Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 1 of 18 Treatment of copper-containing leaching residue by sulfation roasting followed by acid/water leaching Nyamdelger Shirchinnamjil, Narangarav Tumen-Ulzii, Nemekhbayar Davaadorj, Khulan Byambasuren, Sarantsetseg Purevsuren, Ulziibadrakh Erdenebat, Enkhtuul Surenjav* Institute of Chemistry and Chemical Technology, Mongolian Academy of Sciences, Ulaanbaatar 13330, Mongolia *Author to whom correspondence should be addressed Enkhtuul Surenjav Laboratory of Inorganic Chemistry Institute of Chemistry and Chemical Technology Mongolian Academy of Sciences Ulaanbaatar, Mongolia E-mail: enkhtuul@mas.ac.mn ORCID: https://orcid.org/0000-0002-2357-5339 This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, and proofreading process, which may lead to differences between this version and the official version of record. Please cite this article as: Nyamdelger Sh., Narangarav T., Nemekhbayar D., Khulan B., Sarantsetseg P., Ulziibadrakh E., Surenjav E. Treatment of copper-containing leaching residue by sulfation roasting followed by acid/water leaching. Mongolian Journal of Chemistry, 24(50), 2023, xx-xx https://doi.org/10.5564/mjc.v24i50.1310 mailto:enkhtuul@mas.ac.mn https://orcid.org/0000-0002-2357-5339 https://doi.org/10.5564/mjc.v24i50.1310 Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 2 of 18 Treatment of copper-containing leaching residue by sulfation roasting followed by acid/water leaching Nyamdelger Shirchinnamjil, https://orcid.org/0000-0003-1242-7776 3 Narangarav Tumen-Ulzii, https://orcid.org/0000-0003-0010-1402 Nemekhbayar Davaadorj, https://orcid.org/0000-0001-5484-1807 Khulan Byambasuren, https://orcid.org/0000-0002-5617-1605 6 Sarantsetseg Purevsuren, https://orcid.org/0009-0005-8860-0928 Ulziibadrakh Erdenebat, https://orcid.org/0000-0002-4397-9525 Enkhtuul Surenjav*, https://orcid.org/0000-0002-2357-5339 9 Institute of Chemistry and Chemical Technology, Mongolian Academy of Sciences, Ulaanbaatar 13330, Mongolia 12 ABSTRACT 15 This research investigates the extraction of copper from copper-containing leaching residue, which includes 33.45% of copper, 14.14% of iron, 23.87% of sulfur and trace amounts of silver and other elements. Roasting the copper-containing residue under air and oxygen flow convert 18 sulfides into sulfate, followed by water and acid leaching to extract copper. The process parameters, including leaching temperature, sulfuric acid concentration, leaching time, solid-to- liquid ratio, and agitation speed, were optimized for both water and acid leaching methods. 21 Results showed that the maximum copper dissolution efficiency was 93.12% with water leaching, and 97.16% with acid leaching. Chemical analysis revealed that the water and acid leaching residue contained 48.13% and 31.64% of iron, respectively. This study provides 24 valuable insights into the process optimization for copper extraction from copper-containing leaching residue, which can inform the development of more efficient and sustainable methods for metal recovery. 27 Keywords: copper technogen concentrate, thermal analysis, air- and oxygen roasting, acid/water leaching 30 https://orcid.org/0000-0003-1242-7776 https://orcid.org/0000-0003-0010-1402 https://orcid.org/0000-0001-5484-1807 https://orcid.org/0000-0002-5617-1605 https://orcid.org/0009-0005-8860- https://orcid.org/0000-0002-4397-9525 https://orcid.org/0000-0002-2357-5339 Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 3 of 18 INTRODUCTION The growing demand for copper has resulted in the depletion of copper ores with higher copper content, leading to the treatment of complex polysulfides or copper ore with higher contents of 33 impurities such as Sb, Pb, Zn, As, Hg, Ni etc. Among these impurities, arsenic is particularly challenging due to its toxicity. There are several significant polymetallic ore deposits in Mongolia including Tsav, Boorchi, Tolbo, Kharmagtai and Asgat. In recent years, there has been interest 36 in developing the Asgat deposit as well as other mineral deposits in the country, to meet the growing demand for metals and minerals worldwide. Asgat polymetallic deposit is estimated to hold approximately 6402.6 thousand of tonnes of ore, boasting a valuable metal reserve 39 including 