Ore Surface Research Articles

Preparation of L(+)-cysteine-modified low-grade palygorskite ore and study on the reinforcing property for EPDM rubber

ABSTRACT: The development of palygorskite rubber filler meets the rubber industry's demand for low-cost green filler, but the high cost of mineral purification and the price of modifiers limit the industrialization of palygorskite rubber filler. To decrease the expenses of mineral purification and modification of palygorskite rubber reinforcing filler, this study opted for eco-friendly L(+)-cysteine as the modifier for the organic grafting on the surface of low-grade palygorskite ore. L(+)-cysteine modified low-grade palygorskite rubber reinforcing filler (CYS@PAL) was successfully prepared through ultrafine ball milling and modification. Under the condition that the modifier dosage is 1 wt% and the filling amount of modified powder is 90 phr, the 100% and 300% constant tensile stress, tensile strength, and elongation at break of reinforced EPDM composite rubber reached 4.07 MPa, 7.66 MPa, 24.78 MPa, and 764.70%, respectively. Additionally, after thermo-oxidative aging at 70° for 48 h, the aging coefficient of the composite rubber reached 0.873. This work provides a low-cost and environmentally friendly method for the utilization of the preparation of high-performance low-grade palygorskite rubber reinforcing filler.

Research on image preprocessing algorithm based on mixed denoising and texture weakening of ore images

Ore particle size information is an important basis for mining enterprises to regulate crushing parameters, due to the complex and harsh environment during the acquisition of ore images on the conveyor belt, resulting in the existence of a variety of composite noise interference in the motion target image, the surface texture characteristics of the ore and the edge of the fuzzy and other problems, thus affecting the effective acquisition of ore particle size information. To address the above issues, an image-denoising network based on global and local feature extraction and an edge enhancement algorithm for texture feature weakening is proposed. The denoising network consists of a shallow local feature extraction module and a Transformer-based U-Net global feature extraction module, which aims to combine the powerful global modeling capability of the Transformer with the local modeling advantage of convolutional network, and reconstructs the image resolution through the dual up-sampling structure, to realize the accurate output of contextual detail information. A texture weakening method based on wavelet transform and fast non-local averaging is proposed to smooth the image and weaken the texture characteristics of the ore surface, and edge sharpening is combined with Bilateral- USMR to enhance the edges of the ore particles to realize the preprocessing of the ore image. The preprocessing results were objectively evaluated and experimentally verified. The results show that the image preprocessing method improves the accuracy of image segmentation and the applicability of the ore particle size measurement technology in complex environments.

Diversity of Fungal Community and Its Constraints in the Yifeng Lithium Mines, Eastern China.

It is well accepted that biodiversity and ecosystem functions are strongly shaped by environmental conditions; however, relatively little is known about how they depend on the mineralogical assemblage of local environments, especially in mines. This study aims to reveal the diversity characteristics of the fungal community in the surface of granite lithium ores and their weathering products sampled from the Yifeng lithium mines in Jiangxi Province, eastern China. According to the analysis of internal transcribed spacer1 (ITS1) high-throughput sequencing, significant differences in fungal community diversity on the surface of lithium ores and their weathering products have been revealed. The operational taxonomic unit (OTU) of the ore surface and its weathering products ranged from 280 to 624, which may depend on the mineral composition as well as the degree of weathering. The community composition of each sample was significantly different at the phylum level, especially between the weathering products in Ascomycota and Basidiomycota. Although Ascomycota and Basidiomycota were the dominant fungal communities in all samples, each sample has its own distinctive fungi. The trophic modes of the fungi were more complex than that of the bacteria. 10 different fungal trophic modes and 25 dominant functional fungal groups were disclosed, and the saprophytic community was found to be the dominant group. These fungi could accelerate the decomposition of environmental organic matter in the environment by producing hydrolases and oxidases. Chytridiomycota with the function of producing and regulating secondary metabolites were the representative fungi in all samples. Our findings would provide theoretical basis and research clues for understanding the relationship between weathering of granite lithium and fungal communities.

