Dmitry Golovkin

Kinetics of stibnite dissolution in nitric acid in the presence of tartaric acid | Dizer | iPolytech Journal Исследование кинетики растворения стибнита в азотной кислоте в присутствии винной кислоты | Дизер | iPolytech Journal

The nitric acid leaching of antimony from stibnite using organic (tartaric and citric) acids as complexing agents was investigated. Tartaric acid has been found to be a more effective complexing agent, providing up to 90% antimony recovery, while citric acid achieves 54% only. SEM and X-ray diffraction analysis showed tartaric acid to prevent antimony hydrolysis, preserving unreacted stibnite in the residue, while Sb₄O₄(OH)₂(NO₃)₂ particles were formed in the system with citric acid. Kinetic calculations have revealed that the nitric acid leaching of antimony with the addition of tartaric acid is limited by internal diffusion (R² > 0.94), the activation energy is 62.5 kJ/mol, and the empirical reaction orders for tartaric and nitric acids are 2.3 and 2.7, respectively. These data are confirmed by morphological and phase analyses, the mechanisms of action of organic acids have been substantiated, and a generalized kinetic equation describing the nitric acid leaching of antimony with the addition of tartaric acid is proposed.

This study explores the nitric acid leaching of stibnite in the presence of tartaric acid, which acts as a complexing agent. The proposed approach is of considerable interest, as antimony is widely used across industries, from electronics to alloying applications. Thermodynamic analysis showed that nitric acid dissolution of stibnite inevitably leads to the formation of antimony oxides, which markedly reduces the extraction of the target metal into solution. To counteract these losses and enhance process efficiency, tartaric acid was introduced as an additive. The results demonstrated that tartaric acid promotes the formation of stable complexes with antimony ions, thereby retaining the metal in solution and minimizing the risk of oxide precipitation. Experimental design analysis revealed that the mass ratio of tartaric acid to antimony and the nitric acid concentration exert a stronger influence on leaching efficiency than temperature and leaching duration. Optimal conditions were established, achieving an antimony extraction of 87 %: temperature 35 °C, nitric acid concentration 5 mol/dm3 , leaching time 45 min, and a tartaric acid-to-antimony mass ratio of 4.5 : 1.0.

The kinetic characteristics of dissolution of copper-bearing sulfides – chalcopyrite (CuFeS₂) and bornite (Cu₅FeS₄) – in nitric acid were studied. The kinetics of the dissolution process was described using a compressible nucleus model. Chalcopyrite of the Vorontsovskoye deposit and bornite of the Karabash deposit were used as research objects. Solution and cake samples were analyzed by optical emission spectrometry and X-ray fluorescence analysis, respectively. The results obtained were processed in the MS Excel software package. The influence of various factors, including temperature, solvent concentration, particle size, and process duration on the dissolution degree of minerals was studied. The process parameters were varied as follows: temperature – from 35 to 95°C; HNO₃ concentration – from 1 to 9 mol/dm³; particle size – from +0.1 to 0.056 mm; duration – from 0 to 60 min. It was established that an increase in temperature and acid concentration leads to a significant increase in the degree of dissolution of both chalcopyrite and bornite. A decrease in particle size also contributes to a more efficient dissolution of both minerals in nitric acid. The calculated activation energy values were 55 kJ/mol for chalcopyrite and 43 kJ/mol for bornite, which is characteristic of the kinetic region of the process. The reaction orders in terms of reactant were determined: 1.62 for chalcopyrite and 1.57 for bornite. In terms of particle size, these were -1.16 for chalcopyrite and -2.53 for bornite. On this basis, generalized equations of dissolution kinetics for both minerals were derived. The results obtained allow an assumption about the kinetic nature of dissolution of chalcopyrite and bornite under the studied conditions.

The paper presents a study of the process of nitric acid dissolution of the natural minerals chalcopyrite and bornite. The influence of various parameters, including temperature, nitric acid concentration and particle sizes, on this process was examined. Based on the data obtained, the values of apparent activation energy (57.41 and 42.98 kJ/mol for chalcopyrite and bornite, respectively), empirical orders with respect to nitric acid (1.62 and 1.57 for chalcopyrite and bornite, respectively) and with respect to particle size (–1.16 and –2.53 for chalcopyrite and bornite, respectively) were calculated using the shrinking core model. Generalized kinetic equations for the dissolution process of both minerals were derived. Based on the calculations performed, it was suggested that the dissolution processes of chalcopyrite and bornite under these conditions are limited by internal diffusion.

