Key Takeaways & Executive Findings
- •• A hydrothermal method using scorodite formation selectively removes arsenic from acid polymetallic solutions containing high concentrations of Cd and Zn. • Thermodynamic analysis identified a pH range of 1.8–3.9 for selective As removal as FeAsO4, preventing Cd precipitation as Cd5H2(AsO4)4. • Under optimized conditions (pH adjusted to 1.0), 88.96% of As was removed as scorodite with minimal loss of Cd (2.44%) and Zn (1.13%). • The study provides a practical approach to recover valuable metals from arsenic-bearing metallurgical wastes while achieving stable arsenic disposal.
Abstract
Arsenic-contained acid polymetallic solutions (AAPS) are produced from the H2SO4 leaching of dust generated during nonferrous metals pyrometallurgy such as copper, lead, and zinc. It is difficult to selectively remove As and efficiently recover valuable metals simultaneously. In this study, arsenic was removed from an acid polymetallic solution containing As, Cd, and Zn via scorodite formation using a hydrothermal method. First, a thermodynamic analysis of the Cd2+-Zn2+-Fe3+-AsO4 3−-SO4 2−-H2O system showed that the pH range for selective As removal as FeAsO4 was 1.8−3.9, and a higher pH will result in the precipitation of Cd in the form of Cd5H2(AsO4)4. Second, the experimental investigations, including neutralization and hydrothermal processes, showed that 88.96% As was selectively removed as scorodite with a flower cluster morphology in a hydrothermal process after adjusting the pH of AAPS to 1.0 via a neutralization process, while the total loss ratios of Cd and Zn were 2.44% and 1.13%, respectively. This study realized selective separation of Zn and Cd from AAPS by controlling the pH to avoid their loss into scorodite.
1. Introduction
Arsenic is widely associated with sulfide ores of lead, copper, zinc, and bismuth. Its presence cannot be avoided in nonferrous metallurgy and a large amount of As-bearing polymetallic waste is produced, such as smelting dust, waste water and slag. Owing to the volatility of As, a large amount of As accumulates with valuable metals Pb, Cu, and Zn in smelting dust. These dusts are significant resources and hazardous materials, and it is challenging to realize their resource utilization and harmless disposal.
Therefore, significant research has been conducted for the treatment of As-bearing dust, including pyrometallurgical and hydrometallurgical processes. Based on the volatility of As2O3, direct roasting, H2SO4 roasting, reduction roasting were used to separate As, and the product could be further purified for As recovery. However, pyrometallurgical processes have some disadvantages such as high energy consumption. Hydrometallurgical processes, including alkaline and acid methods, have been widely studied. The alkaline method mainly involves As separation via NaOH, NaOH-Na2S, or NaOH oxidative leaching and As precipitation via calcium arsenate formation. The method has the advantage of good selectivity for As but is unsuitable for treating As-bearing dust containing Pb and Zn because of the amphoteric nature of both metals. Acid leaching, such as H2SO4 or H2SO4 oxidative leaching, can separate Pb from As-bearing dust; however, it is necessary to selectively precipitate As from the generated As-bearing acid solution.
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LIU Shu-fen, YANG Sheng-hai, YE Long-gang, CHEN Yong-ming (2025). Selective separation of Zn and Cd from arsenic-contained acid polymetallic solution. Journal of Central South University. https://doi.org/10.1007/s11771-025-6057-5
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Frequently Asked Questions
What is the main challenge in treating arsenic-contained acid polymetallic solutions?
The main challenge is to selectively remove arsenic while efficiently recovering valuable metals like zinc and cadmium, as conventional methods often cause co-precipitation or loss of these metals.
How does the hydrothermal method achieve selective arsenic removal?
The hydrothermal method promotes the formation of scorodite (FeAsO4·2H2O) under controlled pH conditions, which selectively precipitates arsenic while leaving zinc and cadmium in solution.
What pH range is optimal for selective arsenic removal?
Thermodynamic analysis indicates that a pH range of 1.8–3.9 is optimal for selective arsenic removal as FeAsO4, preventing cadmium precipitation as Cd5H2(AsO4)4.
What are the recovery rates for zinc and cadmium in this process?
The process achieves high recovery rates, with loss ratios of only 2.44% for cadmium and 1.13% for zinc, meaning over 97% of these valuable metals are retained.
What is the significance of this study for industrial applications?
This study provides a practical and efficient method for treating arsenic-bearing metallurgical wastes, enabling both environmental remediation and resource recovery, which is crucial for sustainable nonferrous metal production.
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