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Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control

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A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Processing and Extractive Metallurgy".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 31311

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Special Issue Editors

Prof. Dr. Shenghua Yin

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Guest Editor

School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China
Interests: solution mining (heap leaching; flow behavior; in-situ leaching, etc.); backfill technology (paste backfill, cemented backfill, etc.); rock mechanics
Special Issues, Collections and Topics in MDPI journals

Dr. Leiming Wang

E-Mail Website
Guest Editor

School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China
Interests: solution mining (copper sulfides leaching; ore agglomeration; microbial succession of bioleaching; flow behavior in heap leaching, etc.); paste backfill
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Mineral resources provide an important material foundation for industrial construction and are important to the economy, thus being closely related to our daily lives and approaching future. However, mineral resources still possess limitations, such as low mineral grade and serious secondary/concomitant deposits. This undesirable situation causes great difficulty in traditional underground/surface mining, increasing operational costs.

In this regard, solution mining (heap leaching, in situ leaching, etc.) offers an environmentally friendly, low-cost, and efficient method to extract these minerals, especially copper sulfides (chalcopyrite, chalcocite, etc.), sandstone uranium, and sandstone gold deposits. After years of development, solution mining has made great progress, but it has also encountered some technical bottlenecks.

This Special Issue focuses on low-grade metal ores or wastes, including tailings, low-grade copper ore, uranium ore, and gold ore, and introduces the latest progress in leaching reaction mechanisms, process enhancement, and regulation. Both original research articles and reviews are acceptable.

This Special Issue is organized into three sections:

Section 1: Reaction mechanisms of chemical/bio-leaching—includes the leaching kinetics of copper sulfides, assisted leaching (chloride acidic leaching, iodide assisted leaching, etc.), in situ leaching of uranium and salt deposits, etc.
Section 2: Process detection, characterization, and visualization—includes the detection of reaction products, visualization of fluid flow and mass transfer, pore strucutre characterization of leaching systems (ore-packed beds, etc.), microbial successions of leaching bacteria, etc.
Section 3: Recovery, recycle, and reuse of mine wastes—includes cleaner leaching, disposal or production methods (dump leaching, etc.), the recovery of mine waste (waste rock, tailings, etc.), systemic assessment of operations and environmental problems, etc.

This Special Issue aims to provide a useful reference for researchers in the next phase of mining industry development.

Prof. Dr. Shenghua Yin
Dr. Leiming Wang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

advances in solution mining
chemical/bio-leaching of low-grade minerals
green recovery of mine waste
in situ leaching of uranium and salt deposits
process control and improvements in leaching operation methods
precise detection and visualization of leaching processes
intelligent technology and prospects in solution mining

Published Papers (14 papers)

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Editorial

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3 pages, 189 KiB

Open AccessEditorial

Editorial for Special Issue: “Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control”

by Shenghua Yin and Leiming Wang

Minerals 2023, 13(6), 778; https://doi.org/10.3390/min13060778 - 07 Jun 2023

Viewed by 682

Abstract

Mineral resources provide an important material foundation for industrial construction and are important for the economy, thus being closely integrated into our daily lives and near future [...] Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

Research

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15 pages, 4119 KiB

Open AccessArticle

Hydrodynamic Hysteresis and Solute Transport in Agglomerated Heaps under Irrigation, Stacking, and Bioleaching Controlling

