Low-toxicity non-cyanide recovering high-sulfur refractory gold ore via microwave roasting self-leaching process: Response surface optimization and mechanism study

Abstract

Microwave roasting self-leaching is an innovative method for recovering gold from high-sulfur refractory gold concentrates, without using deadly toxic cyanide reagents. However, the mechanism of gold self-leaching, which relies on lixiviants prepared using volatilized sulfur obtained from roasting, has not been fully elucidated. This study employs the response surface methodology to optimize processing parameters, resulting in an increased gold extraction rate of 96.18%. Analytical factorization and the Tafel curve indicate that CuSO₄ and NH₃·H₂O significantly influence the self-leaching process. Furthermore, X-ray photoelectron spectroscopy (XPS) analysis reveals that S²⁻, S₂²⁻, polysulfides (S_n²⁻), and thiosulfate (S₂O₃²⁻) are involved in the gold leaching reaction, with S²⁻, S₂²⁻, and S_n²⁻ serving as primary ligands for gold complexation. The role of S₂O₃²⁻ in the early stages of the gold-leaching reaction is also noteworthy. The copper–ammonia complex catalyzes the self-leaching gold reaction; however, an improper addition ratio can lead to copper-sulfur compound precipitates, reducing the extraction rate.

Keywords

low-toxicity non-cyanide leaching / microwave roasting self-leaching / high-sulfur refractory gold ore / response surface methodology / sulfide lixiviant

References

[1] H. Qin, X.Y. Guo, Q.H. Tian, D.W. Yu, and L. Zhang, Recovery of gold from sulfide refractory gold ore: Oxidation roasting pretreatment and gold extraction, Miner. Eng., 164(2021), art. No. 106822.

[2] Lopez-Arce P, Garcia-Guinea J, Garrido F. Chemistry and phase evolution during roasting of toxic thallium-bearing pyrite. Chemosphere, 2017, 181: 447

[3] De Michelis I, Olivieri A, Ubaldini S, Ferella F, Beolchini F, Vegliò F. Roasting and chlorine leaching of gold-bearing refractory concentrate: Experimental and process analysis. Int. J. Min. Sci. Technol., 2013, 235709

[4] Zhu XR, Chen YG, Liu X, Sun YS, Han YX. Microwave fluidization magnetization roasting of limonite ores: Phase transformation, microstructure and kinetics. Int. J. Miner. Metall. Mater., 2025, 3271519

[5] Li S, Zhang YM, Yuan YZ, Hu PC. An insight on the mechanism of efficient leaching of vanadium from vanadium shale induced by microwave-generated hot spots. Int. J. Miner. Metall. Mater., 2023, 302293

[6] Zhang FJ, Liu CH, Chandrasekar S, Li YW, Xu FC. Preparation of sodium molybdate from molybdenum concentrate by microwave roasting and alkali leaching. Int. J. Miner. Metall. Mater., 2024, 31191

[7] Su XL, Li DY, Zhao JJ, Wang MM, Su X, Zhou AH. Numerical simulation of microwave-induced cracking and melting of granite based on mineral microscopic models. Int. J. Miner. Metall. Mater., 2024, 3171512

[8] Jones DA, Lelyveld TP, Mavrofidis SD, Kingman SW, Miles NJ. Microwave heating applications in environmental engineering: A review. Resour. Conserv. Recycl., 2002, 34275

[9] Amaya I, Bernal D, Garnica S, Reslen M, Correa R. Improved roasting of some colombian gold ores. Dyna, 2013, 8017870

[10] Amankwah RK, Ofori-Sarpong G. Microwave heating of gold ores for enhanced grindability and cyanide amenability. Miner. Eng., 2011, 246541

[11] Amankwah RK, Pickles CA. Microwave roasting of a carbonaceous sulphidic gold concentrate. Miner. Eng., 2009, 22131095

[12] Zhang XL, Kou J, Sun CB. A comparative study of the thermal decomposition of pyrite under microwave and conventional heating with different temperatures. J. Anal. Appl. Pyrolysis, 2019, 138: 41

[13] X.L. Zhang, Y.G. Zhu, C.B. Sun, and J. Kou, The mechanism of microwave-induced phase transformation and sulfur conversion in gold-bearing pyrite under inert atmospheres, Miner. Eng., 186(2022), art. No. 107742.

[14] Sun CB, Zhang XL, Kou J, Xing Y. A review of gold extraction using noncyanide lixiviants: Fundamentals, advancements, and challenges toward alkaline sulfur-containing leaching agents. Int. J. Miner. Metall. Mater., 2020, 274417

[15] M. Sarvar, Z. Shafaei Tonkaboni, M. Noaparast, A.R. Badiei, and A. Amiri, Application of amino acids for gold leaching: Effective parameters and the role of amino acid structure, J. Clean. Prod., 391(2023), art. No. 136123.

[16] Z.Y. Liu, J. Kou, and C.B. Sun, Highly efficient electroextraction of gold and simultaneous iodine regeneration using ionic liquid 1-ethyl-3-methylimidazolium dicyanamide, Sep. Purif. Technol., 318(2023), art. No. 123961.

[17] Z.Y. Liu, J. Kou, L.P. Fan, et al., Research on enhancing copper-ammonia-thiosulfate eco-friendly gold leaching by magnetization of lixiviant solution and their kinetic mechanism, Minerals, 14(2024), No. 7, art. No. 697.

[18] Zhao LC, Sun CB, Li SY, Gong DZ. Effects of lime sulphur synthetic solution on leaching characteristic of gold concentrates. Chin. J. Nonferrous Met., 2015, 253786

[19] J.L. Li, J. Kou, C.B. Sun, N. Zhang, and H. Zhang, A review of environmentally friendly gold lixiviants: Fundamentals, applications, and commonalities, Miner. Eng., 197(2023), art. No. 108074.

[20] Li JL, Sun CB, Kou J, Wang PL, Liu XY. Development of a gold leaching reagent as an alternative to cyanide: Synthesis and performance evaluation. Int. J. Miner. Metall. Mater., 2025, 324835

[21] G.W. Zhang, L. Hou, P. Chen, et al., Efficient and stable leaching of gold in a novel ethydiaminedhephen acetic-thiosulfate system, Miner. Eng., 209(2024), art. No. 108639.

[22] Zhao LC, Kou J, Sun CB, Zhang ST, Wang PL, Liu K. Roasting and self-leaching process research of gold-bearing sulfides. Chin. J. Eng., 2015, 3781000

[23] Zhang XL. Study on the Release of Elemental Sulfur From Gold-Bearing Sulfides under Microwave Irradiation and Its Mechanism of Action in Gold Leaching, 2021, Beijing, University of Science and Technology Beijing88

[24] Nie YH, Yu Q, Hu XZ, Zi FT, Yu H. The effect of ammonia on the anodic process of gold in copper-free thiosulfate solution. J. Electrochem. Soc., 2016, 1635E123

[25] Y. Ou, Y.B. Yang, L. Wang, et al., A clean and efficient innovative technology for refractory sulfide gold ore: in situ gold extraction via self-generated thiosulfate, J. Clean. Prod., 419(2023), art. No. 138280.

[26] National Institute of Standards and Technology, NIST X-ray Photoelectron Spectroscopy Database. https://srdata.nist.gov/xps/QueryByElmType.

RIGHTS & PERMISSIONS

University of Science and Technology Beijing