Research Achievements - Other -

Selective Leaching of Copper and the Removal of Arsenic from Enargite Using High-pressure Oxidative Leaching

GODIRILWE Labone L., HAGA Kazutoshi, OINUMA Ryuji, BATNASAN Altansukh, SHIBAYAMA Atsushi

環境資源工学 ( 一般社団法人 環境資源工学会 )  71 ( 3 ) 138 - 144   2025

<p>High arsenic (As) content in copper ores and concentrates poses challenges to the smelting/converting process, particularly the environmental implications of arsenic emissions. As an alternative, high-pressure oxidative leaching (HPOL) of enargite ore was investigated in this study to achieve selective dissolution of copper and separation of arsenic from high arsenic-containing copper ore. The effects of leaching conditions such as the type of leaching medium, leaching temperature, and total pressure, were investigated. Ferric sulfate (Fe₂(SO₄)₃) was used as the leaching medium under optimized leaching conditions (160°C and 1.0 MPa total pressure). The results showed that the dissolution of copper from enargite ore was limited to around 65%, due to the agglomeration and passivation of mineral particles caused by elemental sulfur, as shown by SEM-EDS. However, the addition of NaCl as an additive significantly improved the copper dissolution rate to about 82%, while about 98% of arsenic was removed as scorodite (FeAsO₄•2H₂O).</p>

DOI CiNii Research

Copper Recovery from Chalcopyrite Concentrate by Oxidative Roasting and Acid Leaching

TUMEN-ULZII Narangarav, GARNAAD Ariunaa, SILAM Alen, TUMENDELGER Azzaya, GUNCHIN Burmaa, SHIRCHINNAMJIL Nyamdelger, HAGA Kazutoshi, SHIBAYAMA Atsushi, BATNASAN Altansukh

Ｉｎｔｅｒｎａｔｉｏｎａｌ　Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ｓｏｃｉｅｔｙ　ｏｆ　Ｍａｔｅｒｉａｌｓ　Ｅｎｇｉｎｅｅｒｉｎｇ　ｆｏｒ　Ｒｅｓｏｕｒｃｅｓ ( 日本素材物性学会 )  25 ( 1 ) 56 - 62   2022.04

<p>In this study, a combined process consisting of salt roasting and acid leaching was conducted to recover copper per sulphide concentrate with 43.5% of chalcopyrite. The chalcopyrite concentrate was roasted in the absence and the presence of potassium chloride (mass ratio of concentrate:KCl from 1:0.5 to 1:0.9) at various temperatures (400-600°C) and different roasting times (1-4 hours) under air atmosphere. The roasted concentrate was dissolved in sulphuric acid solution (60 g/L) with a solid-liquid ratio of 1:8 at an ambient temperature for 2 hours. The chalcopyrite concentrate, roasted samples, and leached residues were analyzed using atomic absorption spectrometry, UV-VIS spectrophotometer, and X-ray diffractometer. Thermogravimetry and differential thermal analyses were applied on the chalcopyrite concentrate and the concentrate with KCl up to 1000°C. Results showed that about 80% and 90% of chalcopyrite decomposed under the conditions with the copper concentrate:KCl ratio of 1:0.6, roasting time of 2 hours at 500°C and 550°C, respectively. The DTA-TG analyses revealed variant phase regions associated with chalcopyrite decomposition through the roasting. Copper dissolution with the sulphuric acid solution from the roasted concentrates was over 99.7% and 99.0% under the determined conditions. The thermodynamic stability of chalcopyrite with KCl was discussed by calculating Gibb's free energy.</p>

DOI CiNii Research

Removal of Silicon, Aluminum and Phosphorus Impurities from Low-grade Iron Ore by Reverse Froth Flotation and Alkaline Roasting

BATNASAN Altansukh, SHIBAYAMA Atsushi, TAKEUCHI Hiroya, HAGA Kazutoshi, MIZUTANI Moritoshi, HIGUCHI Ken-ichi

Ｉｎｔｅｒｎａｔｉｏｎａｌ　Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ｓｏｃｉｅｔｙ　ｏｆ　Ｍａｔｅｒｉａｌｓ　Ｅｎｇｉｎｅｅｒｉｎｇ　ｆｏｒ　Ｒｅｓｏｕｒｃｅｓ ( 日本素材物性学会 )  25 ( 1 ) 122 - 128   2022.04

<p>In this paper, the removal processes for silicon (Si), aluminum (Al) and phosphorus (P) impurities from low-grade iron ore, in which hematite (Fe₂O₃), goethite (FeO(OH)), and quartz (SiO₂) are the main mineral constituents, have been presented. The reverse froth flotation process was applied to remove silicon and aluminum impurities from the iron ore using dodecyltrimethylammonium bromide (DTAB) and dodecylamine acetate (DAA) cationic collectors at a broad slurry pH ranging from 2 to 12. Whereas alkaline roasting followed by a water washing process was employed to remove phosphorus impurity from the iron ore under the various sodium hydroxide concentrations, different roasting temperatures, and prolonged varying times. Results showed that the maximum removal rate of SiO₂ and Al₂O₃ achieved were 58.3% and 31.0% via reverse froth flotation using DTAB collector at pH 12, whereas 38.7% SiO₂ and 10.0% Al₂O₃ with DAA collector. The level of total (SiO₂+Al₂O₃) impurities in the tailing as iron ore product from the reverse flotation was reduced from 7.4 mass% to 4.4 mass% as the initial level. On the other hand, about 61% of phosphorus in the iron ore was removed by the combined alkaline roasting and water washing at the conditions optimized as 50 g/kg-ore NaOH at 300°C for 0.5 h. The grade of phosphorus impurity reached 0.04 mass% from 0.09 mass% (initial grade). Simultaneously, the iron grade and level of SiO₂+Al₂O₃ impurity in the iron ore product from reverse flotation of the low-grade iron ore with DTAB collector reached 60.0 mass% and 4.4 mass%, which are acceptable levels for ironmaking.</p>

