Green Low-Carbon Technology for Metalliferous Minerals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Energies energies	3.0	6.2	2008	17.5 Days	CHF 2600
Metals metals	2.6	4.9	2011	16.5 Days	CHF 2600
Minerals minerals	2.2	4.1	2011	18 Days	CHF 2400
Processes processes	2.8	5.1	2013	14.4 Days	CHF 2400
Sustainability sustainability	3.3	6.8	2009	20 Days	CHF 2400

19 pages, 2797 KiB

Open AccessArticle

An Underground Mine Safety-Oriented Optimization Model for Mine Tailings Backfill Scheduling Considering Multi-Process and Multi-Cycle Issues

by Yuhang Liu, Guoqing Li, Jie Hou, Guangjun Guo, Dong Pan and Qianqian Yu

Minerals 2023, 13(11), 1409; https://doi.org/10.3390/min13111409 - 3 Nov 2023

Cited by 2 | Viewed by 1102

Abstract

The backfill mining method is adopted in many mines around the world because it can reliably handle underground mine tailings and eliminate dangers in goafs. It is necessary to improve backfilling resource allocation and efficiency, thereby eliminating safety hazards and providing reliable support [...] Read more.

The backfill mining method is adopted in many mines around the world because it can reliably handle underground mine tailings and eliminate dangers in goafs. It is necessary to improve backfilling resource allocation and efficiency, thereby eliminating safety hazards and providing reliable support for the next stage of mining as quickly as possible. In this paper, we propose a backfill-scheduling optimization model that considers multiple processes, resource constraints, and operating capabilities. The purpose of this model is to minimize the exposure time of goafs. This NP-hard (Nondeterministic Polynomial-time hard) problem has a non-inferior implemented solution through multiple iterations of genetic, crossover, and mutation operations of the genetic algorithm. The results show that the model significantly reduces the backfilling-delay time and backfilling-operation time. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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12 pages, 3029 KiB

Open AccessArticle

Effect of Polymeric Agent on the Strength and Water Stability of Cement-Stabilized Construction Waste Soil

by Haoran Li, Peiwei Gao, Chen Zhang, Shipeng Guo and Jun Zhang

Sustainability 2023, 15(21), 15571; https://doi.org/10.3390/su152115571 - 2 Nov 2023

Viewed by 1151

Abstract

Due to the large output of construction waste soils, it has become an enormous challenge for human society and the ecological environment. The purpose of this paper is to discuss the possibility of using a stabilized waste soil in road engineering. Cement and [...] Read more.

Due to the large output of construction waste soils, it has become an enormous challenge for human society and the ecological environment. The purpose of this paper is to discuss the possibility of using a stabilized waste soil in road engineering. Cement and polymer stabilizers were added to the waste soil, and the effect of the stabilizer on the strength and water stability of the stabilized soil was studied. The structure and morphology of the specimens were analyzed using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). The results show that the unconfined compressive strength increases by 25.0% and the 28-day water stability coefficient, K increases by 59.6% after the addition of the stabilizer. The XRD curve shows that the addition of the new stabilizer does not produce a new characteristic peak, but the diffraction peak strength of some minerals can be improved. SEM shows that the surface of stabilized soil particles is covered by materials, and the particles show obvious agglomeration, forming a network structure, which improves the strength and water stability of the soil. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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14 pages, 8487 KiB

Open AccessArticle

Study of Using Quartz Powder as a Mineral Admixture to Produce Magnesium Oxysulfate Cement

by Shaoyan Wang, Daijun Pang, Shengyang Chen, Tongqing Zhang, Wanli Bi and Xiaoyang Chen

Minerals 2023, 13(10), 1240; https://doi.org/10.3390/min13101240 - 23 Sep 2023

Viewed by 1297

Abstract

Magnesium oxysulfate (MOS) cement features potential advantages, including light weight, green and environmental protection, low thermal conductivity, and high frost- and fire-resistance, but its poor mechanical strength limits the extensive utilization in the architectural engineering. In this study, low-cost quartz (Q) was used [...] Read more.

Magnesium oxysulfate (MOS) cement features potential advantages, including light weight, green and environmental protection, low thermal conductivity, and high frost- and fire-resistance, but its poor mechanical strength limits the extensive utilization in the architectural engineering. In this study, low-cost quartz (Q) was used as a mineral admixture to increase the mechanical strength of MOS pastes. The impact of the filler Q on the early and later mechanical strength of MOS cement was investigated, in which also had an impact on fluidity, setting times, volume stability, hydration processes, phase transformations, and microstructure. The results show that hydration of periclase to form 5Mg(OH)₂·MgSO₄·7H₂O (phase 5-1-7) in this system was a multi-stage reaction process. 3Mg(OH)₂·MgSO₄·8H₂O was the first sediment in this system and was converted into phase 5-1-7. The dilution and dispersion effects of the filler Q increased the early hydration rate, shortened the setting time, and increased the content and crystallite size of phase 5-1-7, increasing the early mechanical strength of MOS cement, while the volume-filling effect of the filler Q reduced the content of large pore and total pore volume, and improved the pore structure of the MOS cement, improving the later mechanical strength of MOS cement. MOS cement containing 15 wt.% of filler Q exhibited the highest early and later mechanical strength, and the lowest volume shrinkage, which is more suitable for application in architectural engineering. Based on these results, filler Q can be used as an enhancer in MOS cement, however its enhancement mechanisms are effective only when the content of filler Q is no more than 20 wt.%. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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11 pages, 3543 KiB