2247.8 tonnes of silver, 7264.6 tonnes of copper, 31830.9 tonnes of antimony and 3319.8 tonnes of bismuth. Although Asgat is primarly known for its polymetallic ore composition, it can also be regarded as a potential source of copper due to the significant presence of 42 tetrahedrite, which constitutes 72% of the Asgat concentrate [1-3]. Processing of polymetallic concentrates is difficult task as it involves a variety of minerals such as enargite (Cu3AsS4), tennantite (Cu12As4S13) and tetrahedrite (Cu12Sb4S13) associated with 45 other sulfide minerals [4]. To separate the target metals from the polymetallic ore concentrate, scientists have focused on removing harmful impurities. Comprehensive study on thermal and kinetic study of polymetallic copper concentrate was conducted by Mitovski et. al [5]. 48 Tetrahedrite represents the main chemical source of copper (40-46%) and antimony (27-29%) along with other important elements including arsenic, bismuth, mercury, and silver. Two main leaching methods for tetrahedrite have been identified- alkaline and acidic leaching [6]. Balaz 51 et.al studied leaching of mercury and antimony from tetrahedrites of different characteristics using an alkaline solution [7] while the leaching of tetrahedrite using HCI in the presence of ozone was studied by Ukasik et. al [8]. 54 The leaching residue can be further processed through an appropriate roasting process to convert the metals into extractable form by heating at high temperature [9-11]. Three types of roasting methods are commonly used including oxidation roasting, chlorination roasting, and 57 sulfation roasting [12]. However, oxidation roasting requires high temperatures and may lead to copper loss as copper ferrite. Chlorination roasting tends to generate toxic and corrosive oxychlorides [13]. On the other hand, sulfation roasting has been found to be quite suitable for 60 subsequent processing. Nevertheless, during sulfation roasting, the reaction becomes complex when more than one sulfide is present in the sample. Roasting is a surface reaction that results in the formation of an oxide layer. This layer remains 63 porous allowing oxygen to pass into the unreacted inner sulfide portion of the particle, while the resulting SO2 gas is released [14]. The sulfuric gas then reacts with metal oxides and excess Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 4 of 18 oxygen to form sulfates, making the sulfation roasting process an environmentally friendly 66 technology. To produce a mixed oxide- sulfate product sulfation roast is preferred, making it an ideal process for polysulfide compound. While there have been numerous investigations conducted, our study provides a comprehensive analysis of copper extraction from copper 69 technogen concentrate sourced from domestic ore deposits. This study aimed to assess the effectiveness of extracting copper from copper-containing leaching residue of polysulfide concentrate. The process involved sulfation roasting followed by 72 leaching with water and sulfuric acid. To determine the optimal conditions for sulfation roasting, the study examined the effects of roasting temperature and time under an air and oxygen atmosphere. After roasting, the resulting product was leached using water and sulfuric acid to 75 obtain a copper-bearing aqueous solution. Copper sulfate was the predominant compound in the solution. EXPERIMENTAL 78 Materials: The raw material used in this study was the polysulfide concentrate obtained from the Asgat mining ore in Mongolia. The concentrate was initially subjected to alkaline-sulfide leaching (using NaOH/Na2S x 9H2O) to obtain a technogen concentrate also named copper containing 81 leaching residue, containing 33.45% copper, which was subsequently utilized for copper extraction. TG/DTA analysis: Thermal analysis of the copper technogen concentrate was carried out using 84 Hitachi-TG/DTA 7300. The TGA/DTA analysis was performed under air atmosphere, in the temperature range of 30-1000 oC, at a heating rate of 20.0 oC /min. Sulfation roasting: Sulfation roasting experiments were conducted under air atmosphere using 87 a temperature-controlled tube furnace equipped with a quartz tube. For comparison purposes, sulfation roasting experiments under oxygen were also carried out using a home-made tube furnace. The oxygen flow is controlled via Brooks Sho-Rate flowmeter installed on the inlet. 