfaces. Metastable ethyl monothiocarbonate is a significant derivative of ethyl xanthate adsorption on galena in the absence of sulphite. The concentration of surface sites which produce monothiocarbonate increases with the initial state of galena oxidation, which, is in turn, apparently dependent upon galena preconditioning time, temperature and oxygen concentration. Significantly different ethyl xanthate adsorption characteristics were found, after sulphite conditioning of the galena surface. In this case, ethyl xanthate adsorption rate was significantly reduced, as was the formation of monothiocarbonate. Surface complexation of lead hydroxide by adsorbed sulphite decreases the rate of ethyl xanthate adsorption onto sites which, potentially, can produce monothiocarbonate. Galena dissolution studies and XPS examination of the galena surfaces together, confirmed the formation of insoluble lead sulphite precipitates at the galena surface. The effectiveness of sulphite depression of galena flotation is enhanced by adsorbed lead hydrolysis products on galena.