Open AccessArticle

High-Speed Dynamic Camera Analysis of the Hematite Floc–Bubble Mineralization Process

by Fusheng Niu, Yuying Chen, Jinxia Zhang and Zhenjia Chang

Minerals 2023, 13(7), 964; https://doi.org/10.3390/min13070964 - 20 Jul 2023

Cited by 2 | Viewed by 1153

Abstract

The most efficient method for recovering microfine-grained hematite ore is flocculation flotation. Because the flocculation–bubble mineralization process in flocculation flotation has yet to be well investigated, a series of experimental investigations on hematite flocculation–bubble were conducted to better understand the hematite flocculation–bubble interaction [...] Read more.

The most efficient method for recovering microfine-grained hematite ore is flocculation flotation. Because the flocculation–bubble mineralization process in flocculation flotation has yet to be well investigated, a series of experimental investigations on hematite flocculation–bubble were conducted to better understand the hematite flocculation–bubble interaction process. The results show that as the flocculant size increases, the sliding time of the flocculant to the bottom of the bubble shortens, and the change in the instantaneous dynamic velocity is slower when the diameter of the fixed bead is 544.52 μm, which is more favorable to flocculant adhesion on the bubble surface. When the bubble diameter is 544.52 μm and the floc diameter is 39.65 μm, the shortest time is 49.5 ms, and the maximum value of instantaneous velocity is 28.67 μm·ms⁻¹. According to the force analysis of the floc on the bubble surface, when the particle size of the floc is 39.65 μm and the bubble diameter is 544.52 μm, the desorption force is 4.99 × 10⁻³ mN·m⁻¹ larger, and the adhesion force is 7.08 × 10⁻⁴ mN·m⁻¹ smaller. The smaller Bond constant Bo′ is 0.14. In that moment, the flocs in the sodium solution are very stable. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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18 pages, 7437 KiB

Open AccessArticle

Zn Extraction from Zinc-Containing Sludge Using Ultrasonic Treatment Leaching with ChCl-MA DES

by Fusheng Niu, Ziheng Bu, Jinxia Zhang, Shengtao He and Zhenjia Chang

Metals 2023, 13(7), 1192; https://doi.org/10.3390/met13071192 - 27 Jun 2023

Cited by 2 | Viewed by 1686

Abstract

The recovery of zinc from metallurgical dust sludge is a crucial component of using solid waste as a resource in the metallurgical process, and deep eutectic solvent–ultrasonic synergistic enhanced leaching is an efficient method of doing so with excellent economic effects. The leaching [...] Read more.

The recovery of zinc from metallurgical dust sludge is a crucial component of using solid waste as a resource in the metallurgical process, and deep eutectic solvent–ultrasonic synergistic enhanced leaching is an efficient method of doing so with excellent economic effects. The leaching rate of zinc is used as the value of response in this study, along with the four process conditions of leaching temperature, leaching time, liquid–solid ratio, and ultrasonic power. By building a regression model, the relationship between the various parameter components is investigated, and a strategy for optimization is then chosen and confirmed. The findings indicate that, for the parameters of temperature 40 °C, ultrasonic power 90 W, liquid–solid ratio 7:1 g/L, stirring speed 250 rpm, and leaching duration 80 min, the prediction value of the regression model of the zinc leaching rate is 98.47%. The average zinc leaching rate obtained by the 3 parallel verification experiments was 98.49%; the deviation from the regression model’s predicted value was 0.02%. This demonstrated that the experimental results were consistent with those predicted by the regression model, the experimental results were reliable and trustworthy, and the optimization scheme was reasonable and accurate. Compared with the conventional leaching method (leaching rate: 91.61%), the method under ultrasound increased the zinc leaching rate by 6.88%. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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19 pages, 5896 KiB

Open AccessArticle

Effects of Shaft Tuyere Parameters on Gas Movement Behavior and Burden Reduction in Oxygen Blast Furnace

by Zedong Zhang, Jue Tang, Quan Shi and Mansheng Chu

Sustainability 2023, 15(12), 9159; https://doi.org/10.3390/su15129159 - 6 Jun 2023

Cited by 2 | Viewed by 1226

Abstract

Parameters of shaft tuyere have vital effects on the gas flow distribution and working condition in the TGR-OBF, which determine the production index, CO₂ emission reduction, and economic benefit. To clarify the effects of shaft tuyere parameters on gas movement behavior and [...] Read more.

