Deposition of Arsenic from Nitric Acid Leaching Solutions of Gold–Arsenic Sulphide Concentrates

Abstract

At present, the processing of refractory gold–arsenic sulphide concentrates is becoming more relevant due to the depletion of rich crude ore reserves. In the process of the nitric acid leaching of arsenic sulphide minerals, solutions are formed containing 20–30 g/L of arsenic (III). Since market demand for arsenic compounds is limited, such solutions are traditionally converted into poorly soluble compounds. This paper describes the investigation of precipitating arsenic sulphide from nitric acid leaching solutions of refractory sulphide raw materials of nonferrous metals containing iron (III) ions using sodium hydrosulphide with a molar ratio of NaHS/As = 2.4–2.6, which is typical for pure model solutions without oxidants. The work studied the effect of temperature, the pH of the solution and the consumption of NaHS and seed crystal on this process. The highest degree of precipitation of arsenic (III) sulphide (95–99%) from nitric acid leaching solutions containing iron (III) ions without seed occurs with a pH from 1.8 to 2.0 and a NaHS/As molar ratio of 2.8. The introduction of seed crystal significantly improves the precipitation of arsenic (III) sulphide. An increase in seed crystal consumption from 0 to 34 g/L in solution promotes an increase in the degree of transition of arsenic to sediment from 36.2 to 98.1% at pH = 1. According to SEM/EDS and XRF sediment data, from the results of experiments on the effect of As2S3 seed crystal consumption, acidity and molar ratio of NaHS/As on the precipitation of arsenic (III) sulphide and the Fetotal/Fe2+ ratio in the final solution, it can be concluded that the addition of a seed accelerates the crystallisation of arsenic (III) sulphide by increasing the number of crystallisation centres; as a result, the deposition rate of As2S3 becomes higher. Since the oxidation rate of sulphide ions to elemental sulphur by iron (III) ions does not change significantly, the molar ratio of NaHS/As can be reduced to 2.25 to obtain a precipitate having a lower amount of elemental sulphur and a high arsenic content similar to that precipitated from pure model solutions.

Development of a Two-Stage Hydrometallurgical Process for Gold–Antimony Concentrate Treatment from the Olimpiadinskoe Deposit

“…The resulting solution obtained after this step exhibited iron and arsenic concentrations of 41.5 g/L and 23.4 g/L, respectively. Arsenic precipitation was conducted based on the previous research [ 26 ] under specific conditions: a stoichiometric flow rate of NaHS/As of 1.6 and a pH of 1.96. Following the sedimentation process, the pulp underwent metabolic reactions between iron and arsenic for 10–20 min.…”

“…A filtrate volume of 70 cm 3 was transferred to a 200 cm 3 glass vessel and thoroughly mixed. Sodium hydrosulfide (NaHS) with a concentration of 72 g/L was added to initiate the sulfuric–arsenic precipitation process, which lasted approximately one hour as determined in a previous study [ 26 ]. After the precipitation process, the pulp was filtered, and the obtained sediment was dried at 60 °C until a constant mass was achieved.…”

“…The implementation of hydrometallurgical methods [ 17 , 18 , 19 , 20 , 21 , 22 , 23 ] provides a solution for recycling low-grade raw materials, thereby addressing the disposal challenges associated with toxic elements and reducing the loss of valuable components through exhaust gases [ 24 , 25 , 26 ]. In Russia, the use of POX [ 27 , 28 ] and BIOX [ 29 , 30 ] methods have been explored.…”

Leaching/Bioleaching and Recovery of Metals

“…Leaching kinetics of the leaching solution through the porosity were explained by the intraparticle diffusion model (the reaction order was 1.2, and the activation energy was 42.3 kJ/mol between 283 and 333 K). Karimov et al [3] studied the precipitation arsenic sulfide from the nitric acid leachate of refractory sulfide concentrates of nonferrous metals containing iron (III) ions using sodium hydrosulfide (NaHS/As = 2.4-2.6). The highest degree of precipitation of arsenic (III) sulfide (95-99%) without seed occurs at a pH range of 1.8 to 2.0 and a NaHS/As molar ratio of 2.8.…”

Acidithiobacillus ferrooxidans Leaching of Silica-Sulfide Gold Ores from May-Hibey Deposits, Tigray, Ethiopia

“…Te best-studied leaching bacteria are the genus Acidithiobacillus, which includes sulfur-oxidizing species and sulfur-and ferrous-oxidizing bacteria and which are common inhabitants of extremely acidic ecological sites, rich metals, has been extensively used in the bioleaching of concentrates, sludge, and metal-sulfde ores [13,14]. Despite its high bioleaching efciency, the genus Acidithiobacillus is often found at low densities in indigenous microbial consortia, which is still not fully understood and, conversely, Acidithiobacillus ferrooxidans bacterium is most commonly found in bioleaching [2,3,5].…”