by Leiming Wang, Shenghua Yin, Xuelan Zhang, Zepeng Yan and Wensheng Liao

Minerals 2022, 12(12), 1623; https://doi.org/10.3390/min12121623 - 16 Dec 2022

Cited by 4 | Viewed by 1160

Abstract

Hydrodynamic hysteresis exists widely in agglomerated heaps with well-developed intra-pores, and it directly affects solute transports and bioleaching reaction. In this paper, the dynamic liquid retention behavior under different heap porosity and irrigation condition is quantified via a novel real-time, in-situ liquid retention characterizing system (RILRCS), and the potential effects of initial liquid retention on solute transport and leaching reaction are carefully discussed. The results show that the immobile liquid is dominant in agglomerated heaps. The ratio of immobile and mobile liquid (η) dynamically changes due to mineral dissolution and new flow path appearances. The η normally increases and mobile liquid occupies a higher proportion due to acidic leaching reactions, especially at a smaller R_g (10.32 mm) and a larger u (0.10 mm/s). The dynamic liquid retention is more sensitive to the diameter of packed feeds (R_g) and superficial flow rate (u) instead of leaching reactions. This might be because the damage of leaching reaction on minerals pores/voids is limited and cannot extensively change the potential pore channels or fluid flow paths. Based on pulse tracing and conductivity tests, we reveal that the solute resides longer under a slower u and smaller packed R_g condition, which corresponds well with desirable copper leaching efficiency. Specifically, the liquid hysteresis behavior is more obvious at a lower u (0.01 mm/s) and smaller R_g (10.32 mm). This paper gives a good reference to ascertain the liquid retention and hydrodynamic hysteresis and promote mineral leaching performance. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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13 pages, 3295 KiB

Open AccessArticle

Recovery Potential of Rare Earth Elements (REEs) from the Gem Mining Waste of Sri Lanka: A Case Study for Mine Waste Management

by Nimila Dushyantha, I. M. Saman K. Ilankoon, N. P. Ratnayake, H. M. R. Premasiri, P. G. R. Dharmaratne, A. M. K. B. Abeysinghe, L. P. S. Rohitha, Rohana Chandrajith, A. S. Ratnayake, D. M. D. O. K. Dissanayake and N. M. Batapola

Minerals 2022, 12(11), 1411; https://doi.org/10.3390/min12111411 - 07 Nov 2022

Cited by 3 | Viewed by 2643

Abstract

Sri Lanka is one of the wealthiest countries in terms of gems. Therefore, gem mining is extensively carried out in many areas of Sri Lanka, including districts such as Ratnapura, Monaragala, Matale, and Kalutara. During the mining process, only valuable gemstones are collected, and the remaining gravel fraction with many heavy minerals is discarded. Therefore, the gem mining industry produces a large amount of waste that is mainly used only for backfilling. To sustainably manage this waste stream, gem mining waste collected from a gem pit at Wagawatta in the Kalutara district in Sri Lanka was investigated for value recovery, specifically for rare-earth elements (REEs). The gem-bearing alluvial layer contained 0.3% rare-earth oxide (REO) that could easily be upgraded up to 2.8% (LREEs = 94%) with wet sieving and subsequent density separation via a shaking table. Therefore, the concentrates of gem mine tailings with REE-bearing minerals have the potential to be a secondary source for LREEs. The organic-rich clay layer underlying the gem-bearing alluvial layer contained 0.6% REO with 49% HREEs, including Gd, Dy, Er, Yb, and especially Y enrichments. Detailed explorations are thus necessary to assess the REE potential in Sri Lanka’s gem mining waste, and value recovery flowsheets should be subsequently developed to economically extract REEs. In addition, the presence of high U concentrations (800 mg/kg) in the concentrated samples could be alarming when considering the health and safety of the people engaged in gem mining. This aspect also requires detailed research studies. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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11 pages, 5431 KiB

Open AccessArticle

Evaluation of Stope Stability and Displacement in a Subsidence Area Using 3Dmine–Rhino^3D–FLAC^3D Coupling

by Leiming Wang, Xingquan Zhang, Shenghua Yin, Xuelan Zhang, Yifan Jia and Helin Kong

