Smelting Residues Research Articles

Upcycling of Pb from lead smelting residues to lead halide perovskite for piezocatalytic hydrogen production

Organic lead halide perovskite is a promising piezocatalyst for piezocatalytic H2 production, meanwhile, large amount of unutilized lead resources in lead smelting residues have caused ecological security and resource waste problems. Here, we report an efficient Pb upcycling approach to recover lead halides from lead smelting residues to create lead halide perovskites (r-FAPbBr3-xIx), distinguished by the remarkable piezoelectric properties, for piezocatalytic H2 evolution. Zinc impurities, concurrently from these residues, found their utilization in the partial substitution of Pb2+ within the halide octahedra of r-FAPbBr3-xIx. The intervention of zinc enhancing desorption of hydrogen from r-FAPbBr3-xIx and culminating in a pronounced H2 yield as 157.80 μmol·g−1·h−1. Notably, the used r-FAPbBr3-xIx that lost its functional prowess could be regenerated and exhibited a piezocatalytic capacity similar to its initial state, perpetuating a sustainable cycle of utility. This pioneering route to Pb upcycling furnishes an alternative avenue for the preparation and utilization of lead-based perovskites.

Clean hydrometallurgical route for highly efficient decontamination and recycling of multiple heavy metals from hazardous Pb smelting residues: Multi-objective leaching optimization, adsorption, and risk assessment

Huge amounts of Pb smelting residues were generally stored in landfills or unprocessed worldwide, and thus demand novel strategies to implement clean production. In this paper, we proposed a clean, efficient and economical hydrometallurgical route to recycle the toxic heavy metals including Zn, Pb and Cd from the Pb residue by the biodegradable low-molecular-weight organic acids (LMWOAs) and the cation exchange resin (CER, 001 × 7). The multi-objective leaching process of the three metals was optimized by combining saturated D-optimal design with desirability function simultaneously. The recovery rates of Zn, Pb and Cd were 88.72–96.36, 65.40–85.31 and 92.63–97.10% at the optimal conditions of 0.73–1.00 mol L−1 agent concentrations, 2.0–3.3 solution pH values and 71–120 min durations, respectively. Adsorption with CER from the resulting leachates recycled over 91.48% of the metal ions. The treated residues were almost completely decontaminated. Therefore, this research filled the gap of clean production route of hydrometallurgical recycling for metal resources from the low-grade slag.

Long-term leachability of Sb in smelting residue stabilized by reactive magnesia under accelerated exposure to strong acid rain

This study investigated the long-term leachability of antimony (Sb) in a smelting residue (39519 mg/kg) solidified/stabilized by reactive magnesia (MgO). Different dosages of MgO (0% as control, 2%, 5%, and 10% on a dry basis) were compared, and the long-term performance was evaluated by an accelerated exposure test consist of 20 consecutive leaching steps with simulated strong acid rain (SAR, HNO3: H2SO4 = 1:2, pH = 3.20) as the extractant. Notably, the MgO treatments efficiently reduced the Sb leachability. Compared to the original slag (8.3 mg/L), the leaching concentrations based on a Chinese standard HJ/T299-2007 were reduced by 58%, 79%, 85%, and 86% at MgO dosages of 0%, 2%, 5%, and 10%, respectively. Because the studied slag was rich in oxides like SiO2, CaO, and MgO, the hydration reactions probably happened during the aging processes with oxic water. It was inferred that the formed hydration products have a self-solidification/stabilization function to suppress the Sb leaching from the solid phase. The mineralogical characterization results proved that the hydrated Mg(OH)2 played an essential role in the decrease of Sb leachability. Besides, the MgO addition promoted the hydration of this smelting slag and formed new hydrate gels that immobilize Sb in this slag. Our results confirmed that MgO-amended slags were resistant to continuous SAR corrosion. Compared to the control, the dosage of 5% MgO could effectively reduce the cumulatively released Sb by 57%, with only 0.46% of total Sb could be leached. The decomposition of Mg(OH)2 and hydrate gels determined the re-release of Sb in a long term. Our work has demonstrated that reactive MgO amendment could be potentially selected as an effective strategy for the treatment of Sb-containing smelting residues in field conditions.

