The formation of lead(II) chloride complexes to 300°C: A spectrophotometric study     

T.M Seward 《Geochimica et cosmochimica acta》1984,48(1):121-134

The spectra of chlorolead(II) complexes in the ultraviolet region have been measured in acid chloride solutions from 0.0012 to 3.223 m and at temperatures from 25 to 300°C. The thermodynamic cumulative and stepwise formation constants as well as the spectra of the individual chlorolead(II) species have been calculated from the spectrophotometric data. At 25°C, the five species PbCl^2?n_n (0 ≤ n ≤ 4) occur, however, at 300°C the predominant species were PbCl⁺, PbCl⁰₂ and PbCl^?₃. Pb²⁺ occurs as a minor species in dilute solutions where total chloride is <0.003 m at 300°C and the presence of PbCl^2?₄ in concentrated solutions was not detected above 150°C. With increasing temperature, chlorolead(II) complex stability is characterised by large endothermic enthalpies and large positive entropies of formation. Lead(II) chloride complexes are important in the transport and deposition of lead by hydrothermal ore solutions of moderate to high salinity.  相似文献   

Lead orthophosphates—II. Stability of cholopyromophite at 25°c     

Jerome O. Nriagu 《Geochimica et cosmochimica acta》1973,37(3):367-377

The conversion of secondary lead orthophosphate [PbHPO₄] into chloropyromorphite [Pb₅(PO₄)₃Cl] in ca. 10^?1 M NaCl solutions has been investigated at 25°C. From the composition of the supernatant solutions, the solubility product constant for Pb₅(PO₄)₃Cl has been calculated to be 10^?84.4±0.1, corresponding to $\text{ΔG}{}_{\mathrm{?}}\text{°}$ of ?906.2 kcal mol^?1. The solution equilibria and phase relationships in the system PbCl₂-PbO-P₂O₈-H₂O are discussed along with the geological implications.  相似文献   

Zn and Pb solubility and speciation in aqueous chloride fluids at T-P parameters corresponding to granitoid magma degassing and crystallization     

O. A. Lukanin  B. N. Ryzhenko  N. A. Kurovskaya 《Geochemistry International》2013,51(10):802-830

The solubility of all possible Zn and Pb species in aqueous chloride fluids was evaluated by means of thermodynamic simulations in systems ZnO(PbO)-aqueous solution of NaCl (KCl, NaCl + HCl) within broad ranges of temperature (600–900°C), pressure (0.7–5 kbar), and chloride concentrations, under parameters corresponding to the crystallization and degassing of granitoid magmas in the Earth’s crust. Our simulation results demonstrate that the addition of Cl to the fluid phase in the form of Na(K)Cl and HCl significantly increases the concentrations of Cl-bearing Zn and Pb complexes and the total concentration of the metals in the solutions in equilibrium with the solid oxides. In Zn-bearing fluids, the Zn(OH) ₂ ⁰ , ZnOH⁺, and Zn(OH) ₃ ^? —hydroxyl complexes and the ZnCl ₂ ⁰ , and ZnCl⁺ chlorocomplexes, which are predominant at low Cl concentrations (C_Cl < 0.05–0.1 m) give way to ZnCl ₄ ^2? with increasing C_Cl, which becomes the predominant Zn species of the fluid at C_Cl > 0.1–0.5 m throughout the whole temperature range in question and pressures higher than 1 kbar. For Pb-bearing fluids, the T-P-X region dominated by the Pb(OH) ₂ ⁰ , and Pb(OH) ₃ ^? hydroxyl complexes is remarkably wider than the analogous region for Zn, particularly at elevated temperatures (≥700°C) in alkaline solutions. An increase in C_Cl is associated with an increase in the concentration and changes in the speciation of Pb chlorocomplexes: PbCl ₂ ⁰ → PbCl ₃ ^? → PbCl ₄ ^2? . The concentrations of Zn and Pb chlorocomplexes increase with increasing pressure, decreasing temperature, and decrease pH with the addition of HCl to the system. It is demonstrated that the solubility of ZnO at any given T-P-X in alkaline solutions with low chloride concentrations are lower than the solubility of PbO. The Zn concentration increases more significantly than with the Pb concentration with increasing C_Cl and decreasing pH, so that the Zn concentration in acidic solutions is higher than the Pb concentration over broad ranges of temperature, pressure, and Cl concentration. Chloride complexes of Zn (ZnCl ₂ ⁰ , and ZnCl ₄ ^2? ) and Pb (PbCl ₂ ⁰ , and PbCl ₃ ^? are proved to be predominant within broad T-P-X-pH ranges corresponding to the parameters under which magmatic fluid are generated. Our simulation results confirm the hypothesis that chlorocomplexes play a leading role in Zn and Pb distribution between aqueous chloride fluids and granitic melts. These simulation results are consistent with experimental data on the Zn and Pb distribution coefficients (D(Zn)^f/m and D(Pb)^f/m, respectively) between aqueous chloride fluids and granitic melts that demonstrated that (1) D(Zn)^f/m and D(Pb)^f/m increase with increasing Na and K chloride concentrations in the aqueous fluid, (2) both D(Zn)^f/m and D(Pb)^f/m drastically increase when HCl is added to the fluid, and (3) (D(Zn)^f/m is higher than D(Pb)^f/m at any given T-P-X parameters. The experimentally established decrease in D(Zn)^f/m and D(Pb)^f/m with increasing pressure (at unchanging temperature and Cl concentration) is likely explained by an increase in the alkalinity of the aqueous chloride fluid in equilibrium with granite melt and, correspondingly, a decrease in the Zn and Pb solubility in this fluid.  相似文献   