90 Sulfuric acid leaching: Acid leaching experiments were conducted to evaluate the effect of various parameters, including acid concentration, temperature, leaching time, solid-to-liquid ratio and agitation speed. For each leaching experiment, 1.5-3 g of sample and 20 ml of acid with 93 appropriate concentration were placed in a round bottom flask. The leaching time was varied from 30 to 120 mins, while the acid concentration used were 0.4M, 0.8M, 1.2M and 1.6M. The leaching temperature ranged from 25 oC to 70 oC with solid-to-liquid ratio of 1:6.67 (15%), 1:8 96 (12.5%), 1:10 (10%), 1:13.33 (7.5%). Agitation speeds of 200, 300 and, 400 rpm were used with magnetic stirrer. Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 5 of 18 Water leaching: In the water leaching experiment 0.27-0.84 g sample and 20 ml of water were 99 placed in a conical flask and subjected to different temperature ranging from 25 oC to 70 oC, with agitation speeds ranging from 200 to 500 rpm at 100 rpm intervals. The leaching time varied between 30, 60 and 120 mins, with solid/liquid ratios of 1:25, 1:50 and 1:75. 102 After completion of the leaching process, the slurry was filtered and the leaching residue was washed continuously with distilled water and dried in an oven. The leachates and leach residue were analyzed using ICP-OES, XRD, SEM and chemical analysis to determine the constituents. 105 RESULTS AND DISCUSSION Asgat polymetallic ore concentrate is composed of several metals, including 0.91% silver, 18.2% copper, 19.4% antimony, 2.03% arsenic, and 1.6% bismuth, as well as other elements. In order 108 to remove toxic contaminants such as antimony, arsenic, and bismuth, the concentrate was subjected to alkaline-sulfide leaching. The activation energy for antimony leaching from the tetrahedrite by alkaline-sulfide leaching was calculated as 81.43 kJ/mol which indicates the 111 leaching is controlled by surface chemical reaction [15]. These findings are consistent with those of other researchers [16]. The elemental composition of Asgat concentrate and leaching residue are compared in Table 1 114 [15]. The alkaline-sulfide leaching residue contains 33.45% of copper, 14.14% of iron, 23.87% of sulfur, 0.73% of silver and other trace elements such as silicon, aluminium and sodium. According to the XRD analysis, the leaching residue contains chalcopyrite (CuFeS2), covellite 117 (CuS), chalcocite (Cu2S), pyrite (FeS) and argentite (Ag2S) as well as non-ore sulfide minerals as shown in Fig. 1 and Table 2. 120 Table 1. The elemental composition of concentrate and the leaching residue Sample Elements, % Ag Sb As Cu Fe Zn Pb Bi S Concentrate 0.91 19.40 2.03 18.20 10.6 0.51 0.09 1.67 13.60 Leaching residue 0.73 0.14 0.22 33.45 14.14 0.93 23.87 Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 6 of 18 123 Fig. 1. XRD analysis of copper-containing leaching residue Table 2. Phase identification by XRD analysis of copper-containing leaching residue 126 Minerals Formula Contents, % Chalcopyrite CuFeS2 43.24 Chalcocite Cu2S 6.03 Covellite CuS 3.51 Argentite Ag2S 6.95 Albite NaAlSi3O8 38.47 TG/DTA analysis: TGA/DTA thermogravimetric analysis was conducted to study the sample’s initial oxidation temperature, and mass change during the 30-1000 oC temperature range. The 129 comparison of TGA/DTA results with XRD phase identification of the sample will help to understand the complex reaction mechanism during the sulfation roasting. TGA/DTA analysis was done for copper-containing leaching residue at a heating rate of 20.0 oC/min in the 132 temperature range of 30-1000 oC under air atmosphere. As seen from the thermogravimetric curve cf. Fig 2 when the sample is heated from room temperature till 315 oC there is slow weight loss of 2.9% was observed due to the evaporation of 135 moisture and organics as well as hydrates decomposition. Eventually, the weight increase was observed and become 100.02% at 343.29 oC indicating the sulfides are oxidized and sulfates produced. Roasting the sample further from 343 to 600 oC results in weight gain of a maximum 138 of 128.99% at 600.79 oC indicating the sulfation roasting fully occurred at this temperature range based on the theoretical calculation. The weight increase up to 600 oC is attributed to the production of copper sulfate. However, the iron sulfate production will also affect weight 141 increase. After 600 oC the weight loss occurs till 943.52 oC resulting the sulfur oxide which is associated with the decomposition of sulfates. To summarize, when copper-containing leaching residue is subjected to thermal analysis, weight gain of 28.7% occurs at a temperature range of 144 350-600 oC, whereas the total weight loss is 14% during the entire roasting at 25-1000 oC. Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 7 of 18 During the thermal treatment the following reactions are predicted. For example: 2CuFeS2 + 7.5O2 = 2Cu2S + 2FeS + 2SO2 ∆G823,15К = 190 kJ/mol (1) 147 3FeS + 5O2 = Fe3O4 + 3SO2 ∆G823,15К = -1443.78 kJ/mol (2) 2FeS + 3.5O2 = Fe2O3 + 2SO2 ∆G823,15К = -1049.76 kJ/mol (3) Cu2S + SO2 + 3O2 → 2CuSO4 ∆G823,15К = -533.06 kJ/mol (4) 150 2CuS + SO2 + 3O2 → 2CuSO4 ∆G823,15К = -658.21 kJ/mol (5) Ag2S + 2O2 = Ag2SO4 ∆G823,15К = -392.71 kJ/mol (6) FeS2 + 3O2 = FeSO4 + SO2 ∆G823,15К = -809.08 kJ/mol (7) 153 Fig. 2. Thermogravimetric analysis of copper-containing leaching residue ∆GoT values for proposed reactions are calculated at 823.15K and it was found that all values 156 except for Eq.1 are negative. This indicates that the reactions are thermodynamically feasible at the calculated temperature. Roasting under air: The purpose of the roasting stage was to convert copper sulfide into easily 159 soluble copper sulfate. In comparison to conventional roasting processes, we have an advantage in using lower roasting temperature and eliminating the need for added sulfuric acid [9] or sodium sulfite as sulfation agent [12]. To achieve this, the copper-containing leaching 162 residue was underwent roasting in a Nabertherm tube furnace under an air atmosphere at varying temperatures, ranging from 400 to 600 oC as determined by TG/DTA analysis. Roasting times varied from 15 minutes to 3 hours. 165 In this study, we examined the weight increase during sulfation roasting under varying times and temperatures. The results showed that the highest weight increase of 32.21% is occurred at 550 oC for one hour of roasting time under air atmosphere as shown in Fig. 3. Additionally, the color 168 difference of the roasted products can indicate whether sulfation roasting is complete. Lighter Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 8 of 18 colors were observed at lower temperatures or shorter roasting times, whereas completed roasting resulted in darker colors due to copper sulfation. 171 The chemical composition of the roasted product is confirmed through an XRD study (refer Fig. 4) revealing that 67.8% of the product was comprised of copper sulfate, while 27.2% composed goethite and 4.8% albite. This finding indicates that almost 95% of copper was successfully 174 converted to copper sulfate during the roasting process. The oxidation of chalcopyrite, covellite and chalcocite during roasting was responsible for this conversion [17]. Furthermore, iron compounds were also present in the roasted product in addition to copper sulfate. 177 Roasting under oxygen: The copper-containing residue was subjected to roasting under varying conditions of temperature, time, and oxygen flow rate. The results of the study, depicted in Fig. 3, showed that the maximum weight gain for air roasting was 32.21% at one hour of roasting 180 time, while oxygen roasting produced a maximum weight gain of 29.85%. However, when the roasting time was increased to three hours, the maximum weight gain for oxygen roasting was found to be 33.15%. X-ray diffraction (XRD) data indicated that with roasting times less than 183 three hours at temperature less than 400 oC for oxygen roasting, FeS2 and CuS still existed, suggesting that the sulfation roasting was not complete. At three hours of roasting time, copper sulfates dominated, along with other minerals such as magnetite (Fe3O4), goethite FeO(OH), 186 and iron sulfates Fe2(SO4)3. Therefore, the optimum conditions for oxygen roasting were determined to be a roasting temperature of 400 oC, a roasting time of 3 hours, and an oxygen flow rate of 20 ml/min (refer Table 3). XRD analysis of the roasted sample revealed a 189 composition of 64.8% copper sulfate, 3.6% goethite, 4.5% hematite, 3.5% magnetite, and 18.7% albite with approximately 12% iron compounds present in the roasted product. 