Minerals 2022, 12(10), 1202; https://doi.org/10.3390/min12101202 - 24 Sep 2022

Cited by 7 | Viewed by 1431

Abstract

Underground stope stability has important implications for the safety and efficiency of metal mining, especially when there are subsidence zones above. To analyze the stope stability around the subsidence area of the Hongling ore body, this paper innovatively adopts the 3Dmine–Rhino^3D–FLAC^3D coupled modeling numerical method to model and predict the excavation process of the stope around the Hongling subsidence area; it monitors and analyzes the displacement and stress-distribution changes in a selected stope roof, and its left-hand side and right-hand side walls. This paper realizes the separation and extraction of the special ore body and surface topographic features of the Hongling ore body; it discusses the stope stability characteristics around a subsidence area based on the real topography of the mining area and the occurrence form of the ore body. The study found that the influence of the upper collapse area on the undesired displacement of the downhole stope is mainly reflected in the roof displacement. As the stope position moves away from the collapse area, the roof displacement decreases significantly, the maximum displacement is at the center of the stope roof, and the maximum principal stress occurs at the corner of the stope. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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12 pages, 1319 KiB

Open AccessArticle

Improving the Efficiency of Downhole Uranium Production Using Oxygen as an Oxidizer

by Bayan Rakishev, Zhiger Kenzhetaev, Muhametkaly Mataev and Kuanysh Togizov

Minerals 2022, 12(8), 1005; https://doi.org/10.3390/min12081005 - 10 Aug 2022

Cited by 7 | Viewed by 1446

Abstract

The features occurring during borehole uranium mining in deposits with low filtration characteristics, as well as the conditions and reasons for the reduction of geotechnological parameters of uranium mining by the well are considered in this study. Core material samples were taken from the productive horizon of the Chu-Sarysui province deposit and granulometric compositions were established. The contents of uranium, aluminum, calcium, magnesium, iron and carbonate minerals in the samples were determined by atomic emission spectroscopy. The X-ray phase analysis method established the features and quantitative and qualitative characteristics of ore-containing minerals. A special technique has been developed for conducting experiments in laboratory conditions using core samples, where the intensity of uranium leaching in tubes is determined. The results of laboratory studies are analyzed and discussed and graphs are constructed, to show the dependencies of change in: the filtration coefficients of K_f; the uranium content in solution; the extraction coefficient; and the specific consumption of sulfuric acid on the values of L:S (the ratio of liquid to solid) in the experiments. The effectiveness of using a mild acidity regime, with the addition of oxygen as an oxidizer, is determined and shown. The values of the uranium content in the productive solution, with the addition of oxygen as an oxidizer, reached 220 mg/L, which exceeds the design parameters. The results of uranium extraction from ore show a positive trend, reaching 68%, with L:S from 1.7 to 3.0, low acidity values and the addition of oxygen as an oxidizer. The specific consumption of sulfuric acid reaches the minimum values when using leaching solutions with reduced acidity of 26 kg/kg. The obtained results, on the flow rate of the solution in the tube, the extraction of uranium from ore and the specific consumption of sulfuric acid, indicate a decrease in sedimentation in a porous medium and increased filtration characteristics, with reduced acidity values in the leaching solution. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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11 pages, 5481 KiB

Open AccessArticle

Mineralogical Characteristics of Pegmatite Tailings and Beneficiation Assessment of Pollucite in Recovering Cesium

