Galena Ore Research Articles

Study of Galena Ore Powder Sintering and Its Microstructure

Galena is a natural mineral enriched with lead sulfide (PbS). It typically forms in hydrothermal veins associated with igneous rocks and can also occur as a gangue mineral in other ore deposits. PbS is of special importance for scientific research applications due to the possibility of tuning its semiconductor energy gap using nanotechnology in conjunction with powder metallurgy as an easy, controllable production route. In this paper, almost pure PbS was successfully produced starting from a high ratio of PbS phase galena ore. As-received galena lumps were roughly pulverized and milled to produce four particle size ranges of 38, 63, 125, and 250 µm prior to compaction and sintering in a vacuum (pre-flushed with argon gas). SEM coupled with the EDAX analysis unit was employed to investigate the microstructure and chemical composition of the as-received galena and the subsequent products after sintering. The chemical analysis confirmed the high ratio of PbS compound in the as-received galena and sintered products with approximately 85% Pb and 13% S mass ratio. The sintering process of the galena powder was carried out at different values of temperature, time, and compaction pressure. Additionally, the effect of length to diameter ratio of compacted and sintered samples was investigated. XRD analysis confirmed the existence of the PbS phase in the as-received and sintered samples at 700 °C with approximately 98 wt.%, as well as a new phase that is formed at 800 °C with a lower percentage. The micro-hardness of the as-received and sintered samples was measured and compared with the as-received galena ore. The results showed a significant reduction in the hardness of sintered galena powder compared with the bulk as-received galena by 52%. Furthermore, a relative sintered density of 99.3% for the as-received galena density signifies a novel result using powder metallurgy techniques.

AMALIA, A Matching Algorithm for Lead Isotope Analyses: Formulation and proof of concept at the Roman foundry of Fuente Spitz (Jaén, Spain)

This article presents A Matching Algorithm for Lead Isotope Analyses (AMALIA) that yields analytical coincidences in lead isotope databases, allowing a fast selection of potential candidates for metal provenance. As a proof of concept, potential ore sources for 29 Roman lead artifacts from the archaeological site of Fuente Spitz (Jaén, Spain) are provided. Additionally, a reassessment of legacy, TIMS lead-isotope analyses is conducted by re-analysis of 26 galena samples from nearby mining districts by MC-ICP-MS. The study demonstrates the accuracy and reliability of AMALIA and stresses the need to assess the isotope ratio data obtained without lead isotopic tracers (spikes) by TIMS carefully on a case-to-case basis. At the archaeological level, our study shows that the foundries and smelting sites at Fuente Spitz and Cerro del Plomo processed galena ores from the mining districts of La Carolina and Linares to produce a variety of lead products and lead ingots that have been found at several places thorough Europe, thereby providing tangible evidence of the regional and long-distance commercial circuits that these foundries were supplying.

Facile Production Method of PbS Nanoparticles via Mechanical Milling of Galena Ore

In this research, some physical properties such as the density, specific heat capacity, and micro-hardness of galena ore lumps purchased from the public market were determined. The microscopic study, using the scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), confirmed that the as-received galena ore was mostly lead sulfide (PbS). The XRD pattern of the galena powder also elucidated that all the peaks were assigned to PbS. In addition, the as-received galena was roughly crushed, and fine-milled using a high-vibration milling machine with tungsten carbide rings. Nanoscale particles of about 90 nm were produced in a very short milling time of around 15 min. The obtained nanoscale powder was well investigated in the SEM at low and high magnifications to assess the exact range of particle size. Meanwhile, the SEM was employed to investigate the microstructure of sintered samples, where a part of the milled galena powder was compacted and sintered at 700 °C for 2 h. Again, the result of this investigation proved the formation of PbS with even smaller grain size compared with the grain size of the starting galena ore. A high relative sinter density of approximately 97% for galena powder was achieved by sintering under vacuum.

