Selective Separation of Arsenic from Lead Smelter Flue Dust by Alkaline Pressure Oxidative Leaching

Eco-friendly treatment of copper smelting flue dust for recovering multiple heavy metals with economic and environmental benefits

Handling flue dust in an environmentally friendly manner has become an urgent task for pollution prevention in the copper industry. Here, driven by the low-carbon notion, we report a process that enables the selective retrieval of multiple metals (As, Cu, Pb, Zn, and Bi) from copper smelting flue dust (CSFD). This process employed low-temperature roasting to separate arsenic from heavy metals, thereby eliminating the tedious separation steps required by existing processes. Subsequently, Zn and Cu were dissolved in water, while Pb and Bi were left as a solid residue. We achieved 98.23% extraction of Cu via Zn cementation at a micro-voltage of 0.50 V. Utilizing the difference in solubility, Bi was selectively dissolved from the residue using a NaCl-HCl medium, which enabled the subsequent production of metallic Bi through electrowinning. Finally, more than 99% of Pb in the solid was reduced to elemental Pb by mechanochemical reduction. Through optimized process conditions, high-purity As2O3 (99.04%), lead ingot (99.95%), metallic copper (94.16%), and bismuth (99.20%) were obtained. Our economic assessment revealed significant advantages, demonstrating the industrial feasibility of this process. Consequently, this study presents an effective and cost-efficient system for CSFD disposal while minimizing the environmental impact and fostering a circular economy.

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.

Recycling and reutilization of smelting dust as a secondary resource: A review

Smelting dust is a toxic waste produced in metal-mineral pyrometallurgical processes. To eliminate or reduce the adverse environmental impacts of smelting dust, valuable components need to be selectively separated from the toxic components present in the waste. This paper reviews the chemical composition, phase composition and particle size distribution characteristics of smelting dust, and the results show that smelting dust has excellent physicochemical characteristics for recovering valuable metals. The process flow, critical factors, development status, advantages and disadvantages of traditional technologies such as pyrometallurgy, hydrometallurgy and biometallurgy were discussed in depth. Conventional treatment methods typically prioritize separating and reclaiming specific elements with high concentrations. However, these methods face challenges such as excessive chemical usage and limited selectivity, which can hinder the sustainable utilization of smelting dust. With the increasing scarcity of resources and strict environmental requirements, a single treatment process can hardly fulfil the demand, and a physical field-enhanced technology for releasing and separating valuable metals is proposed. Through analysing the effect of electric field, microwave and ultrasound on recovering valuable metals from smelting dust, the enhancement mechanism of physical field on the extraction process was clarified. This paper aimed to provide reference for the resource utilization of smelting dust.

Formation and Inhibition Mechanism of Na8SnSi6O18 during the Soda Roasting Process for Preparing Na2SnO3

To produce Na₂SnO_3, which is widely used in the ceramics and electroplating industries, a novel process for the preparation of sodium stannate from cassiterite concentrates was developed successfully by the authors' group. It was found that sodium stannosilicate (Na₈SnSi₆O₁₈) was easily formed due to the main gangue of quartz in cassiterite concentrates, which was almost insoluble and decreased the quality of Na₂SnO₃. The formation and transitions of Na₈SnSi₆O₁₈ in the SnO₂-SiO₂-Na₂CO₃ system roasted under a CO-CO₂ atmosphere were determined. The results indicated that the formation of Na₈SnSi₆O₁₈ could be divided into two steps: SnO₂ reacted with Na₂CO₃ to form Na₂SnO₃, and then Na₂SnO₃ was rapidly combined with SiO₂ and Na₂CO₃ to form low melting point Na₈SnSi₆O₁₈. In addition, Na₈SnSi₆O₁₈ can be decomposed into Na₂SiO₃ and Na₂SnO₃ by using excess Na₂CO₃.

Jute Fibers Synergy with nZVI/GO: Superficial Properties Enhancement for Arsenic Removal in Water with Possible Application in Dynamic Flow Filtration Systems

Groundwater is one of the primary sources of water for both drinking and industrial use in northeastern Mexican territory, around 46% of the total, due to the lack of precipitation during the year and solar radiation index. The presence of arsenic in brackish soil and groundwater is a severe health issue, specifically in semi-arid and arid regions in the north of Mexico. Additionally, it represents the only source of drinking water in communities far from big cities, mainly due to the absence of hydric infrastructure. This work presents a new approach to treating polluted water with arsenic. The system based on activating jute fiber with nanoparticles of zero-valent iron immobilized over graphene oxide will allow nZVI particles to preserve their unique qualities for water sanitization. A dynamic flow test was designed to determine the effectivity of activated jute fibers as a water sanitation system. The results showed a reduction in the total arsenic content from 350 ppb to 34 ppb with a filtrate flow of 20 mL/min. The above represents 90% adsorption by the activated fiber. The analyzed sample corresponds to contaminated groundwater taken from Coahuila, Mexico. This sanitation system could be applied to low-income populations lacking robust infrastructure, such arsenic treatment plants.

Comparative Study for Flue Dust Stabilization in Cement and Glass Materials: A Stability Assessment of Arsenic

Arsenic is a poisonous element and its super mobility can pose a major threat to the environment and human beings. Disposed arsenic-bearing waste or minerals over time may release arsenic into the groundwater, soil and then the food chain. Consequently, safe landfill deposition should be carried out to minimize arsenic bleeding. Cement-based stabilization/solidification and glass vitrification are two important methods for arsenic immobilization. This work compares the stability and intrinsic leaching properties of sequestered arsenic by cement encapsulation and glass vitrification of smelter high-arsenic flue dust (60% As2O3) and confirms if they meet or exceed the requirement of landfill disposition over a range of environmentally relevant conditions. The toxicity characterization leaching procedure (TCLP, 1311), synthetic precipitation leaching procedure (SPLP, 1312) and Australian standard (Aus. 4439.3) in short-term (18 h) and mass transfer from monolithic material using a semi-dynamic leaching tank (1315) in longer-term (165 days) were employed to assess arsenic immobility characteristic in three arsenic-cement (2%, 8.4% and 14.4%) and arsenic-glass (11.7%) samples. Moreover, calcium release from different matrices has been taken into consideration as a contributor to arsenic bleeding. Based on the USEPA guidelines, samples can be acceptable for landfilling only if As release is < 5 mg/L. Results obtained from short-term leaching were almost similar for both cement and glass materials. However, high calcium release was observed from the cement-encapsulated materials. The pH of leachates after the test was highly alkaline for encapsulated materials; however, in glass material it was near neutral or slightly acidic. Method 1315 tests made a huge difference between the two materials and confirmed that cement encapsulation is not the best method for landfilling arsenic waste due to the high arsenic and calcium release over time with alkaline pH. However, glass material has shown promising results, i.e., the insignificant release of arsenic over time with an acceptable change in pH value. Overall, arsenic sequestration in glass is a better option compared with the cement-based solidification process.