Editorial

5 pages, 210 KiB

Open AccessEditorial

Editorial for Special Issue “Sustainable Production of Metals for Low-Carbon Technologies”

by Ilhwan Park and Marthias Silwamba

Minerals 2023, 13(1), 88; https://doi.org/10.3390/min13010088 - 06 Jan 2023

Cited by 1 | Viewed by 948

In 2015, 193 governments agreed to act on climate change by drastically reducing carbon dioxide (CO₂) emissions as envisaged in the sustainable development goal (SDG) number 13 [...] Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

Research

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14 pages, 4253 KiB

Open AccessArticle

Flotation of Copper Ores with High Cu/Zn Ratio: Effects of Pyrite on Cu/Zn Separation and an Efficient Method to Enhance Sphalerite Depression

by Kosei Aikawa, Mayumi Ito, Nodoka Orii, Sanghee Jeon, Ilhwan Park, Kazutoshi Haga, Taro Kamiya, Tatsuru Takahashi, Kazuya Sunada, Taisuke Sakakibara, Tatsuhiro Ono, Refilwe S. Magwaneng and Naoki Hiroyoshi

Minerals 2022, 12(9), 1103; https://doi.org/10.3390/min12091103 - 30 Aug 2022

Cited by 2 | Viewed by 2505

Abstract

Porphyry copper deposits are important sources of copper and typically processed by flotation to produce copper concentrates. As mining areas become deeper, the amounts of impurities, such as sphalerite, can be increased in copper ores, so the appropriate depression of sphalerite floatability should [...] Read more.

Porphyry copper deposits are important sources of copper and typically processed by flotation to produce copper concentrates. As mining areas become deeper, the amounts of impurities, such as sphalerite, can be increased in copper ores, so the appropriate depression of sphalerite floatability should be achieved to obtain saleable copper concentrates. In this study, the flotation behaviors of chalcopyrite and sphalerite in model samples mimicking copper ores with high Cu/Zn ratios (i.e., the ratio of chalcopyrite/sphalerite = 13:1) were investigated with zinc sulfate as a depressant for sphalerite. In addition, the effect of pyrite—a major gangue mineral in copper ores—on the depression of sphalerite floatability with zinc sulfate was examined. When sphalerite and chalcopyrite coexisted, the floatability of the former was effectively depressed by zinc sulfate (Zn recovery: <12%), whereas the presence of pyrite promoted the release of Cu²⁺ due to the galvanic interaction with chalcopyrite, which resulted in the elimination of the effectiveness of zinc sulfate in depressing sphalerite floatability (Zn recovery: >90%). Despite the presence of much higher amounts of chalcopyrite and pyrite than sphalerite, the application of nitrogen (N₂) gas limiting the galvanic interaction between pyrite and chalcopyrite by reducing the dissolved oxygen (DO) concentration in the system effectively depressed the floatability of sphalerite (Zn recovery: <30%). Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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10 pages, 2834 KiB

Open AccessArticle

Carbothermic Reduction Roasting of Cathode Active Materials Using Activated Carbon and Graphite to Enhance the Sulfuric-Acid-Leaching Efficiency of Nickel and Cobalt

by Youngjin Ahn, Wonbeom Koo, Kyoungkeun Yoo and Richard Diaz Alorro

Minerals 2022, 12(8), 1021; https://doi.org/10.3390/min12081021 - 14 Aug 2022

Cited by 5 | Viewed by 2035

Abstract

Carbothermic reduction-roasting tests of NCM (nickel, cobalt, and manganese) cathode active materials with carbon sources such as activated carbon and graphite followed by sulfuric acid leaching were performed to investigate the effects of roasting temperature, molar mixing ratio of cathode active materials and [...] Read more.