by Yong Chen, Jiankang Wen, Yongsheng Song, Wenjuan Li, Shuang Liu and Ying Liu

Minerals 2022, 12(5), 541; https://doi.org/10.3390/min12050541 - 27 Apr 2022

Cited by 2 | Viewed by 1519

Abstract

The technological mineralogical characteristics of cesium-containing minerals in tailings were examined by means of chemical analysis, the energy spectrum analysis method, and MLA (mineral liberation analyzer) to determine the element content, phase analysis, associated mineral components, degree of liberation, particle size, etc. The results showed that the samples mainly contained spodumene, quartz, feldspar, mica, and other minerals. Pollucite was the main cesium-containing mineral in the sample, which had a cesium oxide content that was as high as 34.58%. The mineral content of pollucite in the sample was relatively low—only 1.23%. The pollucite monomer content and the amount of rich intergrowth was 85.25%, and the metal distribution of cesium in the +0.074 mm sample was as high as 87.06%. Spodumene was the main mineral associated with pollucite. The beneficiation evaluation of this tailing sample was conducted using a combined process that integrated desliming, magnetic separation, and froth flotation, and a pollucite concentrate containing 4.45% Cs₂O was obtained with a 63.71 recovery rate. This indicates that little pollucite was removed by means of desliming and magnetic separation before froth flotation recovery, but during the froth flotation stage in spodumene and feldspar, a large pollucite loss was observed. Therefore, to improve pollucite recovery, a pollucite-specific adsorption reagent should be synthesized. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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20 pages, 10384 KiB

Open AccessArticle

The Energy Dissipation, AE Characteristics, and Microcrack Evolution of Rock–Backfill Composite Materials (RBCM)

by Jie Wang, Chi Zhang, Weidong Song and Yongfang Zhang

Minerals 2022, 12(4), 482; https://doi.org/10.3390/min12040482 - 14 Apr 2022

Cited by 8 | Viewed by 1669

Abstract

The backfill in the stope usually forms a composite structure with the surrounding rock in order to bear pressure together to support the goaf and ensure the safe mining of subsequent ores. Based on laboratory tests and theoretical analysis, the energy and damage evolution of the rock–backfill composite materials (RBCM) are studied deeply. The results show that: (1) The σ_p (peak stress), ε_p (peak strain), and E (elasticity modulus) decreased with the increase of the internal backfill diameter. When the diameter of the backfill increases from 10 mm to 40 mm, σ_p decreases from 50.15 MPa to 18.14 MPa, ε_p decreases from 1.246% to 1.017%, and E decreases from 7.51 GPa to 2.33 GPa. The U^T shows an S-shaped distribution, the U^E shows an inverted U-shaped distribution, and the U^D first increases slowly and then increases rapidly. The U^T_p, U^E_p, U^D_p, U^E_p/U^D_p, and U^E_p/U^T_p decrease by 67.38%, 97.20%, 58.56%, 32.64% and 13.64% respectively, and the U^D_p/U^T_P increases by 20.93% with the increases of the backfill diameter. (2) A damage constitutive model of the RBCM is established based on the energy consumption characteristics. The damage evolution curve shows an S-shaped distribution, and the damage rate evolution curve shows an inverted U-shaped distribution. (3) The AE correlation fractal dimension decreases with the increase of the strain gradient and damage value, and the AE correlation fractal dimension presents linear and exponential functions with them, respectively. With the increase of stress, microcracks first appear and gather in the internal backfill of the RBCM, and then microcracks appear and gather in the peripheral rock, which together lead to the macro penetration failure of the RBCM. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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23 pages, 44619 KiB

Open AccessArticle

The Energy Dissipation Mechanism and Damage Constitutive Model of Roof–CPB–Floor (RCF) Layered Composite Materials