Separation and recovery of arsenic and alkali products during the treatment of antimony smelting residues

For the comprehensive utilization of antimony smelting arsenic-alkali residue, there are some problems such as the incomplete separation and low recoveries of arsenic and alkali, and the formation of arsenic-alkali mixed salts with secondary pollution. In order to solve these problems, the leaching solution of arsenic-alkali residue (arsenic-alkali solution) was used as a raw material in this study, and a novel process of twice alkali recovery with CO2, deep alkali removal with H2SO4, As(V) reduction with SO2 and evaporation concentration to recover arsenic was proposed to dispose of the arsenic-alkali solution. The total recovery of alkali was 87.8% by twice alkali recovery from the arsenic-alkali solution. After washing and thermal decomposition of crude NaHCO3, the obtained Na2CO3 product can be used as the reagent of arsenic removal in the refining process of crude antimony. In the process of deep alkali removal, compared with the direct treatment, the consumption of H2SO4 after twice alkali recovery was markedly reduced from the arsenic-alkali solution, and also no mirabilite was precipitated. The total recovery of arsenic was 80.6% in the process of arsenic recovery, and the purity of As2O3 in arsenic trioxide product reached 95.2% after washing, which meets the third grade standard of arsenic trioxide (GB 26721–2011). This process realizes the efficient separation and recovery of arsenic and alkali from the arsenic-alkali solution, and also no arsenic-alkali mixed salts are produced.

Molecular Dynamics Simulation on Microstructure and Physicochemical Properties of FexO-SiO2-CaO-MgO-“NiO” Slag in Nickel Matte Smelting under Modulating CaO Content

To improve the conditions of extracting iron from nickel smelting residues, the composition modulating from FexO-SiO2-CaO-MgO-“NiO” slag source for matte smelting using high MgO nickel sulfide concentrate was carried out. Based on the molecular dynamics simulation and experimental characterization, the effect of CaO content in nickel slags on the physicochemical properties, the microstructure evolution, and the feasibility of subsequent iron extraction were analyzed. The results showed that, for nickel smelting slag with 9 wt.% MgO, 13–15 wt.% CaO and Fe/SiO2 ratio of 1.2, the melting temperature of nickel slag was lower than 1200 °C, and the viscosity was lower than 0.22 Pa·s at 1350 °C. The electric conductivity was similar to that of the industrial slag, and the interfacial tension between slag and matte was relatively large, which ensured a good separating characteristic. It not only met the requirements for the slag performances in the existing flash smelting process but also improved conditions for the subsequent iron extraction. Additionally, it could be adapted to the current situation where an increasing MgO content exists in the nickel sulfide concentrate.

Selective leaching of Pb, Cu, Ni and Zn from secondary lead smelting residues

Several HNO3-based leaching approaches were tested and optimized to selectively recover Pb and other minor metals (Cu, Ni, Zn) from secondary lead smelter residues (i.e., slag and matte). Firstly, the leaching behaviors of Pb and the matrix element Fe were studied at atmospheric pressure in the temperature range 25—70°C. These elements were present in both materials studied as sulfide and oxide phases. For the sulfur-rich matte residue, the Pb leaching increased from 63% to 69% upon increasing the HNO3 concentration from 0.2M to 0.5M. However, by adding Fe(III) as an oxidation agent, Pb leaching from the matte amounted to 90% at 25°C. At a higher temperature, Pb leaching was reduced due to PbSO4 precipitation. In this process, Cu, Zn and Ni leaching was insignificant. For the slag residue, HNO3 could not leach Pb (0.03% Pb leached), while Fe leaching was 19.8% due to a galvanic effect. However, Pb leaching of the slag was 82% in the presence of additional Fe(III). Secondly, to enhance leaching of the other base metals (Cu, Zn and Ni) from the matte, roasting followed by water leaching and (microwave assisted or autoclave) pressurized leaching in 0.5M HNO3 were applied. During roasting, the FeS phase converted to Fe2O3 above 500°C, and PbS and Pb phases were transformed into insoluble PbSO4 above 400°C. Cu, Ni and Zn leaching was drastically enhanced by a roasting step at 600°C followed by leaching with 0.5M HNO3 at 50°C, or by pressurized HNO3 leaching above 130°C, whereby Pb leaching almost ceased due to PbSO4 precipitation. During the roasting above 600°C, or microwave assisted extraction (MAE) at 160°C for 15min, FeS was completely converted to iron oxides that can be used as raw material for pig iron production. Based on the results, the methods investigated can be combined as process steps of two possible routes for the selective recovery of valuable metals and the production of a clean source of Fe oxides from the secondary lead smelting residues studied.