Parameters of shaft tuyere have vital effects on the gas flow distribution and working condition in the TGR-OBF, which determine the production index, CO₂ emission reduction, and economic benefit. To clarify the effects of shaft tuyere parameters on gas movement behavior and burden reduction in oxygen blast furnaces, a 2D steady-state model based on actual plant conditions in China is published in this study. The shaft of the blast furnace can be divided into region I near the wall and region II close to the center, which was influenced by top gas and bosh gas, respectively. The farthest movement distance of the top gas along the radial direction was defined as the penetration depth decided by its kinetic energy ratio. As the height of shaft tuyere decreased from 5/10 L to 1/10 L, the penetration depth decreased from 1.615 m to 1.308 m, and the reduction degree of iron-bearing burden before entering the cohesive zone increased from 0.925 to 0.982. With the shaft tuyere diameters increased from 0.088 m to 0.096 m with a constant blast velocity, the penetration depth was kept elongated at 1.24 m, and the reduction degree before entering the cohesive zone increased from 0.972 to 0.983. While the blast volume of top gas was kept constant, the reduction degree before entering the cohesive zone increased from 0.969 to 0.986. When the shaft tuyere angles increased from −20° to 20°, both the distribution of temperature and CO fraction moved towards the upper shaft slightly, and the penetration depth was kept around 1.24. Under experimental conditions, a low-height shaft tuyere was appropriate for an oxygen blast furnace. Within a certain control range, the changes of shaft tuyere diameters and angles had a small effect on the oxygen blast furnace. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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13 pages, 8897 KiB

Open AccessArticle

Effects of Borax and Grinding Alkalinity on the Reduction–Magnetic Separation of Beach Placer

by Bing Hu, Peiwei Hu, Runqin Gao, Chao Hu and Fuqiang Zheng

Metals 2023, 13(5), 868; https://doi.org/10.3390/met13050868 - 29 Apr 2023

Viewed by 1304

Abstract

The effect of borax on the reduction characteristics of Indonesia beach placers was investigated. The effect of grinding alkalinity on the magnetic separation of the reduced sample was also studied in this paper. The mineral phase transformation, microstructures of reduction, and magnetic separation [...] Read more.

The effect of borax on the reduction characteristics of Indonesia beach placers was investigated. The effect of grinding alkalinity on the magnetic separation of the reduced sample was also studied in this paper. The mineral phase transformation, microstructures of reduction, and magnetic separation products were analyzed to reveal the enhanced separation mechanism of titanium and iron in beach placer. The borax could effectively improve the metallization rate and the growth of iron grains in a reduced sample. When 3% borax was added to the reduction process, the metallization rate of the reduced beach placer reached 95.64%, and the metal iron grains grew to about 50 μm. Adjusting the grinding alkalinity could prevent the metallic iron from being oxidized and promote the monomer dissociation between mineral particles. The iron powder concentrates with 94.07% total Fe and vanadium-rich titanium slag with 36.32% Ti were obtained by grinding magnetic separation as the grinding alkalinity pH was 13. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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16 pages, 5703 KiB

Open AccessArticle

Deformation Mechanisms of Magnesium Silicate Hydrate Cement with a Shrinkage-Reducing Admixture under Different Curing Conditions

by Tingting Zhang, Hao Fu and Junnan Han

Minerals 2023, 13(4), 563; https://doi.org/10.3390/min13040563 - 17 Apr 2023

Cited by 4 | Viewed by 1499

Abstract

Magnesium silicate hydrate (M-S-H) cement, a type of green building material, has poor volume stability (i.e., large shrinkage deformation), which limits its application. As a new type of admixture, the behavior of a shrinkage-reducing admixture (SRA) in M-S-H cement has not been studied. [...] Read more.

Magnesium silicate hydrate (M-S-H) cement, a type of green building material, has poor volume stability (i.e., large shrinkage deformation), which limits its application. As a new type of admixture, the behavior of a shrinkage-reducing admixture (SRA) in M-S-H cement has not been studied. Therefore, in this research, the effect of SRA on the shrinkage properties of the M-S-H cement system was evaluated. The mechanism of SRA was investigated by surface tension measurement, hydration heat testing, thermogravimetric analysis, and pore structure analysis. Experimental results indicate that SRA can reduce the shrinkage of the M-S-H mortar, and the optimal effect is exerted when the dosage is 3.0%, drying shrinkage decreases by 22.6%, and autogenous shrinkage decreases by 60% on day 28. However, it may also adversely affect strength development. The presence of SRA in M-S-H cement can reduce pore solution surface tension, delay hydration, and maintain relative humidity within the slurry, which can be maintained at 82.0% on day 28. It can also increase pore size and porosity. The inhibitory effect of SRA on the shrinkage of M-S-H mortar is valuable for its future practical applications. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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14 pages, 6619 KiB

Open AccessArticle

Effect of Sodium Silicate on the Hydration of Alkali-Activated Copper-Nickel Slag Materials

by Jie Yang, Tingting Zhang, Lijie Guo, Shiwei Zhi and Junnan Han

Metals 2023, 13(3), 596; https://doi.org/10.3390/met13030596 - 15 Mar 2023

Cited by 2 | Viewed by 1810

Abstract

This paper studied the influence of the modulus and dosage of sodium silicate on the hydration of alkali-activated copper-nickel slag (CNS) materials. CNS was used as the main raw material, and ground granulated blast furnace slag (GBFS) powder was selected as the mineral [...] Read more.

