Smelter Dust Research Articles

Extraction of lead from sulfate cakes of copper smelter dust leaching

Extraction of lead from sulfate cakes of copper smelter dust leaching

Novel Strategy for Efficient Recovery of CuO-Based Multiple-Metals from Copper Smelter Dust toward CO2 Electrocatalytic Reduction.

Copper smelter dust, a typical hazardous waste that is abundant in valuable heavy metals, holds the potential to be regarded as a promising resource. This study introduces a new approach that integrates chlorination roasting and cascade condensation to efficiently recover heavy metals from copper smelter dust. The findings demonstrate the successful separation of heavy metals (Cu, Pb, and Zn) as chlorides at nearly 100% efficiency while also effectively converting trivalent arsenic (As(III)) into pentavalent arsenic (As(V)) and immobilizing it in the roasting residues, thereby reducing environmental risk. Through the utilization of thermogravimetric mass spectrum analysis and thermodynamic equilibrium calculations, the chlorination process for heavy metals was investigated, revealing both direct and indirect chlorination processes. Additionally, the study resulted in the development of a CuO-based multiple-metals electrocatalyst from the oxidized roasting-recovered heavy metal chlorides, exhibiting significantly enhanced catalytic activity and faradaic efficiency for the electroreduction of CO2 into CO and CH4 compared to pure CuO electrocatalyst under similar electrocatalytic conditions. Overall, this work presents a sustainable and scalable method and new insights for addressing environmental risks while repurposing copper smelter dust.

Staged separation and recovery of As, Pb, Bi, and Zn from lead smelting dusts

The lead smelting dust is extensively produced in the lead smelting process. It poses a huge threat to environmental safety if not properly disposed, because of its high contents of heavy metals. Wherever, from another point of view, it is a high-valued resource for heavy metals. This study proposed an efficient approach to gradually separate and recycle As, Pb, Bi, and Zn from it. FeS2 was firstly used as a reductant for the As separation and recovery, via which As2O5, BiAsO4, and Pb3(AsO4)2 from the dust were reduced to volatile As2O3&As2S3 and then separated. Moreover, Pb3(AsO4)2 and PbSO4 could be sulfurized to PbS, decreasing the formation of PbO·PbSO4 and then the sintering of the residue. The As volatilization was accelerated and achieved 95.4 %. Pb, Zn, and Bi retained in the residue in the sulfur compounds of PbS, PbSO4, ZnS, and Bi2S3. In the followed smelting reduction, Na2CO3 was used as an additive to promote these sulfur compounds conversion, reduction and recycle. The recovery rates of Pb, Bi, and Zn achieved up to 96.5 %, 95.9 %, and 94.3 % respectively. While, with an excess Na2CO3 in the presence of 7.50 % coke, a sodium matte named Na-Pb-Bi-S was formed, decreasing the metals reduction and recycling. This study provided an efficient method to separate and recover As, Pb, Zn, and Bi gradually from solid wastes.

Separation of halogens and recovery of heavy metals from secondary copper smelting dust

The separation of halogens and recovery of heavy metals from secondary copper smelting (SCS) dust using a sulfating roasting−water leaching process were investigated. The thermodynamic analysis results confirm the feasibility of the phase transformation to metal sulfates and to gaseous HF and HCl. Under the sulfating roasting conditions of the roasting temperature of 250 °C and the sulfuric acid excess coefficient of 1.8, over 74 wt.% of F and 98 wt.% of Cl were volatilized into flue gas. Approximately 98.6 wt.% of Zn and 96.5 wt.% of Cu in the roasting product were dissolved into the leaching solution after the water leaching process, while the leaching efficiencies of Pb and Sn were only 0.12% and 0.22%, respectively. The mechanism studies indicate the pivotal effect of roasting temperature on the sulphation reactions from various metal species to metal sulfates and the salting out reactions from various metal halides to gaseous hydrogen halides.