Separation and recovery of ammonium sulfate and sodium sulfate from vanadium smelting residues by medium temperature calcinations

Separation and recovery of ammonium sulfate and sodium sulfate from vanadium smelting residues by medium temperature calcinations

Weathering of Sb-rich mining and smelting residues: Insight in solid speciation and soil bacteria toxicity

Tailings and slag residues from the most important antimony mine of the French Massif Central were analysed for their mineralogical and chemical contents by conventional X-ray powder diffraction and synchrotron-based X-ray microdiffraction (μ-XRD). Results show that ∼2000 metric tons of Sb are still present at the abandoned mining site. Mean concentrations of Sb in slags and tailings are 1700 and 5000mgkg−1, respectively. In addition, smaller quantities of As were also measured (∼800mgkg−1 in tailings). Toxicity tests of As and Sb indicate that the growth of bacteria is severely affected at these concentrations. In particular, Sb was observed to cause negative effects for several types of bacteria. Almost all primary minerals carrying trivalent Sb disappeared during weathering at the expense of phases in which Sb5+ is the most abundant form. Instead of sulphides, Sb-bearing Fe hydroxides (goethite and lepidocrocite) are now present in the residues together with Sb-bearing jarosite and Sb(-Fe) oxides and hydroxides such as tripuhyite, senarmontite, romeite, cervantite, and valentinite. Water analyses of the main local stream indicate little remobilization of Sb downstream the site and despite the acidic pH of the surface tailings, pH values show neutral or near-neutral values on all locations of the site.

LIXIVIAÇÃO DE CHUMBO E ZINCO EM SOLO TRATADO COM RESÍDUOS DE SIDERURGIA

In order to evaluate the dynamics of Zn and Pb in the soil, a greenhouse experiment was set up in pots filled with soil samples (Typic Hapludox) treated with increasing doses of iron smelting residues. It was set under a completely randomized design, in a 3×5 factorial scheme, with three replications, combining three iron smelting residues (mill scale, filter press mud, and phosphate mud), with five doses for each residue (0 t ha-1, 1 t ha-1, 2 t ha-1, 4 t ha-1, and 8 t ha-1). Elephant grass was cultivated during 120 days, followed by common beans, for 75 days. In that period, contents of Zn and Pb were determined in the leachate. No Pb was found in the leachate, but Zn proved to be quite mobile in this soil. In soils treated with mill scale and filter press mud, no risk of groundwater contamination was observed, however, the 8 t ha-1 phosphate mud rate increased Zn contents in the leachate above the maximum allowed by environmental regulations. This fact limits the use of such residue for agricultural purposes. The other two residues should be evaluated in field-scale tests aiming their agricultural use. KEY-WORDS: Industrial residue; heavy metal; mill scale; filter press mud; phosphate mud.

Lixiviação de chumbo e zinco em solo tratado com resíduos de siderurgia

Objetivou-se, com este estudo, avaliar a mobilidade de Pb e Zn no solo. Instalou-se um experimento, em casa-de-vegetação, em vasos preenchidos com amostras de Latossolo Vermelho-Amarelo, submetidas a doses de resíduos siderúrgicos, sob delineamento inteiramente casualizado, em esquema fatorial 3×5, com três repetições, combinando-se três resíduos siderúrgicos (carepa de aciaria, lama de filtro-prensa e lama de fosfato), com cinco doses de cada resíduo (0 t ha-1, 1 t ha-1, 2 t ha-1, 4 t ha-1 e 8 t ha-1). Cultivou-se capim-elefante, por 120 dias, e, posteriormente, realizou-se o cultivo de feijão, durante 75 dias. Neste período, avaliaram-se as concentrações de Pb e Zn no lixiviado. Não houve lixiviação de Pb, porém, o Zn apresentou bastante mobilidade na coluna de solo. Em solo adubado com carepa de aciaria e lama de filtro-prensa, não foram observados riscos de contaminação do lençol freático por Zn e Pb, entretanto, a dose de 8 t ha-1 de lama de fosfato elevou os teores de Zn no lixiviado acima do máximo permitido pela legislação. Tal fato limita o uso deste último resíduo em doses altas. Os demais resíduos (carepa de aciaria e lama de filtro-prensa) devem ser testados em experimentos de campo, visando à sua possível utilização agrícola.

Treatment of smelting residue for arsenic removal and recovery of copper using pyro–hydrometallurgical process

During pyro-metallurgical processing of non-ferrous metals, smelting residues such as smelter slag, flue gas, containing value metals and also harmful substances are inevitably generated as secondary product. For reduction of environmental loading and recovery of the value metals, such materials demand proper treatment options. In this research, some experimental steps were investigated to remove high arsenic (As: 19.5 wt%) and recover copper (Cu: 3.1 wt%) contained in such smelting residues. In the first-stage arsenic and other volatile materials were removed by pyro-metallurgical treatment and in the second-stage the treated residue from pyro-processing was treated in hydrometallurgical processing involving a two-stage leaching operation in H 2SO 4 solution to dissolve the metals followed by solvent extraction using LIX-84I as extractant to recover dissolved Cu in final leached solution. The results showed that over 90% of arsenic in smelting residue was removed by volatilization and recovered as As 2O 3 while copper content increased to 4.2 wt%. In the two-stage leaching process, first up to 90% of arsenic was selectively dissolved in 0.25 mol/L H 2SO 4 solution and second, the solids were further leached in 1.0 mol/L H 2SO 4 solution giving 85% of copper dissolution. Over 90% of copper dissolved into solution was recovered by solvent extraction. Finally over 99% of arsenic dissolved in the first-stage leach solution was co-precipitated with iron dissolved in second-stage leach solution after copper recovery.