Narrowing provenance for ancient Greek silver coins using Ag isotopes and Sb contents of potential ores

Variations of 109Ag/107Ag in silver coins and ores are particularly useful in assessing the provenance of silver bullion. Silver isotope variability results from the temperature-dependent thermodynamic fractionation of Ag isotopes among the solutions and minerals participating in ore formation. They differ from lead isotopic variations which result from the decay of uranium and thorium and reflect the geochemical properties and the tectonic age of the possible ore sources. A remarkable property of Ag isotopes is the very narrow range of isotopic variations in silver bullion used for coinage (±1×10−4) with respect to the range of ores (±1×10−3). To test the practical usefulness of the technique, we analyzed the Ag isotopic abundances of 29 ore samples from ancient mining districts in the Aegean with major and minor Ag-bearing mineralizations, and of 34 ancient Greek coins minted from the sixth to late fourth centuries BC. We distinguished two groups among the coins: a dominant population (93% of the samples) with 109Ag/107Ag consistent with literature data (ε109Ag = −1 to +1) and an isotopically lighter population (ε109Ag = −2 to −1) which we show originated from Ag-bearing mineralizations in Lavrion (Attica). We further found that sulfur (also analyzed in this study) and silver isotope compositions in Aegean ores do not correlate, a finding that we confirmed on a selection of Iberian galena samples. This shows that the genetic ore type (whether hypo, meso, or epithermal) and silver productivity are not related. Finally, we undertook chemical analysis of the Aegean ore samples and confirmed that Ag-rich ores are also Sb-rich in both Greece and Iberia.A remarkable outcome of the present Ag isotope studies of galena ores from Iberia and Greece is that silver isotope compositions can exclude, with a high degree of reliability, the majority of mines identified by lead isotope analysis as sources from which coinage silver could plausibly have been extracted and thus significantly narrow down the actual source(s). Silver isotope data on galena ores are thus a useful tool for deciding which Pb isotope data included in ore databases should be included in provenance assessment studies. Contrary to some earlier assessments, subtle silver isotope variations can occasionally help determine ore provenance within a single mining district such as Lavrion.

Recycling REEs from the Waste Products of Silius Mine (SE Sardinia, Italy): A Preliminary Study

The present research represents an approach toward the recycling of extractive waste inspired by circular economy and sustainability that is developed in accordance with Goal 12 of the United Nations 2030 Agenda for Sustainable Development Goals. A new procedure for the recovery of REEs from fluorite–barite–galena ores with calcite gangue from the Silius mine (Sardinia, Italy) is presented. The considered samples are waste materials of Silius mineralization, collected in the old processing plant of Assemini (near Cagliari). In this orebody, REE minerals consist of prevailing synchysite (a REE-bearing fluorocarbonate) and subordinate xenotime-Y (a Y-bearing phosphate). REE fluorocarbonates are extracted using 50% K2CO3 as the leaching solution, at 100 °C. Using a solution (mL)/sample (g) ratio of 25, about 10% of the total REE content of the considered sample is extracted within 1 h. At the laboratory scale, such alkaline leaching of REE from the waste materials allows the recovery of the CO2 produced as K2CO3 from concentrated KOH, in accordance with a circular flow. Further work is ongoing to scale up the process into a pilot plant, to prove that the method developed within this research can be economically feasible, socially suitable, and environmentally respectful.

A novel technology of high-voltage pulse discharge for comminution of galena ore

An innovative technology of high-voltage pulse discharge (HVPD) was proposed to investigate the comminution characteristics of galena ore. The optimal experiment parameters were determined as follows: spark gap spacing of 25 mm, pulse number of 120, and voltage of 25 kV. The mass fraction with size <0.074 mm in ground products was improved by the HVPD. Meanwhile, the relative grindability declined with the increase of the grinding time, which indicated that the superiority of HVPD was weakened. The ground products of HVPD were distributed more homogeneously than those of mechanical crushing. The liberation of breakage products was improved by 24.57% via the HVPD. Moreover, the Brunauer–Emmett–Teller (BET) specific surface area, pore volume, and average pore size were increased via the HVPD. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses suggested that obvious grain-boundary breakage and several stomatal traces were observed in the HVPD products.

