Investigation of the process of sulfiding of gold-arsenic containing ores and concentrates

Abstract

Purpose. Research of the removal of arsenic by sulfiding from gold-arsenic containing concentrates of the Bakyrchik deposit. Methodology. To determine the composition of the samples, chemical and electron probe analysis were carried out; to determine the phase composition of materials, X-ray analysis was conducted. In order to predict the process of sulfidation of arsenic and its compounds in the range of 2982000 K, a thermodynamic analysis was performed. To establish the optimal conditions for the process of sulfiding arsenic and its compounds, studies were carried out to determine the effect of temperature and the consumption of elemental sulfur on the degree of sublimation of arsenic from gold-arsenic concentrate. The sulfiding roasting of the concentrate was carried out with elemental sulfur vapor coming from a new design evaporator with a mixture of gaseous nitrogen. Findings. The main minerals of the original concentrate are pyrite, marcasite, arsenopyrite, native gold and silver. Significant elements in the concentrate are, %: arsenic 2.93.1, iron 707.3, gold 40. It has been calculated by thermodynamic analysis that when the main minerals of gold-arsenic containing refractory ores and concentrates interact with sulfur in a neutral environment and in the range of 5001000 C, reactions of formation and removal of arsenic in the form of sulfides As2S3 and As4S4 occur. When a new design evaporator supplies elemental sulfur in a mixture with neutral gas and with an increase in firing temperature from 700 to 850 C at S : As = 0.35 : 1, the degree of sublimation of arsenic increases from 94.7 to 98.2%, with FeS2 : As = 1.3:1 from 94.0 to 99.5%. With an increase in the consumption of elemental sulfur vapor (with an increase in the S : As ratio from 0.35:1 to 0.6 : 1 and a temperature from 700 to 800 C), the degree of sublimation of arsenic from the gold-arsenic product reaches up to 99%. The condensed sublimes contained up to 98.599% As4S4 and As2S3, the dust caught in cyclones is close in its composition to the composition of cinder. Originality. A new technology for the removal of arsenic from gold-arsenic containing concentrates in an oxygen-free atmosphere in the temperature range of 700850 C with the removal and capture of arsenic sulfides up to 100% is proposed. The regularity of the degree of sulfidation of arsenic and its oxidized compounds by elemental sulfur vapors in a mixture with a neutral gas to As4S4 and As2S3 has been established. Practical value. The use of the new technology makes it possible to completely convert arsenic into sulfide forms which are environmentally friendly, convenient for storage, burial, or for use as antiseptics. The development can be used for processing arsenic-containing polymetallic ore materials.