Pyrometallurgical relics of Pb–Cu–Fe deposits in south-eastern Germany: An exploration tool and a record of mining history

Pyrometallurgical relics from smelting of iron as well as base metal ores are mineralogically and chemically investigated and dated using the radiocarbon method and optically stimulated luminescence. This study addresses the question whether these pyrometallurgical remains may be used as an exploration tool enabling geologists to discriminate between false and true gossans. Moreover, these investigations make a historical contribution and demonstrate how mining and smelting activities spread across NE Bavaria, Germany. Iron minerals in slags may be used to interpret the physicochemical conditions during which these artifacts formed, while Ca–Mg–Fe silicates provide additional information serving as a rough indicator for stratabound ore deposits. Multicolored glassy smelting residues and secondary minerals staining slags may be taken as an indication of the existence of pyrite-bearing Cu ore deposits. Slags originating from false gossans are enriched in P and Mn, with base metal contents not exceeding crustal background values. True gossans evolving from SEDEX Fe deposits are rich in Fe and Mn. Vein-type siderite deposits create slags rich in Pb, Cu, Zn and Sn. Around 400 BC, Celtic miners headed N following the Regensburg Embayment where soft iron ores were easily accessible. From 700 to 1000 AD they entered the densely forested NE Bavarian Basement for firewood to run the kiln. Between 900 AD and 1630 AD siderite veins and SEDEX Fe deposits were exploited in NE Bavaria. It was not until the 17th century that stratabound sulphidic ores were discovered in this region.

Mineralogical and chemical distribution patterns of placers and ferricretes in Quaternary sediments in SE Germany: The impact of nature and man on the unroofing of pegmatites

Placer deposits mark the ultimate stage of mineral separation in clastic sediments by physical processes in an aquatic regime, whereas duricrusts are an example of extreme element separation by chemical processes in continental environments of deposition. In Quaternary sediments in SE Germany such contrasting types of sediments formed on the NE Bavarian Basement which is underlain by metamorphic and pegmatitic rocks reflecting intense primary element differentiation by themselves. The placer deposits were subdivided into trap and bed placers. Together with three types of encrustation they were put into a scheme illustrating six stages of land formation. The first-mentioned group of placer deposits formed from the Late Cretaceous to the Late Tertiary on a vast peneplain under subtropical conditions (stages I–II). Towards the Quaternary its more acidic meteoric fluids turned alkaline and linear erosion gradually replaced peneplanation as the main process of shaping the landscape (stage III). Evidence for these types of alluvial–fluvial Ti and Sn heavy mineral accumulations and the subtropical climatic conditions can only be found in the major placer mineral aggregates nigrine and cassiterite which preserved a great variety of marker minerals in fractures and vugs. Duricrust I consist of aluminum–phosphate (APS)-bearing phoscretes. Bed placer deposition started off with colluvial to alluvial placers passing eventually into fluvial placers (stages IV–V). Type II duricrusts evolved under humid temperate conditions in the aftermaths of the glacial period. Per-descensum fluids provoked the precipitation of these phosphate-bearing ferricretes. The clastic sediments were reworked in a low-sinuosity fluvial drainage system during stage VI. In addition to the ferricretes mentioned above another type of ferrous encrustations was added to the depositional system by man in form of fayalite-bearing slags from blast furnaces. These smelting artifacts were dumped on the floodplain of the modern river system and kilns which they derived from, were fed with phosphorous iron from duricrusts of type II. Age data for the latest stages of placer formation have been obtained from radio-carbon dating of drift wood and luminescence analyses of quartz and feldspar in placer deposits. These data reveal that morphological processes sparking placer deposition have obviously been influenced by the intensive clearing of settlers in the “Oberpfälzer Wald” (= Forest of Upper Palatinate). The results of the present study may be of assistance to geomorphologists dealing with continental placer deposits (Sn, Ti, Ce, Zr) and chemical sediments (ferricretes, phoscretes) which developed in-situ on ancient and modern peneplains. This is true for geomorphologists in academia and consulting companies alike. Archaeometallurgists may benefit from these results as they were investigating smelting residues scattered within alluvial and fluvial deposits of Quaternary age. Commonly they focus their attention on waste disposals and smelting sites and to a lesser extent on reworked smelting residues in drainage systems. The target group number one is among exploration geologists who are in search of continental placer deposits and want to know more about the clastic dispersion haloes around phosphate- and oxide-bearing pegmatites. Alluvial to fluvial placer deposits containing stable and ultrastable heavy minerals may well be preserved as to their mineralogical composition and chemical patterns even through long-lasting periods of shaping the landscape. These mineralogical and chemical patterns can be used to reconstruct the original morphology of a pegmatitic body which today is present only as “pegmatite ruin”.