by Jie Wang, Chi Zhang, Jianxin Fu, Weidong Song and Yongfang Zhang

Minerals 2022, 12(4), 419; https://doi.org/10.3390/min12040419 - 29 Mar 2022

Cited by 10 | Viewed by 1576

Abstract

The stability of composite material that is composed of roof rock, cemented paste backfill (CPB), and floor rock has an important impact on safe mining within metal mines. In order to explore the mechanical properties, acoustic emission (AE), energy dissipation, and damage evolution of roof–CPB–floor (RCF) layered composite materials, uniaxial compression (loading rate 0.02 mm/min) AE tests on RCF materials with different CPB height ratios were performed. The test results show that: (1) the uniaxial compressive strength (UCS) and elastic modulus (E_R) of the RCF material were lower than those of the roof or floor rock and higher than that of the CPB. With the increase in the CPB’s height ratio from 0.2 to 0.7, the UCS and the E_R decreased from 18.42 MPa to 10.08 MPa and 3.15 GPa to 1.79 GPa, respectively, and the peak strain first decreased from 0.695 to 0.510 and then increased from 0.510 to 0.595. The UCS increased as a polynomial function with the increase in the E_R. (2) The AE ring count first increased slowly, then increased rapidly, and finally maintained a high-speed increase. The AE cumulative ring count at the peak point decreased with the increase in the CPB height ratio. The energy dissipation showed that the elastic energy U_E accumulated slowly at first, then the dissipated energy U_D increased, and finally the U_E decreased and the U_D increased almost linearly. The U_T, U_E, U_D, U_E–U_T ratio and U_D–U_T ratio showed a decreasing trend, and the U_E–U_D ratio showed an increasing trend at the peak point with the increase in the CPB height ratio. (3) Two damage constitutive models were established based on the AE ring count and energy principle. The damage evolution process of RCF materials can be divided into three stages: the slow damage accumulation stage, stable damage growth stage, and rapid damage accumulation stage. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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15 pages, 7377 KiB

Open AccessArticle

Flocculation and Settlement Characteristics of Ultrafine Tailings and Microscopic Characteristics of Flocs

by Chongchong Han, Yuye Tan, Lishen Chu, Weidong Song and Xin Yu

Minerals 2022, 12(2), 221; https://doi.org/10.3390/min12020221 - 09 Feb 2022

Cited by 5 | Viewed by 1765

Abstract

Aiming to solve the problems related to the slow settling speed and the long-term consumption of ultra-fine tailings in mine filling, the effect of flocculant type on the flocculation and settling performance of ultra-fine tailings was studied through static sedimentation experiments on tailings. The microstructure of the flocculation was observed and analyzed using an electron microscope. On this basis, the selection of the optimum flocculant type and dosage parameters was carried out. The results show that the best addition amount of the AZ9020 anionic flocculant was 30 g/t, a solution concentration of 0.3%, and a stirring time of more than 45 min. The floc structure of the full-tailings flocculation solution was formed by the AZ9020 anionic flocculant. Moreover, the size of less than 0.1 μm was still relatively large; thus, the overall size of the structure was small and uniformly dispersed. The floc solution had the smallest porosity, the fractal dimension was the largest, the molecular weight of the floc was the largest, and the floc was the most compact, making it appropriate for the rapid removal of floc structures from water. Sedimentation is also the best flocculant for flocculation and sedimentation. The size of the flocs decreased as the height of the flocculation sediment bed increased during flocculation and sedimentation. The research results provide a microscopic view for the selection of the best flocculant type. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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16 pages, 4216 KiB

Open AccessArticle

Process Mineralogy of the Tailings from Llallagua: Towards a Sustainable Activity

by Pura Alfonso, Miguel Ruiz, Rubén Néstor Zambrana, Miquel Sendrós, Maite Garcia-Valles, Hernan Anticoi, Nor Sidki-Rius and Antonio Salas

Minerals 2022, 12(2), 214; https://doi.org/10.3390/min12020214 - 07 Feb 2022

Cited by 4 | Viewed by 1844

Abstract

There are significant tin reserves in the dumps and tailings from Llallagua. Currently, this waste is being processed using gravity concentration or a combination of gravity concentration with a final stage of froth flotation. A process mineralogy study of the tailings and their products after processing in Llallagua was carried out to determine the failings of the processing system in order to contribute to designing an improved new processing scheme. The mineralogy of the feed tailings, concentrate, and final tailings was determined by X-ray diffraction, scanning electron microscopy, and mineral liberation analysis. The tailings were composed of quartz, tourmaline, illite, K-feldspar, plagioclase, cassiterite, rutile, zircon, and monazite. The concentrate essentially contains cassiterite (57.4 wt.%), tourmaline, quartz, hematite, rutile and rare earth minerals, mainly monazite and minor amounts of xenotime and florencite. The concentrate contained 52–60 wt.% of SnO₂ and 0.9–1.3 wt.% REE. The final tailings contained 0.23–0.37 wt.% SnO₂ and 0.02 wt.% of Rare Earth Elements (REE). Only 57.6 wt.% of cassiterite from the concentrate was liberated. The non-liberated cassiterite was mainly associated with quartz, tourmaline, and rutile. The average grain size of monazite was 45 µm and 57.5 wt.% of this was liberated. In other cases, it occurs in mixed particles associated with tourmaline, quartz, cassiterite, and muscovite. To improve the sustainability of this mining activity, the concentrate grade and the metal recovery must be improved. Reducing the particle size reduction of the processed tailings would increase the beneficiation process rates. In addition, the recovery of the REE present in the concentrate as a by-product should be investigated. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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14 pages, 5353 KiB