This paper studied the influence of the modulus and dosage of sodium silicate on the hydration of alkali-activated copper-nickel slag (CNS) materials. CNS was used as the main raw material, and ground granulated blast furnace slag (GBFS) powder was selected as the mineral additive. The hydration and hardening mechanisms were discussed. The experimental results showed that [SiO₄]⁴⁻ and [AlO₄]⁵⁻ with a high degree of polymerization in the CNS glassy phase more easily underwent depolymerization-condensation and produced more C-S-H gels when the modulus was small and the sodium silicate dosage was high. When the content of sodium silicate was 7.0% and the modulus of sodium silicate solution was 1.0, the 28-day compressive strength of the material reached 125 MPa. This alkali-activated copper-nickel slag material can be used for mine filling, which has certain economic and ecological benefits. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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16 pages, 4394 KiB

Open AccessArticle

Study on Characteristics of Compression Deformation and Post-Peak Stress Rebound for Solid Waste Cemented Body

by Xinyuan Zhao, Ke Yang, Xiang He, Zhen Wei, Jiqiang Zhang and Xiang Yu

Minerals 2023, 13(1), 108; https://doi.org/10.3390/min13010108 - 10 Jan 2023

Cited by 8 | Viewed by 1775

Abstract

Most of the previous studies focused on the mechanical characteristics before the stress peak of solid waste cemented backfill, but in the compression process of a solid waste cemented body, the phenomenon of post-peak stress rebound often occurs. Through the uniaxial compression experiment [...] Read more.

Most of the previous studies focused on the mechanical characteristics before the stress peak of solid waste cemented backfill, but in the compression process of a solid waste cemented body, the phenomenon of post-peak stress rebound often occurs. Through the uniaxial compression experiment of a solid waste cemented body composed of coal gangue, fly ash, desulfurization gypsum, gasification slag, and furnace bottom slag, this paper analyzed the compression deformation characteristics of a solid waste cemented body with different mix proportions before and after the stress peak, established the stress–strain curve model of rebound stress in the rising and descending section after the stress peak, and revealed the reasons for the rebound stress and secondary unloading of the cemented body after the stress peak. The results showed that the maximum rebound stress accounts for 40%–80% of the compressive strength, and the changes in the two are positively correlated. The stress–strain curve model is a cubic function in the post-peak stress rising section and a quadratic rational function in the descending section. With the increase in the maximum compressive strength of the cemented body, its maximum rebound stress also increases, but its corresponding compressive strain generally shows a downward trend. There is a positive correlation between the rebound stress increment and strain increment of the cemented body. The change in the supporting structure and the evolution of the failure form of the cemented body before and after the maximum rebound stress indicate that the compression failure of the residual supporting structure caused by the main crack is the main reason for the rebound of the stress after the peak value of the cemented body to the complete unloading. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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16 pages, 3913 KiB

Open AccessArticle

Strength Development and Environmental Assessment of Full Tailings Filling Materials with Various Water-to-Binder Ratios

by Zhu Ding, Pai Liu, Peng Cui and Chengyu Hong

Metals 2023, 13(1), 122; https://doi.org/10.3390/met13010122 - 7 Jan 2023

Cited by 5 | Viewed by 1460

Abstract

In order to build green mines, goaf is often filled, supported, and sealed with a high-water material to eliminate a series of environmental problems and safety hazards caused by goaf. In this study, ordinary Portland cement, sulphoaluminate cement, and alkali-activated cement were used [...] Read more.

In order to build green mines, goaf is often filled, supported, and sealed with a high-water material to eliminate a series of environmental problems and safety hazards caused by goaf. In this study, ordinary Portland cement, sulphoaluminate cement, and alkali-activated cement were used as binders to prepare full-tailings high-water materials for filling, with various water-to-cement ratios. The compressive strength development of consolidated tungsten tailings specimens prepared with various curing binders was observed, and the influence of various water–cement ratios on the strength development was analyzed. The environmental impact of mine backfill materials was assessed according to the life cycle theory (LCA), and these mine backfill materials were prepared by using various binders. The results show that when the water-to-binder ratio is 3, the strength of alkali-activated cement can reach 3 MPa at 28 days; at that ratio, the microstructure of alkali-activated cement is more compact. Through LCA analysis, the environmental load of alkali-activated cement is shown to be significantly lower than that of either Portland cement or sulphoaluminate cement; the LCA results show that the primary energy consumption using alkali-activated cement is reduced from the Portland and sulphoaluminate cements by 1319.32 MJ and 945 kg, respectively. These unusual reduction percentages are achieved because the production of alkali-activated cement by LCA does not have any negative environmental impact—the production of alkali-activated cement, with its primary component being industrial byproduct slag, so that the use of alkali-activated cement in tailings’ consolidation has a positive environmental impact. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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21 pages, 6005 KiB

Open AccessArticle

Numerical Study of the Layered Blasting Effect on a Cemented Backfill Stope

by Zongnan Li, Bin Yu, Lijie Guo, Wenyuan Xu, Yue Zhao and Xiaopeng Peng

Metals 2023, 13(1), 33; https://doi.org/10.3390/met13010033 - 23 Dec 2022

Cited by 4 | Viewed by 1830

Abstract

The sublevel open stoping with backfill method has recently been widely used in underground metal mines. The primary CPB stope is frequently affected by blasting in the secondary ore stope, leading to stope collapse and ore dilution, which has become a common problem [...] Read more.