Copper Production from Polymetallic Sulphide Ores in the Northeastern Balkan Eneolithic Culture

There is a general view in the archaeological literature that Eneolithic metallurgy in general, and that of the brilliant Eneolithic cultures in the Balkans in particular, was based solely on the smelting of oxide ores. The beginning of sulphide ore processing is usually attributed to the Bronze Age. To test this view a survey of Eneolithic metal and crucibles with smelting residues from the Gumelnitsa and Varna Cultures of Bulgaria was made. These cultures can be dated from the second half of the 5th to the beginning of the 4th millennium bc (cal.).A group of 30 finds with a high content of copper and iron sulphides was the subject of a detailed study using metallography and X-ray microanalysis. The objects included ornaments and small tools from settlements at Dolnoslav, Hotnica, Karanovo, and Ruse, and from the Durankulak cemetery. The sulphide content varied from 0·45 to 5% by volume and the copper plus iron to sulphur ratio for these inclusions was found to be 5:3; this figure is similar to that for “bornite matte” from modern sulphide smelting. The use of sulphides as part of the initial charge can also be confirmed by the presence of lead sulphides and wüstite. It was possible to determine the nature of the process by analysis of the solid layers of residue on the walls of the crucibles found at Dolnoslav and Chatalka (Gumelnitsa Culture). According to the mineralogical, petrological, metallographic and microprobe analyses the layers contain chalcocite and malachite, together with zinc and lead sulphide inclusions. In several places fayalitic slag inclusions were found with copper prills surrounded by chalcocite. These residues should be considered as the products of polymetallic sulphide ore smelting, possibly mixed with malachite. The ore was roasted and then smelted in reducing conditions at 1100 to 1200°C. It is also possible that Eneolithic metallurgists used a single stage process for copper production, consisting of the simultaneous burning of sulphides, ignition and reduction of oxides.

Treatment of metal‐contaminated water using bacterial sulfate reduction: Results from pilot‐scale reactors

Simple anaerobic reactors were installed to treat metal-contaminated water in an underground coal mine and at a smelting residues dump in Pennsylvania. The reactors consisted of barrels and tanks filled with spent mushroom compost, within which bacterial sulfate reduction became established. Concentrations of Al, Cd, Fe, Mn, Ni, and Zn were typically lowered by over 95% as contaminated water flowed through the reactors. Cadmium, Fe, Ni, and some Zn were retained as insoluble metal sulfides following their reaction with bacterially generated H(2)S. Aluminum, Mn, and some Zn hydrolyzed and were retained as insoluble hydroxides or carbonates. Reactor effluents were typically circumneutral in pH and contained net alkalinity. The principal sources of alkalinity in the reactors were bacterial sulfate reduction and limestone dissolution. This article examines the chemistry of the reactor systems and the opportunities for enhancing their metal-retaining and alkalinity-generating potential.

Treatment of Metal-Contaminated Water Using Bacterial Sulfate Reduction: Results from Pilot-Scale Reactors

Simple anaerobic reactors were installed to treat metal-contaminated water in an underground coal mine and at a smelting residues dump in Pennsylvania. The reactors consisted of barrels and tanks filled with spent mushroom compost, within which bacterial sulfate reduction became established. Concentrations of Al, Cd, Fe, Mn, Ni, and Zn were typically lowered by over 95% as contaminated water flowed through the reactors. Cadmium, Fe, Ni, and some Zn were retained as insoluble metal sulfides following their reaction with bacterially generated H2S. Aluminum, Mn, and some Zn hydrolyzed and were retained as insoluble hydroxides or carbonates. Reactor effluents were typically circumneutral in pH and contained net alkalinity. The principal sources of alkalinity in the reactors were bacterial sulfate reduction and limestone dissolution. This article examines the chemistry of the reactor systems and the opportunities for enhancing their metal-retaining and alkalinity-generating potential. © 1992 John Wiley & Sons, Inc.