192 Fig. 3. Weight gain vs. the roasting temperature under the air and oxygen roasting (roasting time is 60 mins) Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 9 of 18 Fig. 4. XRD analysis for effect of roasting time at optimum temperature (at 400 oC, O2 roasted for 180 195 min (a) 120 min (b) 60 min (c); and at 550 oC air roasted for 180 min (d) 120 min (e) 60 min (f)) Table 3. Phase identification by XRD analysis during the sulfation roasting Sample Temp./ oC Gas Time/min Roasted product Major phase Minor phase 1 400 Air 60 CuSO4 FeO(OH), Fe2O3 2 450 Air 60 CuSO4 Fe2O3 3 500 Air 60 CuSO4 CuSO4x5H2O, FeO(OH) 4 550 Air 60 CuSO4 CuSO4x5H2O, FeO(OH) 5 600 Air 60 CuSO4 FeO(OH), Fe2O3 6 650 Air 60 CuSO4 FeO(OH), Fe2O3 7 300 O2 60 CuSO4 CuFeS2, FeS2 8 350 O2 60 CuSO4 CuFeS2, FeS2 9 300 O2 180 CuSO4 FeO(OH), FeS2 10 350 O2 180 CuSO4 FeO(OH), FeS2, CuS 11 400 O2 180 CuSO4 FeO(OH), Fe3O4, Fe2(SO4)3 Composition of our sample, which includes metal sulfides such as chalcopyrite (CuFeS2), 198 covellite (CuS), chalcocite (Cu2S), pyrite (FeS) and argentite (Ag2S), makes the reaction during the roasting process highly complex. The chemical and mineralogical composition of the concentrate, as well as the temperature, are crucial factors in determining the product 201 composition during sulfation roasting. However, other process parameters such as particle size, mixing, reaction time and roasting technique can also significantly impact the final product [18]. The sulfation roasting process is complete at 550 oC during the air roasting, but, when oxygen 204 roasting is used, a lower temperature of 400 oC is required for the sulfation process. Leaching test with water: The copper technogen concentrate was roasted under optimum conditions and subsequently leached using water at various temperature to obtain a copper-207 Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 10 of 18 bearing aqueous solution. The water leaching experiments were conducted by varying the leaching time, temperature, agitating speed and solid-to-liquid ratio. The dissolution efficiency (%), which is a measure of how much of the total copper is dissolved, 210 was calculated using the equation given below: 𝐷𝑖𝑠𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 (%) = 𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑑𝑖𝑠𝑠𝑜𝑙𝑣𝑒𝑑 𝑚𝑒𝑡𝑎𝑙𝑠 𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑚𝑒𝑡𝑎𝑙𝑠 𝑖𝑛 𝑡ℎ𝑒 𝑠𝑎𝑚𝑝𝑙𝑒 ∗ 100 The copper dissolution efficiency was found to be at its highest with a rate of 91.68% at 60 213 minutes for the air roasted sample and 86.42% at 30 minutes for the oxygen roasted sample (refer to Fig. 5). With increase of leaching time, copper dissolution decreased for the oxygen roasted sample. Iron dissolution was generally lower, with about 12% in present in the leaching 216 solution and the majority remaining in the leaching residue. Fig. 5. Copper and iron dissolution efficiency as a function of leaching time 219 (S/L ratio 1:50, 500 rpm, 25 oC) Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 11 of 18 Fig. 6. Copper and iron dissolution efficiency as a function of agitation speed (air: 60 min, S/L ratio 222 1:50, 25 oC; oxygen: 30 min, S/L ratio 1:50, 25 oC) The agitation speed is an another important parameter in leaching experiments, and its effect on copper and iron dissolution was studied within the range of 200-500 rpm. For the air roasted 225 sample, the copper dissolution rate decreased slowly until 400 rpm but, increased to 91.68% at 500 rpm. The copper dissolution rate for the oxygen roasted sample increased gradually with the increase of agitation speed and reached a maximum value of 93.12% at 400 rpm. Iron 228 dissolution was generally low for the air roasted sample, whereas for the oxygen roasted sample, high iron dissolution was observed, especially at 300 rpm (refer to Fig. 6). This can be attributed to the increased molecular motion of iron sulfate as agitation speed increased, leading to a 231 corresponding increase in iron dissolution. The copper and iron dissolution rates were also studied as a function of solid-to-liquid ratio, as shown in Fig. 7. For both air and oxygen roasted sample, the optimum solid-to-liquid phase ratio 234 was found to be 1:50 with copper dissolution rates of 91.68% and 93.12%, respectively. We assume that water-insoluble compounds were also present in the roasted sample. At the 1:50 phase ratio, the iron dissolution rate was low, at 16.49% indicating that most of the iron 237 compound was left in the leaching residue. Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 12 of 18 Fig. 7. Copper and iron dissolution efficiency as a function of solid-to-liquid phase ratio (air: 60 min, 500 240 rpm, 25 oC; oxygen: 30 min, 400 rpm, 25 oC) During the water leaching experiment, the solution temperature was varied from 25 to 70 degree celsius. There was no significant change observed both air and oxygen roasted samples, 243 therefore all other experiments were conducted at room temperature. (refer to Fig. 8). The effect of temperature on iron dissolution was minimal, as most of iron was left in the water leaching residue. 246 Fig. 8. Copper and iron dissolution efficiency as a function of temperature (air: 60 min, S/L ratio 1:50, 500 rpm; oxygen: 30 min, S/L ratio 1:50, 400 rpm) 249 Leaching test with sulfuric acid: To compare the effectiveness of acid versus water leaching, the roasted samples underwent acid leaching experiments with acid concentration, solid-to-liquid 252 Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 13 of 18 ratio, and agitating speed varied. As depicted in Fig. 9, copper dissolution was better with the oxygen roasted sample compared to the air roasted sample. Both air- and oxygen- roasted samples achieved optimal copper dissolution rates with a sulfuric acid concentration of 1.6M. 255 Copper dissolution decreased with lower acid concentrations. The leaching time of 30 minutes was determined to be sufficient for achieving a dissolution efficiency of 98.43% in the oxygen roasted sample. However, the air roasted sample required an extended leaching time of 60 258 minutes to attain a slightly lower dissolution efficiency of 96.01%. Fig. 9. The effect of leaching time and acid concentration on copper dissolution (air: 25 oC, S/L ratio 261 1:10, 300 rpm; oxygen: 25 oC, S/L ratio 1:10, 300 rpm) Fig. 10 shows that the solid-to-liquid ratio had no significant effect on copper dissolution both for 264 air- and oxygen- roasted samples. At an solid-to-liquid ratio of 1:8, the copper dissolution was approximately 90.37% for the air roasted sample and 98.43% for the oxygen roasted sample. However, the dissolution of iron is highest with lower solid-to-liquid ratio, particularly for the 267 oxygen roasted sample. Fig. 11 illustrates the impact of agitation speed on copper dissolution. In the case of the air roasted sample, 200 rpm was determined to be the optimal agitation speed as it resulted in 270 97.16% copper dissolution. However, the iron dissolution rate was found to be relatively high. For the oxygen roasted sample, the highest copper dissolution rate (99.59%) was achieved at 300 rpm, with a lower amount of iron dissolved in the leachate. 273 Leaching processes of copper compounds in the water and sulfuric acid proceeds via diffusion and activation energy were calculated as 6.05 and 8.70 kJ/mol. Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 14 of 18 276 Fig. 10. The effect of solid-to-liquid ratio on copper dissolution (air: 1.6M H2SO4, 25 oC, 60 min, 300 rpm; oxygen: 1.6M H2SO4, 25 oC, 30 min, 300 rpm) 279 Fig. 11. The effect of agitation speed on copper dissolution (air: 1.6M H2SO4, 25 oC, S/L ratio 1:8, 60 min; oxygen: 1.6M H2SO4, 25 oC, S/L ratio 1:13.3, 30 min) 282 Fig. 12 compares the water leaching residue and acid leaching residue obtained. The air- and oxygen- roasted samples (black and pink curves) primarily consist of chalcocyanite and goethite, 285 while the water- and acid-leached samples contain albite, anorthite, hematite, and goethite. The hard residue left after water leaching contains 33.4% albite (Na[AlSi3O8]), 7.1% anorthite (CaAl2Si2O8), 13.7% goethite (FeO(OH)) 14.5% maghemite (-Fe2O3), and 31.0% hematite (-288 Fe2O3) with total iron accounting for 48.13% according to chemical analysis. The SEM-EDX analysis of the leaching residue confirms the presence of a high amount of iron 44.77% along with 44.94% oxygen, 0.82% silicon at measured point (refer Fig.13a). 