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

Wei Liu,Wenqing Qin,Na Wang,Junwei Han,Wenhua Li,Xun Wang,Zihan Li

doi:10.3390/min9050308

Abstract

This study investigated the feasibility of using an alkaline pressure oxidative leaching process to treat lead smelter flue dust containing extremely high levels of arsenic with the aim of achieving the selective separation of arsenic. The effects of different parameters including NaOH concentration, oxygen partial pressure, liquid-to-solid ratio, temperature, and time for the extraction of arsenic were investigated based on thermodynamic calculation. The results indicated that the leaching efficiency of arsenic reached 95.6% under the optimized leaching conditions: 80 g/L of NaOH concentration, 1.0 MPa of oxygen partial pressure, 8 mL/g of liquid-to-solid ratio, 120 °C of temperature, 2.0 h of time. Meanwhile, the leaching efficiencies of antimony, cadmium, indium and lead were less than 4.0%, basically achieving the selective separation of arsenic from lead smelter flue dust. More than 99.0% of arsenic was converted into calcium arsenate product and thus separated from the leach solution by a causticization process with CaO after other metal impurities were removed from the solution with the addition of Na2S. The optimized causticization conditions were established as: 4.0 of the mole ratio of calcium to arsenic, temperature of 80 °C, reaction time of 2.0 h. The resulting product of calcium arsenate may be used for producing metallic arsenic.

Highlights

The smelting utilization of lead concentrate, which is processed in the pyrometallurgical process, produces huge quantities of flue dust with a considerable amount of various elements, such as Pb, Cu, Fe, As, Cd, Sb, Zn, Bi, and Ag [1]
Results and Discussion to provide a sample with the appropriate concentration. 0.1 g of leach-concentrated hydrochloric acid (HCl) and nitric acid (HNO3 ) were place on a hot plate and diluted with 500 mL 10% HNO3 medium
About 95.6% of the arsenic was selectively extracted from lead smelter flue dust by alkaline pressure oxidative leaching under optimized conditions: NaOH concentration of 80 g/L, oxygen partial pressure of 1.0 MPa, liquid-to-solid ratio of 8 mL/g, leaching temperature of 120 ◦ C, leaching time of

Summary

Introduction

The smelting utilization of lead concentrate, which is processed in the pyrometallurgical process, produces huge quantities of flue dust with a considerable amount of various elements, such as Pb, Cu, Fe, As, Cd, Sb, Zn, Bi, and Ag [1]. Arsenic is the main unfavorable element of concern in the dust, and is getting more and more attention with the improvement of public awareness of environmental protection due to its toxicity, volatility, bioaccumulation in the environment, and potential carcinogenic propensities [2]. The main part of the total input of arsenic from the lead concentrate is eliminated through the gas phase, subsequently creating lead smelter flue dust [3]. The high content of arsenic effectively reduces the economic value of lead smelter flue dust due to requirements for further operations of hazardous emissions, and creates great risks to the environment and the human body [4,5]. Arsenic in nature has many negative effects, there is still value and necessity in Minerals 2019, 9, 308; doi:10.3390/min9050308 www.mdpi.com/journal/minerals

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Methods

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Conclusion