The significance of galena Pb model ages and the formation of large Pb-Zn sedimentary deposits

In an attempt to clarify the significance of Pb model ages in Pb-Zn sedimentary deposits, we report high-precision Pb isotopic compositions for 64 galenas and 52 K-feldspars, the former from ores and the latter separated from granites. All samples are from Spain and the French Pyrenees. Lead from galena ores is of unequivocal continental origin. With few exceptions, Pb model ages systematically exceed emplacement ages by up to 400 Ma, a gap which is well outside the uncertainties of ~ 30 Ma assigned to the model. The histogram of the new high-precision Pb isotope data shows prominent peaks of galena Pb model ages at 94 ± 38 Ma and 392 ± 39 Ma. When the data are consolidated with literature data and examined in 3-dimensional Pb isotope space, cluster analysis identifies five groups. The model ages of the peaks occur, in order of decreasing peak intensity, at 395 ± 40 (Middle Devonian), 90 ± 34 Ma (Middle Cretaceous), and 613 ± 42 Ma (Neoproterozoic), with two minor peaks at 185 + 26 Ma (Jurassic) and 313 ± 41 (Upper Carboniferous). To a large extent, the model ages centered around these peaks correspond to distinct localities. The ages of the peaks do not coincide with any of the Betic, Variscan, or Pan-African tectonic events, which are the main tectonic episodes that shaped Iberian geology, but instead match well-known global oceanic anoxic events. It is argued that surges of metals weathered from continental surfaces scorched during anoxic events accumulated and combined in anoxic water masses with unoxidized marine sulfide released by submarine hydrothermal activity to precipitate the primary Pb-Zn stock. Frozen Pb isotope compositions require that galenas from black shales are the source of the final ores. The sulfides were later remobilized by large-scale convective circulation of basinal and hydrothermal fluids. The peaks of K-feldspar Pb model ages are distinct from those of galenas and do not correlate with magmatic emplacement ages. It is suggested that they instead reflect local circulation in Paleozoic sediments surrounding individual plutons. While Pb isotopes can be used as a regional provenance tool, such an approach requires that the data are considered in a fully 3-dimensional space.

Intermediate sulfidation epithermal Pb - Zn (± Ag ± Cu ± In) and low sulfidation Au (± Pb ± Ag ± Zn) mineralization styles in the Gonzalito polymetallic mining district, North Patagonian Massif

The Gonzalito polymetallic mining district is located within the northeast tip of the 600 km-long NE-trending polymetallic belt of the North Patagonian Massif, in Patagonia, Argentina. It comprises Paleozoic igneous-metamorphic rocks of the Mina Gonzalito complex, which are intruded by Middle Triassic trachytic-andesitic dykes of the Monasa Fm. through a complex system of high-angle fractures. Rhyolitic dykes crosscut the pre-Jurassic rocks. Numerous semi-parallel vein-like mineral deposits, whose classification and age have been subject of debate, sharply crosscut the igneous-metamorphic, trachytic-andesitic and rhyolitic units. Mineralization shows a strong structural control through a complex system of semi-parallel NW-N-NE oriented fracture-hosted mineral deposits. Extensional jogs and open dilational fractures allow multiband vein infills, vein-like hydrothermal and fault-tectonic breccias, stockwork veins and veinlets with primary growth open-space and boiling-derived textures, indicating a brittle geological setting that is proper of the epithermal environment. Based on the structural setting, sulfide-gangue-alteration mineral assemblages and textures, sulfide mineral chemistry and whole-rock geochemical analyses, two different styles of hydrothermal deposits can be distinguished: massive-sulfide intermediate sulfidation epithermal Pb – Zn ± Ag ± Cu ± In and disseminated-sulfide low sulfidation Au ± Pb ± Ag ± Zn. The first has a main-stage pyrite – In-rich sphalerite – chalcopyrite – galena ore assemblage in scarce quartz - carbonates gangue. The second shows disseminated pyrite ± sphalerite ± chalcopyrite ± galena with economic grades of Au in abundant quartz – adularia ± fluorite gangue. SHRIMP U–Pb zircon data of rhyolites reveal Early Jurassic ages of 193 ± 2 and 191 ± 2 Ma and, along with their bulk-rock geochemical features, they can be included within the Chon Aike magmatic province, locally known as Marifil volcanic complex. Crosscutting relationships between the Lower Jurassic rhyolites and the epithermal veins in the Gonzalito district, and the presence of Oligocene basalts partially covering the epithermal deposits towards the western area, constrain the mineralization event between the Lower Jurassic and the Oligocene. However, the crosscutting relationships of this district along with the already proven genetic, temporal and spatial links between epithermal ore and fluorite-rich deposits and the Jurassic magmatism-rifting of Patagonia suggest that the studied epithermal deposits might be yielded closer or during the Lower Jurassic.