Crystal chemistry of natural and synthetic lead oxohalides: II. Crystal structure of Pb7O4(OH)4Br2     

O. I. Siidra  S. V. Krivovichev  W. Depmeier 《Geology of Ore Deposits》2008,50(8):801-805

Crystals of lead oxobromide Pb₇O₄(OH)₄Br₂ have been synthesized by hydrothermal method. The structure of the new compound has been studied with X-ray single-crystal diffraction analysis. The compound is monoclinic, space group C112₁; unit-cell dimensions are a = 5.852(4), b = 13.452(7), c = 19.673(9) Å, γ = 90.04°, V = 1548.7(15) ų. The structure has been solved by direct methods and refined to R ₁ = 0.1138 for 1847 observed Pb₇O₄(OH)₄Br₂ unique reflections. The structure contains seven symmetrically independent bivalent Pb atoms. The coordination polyhedrons of Pb are strongly distorted due to stereochemical activity of unshared electron pair 6s ². Oxygen atoms are tetrahedrally coordinated by four Pb²⁺ cations with the formation of oxocentered tetrahedrons OPb₄. The compound is based on [O₂Pb₃]²⁺ double chains formed by OPb₄ tetrahedrons. (OH)Pb₂ dimers combine the [O₂Pb₃]²⁺ chains into 3D framework. Channels in the framework are parallel to [100] and are occupied by Br anions.  相似文献   

Characterization,dissolution and solubility of the hydroxypyromorphite–hydroxyapatite solid solution [(Pb<Subscript>x</Subscript>Ca<Subscript>1−x</Subscript>)<Subscript>5</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>OH] at 25 °C and pH 2–9     

Yinian Zhu  Bin Huang  Zongqiang Zhu  Huili Liu  Yanhua Huang  Xin Zhao  Meina Liang 《Geochemical transactions》2016,17(1):2

  相似文献   

Solubility and equilibrium constants of lead in carbonate solutions (25°C,I = 0.3 mol dm−3)     

Halka Bilinski  Paul Schindler 《Geochimica et cosmochimica acta》1982,46(6):921-928

The solubilities of PbCO₃(s), 2PbCO₂·Pb(OH)₂(s), and of 3PbCO₃ 2Pb(OH)₂(s) have been studied at 25°C ± 0.1°C in solutions of the constant ionic strength I = 0.3 mol/dm³, consisting primarily of sodium perchlorate. A few experiments with hydrocerussite were performed in solutions of 0.1 M KNO₃. The concentrations of lead and hydrogen ions have been determined in solution in contact with the solid phase. From experimental data the following values for equilibrium constants are obtained: log [Pb²⁺]·pCO₂·[H⁺]^?2 = 5.20log [Pb²⁺]·pCO^0.67₂·[H⁺]^?2 = 6.80log [Pb₂₊]³·[CO^2?₃]²·[OH^?]² = ?44.08 (and ?44.8 forI = 0.1 M)log [PbCO⁰₃]·[Pb²⁺]^?1·[CO^2?₃]^?1 = 5.40log [Pb(CO₃)^2?₂]·[Pb₂₊]^?1·[CO^2?₃]^?2 = 8.86 The data indicate that hydrocerussite is the most stable solid phase in natural waters. Comparison with the literature and needs for further research are also presented.  相似文献   