291 Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 15 of 18 This residue could be utilized as an iron resource and further processed to recover iron, thereby ensuring complete utilization of the raw material without generating any waste. The morphology of the leaching residue after the water and acid leaching both for air (a,b) and 294 oxygen (c,d) roasted samples were shown in Fig. 13. SEM-EDS analysis confirmed the intensity of energy peaks corresponding to Fe, O2 and Si with about 44% of Fe content. 297 Fig. 12. XRD analysis of leaching residue compared with the roasted sample. a) acid leaching residue (O2 roasted), b) water leaching residue (O2 roasted), c) oxygen roasted sample, d) acid leaching 300 residue (air roasted), e) water leaching residue (air roasted), and f) air roasted sample 303 a b Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 16 of 18 Fig. 13. SEM micrographs of leaching residue; a) water leaching residue of air roasted sample b) acid leaching residue of air roasted sample; c) water leaching residue of oxygen roasted samples, d) acid 306 leaching residue of oxygen roasted samples Copper bearing aqueous solution: The resulting leach liquor after the water/acid leaching will be 309 further utilized to produce a high-purity electrolyte with a high concentration of Cu through solvent extraction. This electrolyte will then be used to electroplate a pure cathode copper. Our study suggests a shorter flowsheet of extracting the copper from the polysulfide concentrate, 312 which includes a leaching process to remove the impurities such as arsenic, sulfation roasting, water/acid leaching and subsequent solvent extraction. 315 CONCLUSIONS We systematically optimized the leaching processes for extracting copper from air and oxygen roasted samples using both water and sulfuric acid leaching methods. The parameters for water 318 leaching included a temperature of 25 oC, agitation speed of 500 rpm, solid-to-liquid ratio of 1:50 and a leaching time of 60 minutes. For acid leaching, we used a temperature of 25 oC, agitation speed of 200 rpm with a solid-to-liquid ratio of 1:8, and a leaching time of 30 minutes, with 1.6М 321 H2SO4. Our results indicated that acid leaching yielded a higher copper dissolution efficiency compared to water leaching, with values of 97.16% and 91.68%, respectively, for air roasted sample. 324 Similarly, for the oxygen roasted sample, acid leaching achieved a copper dissolution efficiency of 95.53%, while water leaching resulted in 93.12%. Notably, both methods exhibited a certain degree of iron dissolution efficiency, with approximately 15% and 30% present in the leachate 327 for the air roasted and oxygen roasted samples, respectively. XRD analysis confirmed the presence of hematite, goethite, magnetite and albite in the hard residue. After water and acid leaching, the hard residue contained 48.13% and 31.64%, total 330 iron, respectively. This indicates that water leaching was more effective in separating the iron compound, resulting in a higher concentration of iron in the hard residue. In conclusion, our c d Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 17 of 18 study highlights the optimized leaching processes for copper extraction from roasted samples. 333 Acid leaching exhibited superior copper dissolution efficiency, while water leaching demonstrated better separation of iron compounds. These findings contribute to the understanding of efficient extraction methods and the potential for maximizing copper recovery 336 while minimizing the presence of unwanted elements like iron. ACKNOWLEDGMENTS 339 This research was supported by a fundamental research project from the Ministry of Education and Science of Mongolia funded by the Mongolian Foundation for Science and Technology under contract No. ShuSs. 2020/21. 