Carbothermic reduction-roasting tests of NCM (nickel, cobalt, and manganese) cathode active materials with carbon sources such as activated carbon and graphite followed by sulfuric acid leaching were performed to investigate the effects of roasting temperature, molar mixing ratio of cathode active materials and carbon sources, and type of cathode active materials. When the virgin NCM622 materials were roasted with activated carbon, the peaks of Ni and Co metals were observed in the XRD data. The leaching efficiencies of Li, Ni, Co, and Mn increased to over 99.9% within 120 min in all samples roasted at 600 °C–900 °C, but, at the beginning of leaching, the leaching efficiencies increased more slowly with increasing roasting temperature. The leaching efficiencies of Ni and Co decreased with decreasing the molar mixing ratio of active cathode materials and carbon sources, but the leaching efficiencies were more than 99.9% in all ratios. These results indicate that roasting can enhance the leaching of cathode active materials and improve the conventional leaching process using hydrogen peroxide. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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13 pages, 2363 KiB

Open AccessArticle

Development of a Sustainable Process for Complex Sulfide Ores Containing Anglesite: Effect of Anglesite on Sphalerite Floatability, Enhanced Depression of Sphalerite by Extracting Anglesite, and Recovery of Extracted Pb²⁺ as Zero-Valent Pb by Cementation Using Zero-Valent Fe

by Kosei Aikawa, Mayumi Ito, Atsuhiro Kusano, Sanghee Jeon, Ilhwan Park and Naoki Hiroyoshi

Minerals 2022, 12(6), 723; https://doi.org/10.3390/min12060723 - 06 Jun 2022

Cited by 5 | Viewed by 2105

Abstract

The presence of anglesite (PbSO₄) in complex sulfide ores negatively affects the separation of Cu-Pb sulfides and sphalerite (ZnS) due to lead activation, and PbSO₄ rejected to tailings dams contaminates the surrounding environment with lead. To address these problems, this [...] Read more.

The presence of anglesite (PbSO₄) in complex sulfide ores negatively affects the separation of Cu-Pb sulfides and sphalerite (ZnS) due to lead activation, and PbSO₄ rejected to tailings dams contaminates the surrounding environment with lead. To address these problems, this study investigated the application of ethylene diamine tetra acetic acid (EDTA) pretreatment extracting PbSO₄ to ZnS flotation and the recovery of the extracted Pb²⁺ as zero-valent Pb by cementation using zero-valent iron (ZVI). The application of EDTA pretreatment could extract ~99.8% of PbSO₄, thus depressing ZnS floatability from 82% to 30%. In addition, cementation using ZVI could recover ~99.7% of Pb²⁺ from the leachate of EDTA pretreatment. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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11 pages, 3514 KiB

Open AccessArticle

Alkaline Leaching and Concurrent Cementation of Dissolved Pb and Zn from Zinc Plant Leach Residues

by Marthias Silwamba, Mayumi Ito, Naoki Hiroyoshi, Carlito Baltazar Tabelin, Ryota Hashizume, Tomoki Fukushima, Ilhwan Park, Sanghee Jeon, Toshifumi Igarashi, Tsutomu Sato, Imasiku Nyambe, Hokuto Nakata, Shouta Nakayama and Mayumi Ishizuka

Minerals 2022, 12(4), 393; https://doi.org/10.3390/min12040393 - 23 Mar 2022

Cited by 5 | Viewed by 2637

Abstract

Zinc plant leach residues (ZPLRs), particularly those produced using old technologies, have both economic importance as secondary raw materials and have environmental impacts because they contain hazardous heavy metals that pose risks to human health and the environment. Therefore, the extraction and recovery [...] Read more.

Zinc plant leach residues (ZPLRs), particularly those produced using old technologies, have both economic importance as secondary raw materials and have environmental impacts because they contain hazardous heavy metals that pose risks to human health and the environment. Therefore, the extraction and recovery of these metals from ZPLRs has both economic and environmental benefits. In this study, we investigated the removal of lead (Pb) and zinc (Zn) from ZPLRs by alkaline (NaOH) leaching and the concurrent cementation of dissolved Pb and Zn using aluminum (Al) metal powder. The effects of the leaching time, NaOH concentration, solid-to-liquid ratio (S/L), and dosage of Al metal powder on the extraction of Pb and Zn were investigated. Pb and Zn removal efficiencies increased with increasing NaOH concentrations and decreasing S/Ls. The Pb and Zn removal efficiencies were 62.2% and 27.1%, respectively, when 2.5 g/50 mL (S/L) of ZPLRs were leached in a 3 M NaOH solution for 30 min. The extraction of Pb and Zn could be attributed to the partitioning of these metals in relatively more mobile phases—water-soluble, exchangeable, and carbonate phases—in ZPLRs. Around 100% of dissolved Pb and less than 2% of dissolved Zn were cemented in leaching pulp when Al metal powder was added. Minerals in the solid residues, particularly iron oxides minerals, were found to suppress the cementation of extracted Zn in leaching pulp, and when they were removed by filtration, Zn was recovered by Al metal powder via cementation. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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12 pages, 2844 KiB