Use of Pitzer's equations to determine the media effect on the formation of lead chloro complexes     

Frank.J. Millero  Robert H. Byrne 《Geochimica et cosmochimica acta》1984,48(5):1145-1150

The spectrophotometric measurements of chloro complexes of lead in aqueous HCl, NaCl, MgCl₂ and CaCl₂ solutions at 25°C have been analyzed using Pitzer's specific interaction equations. Parameters for activity coefficients of the complexes PbCl⁺, PbCl₂⁰ and PbCl₃^? have been determined for the various media. Values of $\text{K}{}_1\text{= 30.0 ± 0.6}$, $\text{K}{}_2\text{= 106.7 ± 2.1}$ and $\text{K}{}_3\text{= 73.0 ± 1.5}$ were obtained for the cumulative formation constants. [$\text{Pb}{}^{\mathrm{2+}}\text{+ nCl}{}^{\mathrm{?}}\text{→ PbCl}{}_{\mathrm{n}}{}^{\mathrm{2?n}}\text{)}$]. These values are in reasonable agreement with literature data. The Pitzer parameters for the PbCl ion pairs in various media were used to calculate the speciation of Pb²⁺ in an artificial seawater solution.  相似文献   

Crystal chemistry of natural and synthetic lead oxyhalides. Part I. Crystal structure of Pb<Subscript>13</Subscript>O<Subscript>10</Subscript>Cl<Subscript>6</Subscript>     

O. I. Siidra  S. V. Krivovichev  W. Depmeier 《Geology of Ore Deposits》2007,49(8):827-834

Crystals of lead oxychloride Pb₁₃O₁₀Cl₆ have been synthesized on the basis of high-temperature solid-state reactions. The Pb₁₃O₁₀Cl₆ structure was studied using X-ray single-crystal diffraction analysis. The compound is monoclinic, and the space group is C2/c; the unit-cell dimensions are a = 16.1699(14), b = 7.0086(6), c = 23.578(2) Å, β = 97.75°, and V = 2647.6(4) ų. The structure has been solved by direct methods and refined to R ₁ = 0.0505 for 2671 observed unique reflections. The structure is a 3D framework consisting of OPb₄ tetrahedrons. Chlorine atoms are located in the framework channels. The structure contains seven symmetrically independent Pb atoms, which are coordinated by 2 to 4 O^2? and 2 to 4 Cl^? anions. The synthesized compound is compared with other natural and synthetic lead oxyhalides.  相似文献   

Spectroscopic investigation of the formation of PuO2Cl+ and PuO2Cl2 in NaCl solutions and application for natural brine solutions     

《Geochimica et cosmochimica acta》1999,63(19-20):3443-3449

The chloride complexation of the PuO₂²⁺ ion has been studied in acidic NaCl solutions with electrolyte concentrations as high as 5 mol kg⁻¹ at 23°C by using conventional absorption spectrophotometry. Plutonyl and its complexes have ionic strength-dependent molar absorptivities that were determined in NaClO₄, the first essential step in the quantitative analysis of chloride complexation. The distributions of species for the Pu complexes, PuO₂²⁺, PuO₂Cl⁺, and PuO₂Cl₂^o, formed under the conditions investigated, were determined by peak-fitting of optical absorption spectra. The apparent stability constants of the Pu(VI) chloro complexes were calculated at each NaCl concentration. Specific ion-interaction theory parameters were determined for the plutonyl chloro complexes and the electrolyte constituents, then compared with the literature data. The calculated values for log β° were determined to be 0.23 ± 0.03 and −1.7 ± 0.2 for the mono and bis chloro complexes, respectively. Spectra of Pu(VI) in brines representative of waters at the Waste Isolation Pilot Plant, the licensed nuclear waste repository in a salt formation at Carlsbad, NM, USA, were measured and modeled by using the thermodynamic data and ion interaction parameters were determined. In these brines, less than 10% of the total Pu(VI) concentration exists as the Pu(VI) aquo ion, whereas about 90% is present as Pu(VI) chloro complexes.  相似文献   