Influence of pyrite surface defects on xanthate adsorption: A density functional theory perspective

Many scholars have studied the adsorption behavior of various ions and agent molecules on pyrite surfaces based on density functional theory (DFT) calculations, however, the adsorption behavior of pyrite by surface defects has been relatively less studied. In this study, we try to produce defects on the surface of pyrite by hydration and study them systematically. The effects of pyrite surface defects on the molecular adsorption of xanthates were investigated on the atomic scale by combining DFT calculations, and AFM observation methods, respectively. The results indicate that oxygen molecules can indirectly participate in hydration reactions and promote crystal defect generation. In addition, the absence of coordination intensifies the electron transfer of pyrite, which favors the formation of new coordination with xanthates, and the adsorption energy is also reduced. Defects lead to an increase in the number of xanthate molecules at the adsorption site, and the adsorption capacity is also enhanced. The adsorption morphology was analyzed by AFM measurements to confirm the DFT calculation results. The complex interfacial system of sulfide ores was investigated, and it was found that the hydration process of sulfide ores generates surface defects, which further promote xanthate molecules adsorption. The results extend the traditional electrochemical adsorption theory of sulfide ores and provide theoretical support for the study of the molecular dynamics adsorption process on the surface of sulfide ores.

Analysis of bioleaching characteristics and multi-element dissolution behavior of complex zinc ores

In order to recover low-grade complex zinc ore in a reasonable way, this study adopts bioleaching method to study it. The ore samples contain 1.52%, 2.03% and 14.4% zinc, respectively, which occurs in the form of sphalerite. Other major minerals include pyrite, galena, quartz and mica. The inoculation of the domesticated strain was basically free of adaptation period, and the cell concentration could be rapidly increased after a short decrease. The leaching extent of zinc increased continuously, while the leaching rate decreased gradually. After the bioleaching process, sliver, lead and iron were mainly present in the residue phase. X-ray diffraction spectroscopy analysis showed that sphalerite, galena and pyrite were dissolved, and the latter two further precipitated to produce PbSO4 and jarosite. In addition, the dissolution of calcium compounds can lead to the formation of gypsum precipitation. These precipitates covered the fresh ore surface may hinder the further bioleaching process. The Exponential model was used to simulate the bioleaching process, and it was found that the fit coefficients were all greater than 0.98, and a reasonable leaching cycle was further discussed. The results provide a good basis for the economic and environmentally friendly recovery of low-grade complex zinc ores.

Novel approach to locate micro-scale mineral regions of interest in real ores

The surface of minerals plays a pivotal role throughout the process of mineral beneficiation and utilization. Studies on surface properties, such as surface chemistries, of mineral phases of interest in real ores enable the selective separation of minerals, thereby enhancing the utilization of mineral resources. Nevertheless, obtaining specific mineral phases, especially for finely disseminated or poorly crystalized minerals, from real ores without altering their surface chemistries remains a challenge. The challenge also persists in investigating the same micro-scale mineral region in real ores using various surface characterization techniques, such as scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). This paper proposes a novel approach and procedures for locating micro-scale mineral regions of interest in real ores based on a three-dimensional coordinate system etched onto the ore surface using laser etching technology. A copper-nickel ore from Jinchuan, China, served as an illustrative example, with the finely disseminated chalcopyrite and pentlandite regions in the real ore sample being located and investigated using SEM and XPS. The approach presented in this study enables the in-situ detection of surface chemistries of specific mineral phase in real ores, ensuring the homogeneity and in-situ nature of the obtained surface chemistry data. This approach holds considerable promise, especially in the investigation of surface chemistries of minerals with fine dissemination and poor crystallization.

Thiocyanate facilitating thiosulfate extraction of gold via inhibiting formation of passive layer

Thiosulfate leaching is a feasible alternative for cyanidation. However, thiosulfate is easily decomposed and forms the passive layer on the ore surface, thus hindering gold extraction. In this paper, by adding thiocyanate to reduce the undesirable effect, copper-ammonia-thiosulfate leaching system is utilized to extract gold from the calcine. This research investigated the factors affecting gold extraction and kinetics of the leaching system, and the potential reason and reaction mechanism of the thiocyanate for improving gold leaching efficiency were discussed and analyzed. Gold leaching percentage is increased from 62.99% to 88.45% by adding thiocyanate that is close to that of cyanidation. By using X-ray photoelectron spectroscopy, gold in the leachate may be in the form of gold(I) thiosulfate complex. The leaching mechanism and the reason for improving gold extraction by adding thiocyanate were investigated via characterization and the leaching thermodynamic analysis. The possible reason for improving gold leaching percentage lied in that the thiocyanate reduced the decomposition of thiosulfate, thus inhibiting the form of passivation layer. According to the leaching mechanism, thiocyanate is used as an additive in the copper-ammonia-thiosulfate leaching system, which is of great significance for facilitating gold recovery, lessening thiosulfate consumption, and reducing ammonia dosage.

