Advances in the Theory and Technology of Physical Separation

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

Deadline for manuscript submissions: 31 July 2025 | Viewed by 3911

Special Issue Editors


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Guest Editor
School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China
Interests: magnetic separation; dry magnetic separation; preconcentration; numerical simulation; multi-physics
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Guest Editor
1. Minerals Processing Division, Mintek, Randburg 2125, South Africa
2. Faculty of Engineering and the Built Environment, University of the Witwatersrand, 1 Jan Smuts Ave., Johannesburg 2000, South Africa
Interests: flowsheet development; process optimization; modelling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The history of physical separation can be traced back to ancient times, when people began to use the physical properties of substances for separation, such as washing gold-bearing placers with water. With the development of the industrial revolution, physical separation technology has been further developed and applied. At the end of the 19th century, magnetic separation technology began to be applied to the field of mineral processing. At the beginning of the 20th century, electric separation technology was also gradually developed. Since the middle of the 20th century, with the continuous progress of science and technology, the physical separation technology has been continuously improved and innovated, and many new sorting methods and equipment have emerged, e.g., high-gradient magnetic separation, heavy medium separation, radiation separation, etc. Physical separation is of great significance in resource recovery and environmental protection, and it has the following advantages: 1. Improve resource utilization: Through physical separation, valuable minerals such as cassiterite, barite, wolframite, rare earth, etc., can be recovered from rocks, improving resource utilization and reducing dependence on natural resources. 2. Reduce environmental pollution and energy consumption: Physical sorting takes advantage of the difference in physical properties of materials and usually does not require the use of a large number of chemical reagents and energy, so it can reduce energy consumption and production costs and has the characteristics of environmental friendliness. 3. Achieve sustainable development: Physical sorting is one of the important means to achieve resource recycling and sustainable development, which helps to reduce waste generation, protect the environment, and also provide support for social and economic development.

This Special Issue invites submissions that include original scientific research relating to physical separation from well-known and/or new localities worldwide. This Special Issue focuses on the following topics: (1) research on gravity separation theory and its utilization in mineral and secondary resource recovery; (2) theoretical research on magnetic separation, research and development of new magnetic separation equipment, and utilization of magnetic separation equipment in minerals and secondary resources; (3) theoretical research on electric separation and utilization of electric separation equipment in resource recovery; (4) particle classification and its application in resource recovery; and (5) other theories and applications of physical separation, e.g., photoelectric beneficiation, heavy medium pre-separation, color separation, etc.

Dr. Dongfang Lu
Dr. Mehdi Safari
Guest Editors

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Keywords

  • physical separation
  • gravity separation
  • magnetic separation
  • particle classification
  • ray beneficiation
  • mineral preselection

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Published Papers (6 papers)