Amendments affect lead mobility and modulated chemo-speciation under different moisture regimes in normal and salt-affected lead-contaminated soils     

M. M. Iqbal  T. Naz  J. Akhtar  M. Afzal  E. Meers  G. D. Laing 《International Journal of Environmental Science and Technology》2017,14(1):113-122

The total lead content in the soil itself is insufficient as a measure to indicate the actual environmental risks related to the presence of lead in the soil. Understanding the mobility of lead and its chemical speciation in soil solution is of great importance for accurately assessing environmental risks posed by lead. Therefore, a laboratory study was carried out to evaluate the effect of inorganic amendments (gypsum, rock phosphate and di-ammonium phosphate) on lead mobility and chemical speciation under different moisture regimes (flooding regime and 75 % field capacity) in normal and salt-affected lead-contaminated soils. After 2, 7, 15, 30, 100 and 110 days of incubation, pore water samples were collected by using Rhizon soil moisture samplers. In order to estimate the chemical speciation of lead in pore water, Visual MINTEQ 3.0 modeling approach was used. The results showed that presence of free Pb²⁺, PbCl⁺, Pb(SO₄) ₂ ^2? , and PbH₂PO₄ ⁺ was significantly (P ≤ 0.05) affected by the soil moisture regime, incubation time and applied amendments in lead-contaminated soils. The Visual MINTEQ 3.0 predicted free Pb²⁺ species concentration was found higher in lead-contaminated soils, while PbCl⁺ was more pronounced in salt-affected soils. Gypsum increased the occurrence of Pb(SO₄) ₂ ^2? , while di-ammonium phosphate and rock phosphate enhanced the PbH₂PO₄ ⁺ species formation and decreased free Pb²⁺ species in pore water. Thus, gypsum is the most effective in reducing lead and free Pb²⁺ species concentrations in the pore water under different soil moisture regimes and incubation times in normal and salt-affected lead-contaminated soils.  相似文献   

Experimental study of uraninite solubility in aqueous HCl solutions at 500°C and 1 kbar     

N. I. Kovalenko  B. N. Ryzhenko  N. I. Prisyagina  Ya. V. Bychkova 《Geochemistry International》2011,49(3):262-273

Uraninite solubility in 0.001–2.0 m HCl solutions was experimentally studied at 500°C, 1000 bar, and hydrogen fugacity corresponding to the Ni/NiO buffer. It was shown that the following U(IV) species dominate in the aqueous solution: U(OH)₄⁰, U(OH)₂Cl₂⁰, and UOH Cl₃⁰ Using the results of uraninite solubility measurement, the Gibbs free energies of U(IV) species at 500°C and 1000 bar were calculated (kJ/mol): −9865.55 for UO₂(aq), −1374.57 for U(OH)₂ Cl₂⁰, and −1265.49 for UOH Cl₃⁰, and the equilibrium constants of uraninite dissolution in water and aqueous HCl solutions were estimated: UO₂(cr) = UO₂(aq), pK ₀ = 6.64; UO₂(cr) + 2HCl⁰ = U(OH)₂ Cl₂⁰, pK ₂ = 3.56; and UO₂(cr) + 3HCl⁰ = UOHcl₃⁰ + H₂O, pK ₃ = 3.05. The value pK ₁ ≈ 5.0 was obtained as a first approximation for the equilibrium UO₂(cr) + H₂O + HCl⁰ = U(OH)₃Cl⁰. The constant of the reaction UO₂(cr) + 4HCl⁰ = UCl₄⁰ + 2H₂O (pK ₄ = 7.02) was calculated taking into account the ionization constants of U Cl₄⁰ and U(OH)₄⁰, obtained by extrapolation from 25 to 500°C at 1000 bar using the BR model. Intense dissolution and redeposition of gold (material of experimental capsules) was observed in our experiments. The analysis and modeling of this phenomenon suggested that the UO_{2 + x} /UO₂ redox pair oxidized Au(cr) to Au⁺(aq), which was then reduced under the influence of stronger reducers.  相似文献   

Chemical speciation of Cd,Cu, Pb,and Zn in mixed freshwater,seawater, and brine solutions     

David T. Long  Ernest E. Angino 《Geochimica et cosmochimica acta》1977,41(9):1183-1191