Comparative study on grinding kinetics behavior of vanadium-titanium magnetite ore before and after microwave pretreatment

Vanadium-titanium magnetite underwent closed circuit crushing before and after microwave pretreatment. Subsequently, batch grinding tests were conducted on the crushed products, with varying grinding times. Ultimately, the m-order grinding kinetics model of the ore was established both before and after microwave pretreatment. The results show that microwave pretreatment causes a significant increase in the number of micro-cracks on the ore's surface. Moreover, the specific surface area and pore volume of the ore increase by 17.29% and 40.98% respectively. These changes result in a reduction in the mechanical properties of the ore. During the grinding tests, the number of micro-cracks is found to be the primary factor influencing the grinding speed in the initial stage. However, as the grinding progresses, the grinding probability becomes the main factor affecting the grinding speed. The coarse particle size of the microwave-treated ore exhibits a significantly higher grinding speed than the untreated ore. Conversely, the grinding speed of fine particle size ore change slightly. The application of microwave-assisted grinding for vanadium-titanium magnetite proves advantageous in improving the particle size composition of the grinding product. Consequently, this can lead to enhanced separation efficiency and concentrate quality.

Experimental Study on the Influence of Surfactants on Ore Surface Wettability.

To reveal the evolution law of ore surface wettability under the condition of adding surfactant and chemical reaction, the test experiments of ore surface morphology, roughness, and chemical element distribution were carried out. The results show that the contour of the ore surface morphology was relatively flat in the early stage of leaching and the roughness factor increased slowly, while the contour fluctuated significantly in the late stage of leaching and the roughness factor increased sharply. With the leaching reaction, the roughness factor and spreading coefficient of the ore with a 0.008 mol/L surfactant (sodium dodecyl sulfate) concentration were always higher than those without surfactant and the surfactant enhanced the erosion effect of the solution on the ore surface. During the leaching process, the chemical elements Cu, Al, and K were dissolved on the ore surface, and the content of Cu decreased significantly from 2.01 to 0.86%; the leaching rate of copper was about 57.2%. According to the morphology characteristics of the ore surface during leaching and the distribution law of chemical elements on the ore surface before and after leaching, the leaching process was divided into four stages of "contact-penetration-reaction-disintegration". The surfactant had the most obvious effect on the ore surface morphology in the two stages of "reaction" and "disintegration".

Hyphae and organic acids of Aspergillus Niger promote uranium recovery by destroying the ore surface and increasing the porosity and permeability of ores

To elucidate the mechanism of damage caused by hyphae and organic acids produced by Aspergillus Niger on the surface and internal structure of uranium ore, direct uranium leaching, indirect uranium leaching and semi-direct uranium leaching were conducted, and the surface morphology, strength, mineral crystallinity, porosity, and permeability of the ore were analyzed. The results demonstrated that the combination of biomechanical forces exerted by hyphae and the complexation effects of organic acids led to the dissolution of SiO2 and other substances on the surface of ore, resulting in exfoliation from the exterior to the interior, thereby promoting uranium recovery. Furthermore, the proton exchange involving H+ and the complexation of organic acids resulted in the dissolution of cations within the ore, causing destruction to the crystal lattice structure of minerals and increasing the porosity and permeability inside the ore. The dominant factor contributing to ore damage during recovery was organic acids.

Effects of chromate on nitrogen removal and microbial community in two-stage vertical-flow constructed wetlands

Nitrogen and chromium (Cr(VI)) pollution in waterbodies pose great threats to human health, and a cost-effective alternative with Cr(VI) and nitrogen simultaneous removal is still needed. This study investigated the influence of Cr(VI) on nitrogen removal in the two-stage vertical-flow constructed wetlands (TS-VFCWs) along with iron ore and woodchip, and explored relationship between Cr(VI) and nitrogen removal. The results showed that efficient Cr(VI) and nitrogen removal were simultaneously achieved in TS-VFCWs together with iron-ore and woodchip under 2 mg/L-Cr(VI), whereas 10 mg/L-Cr(VI) gave significant and recoverable inhibition of nitrogen removal. Cr(VI) supplementation promoted the beneficiation of Cr(VI)-reducing/resistant bacteria IMCC26207 and Bryobacter on iron-ore. Woodchip enriched Cr(VI)-reducing bacteria Streptomyces and Thiobacillus. XRD and XPS showed that abundant bound-Cr existed in the surface of iron ore and woodchip, and Cr(III) precipitation/oxide was the major product. High abundances of nitrifying and autotrophic/heterotrophic denitrifying bacteria ensured good nitrogen removal at Cr(VI) stress.