An integrated two-stage metallurgical process has been developed to process concentrates from the Olimpiadinskoe deposit, which contain high levels of antimony and arsenic. The optimal parameters for the alkaline sulfide leaching process of the initial concentrate from the Olimpiadinskoe deposit were determined to achieve the maximum extraction of antimony at a 99% level. The recommended parameters include an L:S ratio of 4.5:1, a sodium sulfide concentration of 61 g/L, a sodium hydroxide concentration of 16.5 g/L, a duration of 3 h, and a temperature of 50 °C. A synergistic effect of co-processing alkaline sulfide leach cakes with sulfuric and nitric acids was observed. The pre-treatment step reduced the nitric acid composition by converting carbonates into gypsum and increased the arsenic extraction by 15% during subsequent nitric acid leaching. The laboratory research on the nitric acid leaching of decarbonized cake established the key parameters for the maximum iron and arsenic extraction in solution (92% and 98%, respectively), including an L:S ratio of 9:1, a nitric acid concentration of 6 mol/L, and a time of 90 min. Full polynomial equations for the iron and arsenic extraction from the decarbonized cake were derived. The model demonstrated a high relevance, as evidenced by the determination coefficients (R²) of 96.7% for iron and 93.2% for arsenic. The technology also achieved a high gold recovery rate of 95% from the two-stage alkaline sulfide and nitric acid leach cake. Furthermore, the maximum deposition of arsenic from the nitrate leach solution in the form of insoluble As₂S₃ was determined to be 99.9%. A basic technological flow sheet diagram for processing the flotation gold–antimony concentrate from the Olimpiadinskoe deposit was developed, including two stages: the production of metallic antimony and the gold extraction from the nitric leach cake.

An integrated two-stage metallurgical technology has been developed for processing concentrates from the Olimpiadinskoe deposit with high antimony and arsenic content. The parameters of the alkaline sulphide leaching process of the initial concentrate of the Olimpiadinskoe deposit, providing maximum extraction of antimony in solution at 99% level have been recommended. The L:S ratio = 4,5:1; the concentration of sodium sulphide - 61 g/L; the concentration of sodium-hydroxide – 6,5 g/L; the duration – 3 hours; the temperature – 50 °C. A synergistic effect of alkaline sulphide leach cakes co-processing by sulphuric and nitric acids has been determined. Pre-treatment allows to reduce the composition of nitric acid by converting the carbonates into gypsum and increases the extraction of arsenic by 15 % at the following nitric leaching. Laboratory research of nitric acid leaching of decarbonized cake allowed to set the basic parameters for maximum iron and arsenic extraction in solution (92 and 98 %): the L:S ratio =9:1; the concentration of nitric acid – 6 mol/L; the time – 90 min. The full polynomial equations for iron and arsenic extraction from decarbonised cake have been derived. The model is relevant since the value the determination coefficients for iron and arsenic R2 were 96,7 and 93,2 %. The high value of gold recovery from the cake of two-stage alkaline sulphide and nitric acid leach cake at 95 % has been established. The maximum value of arsenic deposition from the nitrate leach solution in the form of the insoluble deposition As2S3 99,9 %. A basic technological flowsheet diagram for flotation gold-antimony processing for the Olimpiadinskoe deposit has been developed; it includes two redistributions: production of metallic antimony and gold extraction from the nitric leach cake.

This paper covers thermodynamic studies of sulfide-alkaline leaching of antimony from sulfide Au-Sb concentrates have been carried out. Sulfide alkaline leaching were chosen as the best method of dissolving antimony among other hydro and pyrometallurgical ways. The Pourbaix diagram for Sb-S-H₂O, S-H₂O and Au-S-H₂O systems have been studied. The dissolution features of antimony and gold in sulfide-alkaline solutions have been analyzed. Conditions for efficient sulfide-alkaline leaching process, ensuring high antimony extraction along with minimization of losses of gold in the solutions were determined: Eh from -0.8 to -0.6 V at pH no less than 13, temperature – 50 °C, Sb:S molar concentration ratio = 1:3. Extensive laboratory experiments on sulfide-alkaline leaching were provided. Following parameters are recommended: L/S = 4.5:1; sodium sulfide concentration – 61 g/L; sodium hydroxide concentration – 16.5 g/L have confirmed a high antimony recovery rate into solution – 97.6%. Thereby the gold recovery into the cake of 96.9 % has been achieved.

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 Fe_total/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.