A theoretical model was developed to study the chemical speciation of the trace elements Zn, Cd, Cu and Pb aqueous solutions and their responses to variations in ionic strength and complexation. Two mixing solutions were investigated, a freshwater-seawater system and a freshwater-brine system. The brine was a calcium, sodium-chloride solution with a molal ionic strength of two. Trace element associations with the ligands OH^?, Cl^?, CO^2?₃, SO^2?₄, and HCO^?₃ were considered at pHs from 3.5 to 11.0 at 25°C. In general, the relative importance of the various ligand-trace element complexes can be predicted from a comparison of their stability constants. However, the effect of pH on the importance of a given complex is not readily apparent from the stability constants. Freshwater-seawater mixtures, as might be found in a totally mixed estuary, show that seawater composition is the dominant control on chemical complexing. Chloride complexing is similar for lead and zinc in the freshwater-brine mixtures. This similarity may account in part for the association of lead and zinc in strata-bound ore deposits.  相似文献   

The crystal structure of arsentsumebite, Pb2Cu[(As, S)O4]2(OH)     

N. V. Zubkova  D. Yu. Pushcharovsky  G. Giester  E. Tillmanns  I. V. Pekov  D. A. Kleimenov 《Mineralogy and Petrology》2002,75(1-2):79-88

Summary The crystal structure of arsentsumebite, ideally, Pb₂Cu[(As, S)O₄]₂(OH), monoclinic, space group P2₁/m, a = 7.804(8), b = 5.890(6), c = 8.964(8) ?, β = 112.29(6)°, V = 381.2 ?³, Z = 2, d_calc. = 6.481 has been refined to R = 0.053 for 898 unique reflections with I> 2σ(I). Arsentsumebite belongs to the brackebuschite group of lead minerals with the general formula Pb₂ Me(XO₄)₂(Z) where Me = Cu²⁺, Mn²⁺, Zn²⁺, Fe²⁺, Fe³⁺; X = S, Cr, V, As, P; Z = OH, H₂O. Members of this group include tsumebite, Pb₂Cu(SO₄)(PO₄)(OH), vauquelinite, Pb₂Cu(CrO₄)(PO₄)(OH), brackebuschite, Pb₂ (Mn, Fe)(VO₄)₂(OH), arsenbracke buschite, Pb₂(Fe, Zn)(AsO₄)₂(OH, H₂O), fornacite, Pb₂Cu(AsO₄)(CrO₄)(OH), and feinglosite, Pb₂(Zn, Fe)[(As, S)O₄]₂(H₂O). Arsentsumebite and all other group members contain M = M–T chains where M = M means edge-sharing between MO₆ octahedra and M–T represents corner sharing between octahedra and XO₄ tetrahedra. A structural relationship exists to tsumcorite, Pb(Zn, Fe)₂(AsO₄)₂ (OH, H₂O)₂ and tsumcorite-group minerals Me(1)Me(2)₂(XO₄)₂(OH, H₂O)₂. Received June 24, 2000; revised version accepted February 8, 2001  相似文献   

Experimental study of the system H3BO3–NaF–SiO2-H2O at 350–800 °C and 1–2 kbar by the method of synthetic fluid inclusions     

I.S. Peretyazhko  S.Z. Smirnov  A.R. Kotel’nikov  Z.A. Kotel’nikova 《Russian Geology and Geophysics》2010,51(4):349-368

The phase state of fluid in the system H₃BO₃–NaF–SiO₂–H₂O was studied at 350–800 °C and 1–2 kbar by the method of synthetic fluid inclusions. The increase in the solubility of quartz and the high reciprocal solubility of H₃BO₃ and NaF in water fluid at high temperatures are due to the formation of complexes containing B, F, Si, and Na. At 800 °C and 2 kbar, both liquid and gas immiscible phases (viscous silicate-water-salt liquid and three water fluids with different contents of B and F) are dispersed within each other. The Raman spectra of aqueous solutions and viscous liquid show not only a peak of [B(OH)₃]⁰ but also peaks of complexes [B(OH)₄]^–, polyborates [B₄O₅(OH)₄]^2–, [B₃O₃(OH)₄]^–, and [B₅O₆(OH)₄]^–, and/or fluoroborates [B₃F₆O₃]^3–, [BF₂(OH)₂]^–, [BF₃(OH)]^–, and [BF₄]^–. The high viscosity of nonfreezing fluid is due to the polymerization of complexes of polyborates and fluorine-substituted polyborates containing Si and Na. Solutions in fluid inclusions belong to P–Q type complicated by a metastable or stable immiscibility region. Metastable fluid equilibria transform into stable ones owing to the formation of new complexes at 800 ºC and 2 kbar as a result of the interaction of quartz with B-F-containing fluid. At high concentrations of F and B in natural fluids, complexes containing B, F, Si, and alkaline metals and silicate-water-salt dispersed phases might be produced and concentrate many elements, including ore-forming ones. Their transformation into vitreous masses or viscous liquids (gels, jellies) during cooling and the subsequent crystallization of these products at low temperatures (300–400 °C) should lead to the release of fluid enriched in the above elements.  相似文献   