A sustainable approach for recovering copper and zinc from copper smelting flue dust: Paving the path for waste reduction

The recovery of metals without generating secondary waste is a critical focus in the management of hazardous copper smelting dust. To tackle the challenges associated with arsenic-containing solid waste and waste acid generated by traditional recycling processes, we propose a two-stage roasting process that prioritizes low-temperature roasting for arsenic removal, followed by high-temperature roasting for desulfurization of sulfates. This work focuses on the high-temperature desulfurization behavior of residue after arsenic removal. The changes in composition during roasting were analyzed using TG-DSC, XRD, and SEM. The results revealed that the reaction temperature and the addition of bituminite are pivotal in the desulfurization process. The optimal roasting conditions were obtained to be a reaction temperature of 700 °C and a roasting duration of 3 h. Subsequently, approximately 98.77% of copper and 97.17% of zinc could be leached under conditions of a leaching temperature of 80 °C, a reaction time of 4 h, a sulfuric acid dosage of 3 times the theoretical amount, and a liquid-to-solid ratio of 10:1. This process mitigates the generation and accumulation of arsenic-containing waste acid during copper electrodeposition in the traditional hydrometallurgical process of copper smelting flue dust. It lays the foundation for clean and efficient recovery and also provides insights for recycling other copper-containing wastes.

Treatment of chromium (VI) waste solutions with clay-based adsorbents after reduction with acid mine drainage

South Africa has one of the largest Cr-related industries in the world and generates large amounts of Cr-containing smelter dusts. It is normal practice to scrub Cr from the furnace off-gas in water, and to recover the Cr by adsorption, followed by recycling of the loaded adsorbent into the furnace. A study was conducted to find a low-cost adsorbent that is capable of removing sufficient Cr from the solutions generated by scrubbing. The test work focused on the evaluation of different clay minerals (attapulgite, bentonite, and kaolinite) as adsorbents for Cr. Cr(VI) could only be adsorbed after prereduction with e.g. ascorbic acid (ASA). An 80% removal of Cr(VI) could be achieved from a solution containing 20 mg/L Cr using bentonite clay after reduction with ASA. Attapulgite and kaolinite adsorbed less than 55% Cr after reduction with ASA. Both ASA and ferrous salts were found to be suitable reducing agents. The use of acid mine drainage (AMD) was also investigated as a low-cost alternative reducing agent, as AMD usually contains iron. The Cr(VI) reduction potential of the AMD was determined by redox titration against a solution containing 50 mg/L Cr(VI). Studies show that AMD can potentially be used as a reducing agent in a Cr removal process if it is available on site.

Mechanism and kinetics study on waste acid leaching from copper smelting dust

AbstractCopper smelters generate large amounts of copper smelting dust (CSD) that has a high recycling value because it contains about 20% copper. Waste acid can be used to leach CSD. Here, the effects of different temperatures, times and liquid–solid ratios on copper, iron and arsenic leaching rates were investigated. The optimal conditions were determined to be a temperature of 95°C, leaching time of 3 h, and liquid–solid ratio of 7:1. Under these condition, the leaching rate of copper reached 96.37%, and the copper ion concentration was 32.71 g/L. The leaching kinetics date revealed that the leaching of copper and iron was controlled by two different reaction models. The leaching of copper conformed to the Johnson–Mehl–Avrami (JMA) model and was diffusion controlled, and the reaction was rapid in the first 60 min. In contrast, leaching of iron was controlled by a chemical reaction. Copper and iron activation energies were 2.579 and 62.791 kJ/mol, respectively. These results show that CSD waste acid is can be used to dispose of arsenic‐containing hazardous waste in a green, sustainable, and ecologically method.

A novel process for extracting bismuth from high iron content copper smelting dust by magnetic separation and leaching process

In this study, an efficient method for extracting bismuth from copper smelter flue dust with high content of iron was proposed. In this method recovery of bismuth from copper flue dust was carried out after copper and iron separation. To separate copper from dust, this material was leached with water and dilute sulfuric acid (0.6 M). Magnetic separation was performed with field intensities of 0.1 T and 0.4 T to separate iron in the leaching residue. 70 % of bismuth is placed in the non-magnetic fraction. The non-magnetic fraction of this separation was leached with (1.4 M) H2SO4 + (1 M) NaCl solution to recover bismuth. In optimal conditions, more than 98 % of bismuth in the non-magnetic fraction is leached. Bismuth precipitation from this solution was done by adjusting the pH to 2.5 with the ammonia solution. Impurities such as; Pb, Fe, As, and Cu were precipitated with bismuth in this condition. Lead was removed as a PbCl2 compound by leaching the precipitate with 6 M hydrochloric acid. Other elements were leached in this chloride environment and entered the solution phase. Bismuth was separated from this leaching solution by hydrolysis in the form of BiOCl. The purity of the BiOCl product was about 95 %. This substance can be used in photocatalyst and solar cell industries.