DETECTING MOISTURE IN BAUXITE USING MICROWAVES

AbstractMathematical modelling of microwaves travelling through bauxite ore provides a way to compute moisture content in the free space transmission method given data on signal attenuation, phase shift and variable bauxite depth. We extend a recently developed four-layer model that uses coupled ordinary differential wave equations for the electric field together with continuity boundary conditions at interfaces between ore, air and antenna to find a solution that incorporates multiple internal reflections in ore and air. The model provides good fits to data, depending on ore permittivity and conductivity.Our extensions are to use effective medium models to obtain electromagnetic properties of the ore mixture from moisture content and to incorporate the damping effects of scattering from the ore surface. Our model leads to a formula for the received signal showing how signal strengths SS and phase shifts depend on the moisture content of the bauxite ore, through the effects of moisture on permittivity and conductivity. We show that SS may be noninvertible, indicating that attenuation data alone cannot be used to infer moisture content. Combining with phase data typically corrects the noninvertibility. Reducing the operating frequency dramatically improves the usefulness of signal strength data for inferring moisture content.

The oxidation behavior of MnO2 on the surface of a shale vanadium ore

As a typical oxidative leaching aid in the experimental study of vanadium extraction, MnO2 has a strong destructive effect on the lattice of vanadium-containing minerals. Therefore, the effect of manganese dioxide on vanadium leaching was studied by leaching test of shale vanadium ore. Firstly, the phase change, microstructure and possible structure of the compounds during the condition test were studied by EPMA, FT-IR and SEM-EPS. Then the effect of MnO2 on the leaching rate was studied by kinetics. The results show that under the action of manganese dioxide, the leaching control type is changed from chemical reaction control to mixed control type, and the activation energy is greatly reduced. Secondly, the adsorption of shale vanadium ore by manganese dioxide was characterized, and the density of states, the differential charge density under the action of MnO2 and the dissolution behavior of MnO2 on vanadium in minerals during leaching were studied. Based on the simulation results, it is found that there is a molecular orbital interaction between manganese ions and oxygen and hydrogen on the surface of minerals, which will seriously destroy the lattice of vanadium-containing minerals. The strong oxidation of manganese ions will destroy the structure and stability of the whole tetrahedron and accelerate the leaching trend. Under the action of high-valent manganese ions, Al (S7) -O (S1) bond breaks, Al (S7-O) bond breaks, and vanadium is more easily dissociated from minerals. In this paper, the leaching of vanadium from manganese dioxide was studied by the combination of leaching test, kinetics and quantum chemistry. Through the analysis of kinetics, density of states and charge distribution, the leaching process which could not be characterized by the test was analyzed in detail. It also provides a feasible reference for future research.

Problems of Sustainable Development of the Economy of the Regions of Ukraine: Ecological and Economic Study of Iron Ore Surface Utilization of Krivorizh

The purpose of the article is to study the problem of sustainable development on the example of the Kryvorizh region, namely: the level and specificity of landscape destruction in Kryvorizh as a result of the long-term development of iron ore deposits. The research methodology is based on the use of general scientific and specific methods, in particular: analysis and synthesis, induction and deduction, modeling, systematization and generalization. The scientific novelty of the obtained results lies in the well-founded essence of environmental pollution and environmental violations, it was concluded that the current environmental tax does not correspond to the definition of the tax.It is proposed to provide the new payment with the performance of a penal-incentive function, which must be considered as a theoretical concept.The article determines that Kryvorizhia belongs to the most ecologically dangerous territories in Ukraine, where large areas of land have been withdrawn from agricultural use. The authors proposed in the Tax Code of Ukraine to limit preferential taxation for placing on the territory of each ton of mining waste and to raise the tax rate to the objective level of the III class of danger, which is due to the content of highly toxic heavy metals in the composition of this waste. To replace the name and mechanism of payment for environmental pollution, damage to the health of the population in the Tax Code of Ukraine. It is proposed to give the new payment a punitive and stimulating function, which must be considered as a new theoretical concept. Conclusions. The problem of cleaning excessively polluted territory and air in Kryvorizha, in the perspective of improving the landscape structure of the region, can be solved by state measures, joint active activities of regional and city authorities, scientists and the local public.First of all, the state needs to legitimize, that is, at the legislative level, significantly increase the financial responsibility of business entities for violating the requirements of the environmental protection legislation of Ukraine and the recommendations of international environmental programs. Key words: resources, mining industry;mining enterprise;mining and beneficiation plant;environmental protection measures.