Open AccessArticle

Understanding the Effect of Stepwise Irrigation on Liquid Holdup and Hysteresis Behavior of Unsaturated Ore Heap

by Leiming Wang, Shenghua Yin and Bona Deng

Minerals 2021, 11(11), 1180; https://doi.org/10.3390/min11111180 - 25 Oct 2021

Cited by 11 | Viewed by 1410

Abstract

Liquid is a crucial medium to contain soluble oxygen, valuable metal ions, and bacteria in unsaturated heap leaching. Liquid retention behavior is the first critical issue to be considered to efficiently extract low-grade minerals or wastes. In this study, the residual liquid holdup of an unsaturated packed bed was quantitatively discussed by liquid holdup (θ), residual liquid holdup (θ_residual), relative liquid holdup (θ′), and relative porosity (n*) using the designed measuring device. The detailed liquid holdup and the hysteresis behavior under stepwise irrigation are indicated and discussed herein. The results show that relative porosity of the packed bed was negatively related to particle size, and intra-particle porosity was more developed in the −4.0 + 2.0 mm packed bed. The higher liquid retention of the unsaturated packed bed could be obtained by using stepwise irrigation (incrementally improved from 0.001 to 0.1 mm/s) instead of uniform irrigation (0.1 mm/s). It could be explained in that some of the immobile liquid could not flow out of the unsaturated packed bed, and this historical irrigation could have accelerated formation of flow paths. The θ was sensitive to superficial flow rate (or irrigation rate) in that it obviously increased if a higher superficial flow rate (u) was introduced, however, the θ_residual was commonly affected by n* and θ′. Moreover, the liquid hysteresis easily performed under stepwise irrigation condition, where θ and θ_residual were larger at u of the decreasing flow rate stage (DFRS) instead of u of the increasing flow rate stage (IFRS). These findings effectively quantify the liquid retention and the hysteresis behavior of ore heap, and the stepwise irrigation provides potential possibility to adjust liquid retention conditions. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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Review

Jump to: Editorial, Research

19 pages, 3214 KiB

Open AccessReview

Review on Comprehensive Utilization of Magnesium Slag and Development Prospect of Preparing Backfilling Materials

by Xiaobing Yang, Fusong Dong, Xizhi Zhang, Chenzhuo Li and Qian Gao

Minerals 2022, 12(11), 1415; https://doi.org/10.3390/min12111415 - 08 Nov 2022

Cited by 7 | Viewed by 1812

Abstract

China is the largest producer of the metal magnesium, which is the third largest metal after steel and aluminum, and magnesium slag (MS) discharged from magnesium production cannot be treated effectively at present. Large amounts of MS occupy the land, making the land salinized and polluting the groundwater, which will threaten the sustainable development of the inland areas of China. To realize the large-scale utilization of MS, this paper reviews the research on the comprehensive utilization of MS and proposes using MS to prepare backfill materials. Firstly, the source and physical and chemical properties of MS are introduced, and the hazards caused by MS are also pointed out. Then, the several utilization methods of MS are summarized, such as cement admixture, chemically activated cementitious materials, clinker sintering, etc. Thirdly, the effect of MS on the properties of cementitious materials and concrete is summarized, including condensation time, workability, mechanical properties, durability, etc. Finally, based on the cemented backfill mining method, MS replaces Portland cement and blast furnace slag (BFS) to prepare cementitious materials. The mechanical properties and fluidity of backfilling slurry composed of MS, gypsum, BFS, and tailings can meet the requirements of backfilling mining. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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16 pages, 5209 KiB