Progressive low-temperature volatilization control: Efficient separation of arsenic and antimony from smelter dust

Given the high toxicity of arsenic (As) and the strategic importance of antimony (Sb), the separation of As and Sb has become a pivotal concern in the disposal of arsenic‑antimony flue dust and other arsenic‑antimony hazardous wastes. In this study, we propose a controlled roasting process employing anthracite and sulfuric acid additives to efficiently separate As and Sb at relatively low temperatures. Thermodynamic calculations revealed that the interactive reactions between arsenic and antimony oxides in conventional pyrometallurgical processes were the primary hindrance to their effective separation. However, the synergistic effect of anthracite and sulfuric acid not only disrupted the interactive reactions but also promoted the high-efficiency volatilization of As at low temperatures, thereby creating favorable conditions for the separation of As and Sb. Furthermore, a series of comparative experiments and comprehensive analyses regarding the evolution of phase composition, valence state, and morphology were conducted, revealing the underlying mechanisms of the effects of temperature and carbon addition. Through optimization, 91.24 % of As was successfully volatilized, while the volatilization efficiency of Sb was significantly reduced to 9.43 % under optimal conditions, involving a roasting temperature of 400 °C, anthracite addition of 1.6 %, sulfuric acid dosage of 0.135 mL/g, and a roasting duration of 3 h.

Nanosize-effect on the distribution of heavy metals in copper smelting dust: Based on sophisticated dust sorting approach

Nanosize-effect on the distribution of heavy metals in copper smelting dust: Based on sophisticated dust sorting approach

Recovery of Copper, Lead, Zinc, and Arsenic from Copper Smelting Dust by Oxidative Alkaline Leaching and Sulfide Precipitation

Recovery of Copper, Lead, Zinc, and Arsenic from Copper Smelting Dust by Oxidative Alkaline Leaching and Sulfide Precipitation

An efficient and affordable hydrometallurgical process for co-treatment of copper smelting dust and arsenic sulfide residue

We developed a novel method for comprehensive treatment of copper smelting dust (CSD) and arsenic sulfide residue (ASR) using three processes: leaching CSD by sulfuric acid, Cu precipitation with ASR, and FeSO4·7H2O/O2 co-oxidizing and precipitating As. The novel method not only realizes the recovery of valuable metals from dust, but also removes and solidifies As in CSD and ASR in the form of scorodite to achieve harmless treatment. With sulfuric acid as leaching agent, the leaching efficiencies of Cu, Zn and As reached 87.23%, 93.07% and 95.21%, respectively, under the optimum conditions. Subsequently, Cu in CSD leaching solution was precipitated in the form of CuS by ASR, and the Cu precipitation percentage reached 97.39% and 94.86 wt. % of As in ASR entered the solution under the optimum conditions. Finally, FeSO4·7H2O/O2 was used to co-oxidize As(III) and simultaneously precipitate the As in the form of scorodite. The oxidation percentage and precipitation percentage of arsenic reached 98.73% and 96.77%, respectively. The leaching concentration of As in the arsenic precipitate residue (APR) was only 0.17 mg/L in the toxicity characteristic leaching procedure (TCLP). The arsenic precipitate solution can be directly used to recover Zn.

Pyrometallurgical Scheme Intended to Process Arsenic-Containing Concentrates with Recovery of Precious Metals

The practicability of a pyrometallurgical scheme for raw material processing is established as a result of the analysis of methods intended to dearsenate and process gold-arsenic concentrates as well as equipment for the process execution. The conceptual design of vacuum equipment without forced movement of the dispersed material in the sublimator and of the reaction zone materials is proposed. In-process tests for the sublimation of arsenic sulfides from gravity and flotation concentrates received from the Bakyrchik deposit were executed at the pilot facility. As a result, it was found that more than 97–99% of arsenic passes into the gas phase and condenses in a sulfide form suitable for compaction by smelting. More than 99.5% of precious metals are concentrated in the sublimation residue. As a result of smelting residue from the sublimation of arsenic sulfides in a cyclone furnace, together with copper concentrates to copper matte, the gold recovery was 93.7–93.9% of the total amount loaded. Silver was 65.7–68% concentrated in copper matte, with a considerable amount in the dust. If the cyclone smelting dust is involved, the recovery rate of gold and silver can be increased to 97–99% and 94–95%, respectively. As a result of crucible smelting, the degree of recovery of gold in matte was 95.4%, with its content in slag being 3.6 g/t. The received matte according to the proposed scheme can be directed to the conversion process by obtaining blister copper, which is subjected to electrolytic refining with the recovery of gold from slimes.