Formation mechanisms of surface passivating phases and their impact on the kinetics of galena leaching in ferric chloride, ferric perchlorate, and ferric nitrate solutions

Hydrometallurgical leaching of Pb from galena is an environmentally friendly alternative to the traditional pyrometallurgical processing. Leaching produces secondary phases passivating the surface of galena and has a negative impact on the leaching rate and Pb extraction, yet a comprehensive understanding of surface passivation is lacking. Here we studied galena leaching in FeCl3, Fe(ClO4)3, and Fe(NO3)3 solutions, using the ex situ leaching-quenching-characterization method complemented by in situ synchrotron powder X-ray diffraction. We examined the effect of salt concentration (0.42 and 0.84 M), temperature (35–90 °C), time (up to 1440 h), solid-weight-to-fluid-volume ratio (0.5–50 g·L−1), and particle size (up to 355 μm) on the mechanisms and kinetics of galena leaching. The results show that leaching in FeCl3 was least effective due to precipitation of a cotunnite (PbCl2) layer on galena surface, and a layer of elemental sulfur on cotunnite, forming a core/mantle/shell structure (i.e., galena/cotunnite/sulfur), which restricted Pb extraction to less than 9%. Sulfur encapsulated PbCl2 and limited its dissolution even when the bulk solution remained undersaturated with respect to PbCl2. Leaching in Fe(ClO4)3 and Fe(NO3)3 solutions was more effective than in FeCl3, achieving 100% Pb extraction. Leaching in Fe(NO3)3 was fastest among the three iron salts. Porous elemental sulfur was the only secondary phase formed using Fe(NO3)3 and Fe(ClO4)3 and the leaching reactions follow the interface-coupled dissolution-reprecipitation mineral replacement mechanism. The effect of passivation was observed when the elemental sulfur layer reached ~20 μm thick. The activation energies calculated by the modified “time-to-a-given-fraction” method were 5.4–67.2 kJ·mol−1 for leaching with Fe(ClO4)3 and 11.4–56.8 kJ·mol−1 with Fe(NO3)3, indicating that leaching was controlled by surface reactions and phase boundary diffusion. This study provides new insights into the mechanisms controlling surface passivation due to the mineralogical and textural compositions of the passivating layers and the resulting leaching kinetics. It provides scientific bases for the development of heap and in situ leaching protocols for Pb extraction from galena ores.

Silver-rich sulfide mineralization in the northwestern termination of the Western Cycladic Detachment System, at Agios Ioannis Kynigos, Hymittos Mt. (Attica, Greece): A mineralogical, geochemical and stable isotope study

