Influence of microwave pretreatment on sulphide-rich and oxide type gold ore

Date

2026-2

Author

Ulusoy Tasar, Aslı

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Microwave energy, widely applied in communication, presently is finding increasing application in cooking, heating and industry also commercial applications in the sterilization of agricultural products, densification of ceramic etc. for years. Most recently, in the field of research and application of microwave energy in mineral processing is increasing because of the unique heating and decomposition properties. In this research, the power levels and exposure times of microwave pretreatment were determined, and key changes and effects were examined in both oxide-type gold ore (OTGO) and high-sulphide types of gold ore (HSTGO). This study investigates the structural changes induced by microwave pretreatment in both ores and evaluates their effects on grindability and agglomeration behavior. Furthermore, the formation of microcracks and the resulting changes in leaching performance were examined to establish the relationship between microstructural modification and metallurgical response. After microwave pretreatment, mineralogical transformations and significant morphological alterations were observed in the ore matrix. Due to rapid and selective heating, microwave energy induced lattice distortions and thermal stresses, leading to the development of radial and intergranular microcracks, grain-boundary separation, and the formation envisaged to determine the power levels and exposure times of microwave pretreatment and to look at some important changes to enable the macro-scale structure and flow conditions, while microwave pretreatment increases internal porosity. These structural changes were observed and evaluated for both ore types using SEM (Scanning Electron Microscopy)–EDS (Energy-dispersive X-ray Spectroscopy) analyses and polished-sections and thin-sections examinations. Together, these effects enhance leaching performance by improving leaching kinetics and reagent efficiency. Microwave pretreatment resulted in a marked improvement in gold recovery from OTGO samples in bottle roll leaching (BRL), with rising from 64.98% to 81.79%. Furthermore, total NaCN consumption decreased substantially from 5.28 kg/t to 2.37 kg/t, demonstrating greater leaching efficiency and more effective reagent utilization. Microwave pretreatment promotes sulphide mineral decomposition, thereby enhancing gold liberation and leaching efficiency, whereas its combination with acidic conditions further underscores its effectiveness for processing HSTGO. Gold recovery of this ore increased from 61.85% to 78.67% after microwave pretreatment, reaching its highest value at 8 M. Microwave energy exposure induces microcracking within the ore matrix, which facilitates subsequent breakage during grinding. As a result, the target particle-size distribution can be achieved at a lower specific energy than that of the untreated material, thereby enhancing comminution efficiency in mineral processing. According to the results of Micro-CT and Mercury Intrusion Porosimeter, used to evaluate porosity in both ores after microwave pretreatment, microwave pretreatment effectively enhances crack propagation, leading to the formation of microcracks in both ores. Although HSTGO contains fewer detected pores than OTGO, its significantly larger pore area and volume indicate the formation of fewer but larger macropores after microwave pretreatment. Overall, microwave pretreatment improved grindability, leaching kinetics, and gold recovery for both OTGO and HSTGO samples by inducing microcrack formation, increasing porosity, and enhancing solution accessibility.

Subject Keywords

oxide and sulphide-rich gold ore, microwave pretreatment, gold leaching, microcrack, microcrack, grindability, agglomeration

URI

https://hdl.handle.net/11511/118998

Collections

Graduate School of Natural and Applied Sciences, Thesis