Biofilm formation on the surface of monazite and xenotime during bioleaching.

Microbial attachment and biofilm formation is a ubiquitous behaviour of microorganisms and is the most crucial prerequisite of contact bioleaching. Monazite and xenotime are two commercially exploitable minerals containing rare earth elements (REEs). Bioleaching using phosphate solubilizing microorganisms is a green biotechnological approach for the extraction of REEs. In this study, microbial attachment and biofilm formation of Klebsiella aerogenes ATCC 13048 on the surface of these minerals were investigated using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). In a batch culture system, K. aerogenes was able to attach and form biofilms on the surface of three phosphate minerals. The microscopy records showed three distinctive stages of biofilm development for K. aerogenes commencing with initial attachment to the surface occurring in the first minutes of microbial inoculation. This was followed by colonization of the surface and formation of a mature biofilm as the second distinguishable stage, with progression to dispersion as the final stage. The biofilm had a thin-layer structure. The colonization and biofilm formation were localized toward physical surface imperfections such as cracks, pits, grooves and dents. In comparison to monazite and xenotime crystals, a higher proportion of the surface of the high-grade monazite ore was covered by biofilm which could be due to its higher surface roughness. No selective attachment or colonization toward specific mineralogy or chemical composition of the minerals was detected. Finally, in contrast to abiotic leaching of control samples, microbial activity resulted in extensive microbial erosion on the high-grade monazite ore.

Low-temperature oxidation of sulphide ores of sulphide-polymetallic deposits of Azerbaijan


 
 
 The article presents the results of experimental studies to determine the oxidative ac- tivity for the main industrial types of sulphide ores of sulphide-polymetallic deposits in Azerbai- jan. To calculate the amount of heat generated during oxidation, the dependences of the oxygen absorption rate on the temperature and moisture of the ore were established. It was found that with an increase in temperature above 50-80oC, absorption of oxygen slows down with time faster than at low (2.5-50oC) temperatures. If with an increase in temperature from 2.5 to 45-50oC the amount of absorbed oxygen increases by 7.5-12 times, then at a temperature from 45-50oC to 80oC it increases only by 3.6-3.7 times, which is explained by a decrease in moisture of the ore with an increase in temperature, due to evaporation. The time dependence of absorption rate of the oxygen for sulphide ores of sulphide-polymetallic deposits of Azerbaijan has a clearly pronounced break, which indicates a change in the oxidation mechanism. The oxidizing activity of sulphide ores of sulphide-polymetallic deposits of the Balakan ore field of Azerbaijan at low temperatures (2.5-800C) was studied. Determination of the oxidative activity of the main industrial types of sulphide ores of sulphide-polymetallic deposits in Azerbaijan makes it possible to classify ore reserves according to the degree of tendency to spontaneous combustion, which will allow a scientifically sound approach to planning the sequence of their development and designing mines. In addition, the article presents the results of experimental studies to determine the oxidizing activity of the sulfide ores of the Katsdag, Filizchay and Katekh deposits, carried out in laboratory conditions by the method of Institute of Mining named after A.A. Skochinsky. An indicator of oxidative activity is the oxygen absorption rate constant and labeled by the letter U (ml/g hour). The results of laboratory studies show that the oxidation of the ore leads to an increase in temperature and ignition and depends on a large number of factors such as mineralogical composition, chemical activity, humidity, temperature, fragmentation, etc. The dependence of the total amount of oxygen absorbed by sulphide ores on time at various temperatures is obtained. It has been estab- lished that with increasing temperature, the rate of oxygen absorption by sulphide ores increases. The values of the temperature coefficient (Kt < 2.0) in the temperature range of 2.5-800C show that the rate of the oxidation of sulfide ore is controlled by oxygen diffusion, and not by the rate of the chemical reaction. With equal fragmentation and equal distribution of chemical elements in ore samples, the oxidation rate is directly proportional to the outer surface of the sulphide ore.
 