Identification of silver-rich sulfide mineralization in the abandoned mines at northern Hymittos Mt (central Attica, Greece) district has made this region important due to its structural relation to the world-class Lavrion mining district (25 km SE of Hymittos Mt.). At Agios Ioannis Kynigos mine veins of oxidized Fe-Pb-Zn-Ag ore are hosted in mylonitic marbles that were predominantly affected by brittle-ductile deformation associated with the West Cycladic Detachment System. The major sulfides are galena and arsenian pyrite which develop as open-space filling (fractures and vugs), disseminations and veinlets. Galena contains abundant inclusions of Pb-As-Sb-Cu-Ag sulfosalts (tetrahedrite group minerals, bournonite, jalpaite). An unusual silver-rich galena ore i.e from 192 to 1500 ppm Ag, is recorded from the present study, with Ag hosted mainly in Ag-tetrahedrite, acanthite and jalpaite. Compositionally pyrite shows As enrichment and the highest As concentration i.e. up to 3.9 wt% is found in the core of the oscillatory zoned pyrites.Values of δ34S of galena are isotopically light (−11.2 to −12.2‰), which suggests a sedimentary component to the ore fluid, that is likely derived from leaching of the meta-sedimentary (calc-mica schists) wall rocks. Carbon and oxygen isotope compositions of ore-stage carbonates show values i.e δ13CV-PDB (‰) = −8.2 to −11.7‰ and δ18O = 24.3 to 25.9‰ and for the non-mineralized carbonates δ13CV-PDB (‰) = +0.33 to 2.52‰ and δ18O = 20.8 to 26.1‰. The C and O isotopic composition of the carbonate wall rock distal to the orebody is typical of marine carbonates, whereas hydrothermal carbonates (brown calcite and dolomite) are dominated by an external, light C source. The lowest δ13CV-PDB values are recorded from cerussite and correspond to the low temperature supergene alteration from meteoric waters. The homogenized values of δ18O in the mineralized carbonates indicate interaction of fluid with host carbonates under a low fluid/rock ratio. The Pb-Zn-Ag mineralization at Agios Ioannis Kynigos bears many similarities with the low-temperature carbonate replacement-style mineralization in Kamariza, Lavrion area. Ore deposition in the northern Hymittos detachment fault is focused in the structurally upper parts of the detachment fault where circulation of meteoric fluids is dominant in the hydrothermal system.

The earliest lead ore processing in Europe. 5th millennium BC finds from Pietrele on the Lower Danube.

Eleven biconical vessels from the Copper Age sites Pietrele and Blejeşti (Romania) have been investigated using p-XRF. In most cases, traces of lead could be measured on their surfaces. Samples of slag-like material from two vessels and the clay of one vessel were investigated using laboratory methods, namely SEM, XRD, LIA and optical microscopy. The vessels were obviously used as a kind of crucible in which slag-like remains and galena ore were detected. It still remains unclear as to what final product was gained by smelting galena in this way. The amount of these such vessels in the Pietrele settlement, their appearance as grave goods in Pietrele and Vărăști (Romania), and their supposed occurrence in a number of other Copper Age settlements in Romania and Bulgaria show the significance of this phenomenon. It must have been a widespread and more or less well known practice, an important part of cultural habit during a particular period in the Lower Danube region and likely even farther afield. For the first time, extensive experimentation with lead ore can be shown in a clear chronological horizon, ca. 4400–4300 BCE in southeastern Europe.

Adopting Geo-electric Approach in Mineral Characterization of Iyamitet Settlement

The research work epicenters on the delineation of Barite-Galena sediments within Iyamitet settlement of Obrubra region, Present work has become necessary owing to the growing need for the Nigeria and indeed world economy to be funded from proceeds of mineral ores as an alternative source of regional and global revenues. The ore garners some global economic value and importance. In delineating the region which habours the mineral ore, geo-electricity was introduced into the subsurface by employing a pair of current electrodes while the voltage is measured by inserting another pair of potential electrodes. Shlumberger array and Vertical Electrical Sounding (VES) techniques were adopted to measure apparent ground resistivity of the subsurface under investigation. Eighteen Vertical Electrical Sounding Curves, five geo-sections, five Isoresistivity and four Isopach maps were generated respectively. Since mineral-ores (Barite and Galena) are located within the host rocks, all 18 VES results represented in 18 tables show varied depths to these ores--and the rocks which harbours them.. The Iso-resistivity map with red patches bearing resistivities over 1000 Ωm demonstrates potential for Barite which coincide with varying depth of (10-15) m as revealed by the coring and borehole information. The Iso-pach map with the lightest patch represents highest altitude of the area under investigation. The dark blue patch represents the lowest portion of the region under investigation. Though results do not show the presence of Galena ore material, it is possible that multiple ore intrusions could have compromised the resistivity reading of Galena; Galena presence could be uncovered by combining outcome of results from multiple geophysical techniques

Lead isotope ratios of Pueblo I lead-glazed ceramics and galena from Colorado and Pueblo II galena from Chaco Canyon, New Mexico