Lead orthophosphates—III. Stabilities of fluoropyromorphite and bromopyromorphite at 25°C     

Jerome O. Nriagu 《Geochimica et cosmochimica acta》1973,37(7):1735-1743

The reactions of secondary lead orthophosphate with approximately 10^?1 M sodium fluoride and sodium bromide solutions have been investigated at 25°C. Interpretation of the solubility data resulted in solubility product constants for fluoropyromorphite and bromopyromorphite of 10^?71.6 and 10^?78.1, respectively. According to these constants, the stability sequence for lead pyromorphites is Pb₅(PO₄)₃Cl > Pb₅(PO₄)₃Br > Pb₅(PO₄)₃OH > Pb₅(PO₄)₃F. The derived free energy data have been used to evaluate the respective stabilities of fluoro-pyromorphite and bromopyromorphite within the systems PbF₂-PbO-P₂O₅-H₂O and PbBr₂-PbO-P₂O₅-H₂O and to predict the equilibrium behavior of the Pb₅(PO₄)₃F-Pb₅(PO₄)₃OH solid solution under aqueous conditions.  相似文献   

Minerals with Brackebuschite-Like Structures: A Novel Solid Solution System Involving Cr<Superscript>6+</Superscript> and V<Superscript>5+</Superscript>     

D.?A.?KhaninEmail author  I.?V.?Pekov 《Geology of Ore Deposits》2017,59(7):642-651

A novel complex continuous system of solid solutions involving vauquelinite Pb₂Cu(CrO₄)(PO₄)(OH), bushmakinite Pb₂Al(VO₄)(PO₄)(OH), ferribushmakinite Pb2Fe³⁺(VO₄)(PO₄)(OH), and a phase with the endmember formula Pb₂Cu(VO₄)(PO₄)(H₂O) or Pb₂Cu(VO₄)(РО₃ОН)(ОН) is studied based on samples from the oxidation zone of the Berezovskoe, Trebiat, and Pervomaisko-Zverevsky deposits in the Urals, Russia. This is the first natural system in which chromate and vanadate anions show a wide range of substitutions and the most extensive solid solution system involving (CrO₄)^2– found in nature. The major couple substitution is Cr⁶⁺ + Cu²⁺ ? V⁵⁺ + M³⁺, where M = Fe, Al. The correlation coefficients calculated from 125 point analyses are: 0.96 between V and (Fe + Al), 0.96 between Cr and (Cu + Zn),–0.96 between V and (Cu + Zn),–0.97 between Cr and (Fe + Al), and–0.97 between (Fe + Al) and (Cu + Zn). The substitutions V⁵⁺ ? Cr⁶⁺ (correlation coefficient–0.98) and to a lesser extent P⁵⁺ ? As⁵⁺ (correlation coefficient–0.86) occur at two types of tetrahedral sites, whereas the metal–nonmetal/metalloid substitutions, i.e., V or Cr for P or As, are minor. The substitution Fe³⁺ ? Al³⁺ is also negligible in this solid solution system.  相似文献   

Romanorlovite,a New Copper and Potassium Hydroxychloride from the Tolbachik Volcano,Kamchatka, Russia     

I. V. Pekov  V. O. Yapaskurt  S. N. Britvin  M. F. Vigasina  I. S. Lykova  N. V. Zubkova  S. V. Krivovichev  E. G. Sidorov 《Geology of Ore Deposits》2017,59(7):601-608