342 REFERENCES 1. Javkhlan O., Munkhtsengel B. (2021) Silver Deposits. In: Gerel O., Pirajno F., Batkhishig B., Dostal J. (eds) Mineral Resources of Mongolia. Modern Approaches in Solid Earth Sciences, 19, Springer, Singapore. https://doi.org/10.1007/978-981-15-5943-3_9 2. Ochirbat P. (1999) Strategy and ecology of noble minerals complex development. UB, 347 -374 3. Nyamdelger S., Burmaa G., Narangarav T-U. Ariunaa G. (2013) Dissolution behaviour of freibergite-tetrahedrite concentrate in acidic dichromate solution. Mong. J. Chem., 14(40), 36-40. https://doi.org/10.5564/mjc.v14i0.196 4. Schlesinger M.E., King M.J., Davenport W.G. (2011) Extractive metallurgy of copper. Elsevier, UK. ISBN 978-0-08-096789-9 5. Mitovski A., Strbac N., Mihajlovic I., Sokic M., Stojanovic J. (2014) Thermodynamic and kinetic analysis of the polymetallic copper concentrate oxidation process. J. Therm. Anal. Calorim., 118, 1277-1285. https://doi.org/10.1007/s10973-014-3838-8 6. Aghazadeh S., Abdollahi H., Gharabaghi M., Mirmohammadi M. (2021) Selective leaching of antimony from tetrahedrite rich concentrate using alkaline sulfide solution with experimental design: Optimization and kinetic studies. J. Taivan Inst. Chem. Eng., 119, 298- 312. https://doi.org/10.1016/j.jtice.2021.01.021 7. Balaz P., Sekula F., Jakabsky S., Kamme, l.R. (1995) Application of attrition grinding in alkaline leaching of tetrahedrite. Miner. Eng., 8(11), 1299-1308 https://doi.org/10.1016/0892-6875(95)00097-A 8. Ukasik M., Havlik T. (2005) Effect of selected parameters on tetrahedrite leaching by ozone. Hydrometallurgy, 77, 139-45. https://doi.org/10.1016/j.hydromet.2004.10.017 https://doi.org/10.1007/978-981-15-5943-3_9 https://doi.org/10.5564/mjc.v14i0.196 https://doi.org/10.1007/s10973-014-3838-8 https://doi.org/10.1016/j.jtice.2021.01.021 https://doi.org/10.1016/0892-6875(95)00097-A https://doi.org/10.1016/j.hydromet.2004.10.017 Ac ce pt ed m an us cr ip t Mongolian Journal of Chemistry Page 18 of 18 9. Dimitrijevic M. D., Urosevic D.M., Jankovic Z.D., Milic S. M. (2016) Recovery of copper from smelting slag by sulphation roasting and water leaching. Physicoche. Probl. Miner. Process, 52(1), 409-421. https://doi.org/10.5277/ppmp160134 10. Lucheva B., Iliev P., Kolev D. (2017) Hydro-pyrometallurgical treatment of copper convertor flue dust. J. Chem. Tech. Metall., 52(2), 320-325 11. Gorai B., Jana R.K., Kha, Z.H. (2002) Electrorefining electrolyte from copper plant dust. Mater. Trans., 43(3), 532–536. https://doi.org/10.2320/matertrans.43.532 12. Zhao Y., Hou Y., Cui Y., Liang H., Li L. (2015) Recovery of copper from copper sulfide concentrate by sulfation roasting. Inter. J. Nonferrous Met., 4, 9-13. https://doi.org/10.4236/ijnm.2015.42002 13. Priya J., Randhawa N.S., Hait J., Bordoloi N., Patel J.N. (2020) High-purity copper recycled from smelter dust by sulfation roasting, water leaching and electrorefining. Environ. Chem. Lett., 18, 2133-2139. https://doi.org/10.1007/s10311-020-01047-0 14. Shamsuddin M. (2021) Roasting of Sulfide Minerals. In: Physical Chemistry of Metallurgical Processes. Second Edition. The Minerals, Metals & Materials Series, Springer, Cham. https://doi.org/10.1007/978-3-030-58069-8_2 15. Ariunaa G., Burmaa G., Nyamdelger S., Altansukh B., Nazgul M., Narangarav T-U. (2021) Some results of studies on leaching of toxic elements in Asgat polymetallic concentrate. Bulletin of the Institute of Chemistry and Chemical Technology, 4(9), 17-25 https://doi.org/10.5564/bicct.v4i9.1814 16. Samuel A.A., Samuelsson C., Sandström A. (2010) Dissolution kinetics of tetrahedrite mineral in alkaline sulphidemedia. Hydrometallurgy, 103, 167-172 https://doi.org/10.1016/j.hydromet.2010.03.014 17. Prasad S., Pandey B.D. (1999) Thermoanalytical Studies on Copper-Iron Sulphides. J. Therm. Anal. Calorim., 58, 625-637. https://doi.org/10.1023/A:1010108729034 18. Nyamdelger Sh., Narangarav T-U., Nemekhbayar D., Sarantsetseg P., Surenjav E. et al., (2022) Copper extraction from the sulphation roasted copper technogen concentrate. Bulletin of the Institute of Chemistry and Chemical Technology, 10, 1-9. https://doi.org/10.5564/bicct.v10i10.1483 https://doi.org/10.5277/ppmp160134 https://doi.org/10.2320/matertrans.43.532 https://doi.org/10.4236/ijnm.2015.42002 https://doi.org/10.1007/s10311-020-01047-0 https://doi.org/10.1007/978-3-030-58069-8_2 https://doi.org/10.5564/bicct.v4i9.1814 https://www.sciencedirect.com/science/article/abs/pii/S0304386X10000824#! https://doi.org/10.1016/j.hydromet.2010.03.014 https://doi.org/10.1023/A:1010108729034 https://doi.org/10.5564/bicct.v10i10.1483