Open AccessArticle

A Kinetic Study on Enhanced Cementation of Gold Ions by Galvanic Interactions between Aluminum (Al) as an Electron Donor and Activated Carbon (AC) as an Electron Mediator in Ammonium Thiosulfate System

by Sanghee Jeon, Sharrydon Bright, Ilhwan Park, Akuru Kuze, Mayumi Ito and Naoki Hiroyoshi

Minerals 2022, 12(1), 91; https://doi.org/10.3390/min12010091 - 13 Jan 2022

Cited by 6 | Viewed by 1557

Abstract

The enhanced cementation technique by galvanic interaction of aluminum (Al; electron donor) and activated carbon (AC; electron mediator) to recover gold (Au) ions from the ammonium thiosulfate solution is a promising technique to eliminate the challenges of poor recovery in the system. This [...] Read more.

The enhanced cementation technique by galvanic interaction of aluminum (Al; electron donor) and activated carbon (AC; electron mediator) to recover gold (Au) ions from the ammonium thiosulfate solution is a promising technique to eliminate the challenges of poor recovery in the system. This study presents the kinetics of Au ion cementation in an ammonium thiosulfate lixiviant as functions of initial Au concentration, size/amount of Al and AC, temperature, and shaking speed. The recovery results basically followed first order kinetics and showed that the cementation rate increased with a higher initial concentration of Au, smaller electron donor size, greater both electron donor and mediator quantity, decrease in temperature, and higher shaking speed in the system, while size of electron mediator did not significantly affect Au recovery. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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11 pages, 3360 KiB

Open AccessFeature PaperArticle

Recovery of Rare Earth Metals (REMs) from Nickel Metal Hydride Batteries of Electric Vehicles

by Manis Kumar Jha, Pankaj Kumar Choubey, Om Shankar Dinkar, Rekha Panda, Rajesh Kumar Jyothi, Kyoungkeun Yoo and Ilhwan Park

Minerals 2022, 12(1), 34; https://doi.org/10.3390/min12010034 - 25 Dec 2021

Cited by 16 | Viewed by 4434

Abstract

Nickel metal hydride (NiMH) batteries are extensively used in the manufacturing of portable electronic devices as well as electric vehicles due to their specific properties including high energy density, precise volume, resistance to overcharge, etc. These NiMH batteries contain significant amounts of rare [...] Read more.

Nickel metal hydride (NiMH) batteries are extensively used in the manufacturing of portable electronic devices as well as electric vehicles due to their specific properties including high energy density, precise volume, resistance to overcharge, etc. These NiMH batteries contain significant amounts of rare earth metals (REMs) along with Co and Ni which are discarded due to illegal dumping and improper recycling practices. In view of their strategic, economic, and industrial importance, and to mitigate the demand and supply gap of REMs and the limited availability of natural resources, it is necessary to explore secondary resources of REMs. Therefore, the present paper reports a feasible hydrometallurgical process flowsheet for the recovery of REMs and valuable metals from spent NiMH batteries. More than 90% dissolution of REMs (Nd, Ce and La) was achieved using 2 M H₂SO₄ at 75 °C in 60 min in the presence of 10% H₂O₂ (v/v). From the obtained leach liquor, the REMs, such as Nd and Ce, were recovered using 10% PC88A diluted in kerosene at eq. pH 1.5 and O/A ratio 1/1 in two stages of counter current extraction. La of 99% purity was selectively precipitated from the leach liquor in the pH range of 1.5 to 2.0, leaving Cu, Ni and Co in the filtrate. Further, Cu and Ni were extracted with LIX 84 at equilibrium pH 2.5 and 5, leaving Co in the raffinate. The developed process flow sheet is feasible and has potential for industrial exploitation after scale-up/pilot trails. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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13 pages, 3882 KiB