The sublevel open stoping with backfill method has recently been widely used in underground metal mines. The primary CPB stope is frequently affected by blasting in the secondary ore stope, leading to stope collapse and ore dilution, which has become a common problem and has received widespread attention. Numerical simulations are carried out in the present work, and a 1/4 numeral model consisting of a primary CPB stope and a secondary ore stope is built. The secondary ore stope is divided into four layers on average in the simulation model, and the incident stress induced by each blasting at the interface of the CPB and ore is simulated. The results show that the CPB stope in the range within the height of the explosive charge induced horizontal compressive stress and tensile stress induced from the explosive charge height, while the mined section under the charge height has no obvious blasting impact. The maximum incident compressive stress is close to 1.2 MPa and occurs in the area closest to the blast hole The maximum induced tensile stress occurs in the range above the charge height, which is about 0.2 MPa. The stress ratios of the four-layered lift blasts are 3.6%, 3.8%, 4.0%, and 4.8%, respectively, showing a slight cumulative effect of layered blasting. In addition, the positive correlation between incident stress and the stress ratio is studied in the present work, and the results show that the greater the incident stress is, the greater the incident ratio is. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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14 pages, 5009 KiB

Open AccessArticle

Research on the Fracture Properties and Mechanism of Carbon Dioxide Blasting Based on Rock-like Materials

by Jian Chang, Lijun Sun, Bibo Dai, Helin Li, Zhenbiao Liu, Xukun Zhao and Bo Ke

Minerals 2023, 13(1), 3; https://doi.org/10.3390/min13010003 - 20 Dec 2022

Cited by 4 | Viewed by 1869

Abstract

Liquid carbon dioxide blasting technology has a wide range of applications and is characterized by sound fracturing effects, low vibration hazards, and high safety. In order to investigate the characteristics and mechanism of CO₂ phase change rock breaking, liquid CO₂ blasting [...] Read more.

Liquid carbon dioxide blasting technology has a wide range of applications and is characterized by sound fracturing effects, low vibration hazards, and high safety. In order to investigate the characteristics and mechanism of CO₂ phase change rock breaking, liquid CO₂ blasting tests on rock-like specimens were carried out in this paper. The results show that 130 MPa is the threshold value at which a CO₂ blasting system moves from dynamic tensile stress damage to dynamic pressure stress damage. When blasting pressures of 100 MPa and 70 MPa are used, the lumpiness ratio of the fragments does not change much as the strength of the rock changes, so a suitable blasting pressure should be chosen to improve the blasting effect. Under the impact of blast stress and high-pressure gas flow, cracks develop to form a rough failure surface. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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14 pages, 5034 KiB

Open AccessArticle

Properties of Unburned Brick Produced by Entirely Waste-Stream Binder Activated by Desulfurization Gypsum

by Lei Zhang, Lijie Guo, Yue Zhao and Mengyuan Li

Metals 2022, 12(12), 2130; https://doi.org/10.3390/met12122130 - 11 Dec 2022

Cited by 2 | Viewed by 1961

Abstract

The massive accumulation of industrial solid wastes such as circulating fluidized bed fly ash (CFA), silicon-calcium slag (SCS), and desulfurization gypsum (FGD) occupy land resources and bring varying degrees of pollution to soil, water, and atmosphere. Unburned brick is a new construction material [...] Read more.

The massive accumulation of industrial solid wastes such as circulating fluidized bed fly ash (CFA), silicon-calcium slag (SCS), and desulfurization gypsum (FGD) occupy land resources and bring varying degrees of pollution to soil, water, and atmosphere. Unburned brick is a new construction material prepared from industrial waste residues such as fly ash and tailings without high-temperature calcination. It has excellent potential in consuming large quantities of industrial solid waste. In this paper, 70% of CFA and 30% of SCS are used as the primary raw materials, and the FGD is used as the activator to prepare unburned bricks by static pressure forming. The mechanical properties of the specimens at different curing ages were tested by compressive strength test. The hydration mechanism and microstructure of unburned brick were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), thermogravimetric (TG), Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma-optical emission spectrometry (ICP-OES). The results show that the compressive strength of the specimen increases first and then decreases with the increase of FGD content, and the compressive strength reaches the maximum when the FGD content is 5%. The microscopic test results show that the presence of FGD promoted a higher degree of CFA and SCS dissolution, increasing ettringite formation, which is responsible for strength increase, but extreme doses of FGD resulted in strength degradation. Meanwhile, the higher SiO₂/Al₂O₃ ratio confirms the simultaneous formation of hydrated calcium silicate (C-S-H) gel and hydrated calcium aluminosilicate (C-A-S-H) gel within the hydrated product, while a low SiO₂/Al₂O₃ ratio confirms the simultaneous formation of ettringite. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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19 pages, 4841 KiB