The earliest glazes in the American Southwest were produced during the early Pueblo I period (ca. 750–850 CE) in the Upper San Juan region of Colorado. Petrographic and isotopic techniques were used to study these early glaze-painted pots and to address questions of production locales and procurement strategies. The results of this study identify the preferred source of lead utilized by the potters as originating in the Galena District, in the Lake City and Uncompahgre calderas, in the western San Juan Mountains of Colorado. Glaze paints from three locations in the Mesa Verde region were produced with galena from these deposits, indicating that even when potters were choosing to use different clays and temper, the source of lead remained the same. Galena ores from these deposits have additionally been identified at other locations, including Dillard, a Basketmaker III site in southwest Colorado and in Pueblo II contexts in Pueblo Bonito, Chaco Canyon in New Mexico, indicating continuity in knowledge of distant lead sources.

Selective depression mechanism of ferric chromium lignin sulfonate for chalcopyrite–galena flotation separation

Selective recovery of chalcopyrite–galena ore by flotation remains a challenging issue. The development of highly efficient, low-cost, and environmentally friendly depressants for this flotation is necessary because most of available reagents (e.g., K2Cr2O4) are expensive and adversely affect the environment. In this study, ferric chromium lignin sulfonate (FCLS), which is a waste-product from the paper and pulp industry, was introduced as a selective depressant for galena with butyl xanthate (BX) as a collector. Results show that the residue recovery of Pb in Cu concentrate was substantially reduced to 4.73% using FCLS compared with 10.71% using the common depressant K2Cr2O4. The underlying mechanisms were revealed using zeta-potential measurements and X-ray photoelectron spectroscopy (XPS). Zeta-potential measurements revealed that FCLS was more efficiently absorbed onto galena than onto chalcopyrite. XPS measurements further suggested that FCLS enhanced the surface oxidation of galena but prevented that of chalcopyrite. Thus, FCLS could be a potential candidate as a depressant for chalcopyrite–galena flotation because of its low cost and its lack of detrimental effects on the environment.

Record of Anthropocene pollution sources of lead in disturbed peatlands from Southern Poland

The importance of human impacts on Earth has led to the proposal of a new geologic epoch called the Anthropocene. However markers, recognizable in all records, are required to define this period. Here we combine elemental geochemistry with stable lead (Pb) isotopes and mineralogical analyses to decipher the sources of lead in two exploited ombrotrophic peat bogs (Puścizna Mała and Puścizna Krauszowska) from Southern Poland. The most disturbed parts of the cores, distinguished using bulk density and age–depth models (22–45 cm in PM and 22–46 cm in PK), were excluded from the interpretation. The two studied cores record ca. 2000 years of variations in lead accumulation rates and isotopic compositions. In the lowest part of the cores (2nd to 4th century AD for Puścizna Mała and 2nd century BC to 2nd century AD for Puścizna Krauszowska), the 206Pb/207Pb ratios (1.188) are consistent with natural supplies from the erosion of the nearby Tatra Mountains. From the 9th to the 19th century AD, 206Pb/207Pb ratios (1.176–1.179) are similar to the signatures obtained from Polish galena ores. The highest Pb accumulation rates are found around 1950 AD and reflect the primary influence of bituminous coal combustion together with the secondary influence of leaded gasoline. This result agrees with the occurrence and abundance of spheroidal aluminosilicates, an unambiguous marker of human industrial activity and coal burning as well as with the acceleration of Zn, Cd and Fe accumulation rate. Our results provide evidence that similar geochemical patterns exist in both analysed cores despite differences in the history of peatland exploitation. Therefore, given that extra care is taken to identify the disturbed peat layers, exploited peatlands can be used to record past changes in lead isotopic signature during the Anthropocene.