A new mineral romanorlovite has been found in the upper, moderately hot zones of two fumaroles, Glavnaya Tenoritovaya (Major Tenorite) and Arsenatnaya (Arsenate), located at the second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with avdoninite in both fumaroles, and in Glavnaya Tenoritovaya, it is also associated with belloite, sylvite, carnallite, mitscherlichite, sanguite, chlorothionite, eriochalcite, chrysothallite, and mellizinkalite. Romanorlovite occurs as prismatic, equant, or tabular tetragonal crystals up to 0.1 mm in size, crystal clusters up to 0.5 mm, and crusts up to 2 × 2 mm in area. The mineral is transparent with vitreous luster. Its color varies from yellow-brown to dark brown, and tiny crystals are honey- or golden-yellow. Cleavage is not observed. Romanorlovite is brittle. The Mohs hardness is ca ~3. The calculated density varies from 2.72 to 2.79 g/cm³ depending on the content of admixed Pb. The mineral is optically uniaxial (–), ω = 1.727(3), ε = 1.694(2). The Raman spectrum has been reported. The chemical composition of the holotype sample (wt %; electron microprobe data, contents of О and H calculated by stoichiometry) is as follows: 21.52 K, 0.89 Pb, 28.79 Cu, 0.02 Zn, 44.74 Cl, 4.85 O_calc, 0.41 H_calc, total 101.22. Its empirical formula calculated based on Cl₂₅ with (ОН)₄(Н2О)₂ is K_10.90Pb_0.09Cu_8.97Zn_0.01Cl₂₅(OH)₄ · 2H₂O. The simplified formula is K₁₁Cu₉Cl₂₅(OH)₄ · 2H₂O (Z = 4). Romanorlovite is tetragonal, space group[ I4/mmm. The unit cell parameters are (1) holotype: a = 17.5804(7), c = 15.9075(6) Å, V = 4916.5(3) ų; (2) the sample enriched in Pb on which the crystal structure was refined: a = 17.5538(19), c = 15.8620(17) Å, V= 4887.7(9) ų. The strongest reflections of the powder XRD pattern (d, Å–I[hkl]) are 12.48–56[110], 11.74–36[101], 8.80–100[200], 7.97–34[002], 6.71–40[112], 3.165–32[512], 2.933–80[215, 433], 2.607–38[514]. The mineral is named in honor of Roman Yu. Orlov (1929-2005), Russian mineralogist and physicist, who worked in the Department of Mineralogy, Moscow State University.  相似文献   

Thio complexes of gold and the transport of gold in hydrothermal ore solutions   总被引：1，自引：0，他引：1  

T.M Seward 《Geochimica et cosmochimica acta》1973,37(3):379-399

The solubility of gold in aqueous sulphide solutions has been determined from pH_20°C ≈ 4 to pH_20°C ≈ 9.5 in the presence of a pyrite-pyrrhotite redox buffer at temperatures from 160 to 300°C and 1000 bar pressure. Maximum solubilities were obtained in the neutral region of pH as, for example, with m_NaHS = 0.15 m, pH_20°C = 5.96, T = 309°C, P = 1000 bar where a gold solubility of 225 mg/kg was obtained. It was concluded that three thio gold complexes contributed to the solubility. The complex Au₂(HS)₂S^2? predominated in alkaline solution, the Au(HS)₂^? complex occurred in the neutral pH region, and in the acid pH region, it was concluded with less certainty that the Au(HS)° complex was present. Formation constants calculated forAu₂(HS)₂S^2? and Au (HS)₂^? emphasize their high stability. In the temperature range from 175 to 250°C, values of pβ for Au₂(HS)₂S^2? vary from ?53.0 to 47.9 (±1.6) and from ?23.1 to ?19.5 ( ± 1.5) for Au(HS)₂^?. Equilibrium constante for the dissolution reactions, $\text{Au° + H}{}_2\text{S + HS}{}^{\mathrm{?}}\text{? Au(HS)}{}_2{}^{\mathrm{?}}\text{+}\text{1}\text{2}\text{H}{}_2$ and 2Au° + H₂S + 2H8^? ? Au(HS)₂^? + H₂ vary from pK_m = +2.4 to +2.55 (±0.10) for Au₂(HS)₂S^2? and from pK_n = + 1.29 to + 1.19 (±0.10) for Au(HS)₂^? over the temperature range 175 to 250°C. Enthalpies of these dissolution reactions were calculated to be ΔH_m° = ?5.2 ±2.0 kcal/mol and ΔH_n° = +1.7 ±2.0 kcal/mol respectively. It was concluded that gold is probably transported in hydrothermal ore solutions as both thio and chloro complexes and may be deposited in response to changes in temperature, pressure, pH, oxidation potential of the system and total sulphur concentration.  相似文献   