Open AccessArticle

Study on Influencing Factors and Spatial Effects of Carbon Emissions Based on Logarithmic Mean Divisia Index Model: A Case Study of Hunan Province

by Shan Yang, Shangkai Zhu, Gao Deng and Huan Li

Sustainability 2022, 14(23), 15868; https://doi.org/10.3390/su142315868 - 29 Nov 2022

Cited by 3 | Viewed by 1572

Abstract

China has committed to peaking carbon dioxide emissions by 2030 and has set a goal of working towards carbon neutrality by 2060. Hunan province is a vital undertaking place for national industrial transfer. It is of great significance for promoting energy conservation and [...] Read more.

China has committed to peaking carbon dioxide emissions by 2030 and has set a goal of working towards carbon neutrality by 2060. Hunan province is a vital undertaking place for national industrial transfer. It is of great significance for promoting energy conservation and emission reduction to investigate the influencing factors and spatial effects of carbon emissions in Hunan province. Firstly, based on the energy consumption data of Hunan province from 2005 to 2017, this paper uses the method recommended by the Intergovernmental Panel on Climate Change (IPCC) to measure the carbon emissions of Hunan province and its economic zones. Secondly, the five-factor Logarithmic Mean Divisia Index (LMDI) model is constructed to analyze the influence degree of population size, economic development, industrial structure, energy intensity, and energy structure on carbon emissions. Finally, the spatial differences of the influencing factors in the four economic zones of Hunan province are analyzed. The research shows that: (1) An overall carbon emission reduction has been achieved in Hunan province since 2011. (2) Changsha–Zhuzhou–Xiangtan Economic Zone is the key area to achieve carbon emission reduction, while there is still the phenomenon of emission increase in the other three economic zones. (3) For all economic zones, economic development contributes the most to the increase in carbon emissions, while energy intensity shows the strongest inhibitory effect. Other factors have various effects on the four economic zones. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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17 pages, 45166 KiB

Open AccessArticle

Study on Shear Characteristics and Failure Mechanism of Inclined Layered Backfill in Mining Solid Waste Utilization

by Tong Gao, Wei Sun, Zhaoyu Li, Kai Fan, Minggui Jiang and Haiyong Cheng

Minerals 2022, 12(12), 1540; https://doi.org/10.3390/min12121540 - 29 Nov 2022

Cited by 13 | Viewed by 1590

Abstract

To eliminate the massive accumulation of tailings and promote the recycling of mine solid waste to develop green mining, a two-layered cemented paste backfill (CPB) with layering angles of 5°, 10°, 15°, 20° and 25° and complete CPB were prepared to conduct direct [...] Read more.

To eliminate the massive accumulation of tailings and promote the recycling of mine solid waste to develop green mining, a two-layered cemented paste backfill (CPB) with layering angles of 5°, 10°, 15°, 20° and 25° and complete CPB were prepared to conduct direct shear experiments; thus, the effect of the layering angle on their shear mechanical properties can be investigated. Meanwhile, the particle flow analysis program PFC 2D was used to simulate the micro-crack propagation law and reveal the damage mechanism. The results showed that the layered structure weakens the integrity of CPB and significantly reduces its shear strength, cohesion and internal friction angle. When the layered angle increased from 20° to 25°, the shear strength under normal stress of 100 kPa was decreased by 35.13% and cohesion by 43.43%. As the layered angle increased from 5° to 25°, the internal friction angle decreased first and then increased and reached the minimum when the layered angle was 15°. With the increase in the layered angle, the layered CPB gradually generated tension cracks along the layered surface, and the number of cracks gradually increased. The failure mode of each specimen is mainly a shear crack through the shear surface failure, crack expansion in the middle of shear surface on the upper and lower sides of the spindle-shaped failure and an inverted Z-shaped conjugate shear failure. This research can provide a substantial reference in the design and application of layered CPB in underground mines. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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10 pages, 2344 KiB

Open AccessArticle

Comparing Permeability and Drying Shrinkage of the Concrete Containing Mineral Admixtures under the Equal Strength Grade

by Yufeng Fan, Qiang Zhao and Dengquan Wang

Minerals 2022, 12(11), 1477; https://doi.org/10.3390/min12111477 - 21 Nov 2022

Cited by 2 | Viewed by 2064

Abstract

Fly ash (FA) and ground granulated blast-furnace slag (GGBS) are the most widely used mineral admixtures in engineering. However, their roles in concrete under the equal strength grade, a common comparison method in engineering, were seldom reported. This study investigated the chloride ion [...] Read more.