Hydrometallurgical Processing of a Nigerian Galena Ore in Nitric Acid: Characterization and Dissolution Kinetics

The physico-chemical characterization and dissolution kinetics study of a Nigerian galena ore in nitric acid has been undertaken. The effects of acid concentration, temperature, particle size, stirring speed and solid/liquid ratio on the leaching of galena were investigated. The X-ray fluorescence data showed that the galena ore used in the study exists mainly as PbS. Lead (Pb) was detected as the major metal for galena with metals such as Na, Ca, Fe, Zn, Al and Mg occurring as minor elements. The XRD analysis also confirmed the originality of the galena ore as it revealed that galena exists mainly as lead sulphide (PbS). The Fourier transform infrared (FTIR) analysis also supported the XRF and XRD analysis by revealing the presence of sulphur in the ore. The scanning electron micrograph (SEM) analysis revealed a high level of crystallinity of the ore. Results of the leaching studies showed that galena dissolution in nitric acid (HNO3) increases with increasing concentration of nitric acid, temperature and stirring rate, and decreases with increasing particle diameter and solid/liquid ratio. In 10 M HNO3 at a temperature of 90°C using 75 μm particle diameter with solid/liquid ratio of 20 g/L and stirring speed of 540 rpm, about 84.5% of galena was dissolved in 150 minutes. The values of activation energy, order of reaction and Arrhenius constant calculated at the conditions above for galena were 27.01 KJ/mol, 0.93, 26.71 s-1 respectively. The mechanism of dissolution of galena was established to follow the shrinking core model for the diffusion controlled mechanism, with surface chemical reaction as the rate controlling step for the leaching process. Finally, the XRD analysis of the post-leaching residue revealed the presence of gahnite and anglesite.

Modeling and Optimization of Galena Dissolution in Hydrochloric Acid: Comparison of Central Composite Design and Artificial Neural Network

Response surface methodology (RSM) and Artificial neural network (ANN) were used for the simulation and optimization of galena dissolution in hydrochloric acid. The galena ore was characterized for structure elucidation using FTIR, SEM and X-ray diffraction spectroscopic techniques and the results indicate that the galena ore exists mainly as lead sulphide (PbS). A feed-forward neural network model with Leverberg-Marquardt back propagating training algorithm was used to predict the response (lead yield). The leaching temperature, acid concentration, solid/liquid ratio, stirring rate and leaching time were defined as input variables, while the percentage yield of lead was labelled as output variable. The multilayer perceptron with architecture of 5-9-1 provided the best performance. All the process variables were found to have significant impact on the response with p-values of 2 of 0.991 and 1.00, respectively. A non-dominated optimal response of 85.25% yield of lead at 343.96 K leaching temperature, 3.11 M hydrochloric acid concentration, 0.021 g/ml solid/liquid ratio, 362.27 rpm stirring speed and 87.37 min leaching time was established as a viable route for reduced material and operating cost using RSM.

Relationship between Metal Concentrations in Galena Ore and Soil Samples from Galena-rich Farmlands

Relationship between Metal Concentrations in Galena Ore and Soil Samples from Galena-rich Farmlands

Relationship between Metal Concentrations in Galena Ore and Soil Samples from Galena-rich Farmlands

Relationship between Metal Concentrations in Galena Ore and Soil Samples from Galena-rich Farmlands

Lead isotopes and elemental composition of Roman fistulae plumbeae aquariae from Conimbriga (Portugal) using Quadrupole ICP-MS

Lead metal and lead artefacts were widespread over the Roman world, as consequence of its large use in public buildings, namely as plumbing on hydraulic systems of Roman cities and villae. The determination of Pb isotope ratios combined with minor and trace element contents of such lead artefacts may constitute a powerful tool for provenance studies as well as in the assessment of trade routes during the Roman period. In the present work forty four fistulae plumbeae from the hydraulic systems installed at Conimbriga were analysed using a quadrupole based ICP-MS. The overall results demonstrate the suitableness of this well-established and economic analytical technique involving simple sample preparation and high throughput. Pb isotopic patterns present high scattered distributions which suggest different provenances of the raw material. Ag, As, Bi, Cu, Ni, Sb, and Sn contents were determined in an attempt to identify the type of raw materials and the metallurgical process used to obtain the lead metal. Sn content points to the frequent use of recycled lead. The Pb isotope ratios of samples of lead pipes made with metal probably not recycled indicate the use of raw materials (galena ores) from Sierra Morena mines or desilvered litharge resulting from silver cupellation probably using argentiferous jarosite ores from the Iberian Pyrite Belt (Rio Tinto mines).