Lead enrichment, adsorption and speciation in urban garden soils under long-term wastewater irrigation in northern Nigeria     

G. N. Egwu  J. O. Agbenin 《Environmental Earth Sciences》2013,69(6):1861-1870

Unsafe lead (Pb) concentrations in leafy vegetables raised in urban and peri-urban agricultural production systems have been reported across cities in Northern Nigeria, even though Pb concentrations in soils are within regulatory safe levels. This study examined the soil enrichment, adsorption and chemical species of Pb in urban garden fields irrigated with untreated wastewater at three industrial locations in Kano, northern Nigeria. Total Pb in the soil profiles ranged from 9 to 91 mg kg^?1 and decreased rapidly from the surface to the subsurface layer, but attaining nearly constant concentration at depth ≥1.2 m in the profiles. The potentially labile Pb maintained fairly constant concentration with depth up to 0.9 m, but decreased fairly rapidly with depth thereafter. There was a significant Pb enrichment of the soils, extending up to 30–60 cm depth in the soil profiles. The adsorption of Pb by the soils increased drastically with pH, and attained maximum adsorption at pH ≥ 7.0 in the surface layer, and at pH ≥ 6 in the subsurface layer. The surface soils adsorbed between 85 and 97 % of added Pb at pH ≤ 5. Free Pb²⁺ activities in soil solution accounted for between 46 and 87 % at pH 5–7 of total dissolved Pb (Pb_T). The quantifiable chemical species of Pb in solution consisted mainly of PbOH⁺, PbSO ₄ ^· , PbCl⁺ and PbOH ₂ ^· which accounted for between 0.9 and 26 % of Pb_T in soil solution at pH ≥ 5.0, but declining to between 0.1 and 2.1 % at pH ≥ 7.5. There was no apparent equilibrium between Pb²⁺ activities and known Pb-compounds in the soils. It was concluded from the data that reports of excess Pb concentrations in leafy vegetables raised in these soils are consistent with high free Pb²⁺ activities maintained in soil solution by these predominantly sandy-textured soils.  相似文献   

Effectiveness of Mg–Al-layered double hydroxide for heavy metal removal from mine wastewater and sludge volume reduction     

M. Tamzid Rahman  T. Kameda  S. Kumagai  T. Yoshioka 《International Journal of Environmental Science and Technology》2018,15(2):263-272

Health hazards from heavy metal pollution in water systems are a global environmental problem. Of similar concern is sludge that results from wastewater treatment due to unsatisfactory sludge management technology. Therefore, the effectiveness of using Mg–Al-layered double hydroxide in the removal of heavy metals from mine wastewater was tested and compared with that of calcium hydroxide [Ca(OH)₂], which is a common treatment method for heavy metal removal. Initially, the mine wastewater contained cations of the heavy metals iron (Fe), zinc (Zn), copper (Cu), and lead (Pb). The Mg–Al-layered double hydroxides were able to remove 371, 7.2, 121, and 0.4 mg/L of these pollutants, respectively, using the co-precipitation method. The removal of these metals is most effective using 0.5 g Mg–Al-layered double hydroxide (Mg/Al molar ratio 4) and 20 min of shaking. Zn was removed by the formation of Zn(NO₃)(OH)·H₂O and Zn₅(NO₃)₂(OH)₈ when LDH, Mg/Al molar ratios of 4 and 2, respectively, were used. Similarly, Fe, Cu, and Pb were removed by the formation of Fe–Al-layered double hydroxide, Cu₂(OH)₃·NO₃ and Pb₄(OH)₄(NO₃)₄, respectively. While Ca(OH)₂ is also capable of reducing the heavy metal concentrations below the Japanese recommended values, this analysis shows that using 0.5 g Mg–Al-layered double hydroxide is a better treatment condition for mine wastewater, because it generates lower sludge volumes than 0.1 g of Ca(OH)₂. The measured sludge volume was 1.5 mL for Mg–Al-layered double hydroxide and 2.5 mL for Ca(OH)₂, a nearly twofold further reduction.  相似文献