Open AccessEditor’s ChoiceArticle

Beneficiation of Low-Grade Rare Earth Ore from Khalzan Buregtei Deposit (Mongolia) by Magnetic Separation

by Ilhwan Park, Yuki Kanazawa, Naoya Sato, Purevdelger Galtchandmani, Manis Kumar Jha, Carlito Baltazar Tabelin, Sanghee Jeon, Mayumi Ito and Naoki Hiroyoshi

Minerals 2021, 11(12), 1432; https://doi.org/10.3390/min11121432 - 18 Dec 2021

Cited by 23 | Viewed by 4507

Abstract

The global demand for rare earth elements (REEs) is expected to increase significantly because of their importance in renewable energy and clean storage technologies, which are critical for drastic carbon dioxide emission reduction to achieve a carbon-neutral society. REE ore deposits around the [...] Read more.

The global demand for rare earth elements (REEs) is expected to increase significantly because of their importance in renewable energy and clean storage technologies, which are critical for drastic carbon dioxide emission reduction to achieve a carbon-neutral society. REE ore deposits around the world are scarce and those that have been identified but remain unexploited need to be developed to supply future demands. In this study, the Khalzan Buregtei deposit located in western Mongolia was studied with the aim of upgrading low-grade REE ore via magnetic separation techniques. The total REE content in this ore was ~6720 ppm (~3540 ppm light REE (LREE) + ~3180 ppm heavy REE (HREE)) with bastnaesite, pyrochlore, synchysite, and columbite-(Fe) identified as the main REE-bearing minerals. As the particle size fraction decreased from −4.0 + 2.0 mm to −0.5 + 0.1 mm, the recovery by dry high-intensity magnetic separation (DHIMS) increased from 20% to 70% of total rare earth oxide (TREO) while the enrichment ratio reached 2.8 from 1.3. Although effective, gangue minerals such as quartz and aluminosilicates were recovered (~22%) due most likely to insufficient liberation. Meanwhile, the wet high-intensity magnetic separation (WHIMS) could produce a magnetic concentrate with TREO recovery of ~80% and enrichment ratio of 5.5 under the following conditions: particle size fraction, −106 + 75 μm; feed flow rate, 3.2 L/min; magnetic induction, 0.8 T. These results indicate that combining DHIMS and WHIMS to upgrade the low-grade REE ore from the Khalzan Buregtei deposit is an effective approach. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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20 pages, 5234 KiB

Open AccessArticle

Recovery of Magnesium from Ferronickel Slag to Prepare Magnesium Oxide by Sulfuric Acid Leaching

by Juan Yang, Xuqin Duan, Lingchuan Liu, Huifen Yang and Xiaocui Jiang

Minerals 2021, 11(12), 1375; https://doi.org/10.3390/min11121375 - 06 Dec 2021

Cited by 8 | Viewed by 3090

Abstract

This paper provides a technical approach for efficiently recovering Mg from ferronickel slag to produce high-quality magnesium oxide (MgO) by using the sulfuric acid leaching method under atmospheric pressure. The leaching rate of magnesium is 84.97% after a typical one-step acid leaching process, [...] Read more.