 

Changes in Microfine Particle Migration of Ionic Rare Earth Ores during Leaching

The hydration mechanism between the leaching agent and ore surface during the leaching process of ionic rare earth ore is complicated, and the inter-particle bridge cementation is prone to fracture due to the existence of multiple forces and dispersion during ion adsorption and exchange, resulting in migration and rearrangement of microfine particles, and precipitation at the pore throat, producing blockage phenomenon and affecting the leaching efficiency of ionic rare earths. In order to reveal the migration law of microfine particles during in situ leaching of ionic rare earth ores and to find suitable regulation methods, this paper investigates the effects of leaching agent mass concentration, viscosity, flow rate, hydraulic gradient, ore body height, and ore body water content on the migration of microfine particles. We compared ionic rare earth ores as raw ores and rare earth ores with particle sizes ranging from 0.075 to 0.09 mm using the laboratory column leaching method. The results showed that the migration of microfine particles during ionic rare earth ore leaching was an important factor affecting leaching efficiency. Under the action of external forces, the microfine particles tended to migrate with the leaching agent during the leaching process.

A Review on the Humic Substances in Pelletizing Binders: Preparation, Interaction Mechanism, and Process Characteristics

Humic acid is inexpensive, and has a wide range of sources and a strong adsorption force with the surface of iron ore, and the size of its adsorption force is affected by some factors such as humic acid concentration, pH of the solution, and metal cations. The modified humic acid pellet binder (MHA) with strong adhesion and high viscosity was obtained through the separation and purification of solid wastes such as lignite and weathered coal and chemical modification treatment and successfully applied in the production process of iron ore pellets. After industrial tests, MHA can significantly improve the strength of green and dry pellets, less residue after high-temperature roasting, less metallurgical pollution, high strength of fired pellets, and can partially or completely replace bentonite.

Sulfur enhancement effects for uranium bioleaching in column reactors from a refractory uranium ore.

The feasibility of sulfur enhancement for uranium bioleaching in column reactors was assessed with a designed mixed Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferriphilum from a refractory uranium ore. The uranium extraction reached 86.2% with the sulfur enhancement (1 g/kg) in 77 days leaching process, increased by 12.6% vs. the control without sulfur addition. The kinetic analysis showed that uranium bioleaching with sulfur enhancement in columns followed an internal diffusion through the product layer-controlled model. Ore residue characteristics indicated that sulfur enhancement could strengthen the porosity of passivation layer, improving the ore permeability. Notably, bacterial community analysis showed that sulfur enhancement at 1 g/kg could make the iron-oxidizing and sulfur-oxidizing bacteria on the ore surface maintain a good balance (approx. 1:1), and thus decomposing ore more effectively. Lastly, a possible mechanism model for uranium bioleaching with sulfur enhancement was proposed.

Significance of Fe contents on the surface of the gold ores in gold leaching by thiourea and ethylene thiourea

Environmentally friendly ligands, alternatives to cyanide, are desired to extract gold for the sustainable hydrometallurgy of gold. Leaching characteristics of gold were examined using thiourea (TU) and ethylene thiourea (ETU) as ligands from three types of gold ores with different Fe contents from 2.70 to 14.09 wt% under the acidic condition. The Au recovery by TU leaching reached the extractable maximum with the lowest Fe-bearing gold ore. This type of gold ore is suitable for TU/ETU leaching. The highest Fe-bearing gold ore was the most difficult to extract Au in ETU/TU leaching. There are at least two detrimental factors in TU leaching of Fe-rich gold ores, that is (i) the oxidative decomposition of TU, and (ii) complexation of TU with Fe3+, which both cause to deduce the complexation of TU with Au+. However, adding Na2SO3 improved the Au extraction from such an ore to reduce Fe3+ to Fe2+. ETU facilitated the formation of more stable complexes with Au than TU against the coexisting Fe3+. This finding is useful when considering the cyanide-free leaching of different types of gold ores.