Dependence of solar reflector soiling on location relative to a ferromanganese smelter

A solar reflector soiling study was carried out at a ferromanganese smelter in South Africa to assess the soiling rates at different locations around the plant. Several meteorological parameters were monitored to give insight into the conditions that lead to increased soiling. Mineralogical characterization of dust samples collected from the reflectors and the atmosphere revealed that only a certain size fraction is of importance with regard to soiling, and that the dust can be attributed to both raw materials and smelter products. Proximity to the dust source was the primary driver for increased soiling. The site that experienced the most soiling was very close to raw material heaps; this was deemed an outlier and was excluded from the summary statistics. The secondary driver for increased soiling was location relative to the smelter dust sources and the wind's direction and speed. The reflector set at the best location experienced 13.1% less soiling than the set at the 'worst' (but still feasible) location, represented by an averaged mean daily reflectance loss of 0.0186. The study revealed that while there are periods of intense soiling at this particular site, proper planning of reflector location in relation to the smelter dust sources can significantly mitigate the soiling rate. Keywords: Heliostat soiling, energy-intensive industry (EII), solar thermal process heat, concentrating solar thermal (CST).

Technology for Complex Processing of Electric Smelting Dusts of Ilmenite Concentrates to Produce Titanium Dioxide and Amorphous Silica

This paper presents the results of research on the development of a technology intended to process electric smelting dusts of ilmenite concentrate with the extraction of silicon and titanium and the production of products in the form of their dioxides. Dusts were processed for silicon separation using the ammonium fluoride method. The optimum conditions for the fluorination and sublimation process of silicon compounds from the electric smelting dust of the ilmenite concentrate were determined: a temperature of 260 °С, a 6 h duration, and mass ratio of dust to ammonium bifluoride of 1:0.5 ÷ 0.9. The sublimation degree of silicon compounds was ~84–91%. The sublimation of titanium fluorides from the remaining sinter was carried out at a temperature of 600 ± 10 °C for 2 h, the mass ratio titanium-containing residue: ammonium bifluoride of 1:0.5, and the degree of sublimation of titanium fluorides was 99%. Iron, manganese, and chromium impurities in the sublimation of titanium fluorides sublimate to a rather low degree. Pyrohydrolysis of titanium fluoride sublimes at 600 °C and allows for the conversion of fluorides into titanium dioxide by 99.5% in 4–5 h. Titanium dioxide of rutile modification with 99.8% TiO2 was obtained after hydrochloric acid purification and calcination. A technological scheme for the complex processing of dust from the electric smelting of ilmenite concentrates with the production of silica and titanium dioxide is proposed.

Selective Recovery of Copper from Acid Leaching Solution through Slow Release Sulfide Precipitant

A new kind of sulfide precipitant, namely, slow release sulfide precipitant (SRSP), was developed and prepared first to realize the selective recovery of copper from an acid leaching solution. The experimental results indicated that SRSP as a precipitant could selectively and efficiently recover copper and the high purity of copper sulfide slag with a Cu grade of 48.16%, and a Cu recovery rate of 97.84% could be obtained. Moreover, copper in leaching solution could be recovered more efficiently and selectively by SRSP compared with Na2S. The results of H2S gas release, chemical reaction energy calculation, and SEM image analyses illustrated that realizing the selective recovery of copper mainly depended on the ions of S2− and HS− produced by the dissolution of SRSP. Moreover, the concentrations of S2− and HS− should always be kept at a low level in the process of selective recovery of copper; this is the biggest difference from the traditional precipitant and the key to preventing the escape of H2S gas in the copper recovery process. More pivotally, SRSP provides an alternative sulfide precipitant for the selective recovery of copper from the acid leaching solution of copper smelting dust.