DOI CiNii Research

The Role of Lead in Suppressing Passivation of High Silver―Containing Copper Anodes During Electrorefining

GODIRILWE Labone L., TAKASAKI Yasushi, HAGA Kazutoshi, SHIBAYAMA Atsushi, SATO Rie, TAKAI Yoshinari

Ｉｎｔｅｒｎａｔｉｏｎａｌ　Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ｓｏｃｉｅｔｙ　ｏｆ　Ｍａｔｅｒｉａｌｓ　Ｅｎｇｉｎｅｅｒｉｎｇ　ｆｏｒ　Ｒｅｓｏｕｒｃｅｓ ( 日本素材物性学会 )  25 ( 1 ) 137 - 144   2022.04

<p>Passivation behavior of high silver containing copper anodes was investigated using slowly cooled Cu- 1%Ag anodes of different lead (Pb) concentrations. The addition of Pb distributes silver in the Pb phase and reduces the amount of silver that is solidly soluble in copper and, thus, generates a fine silver powder on the anode surface which is a main contributing factor of passivation. Electrorefining experiments were conducted using a synthetic electrolyte containing 40 g/L Cu²⁺ and 180 g/L H₂SO₄, at 60°C. SEM-EDS analysis was used to study the resulting anode slime and showed that increasing Pb content altered the anode slime structure from fine and compact to porous and less adherent to the anode surface. Utilizing a Cu-1%Ag0.2%Pb anode yielded the longest passivation time with a low and stable cell voltage of 0.1V. The slime morphology was characterized by precipitated metallic silver particles either as inclusion or loosely present on the surface of the abundant complex Cu-Ag-Pb sulfate type of compounds. Because of the economic importance of silver recovery from the anode slime, understanding its behavior during electrorefining will enable operating with high impurity anodes especially in secondary copper processing where metallic impurities can result from e-waste and copper alloy scrap.</p>

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Classification of Arsenic Bearing Minerals Using Hyperspectral Imaging and Deep Learning for Mineral Processing

OKADA Natsuo, MAEKAWA Yohei, OWADA Narihiro, HAGA Kazutoshi, SHIBAYAMA Atsushi, KAWAMURA Youhei

Journal of MMIJ ( The Mining and Materials Processing Institute of Japan )  137 ( 1 ) 1 - 9   2021

<p>Currently, there have been issues concerning the depletion and scarcity of mineral resources. This is mostly due to the excavation of high grade minerals having already occurred years and years ago, hence forcing the mining industry to opt for the production and optimization of lower grade minerals. This however brings about a plethora of problems, many of which economic, stemming from the purification of those low grade minerals in various stages required for mineral processing. In order to reduce costs and aid in the optimization of the mining stream, this study, introduces an automatic mineral identification system which combines the predictive abilities of deep learning with the excellent resolution of hyperspectral imaging, for pre-stage of mineral processing. These technologies were used to identify and classify high grade arsenic (As) bearing minerals from their low grade mineral counterparts non-destructively. Most of this ability to perform such tasks comes from the highly versatile machine learning model which employs deep learning as a means to classify minerals for mineral processing. Experimental results supported this statement as the model was able to achieve an over 90% accuracy in the prediction of As-bearing minerals, hence, one could conclude that this system has the potential to be employed in the mining industry as it achieves modern day system requirements such as high accuracy, speed, economic, userfriendly and automatic mineral identification.</p>

DOI

Treatment of Spent LED Light Bulbs for Recycling of Its Components: A Combined Assessment in the Context of LCA and Cost-Benefit Analysis

DODBIBA Gjergj, OSHIKAWA Hiroki, PONOU Josiane, KIM Yonggu, HAGA Kazutoshi, SHIBAYAMA Atsushi, FUJITA Toyohisa

Resources Processing ( The Resources Processing Society of Japan )  66 ( 1 ) 15 - 28   2019

<p>Recently, the demand for LED light bulbs is rapidly increasing due to an increasing demand for energy saving lightning options. In this work, the elemental composition of LED light bulbs is first analyzed, and then a flowsheet for recovering LED chips and other valuable metals from spent LED light bulbs is put forward. The suggested flowsheet includes eddy current separation (ECS) and air tabling, in addition to several refining processes. The experimental results indicated that the eddy current separation and the air tabling are useful techniques for sorting components of LED bulbs, enabling the recycling of aluminium, plastics, and precious metals, such as gold and silver. Next, five different scenarios for treatment of spent LED light bulbs were considered and a combined life cycle assessment (LCA) and cost-benefit analysis was carried out to find out the most suitable alternative. The results of the combined assessment suggested that the recycling of mainly Al and plastics from spent LED bulbs is an environmentally friendly and cost-effective alternative.</p>

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