Fly ash (FA) and ground granulated blast-furnace slag (GGBS) are the most widely used mineral admixtures in engineering. However, their roles in concrete under the equal strength grade, a common comparison method in engineering, were seldom reported. This study investigated the chloride ion permeability and drying shrinkage of concrete samples containing FA or GGBS under an equal strength grade. The samples’ strengths and slumps maintained the same levels by adjusting the water-to-binder ratios and superplasticizer dosages. The results show that both FA and GGBS can promote the resistance to chloride ion penetration and decrease the chloride diffusion coefficients, especially at late ages, due to the hydraulicity of GGBS and pozzolanic activity of FA. Compared with FA, GGBS presents a greater reduction in the concrete permeability due to its higher reactivity. Forty percent replacement levels of FA and GGBS can decrease the penetration level from “high” of plain cement concrete to “moderate” and “low”, respectively. In addition, FA and GGBS can decrease the drying shrinkage of concrete at high replacement levels (30% and 40%). This decrease is more significant in the FA-containing concrete, with the shrinkage decreasing from approximately 400 με to 350 με at a 40% replacement level. The findings can provide scientific guidance for applying FA and GGBS in practical engineering. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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11 pages, 3730 KiB

Open AccessArticle

Selective Separation Recovery of Copper and Arsenic from the Leaching Solution of Copper Soot

by Zhizhao Yang, Yongbing Zhang, Hepeng Zhou, Xianping Luo, Xuekun Tang and Zishuai Liu

Metals 2022, 12(11), 1983; https://doi.org/10.3390/met12111983 - 20 Nov 2022

Cited by 4 | Viewed by 1898

Abstract

Through the main chemical reaction of metal ions and S²⁻, a new type of sulfide precipitant was first prepared and used to realize the selective separation recovery of copper and arsenic from the leaching solution of copper soot. It is proven [...] Read more.

Through the main chemical reaction of metal ions and S²⁻, a new type of sulfide precipitant was first prepared and used to realize the selective separation recovery of copper and arsenic from the leaching solution of copper soot. It is proven by experimental results that the prepared sulfide precipitant could realize the efficient separation recovery of copper and arsenic. Indeed, the copper sulfide slag with Cu grade of about 47% and arsenic trisulfide slag with As operation recovery of about 98% could be obtained. The results of chemical reaction energy calculation analysis and SEM images analysis illustrate that the selective separation recovery of copper and arsenic mainly depended on the chemical reactions of sulfide precipitation. The ions of S²⁻ and HS⁻ produced by the prepared sulfide precipitant could react with Cu²⁺ and arsenic components to form CuS and As₂S, respectively, in the copper and arsenic recovery procedure. In addition, the smaller solubility of CuS and the lower rate of S²⁻ engendered by the sulfide precipitant were key to achieving the efficient separation and recovery of copper and arsenic. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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13 pages, 4805 KiB

Open AccessArticle

Comparison of the Effects of Ultrasonic and Ball Milling on Red Mud Desulfurization

by Xueke Li, Yan Liu and Tingan Zhang

Metals 2022, 12(11), 1887; https://doi.org/10.3390/met12111887 - 4 Nov 2022

Cited by 3 | Viewed by 2185

Abstract

Red mud desulfurization is an environmentally friendly desulfurization technology. After desulfurization, the acidity of red mud slurry continues to be neutralized for processing new red mud, and no waste acid is generated. At present, there is a lack of research on desulfurization intensification [...] Read more.

Red mud desulfurization is an environmentally friendly desulfurization technology. After desulfurization, the acidity of red mud slurry continues to be neutralized for processing new red mud, and no waste acid is generated. At present, there is a lack of research on desulfurization intensification in external fields, etc. To further enhance red mud desulfurization, this paper used an SO₂ detector, X-ray fluorescence spectrometer (XRF), and scanning electron microscope (SEM) to compare and analyze red mud desulfurization under the action of ball mill and ultrasonic external fields. In this study, experiments were conducted using a bubbling and stirring reactor device. The results showed that the suitable red mud slurry concentration was 10 g/L. The raw red mud desulfurization (without external field condition) could reach 100% absorption in the first 25 min, and the desulfurization rate dropped to 81.3% at 80 min. The mechanism of red mud desulfurization was investigated by X-ray diffractometer (XRD), XRF, and infrared spectroscopy. Under the action of the external field of the ball mill, the red mud particles could be refined to prolong the desulfurization time. The red mud after ball milling could reach 100% absorption within 33 min. Under the thermal effect of the ultrasound, 100% absorption could only be achieved within 23 min. From the desulfurization effect and XRF results, it was found that the ball mill was more suitable for promoting red mud desulfurization in the bubbling and stirring reactor. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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16 pages, 3839 KiB

Open AccessReview

Effect of H₂ on Blast Furnace Ironmaking: A Review

by Chenchen Lan, Yuejun Hao, Jiannan Shao, Shuhui Zhang, Ran Liu and Qing Lyu

Metals 2022, 12(11), 1864; https://doi.org/10.3390/met12111864 - 1 Nov 2022

Cited by 26 | Viewed by 6569

Abstract

Under the background of “carbon peaking” and “carbon neutralization”, the green transformation of iron and steel enterprises is imminent. The hydrogen-rich smelting technology of blast furnaces is very important for reducing energy consumption and CO₂ emission in ironmaking systems, and it is [...] Read more.