Composition and Cr- and Fe-speciation of dust generated during ferrochrome production in a DC arc furnace

A potential hazard associated with ferrochrome production is the unintentional generation of Cr(VI) in the off-gas dusts produced during smelting. Cr(VI) is a well-known environmental toxin and genotoxic carcinogen. Although Cr(VI) has been identified in baghouse dusts associated with submerged-arc furnaces, its occurrence in DC-arc-furnace dusts has not been previously investigated. In this study, we report the bulk composition and phase make-up, as well as the surface and bulk speciation of Cr and Fe of dusts generated during smelting of chromite ore under basic slag conditions in a pilot-scale DC arc smelter. Dusts are captured from both within the DC furnace as well as along the off-gas handling stream, after passing through the afterburner. The dusts primarily comprise feed material (chromite, flux, reductant), aerosolized slag, and glassy spherules, interpreted as off-gas condensates. Dusts collected from within the furnace, known as freeboard dusts, are dominated by feed materials, with elevated amounts of flux (lime) and lesser amounts of slag and spherules. In contrast, spherules dominate dusts collected along the off-gas handling stream by dust separators that capture the increasingly fine-grained fraction of dust, with the highest proportion of spherules occurring in baghouse dusts. Chromite is the primary host of Cr in all dust samples, whereas the spherules have low Cr contents. Cr(VI) was identified by X-ray photoelectron spectroscopy in the surfaces of dust collected from all parts of the smelter system considered, including from the furnace freeboard, despite the overall reducing conditions present therein. Cr(VI) concentrations are sufficiently high in dusts collected from the off-gas handling stream (post-afterburner, cyclone, and baghouse) to be detected in the bulk dust samples by X-ray absorption spectroscopy. The higher concentration of Cr(VI) in the finer-grained off-gas dusts, especially the baghouse dusts, is consistent with the increased abundance of spherules, the major Cr(VI)-hosting phase, in these samples. Fe is similarly more oxidized in dusts collected down the off-gas handling stream compared to dusts collected from within the furnace, which are dominated by Fe(II). Fe(III) hosted by FeOOH is predominate in dusts collected from all locations along the off-gas handling stream. These results demonstrate that there is sufficient oxygen ingress and sufficiently high temperatures in the closed DC furnace for Cr(VI) to be generated in the freeboard off-gas dusts. Cr(VI) is associated with the finest grained fraction of dusts, underlining the importance of ensuring the continual improvement of dust-capture systems, especially in terms of their ability to target increasingly finer fractions of dust. • Cr(VI) can form in a closed DC arc furnace. • Cr(VI) forms up to about one-third of the Cr species present on particle surfaces. • Fine-grained dusts captured by the baghouse host the highest proportion of Cr(VI). • Spherules are the major Cr(VI)-bearing phase in off-gas dust. • Chromite is the major source and host of Cr in smelter dusts.

Ultrasonic-enhanced selective sulfide precipitation of copper ions from copper smelting dust using monoclinic pyrrhotite

The sulfide passivation film produced on the surface seriously prevents further reaction in the process of using monoclinic pyrrhotite (MPr) to treat heavy metal ions in wastewater. Ultrasonic technology was introduced to assist MPr to recover the copper ions. XPS result proves that CuS products exist on the surface of MPr. XRD and SEM results show that the CuS on the particles’ surface is stripped under ultrasonic condition. The kinetics results indicate that the reaction under both conventional and ultrasonic conditions conform to the Avrami model. The reaction process changes from diffusion control to chemical reaction control under the ultrasonic condition as the solid layer is stripped off. The presence of ultrasonic significantly reduces the acidity and temperature required for the reaction and enhances the utilization efficiency of MPr; by controlling the amount of MPr, the removal rates of copper and arsenic in copper smelting dust leachate exceed 99% and 95%, respectively.

Treating Secondary Copper Smelting Dust: Selective Separation of Harmful Halogen and Comprehensive Recovery of Valuable Heavy Metal

Treating Secondary Copper Smelting Dust: Selective Separation of Harmful Halogen and Comprehensive Recovery of Valuable Heavy Metal

Evolution of Arsenic-Containing Phase and Reaction Mechanism During Vacuum Vulcanization Roasting for Arsenic Removal in Copper Smelting Dust

Evolution of Arsenic-Containing Phase and Reaction Mechanism During Vacuum Vulcanization Roasting for Arsenic Removal in Copper Smelting Dust