This paper provides a technical approach for efficiently recovering Mg from ferronickel slag to produce high-quality magnesium oxide (MgO) by using the sulfuric acid leaching method under atmospheric pressure. The leaching rate of magnesium is 84.97% after a typical one-step acid leaching process, which is because Mg in FNS mainly exists in the forsterite (Mg₂SiO₄) phase, which is chemically stable. In order to increase the leaching rate, a two-step acid leaching process was proposed in this work, and the overall leaching rate reached up to 95.82% under optimized conditions. The response surface methodology analysis for parameter optimization and Mg leaching rules revealed that temperature was the most critical factor affecting the Mg leaching rate when the sulfuric acid concentration was higher than 2 mol/L, followed by acid leaching time. Furthermore, interactive behavior also existed between the leaching temperature and leaching time. The leaching kinetics of magnesium from FNS followed a shrinkage-nuclear-reaction model with composite control, which were chemically controlled at lower temperatures and diffusion controlled at higher temperatures; the corresponding apparent activation energy was 19.57 kJ/mol. The leachate can be used to obtain spherical-like alkali magnesium carbonate particles with diameters of 5–10 μm at 97.62% purity. By using a further calcination process, the basic magnesium carbonate can be converted into a light magnesium oxide powder with a particle size of 2–5 μm (MgO content 94.85%), which can fulfill first-level quality standards for industrial magnesium oxide in China. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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14 pages, 4326 KiB

Open AccessArticle

Optimal Thermal Treatment for Effective Copper Recovery in Waste Printed Circuit Boards by Physical Separation: Influence of Temperature and Gas

by Boram Kim, Seongsoo Han, Seungsoo Park, Seongmin Kim, Minuk Jung, Chul-Hyun Park, Ho-Seok Jeon, Dae-Weon Kim and Yosep Han

Minerals 2021, 11(11), 1213; https://doi.org/10.3390/min11111213 - 30 Oct 2021

Cited by 2 | Viewed by 2547

Abstract

Printed circuit boards (PCBs) are difficult to recycle because of the layered structure of non-metal (i.e., epoxy resin, glass fiber) and copper. In this work, we conducted a systematic investigation to effectively recover copper from PCB. A thermal treatment was employed for improving [...] Read more.

Printed circuit boards (PCBs) are difficult to recycle because of the layered structure of non-metal (i.e., epoxy resin, glass fiber) and copper. In this work, we conducted a systematic investigation to effectively recover copper from PCB. A thermal treatment was employed for improving the crushing performance of PCB and conducted by varying the temperature and the gas. Then, the mechanical strength, degree of liberation (DL), and copper separation efficiency of the heat-treated and untreated PCBs were investigated. After heat treatment under a 300 °C air atmosphere, the mechanical strength of PCB decreased from 386.36 to 24.26 MPa, and copper liberation improved from 9.3% to 100% in the size range of a coarser size fraction (>1400 μm). Accordingly, when electrostatic separations were performed under these conditions, a high-Cu-grade concentrate and high recovery could be obtained. The results show that the change in the physical properties of the PCBs leads to an improvement in the DL following thermal decomposition at 300 °C in air. Our study elucidates the physical properties of PCBs and the DL under various heat treatment conditions. Furthermore, it shows that the heat treatment condition of 300 °C in air is ideal for recovering copper from the PCB. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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13 pages, 3914 KiB

Open AccessArticle

Diagnosis and Optimization of Gold Ore Flotation Circuit via Linear Circuit Analysis and Mass Balance Simulation

by Seongsoo Han, Minuk Jung, Wonjae Lee, Seongmin Kim, Kyoungmun Lee, Geun-tae Lim, Ho-Seok Jeon, Siyoung Q. Choi and Yosep Han

Minerals 2021, 11(10), 1065; https://doi.org/10.3390/min11101065 - 29 Sep 2021

Cited by 4 | Viewed by 2991

Abstract

The aim of this study is to diagnose and optimize a closed multistage gold ore flotation circuit in an operational industrial plant. Linear circuit analysis (LCA), a partition-based model, and a mass balance model using flotation first-order kinetics are employed to diagnose the [...] Read more.