Under the background of “carbon peaking” and “carbon neutralization”, the green transformation of iron and steel enterprises is imminent. The hydrogen-rich smelting technology of blast furnaces is very important for reducing energy consumption and CO₂ emission in ironmaking systems, and it is one of the important directions of green and low-carbon development of iron and steel enterprises. In this paper, the research status of the thermal state, reduction mechanism of iron-bearing burden, coke degradation behavior, and formation of the cohesive zone in various areas of blast furnace after hydrogen-rich smelting is summarized, which can make a more clear and comprehensive understanding for the effect of H₂ on blast furnace ironmaking. Meanwhile, based on the current research situation, it is proposed that the following aspects should be further studied in the hydrogen-rich smelting of blast furnaces: (1) the utilization rate of hydrogen and degree of substitution for direct reduction, (2) combustion behavior of fuel in raceway, (3) control of gas flow distribution in the blast furnace, (4) operation optimization of the blast furnace. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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17 pages, 7977 KiB

Open AccessArticle

Study on Ultrasonically-Enhanced Deep Eutectic Solvents Leaching of Zinc from Zinc-Containing Metallurgical Dust Sludge

by Fusheng Niu, Shengtao He, Jinxia Zhang and Chen Wen

Metals 2022, 12(11), 1856; https://doi.org/10.3390/met12111856 - 30 Oct 2022

Cited by 5 | Viewed by 1952

Abstract

In this study, the zinc containing dust and sludge of iron and steel smelting was taken as the research object, and the new ionic liquid of choline-urea was prepared and synthesized as the leaching agent. The conventional and ultrasonic leaching of zinc were [...] Read more.

In this study, the zinc containing dust and sludge of iron and steel smelting was taken as the research object, and the new ionic liquid of choline-urea was prepared and synthesized as the leaching agent. The conventional and ultrasonic leaching of zinc were compared, and the influence of liquid-solid ratio, temperature, time, ultrasonic power and other conditions on the zinc leaching rate were analyzed. The leaching residue was characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD), and the kinetic equations of ligand leaching based on ultrasonically enhanced metallurgical dust sludge were constructed. The results showed that the choline chloride-urea ionic liquid has a special solubilization ability for ZnO, and the leaching rate of Zn at temperature 60 °C, ultrasonic power 350 W, and leaching time 240 min reached more than 98%. Kinetic fitting of the ChCl-urea leaching process revealed that the ChCl-urea leaching process was in accordance with the nucleation contraction model under both conventional and ultrasonic conditions, and the leaching process was dominated by interfacial mass transfer and solid film layer diffusion control for the reactions, respectively. The activation energies were Ea₁ = 44.56 kJ/mol and Ea₂ = 23.06 kJ/mol. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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15 pages, 2222 KiB

Open AccessArticle

Evaluation of 20 Elements in Soils and Sediments by ED-XRF of Monochromatic Excitation

by Yan Xing, Haihan Zhang, Zhen Yang, Wei Song, Wenqi Long, Ruirui Zhu, Ruixue Chang and Linlin Zhang

Metals 2022, 12(11), 1798; https://doi.org/10.3390/met12111798 - 24 Oct 2022

Cited by 5 | Viewed by 2162

Abstract

There is an urgent need for the accurate analysis of heavy metal contamination in the field of ecology and environmental sciences, especially in the case of trace heavy metals, such as cadmium. Using doubly curved crystals (DCC) to achieve the monochromatic X-ray excitation [...] Read more.

There is an urgent need for the accurate analysis of heavy metal contamination in the field of ecology and environmental sciences, especially in the case of trace heavy metals, such as cadmium. Using doubly curved crystals (DCC) to achieve the monochromatic X-ray excitation of the sample to be measured and a silicon drift detector (SDD) to collect the fluorescence of the sample elements, combined with an algorithm analysis of the fundamental parameters (FP), the monochromatic energy-dispersive X-ray fluorescence (MED-XRF) system significantly improved the detection limits of the target elements. The detection limits, precision, and accuracy of the MED-XRF acquisition for 20 elements, including cadmium, lead, and arsenic, were evaluated and compared with the Determination of Inorganic Elements in Soil and Sediment Wavelength-Dispersive X-ray Fluorescence Spectrometry report and tested on the actual samples. The test results showed that the detection limit of the inorganic elements in soil and sediment determined by MED-XRF was mostly better than the industry standard, especially the detection limit of Cd, which was 0.04 mg/kg. The accuracy and correctness fully met the requirements for daily laboratory testing and, as a quality control tool, the actual sample testing and laboratory ICP-MS results were consistent. The research conducted in this project constituted a useful attempt to expand and improve the analytical methods for inorganic elements in soil and sediment, showing that MED-XRF is superior to conventional ED-XRF and WD-XRF and is the current new method of analysis for a low content of Cd in soil. MED-XRF offers a very important contribution to research on soil census, conservation, the rational use of agricultural land, and soil restoration and improvement, and provides strong support for field testing. Full article

(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)

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