Open AccessReview

Review on the Art of Roof Contacting in Cemented Waste Backfill Technology in a Metal Mine

by Fengbin Chen, Jiguang Liu, Xiaowei Zhang, Jinxing Wang, Huazhe Jiao and Jianxin Yu

Minerals 2022, 12(6), 721; https://doi.org/10.3390/min12060721 - 04 Jun 2022

Cited by 9 | Viewed by 2627

Abstract

The backfilling mining method can effectively solve the environmental and safety problems caused by mining. It is the key technology to realize green mining. Scientific development has accelerated the pace of research on the rational utilization of mine solid waste and improved the research level of backfilling technology. The development history of the backfilling mining method is introduced in the present paper, and it is determined that roof-contacting backfilling is the key technology of mine-solid-waste backfilling mining. This paper introduces three calculation methods of similar roof-contacted backfilling rates. In this paper, the relationship between the characteristics of backfilling slurry made from solid waste from mines and the roof-contacted backfilling rate is systematically analyzed, such as the flow law in stope (gravity gradient), bleeding shrinkage, and natural sedimentation of backfilling slurry. It is pointed out that the characteristics of the stope, such as washing-pipe water, water for the leading way, filling pipeline, and shape of the backfilling stope, are closely related to the roof-contacted backfilling rate. The influential relationship between objective factors, such as human factors, limited auxiliary leveling measures, and backfilling “one-time operation” in the backfilling process, and high-efficiency top filling are considered, and a schematic diagram of the influencing top-filling rate and structure is drawn. At the same time, this paper summarizes the improvement measures of roof connection from three aspects. These include the use of expansive non-shrinkable materials, forced roof-contacted technology, and strengthening management level. It is pointed out that the roof-contacted filling technology is still facing severe challenges, and the research on the backfilling connection technology needs to be strengthened. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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28 pages, 2980 KiB

Open AccessEditor’s ChoiceReview

Accessing Metals from Low-Grade Ores and the Environmental Impact Considerations: A Review of the Perspectives of Conventional versus Bioleaching Strategies

by Rosina Nkuna, Grace N. Ijoma, Tonderayi S. Matambo and Ngonidzashe Chimwani

Minerals 2022, 12(5), 506; https://doi.org/10.3390/min12050506 - 20 Apr 2022

Cited by 21 | Viewed by 8442

Abstract

Mining has advanced primarily through the use of two strategies: pyrometallurgy and hydrometallurgy. Both have been used successfully to extract valuable metals from ore deposits. These strategies, without a doubt, harm the environment. Furthermore, due to decades of excessive mining, there has been a global decline in high-grade ores. This has resulted in a decrease in valuable metal supply, which has prompted a reconsideration of these traditional strategies, as the industry faces the current challenge of accessing the highly sought-after valuable metals from low-grade ores. This review outlines these challenges in detail, provides insights into metal recovery issues, and describes technological advances being made to address the issues associated with dealing with low-grade metals. It also discusses the pragmatic paradigm shift that necessitates the use of biotechnological solutions provided by bioleaching, particularly its environmental friendliness. However, it goes on to criticize the shortcomings of bioleaching while highlighting the potential solutions provided by a bespoke approach that integrates research applications from omics technologies and their applications in the adaptation of bioleaching microorganisms and their interaction with the harsh environments associated with metal ore degradation. Full article

(This article belongs to the Special Issue Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control)

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Current Status of Low-Grade Minerals and Mine Wastes Recovery: Reaction Mechanism, Mass Transfer, and Process Control

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