The aim of this study is to diagnose and optimize a closed multistage gold ore flotation circuit in an operational industrial plant. Linear circuit analysis (LCA), a partition-based model, and a mass balance model using flotation first-order kinetics are employed to diagnose the current process. The result shows that the current circuit operates with high recovery but the gold grade of the final concentrate is low owing to the low buoyancy ratio. Hence, several alternative circuits with different streamlines and cell arrangements are proposed and simulated using LCA and a mass balance model. The result suggests that if the current process is changed to an alternative circuit in which the floated product stream of the rougher bank is changed, then the gold grade of the concentrate can be improved by 128%. Finally, the current circuit is optimized by changing it to an alternative circuit. This study provides a methodology for adapting the simulation of optimization for the flotation circuit of an industrial plant via LCA and mass balance simulation. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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Review

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20 pages, 3363 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Challenges and Prospects of Recovering Fine Copper Sulfides from Tailings Using Different Flotation Techniques: A Review

by Muhammad Bilal, Ilhwan Park, Vothy Hornn, Mayumi Ito, Fawad Ul Hassan, Sanghee Jeon and Naoki Hiroyoshi

Minerals 2022, 12(5), 586; https://doi.org/10.3390/min12050586 - 06 May 2022

Cited by 12 | Viewed by 7895

Abstract

Flotation is a common mineral processing method used to upgrade copper sulfide ores; in this method, copper sulfide mineral particles are concentrated in froth, and associated gangue minerals are separated as tailings. However, a significant amount of copper is lost into tailings during [...] Read more.

Flotation is a common mineral processing method used to upgrade copper sulfide ores; in this method, copper sulfide mineral particles are concentrated in froth, and associated gangue minerals are separated as tailings. However, a significant amount of copper is lost into tailings during the processing; therefore, tailings can be considered secondary resources or future deposits of copper. Particle–bubble collision efficiency and particle–bubble aggregate stability determines the recovery of target particles; this attachment efficiency plays a vital role in the selectivity process. The presence of fine particles in the flotation circuit is because of excessive grinding, which is to achieve a higher degree of liberation. Complex sulfide ores of markedly low grade further necessitate excessive grinding to achieve the maximum degree of liberation. In the flotation process, fine particles due to their small mass and momentum are unable to collide with rising bubbles, and their rate of flotation is very slow, further lowering the recovery of target minerals. This collision efficiency mainly depends on the particle–bubble size ratio and the concentration of particles present in the pulp. To overcome this problem and to maintain a favorable particle–bubble size ratio, different techniques have been employed by researchers to enhance particle–bubble collision efficiency either by increasing particle size or by decreasing bubble size. In this article, the mechanism of tailing loss is discussed in detail. In addition, flotation methods for fine particles recovery such as microbubble flotation, column flotation, nanobubble flotation, polymer flocculation, shear flocculation, oil agglomeration, and carrier flotation are reviewed, and their applications and limitations are discussed in detail. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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Other

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11 pages, 3161 KiB

Open AccessCase Report

Characterization and Removal Potential of Fluorine in Lignite from a Mine in Shaanxi Province, China: A Case Study

by Chao Ni, Shaoqi Zhou, Xiangning Bu, Muhammad Bilal, Fawad Ul Hassan, Yuran Chen, Guangqian Xu and Guangyuan Xie

Minerals 2022, 12(3), 280; https://doi.org/10.3390/min12030280 - 23 Feb 2022

Cited by 3 | Viewed by 2257

Abstract

Fluorine appears in coal and is released into the atmosphere upon combustion, resulting in harmful impacts on the environment and life, which needs to be removed from coal before utilization. Coal can be processed by flotation and gravity separation to reduce its fluorine [...] Read more.

Fluorine appears in coal and is released into the atmosphere upon combustion, resulting in harmful impacts on the environment and life, which needs to be removed from coal before utilization. Coal can be processed by flotation and gravity separation to reduce its fluorine content. In this study, a lignite sample from a mine in Shaanxi Province, China, was characterized using the float–sink test, sieving test, X-ray diffraction (XRD), and polarized light microscopy. Mineralogical analysis indicated that the fluorine in coal is mainly contained in Muscovite and polylithionite, and partly in pyrite. The washability and floatability analyses were employed to evaluate the extent of fluorine removal from >0.5 and <0.5 mm size fractions of lignite, respectively. Compared to the raw sample that contained 347.74 μg/g fluorine content, the proposed combination of gravity-flotation separation process decreased the fluorine content to 90.14 μg/g, which meets the requisites of coal standards. Full article

(This article belongs to the Special Issue Sustainable Production of Metals for Low-Carbon Technologies)

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