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Research

13 pages, 5666 KiB  
Article
Research on the Dry Deep Flip-Flow Screening of Ilmenite and Its Pre-Throwing Tail Processing Technology
by Wei Shi, Weinan Wang, Pengfei Mao, Xu Hou, Songxue Zhang and Chenlong Duan
Minerals 2025, 15(3), 308; https://doi.org/10.3390/min15030308 - 16 Mar 2025
Viewed by 82
Abstract
Screening is a key step in the mineral process of ilmenite. As the grading particle size decreases, the phenomenon of clogged holes on the screening-plate intensifies, the screening environment deteriorates, and the screening effect deteriorates, seriously restricting subsequent sorting operations. This study proposes [...] Read more.
Screening is a key step in the mineral process of ilmenite. As the grading particle size decreases, the phenomenon of clogged holes on the screening-plate intensifies, the screening environment deteriorates, and the screening effect deteriorates, seriously restricting subsequent sorting operations. This study proposes a 1 mm dry flip-flow screening method for ilmenite to achieve efficient deep classification of fine-grained materials. Firstly, a laser displacement testing system is used to study the dynamic characteristics of the flip-flow screen; based on the characteristics of different feed particle sizes, further research is conducted on the 1 mm dry flip-flow screening effect of ilmenite under different ratios of obstructive particles and difficult-to-screen particles. The 1 mm screening effect can reach 85.41%. Finally, the pre-throwing tailings process based on 1 mm multi-stage screening is put forward. This pre-throwing tail process has the characteristic of not using water and is suitable for sorting in arid, water deficient, and high-altitude frozen soil areas. It has important promotion and application value. Full article
(This article belongs to the Special Issue Advances in the Theory and Technology of Physical Separation)
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23 pages, 6086 KiB  
Article
Effect of Wall Roughness in the Middle Zone of Spiral Concentrator on the Flow Field Evolution of Hematite–Quartz Slurry and Particle Separation Behaviour
by Shuling Gao, Xiaohong Zhou, Bochao Li, Qian Wang and Chunyu Liu
Minerals 2025, 15(3), 208; https://doi.org/10.3390/min15030208 - 21 Feb 2025
Viewed by 184
Abstract
The spiral concentrator is usually the first operation in the combined process of iron ore beneficiation. The industrial separation index decreases as the trough surface undergoes increased wear. A combination of surface roughness measurement and numerical experimental methods is utilized to systematically investigate [...] Read more.
The spiral concentrator is usually the first operation in the combined process of iron ore beneficiation. The industrial separation index decreases as the trough surface undergoes increased wear. A combination of surface roughness measurement and numerical experimental methods is utilized to systematically investigate the effect of wall roughness in the middle zone on the evolution of the flow field of a slurry consisting of hematite, quartz and water in a spiral concentrator. The radial migration and distribution characteristics of hematite and quartz particles are analysed, and the separation indexes are further evaluated. The results show that an increase in wall roughness (Ks value) in the middle zone has been shown to decrease the depth of slurry flow, the velocity and radial flux of secondary flow in the inner and middle zones of the trough, and to narrow the space of inward flow. The variation in hydrodynamic parameters is particularly pronounced as the Ks value increases from 0.1 mm to 0.2 mm, resulting in a significant reduction in the space available to the separation fluid and an observable interruption in the inward flow. The migration tendency of hematite and quartz particles to the inner trough is reduced depending on the flow field parameters, and their enrichment zones are both shifted outward. The migration amount and distance of particles show apparent differences in density and size. The separation indexes decrease slightly as the wall roughness (Ks value) in the middle zone increases in the 0.01 to 0.1 mm range, but the iron grade of concentrate decreases significantly, and the separation effect worsens as the Ks value increases from 0.1 mm to 0.2 mm. The separation effect of hematite and quartz particles in the spiral concentrator is influenced by the comprehensive interaction of feed size and wall roughness in the middle zone. The results of this study provide a theoretical basis for the selection of trough material, surface structure design and the production process control of the spiral concentrator. Full article
(This article belongs to the Special Issue Advances in the Theory and Technology of Physical Separation)
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17 pages, 9523 KiB  
Article
Optimization of the Matrix in a Transverse-Field High-Gradient Magnetic Separator for an Improved Ilmenite Separation
by Jianguo Liu, Huixin Dai, Lili Yu, Chenghang Wang, Jiaying Feng, Peilun Li and Shaohua Xu
Minerals 2025, 15(2), 114; https://doi.org/10.3390/min15020114 - 24 Jan 2025
Viewed by 540
Abstract
Transverse-field high-gradient magnetic separators (HGMSs) are an important complement to longitudinal-field HGMSs in mineral processing due to their several advantages. However, the processing capacity of the transverse-field HGMS is smaller than that of the longitudinal-field HGMS. Consequently, research on the optimization of the [...] Read more.
Transverse-field high-gradient magnetic separators (HGMSs) are an important complement to longitudinal-field HGMSs in mineral processing due to their several advantages. However, the processing capacity of the transverse-field HGMS is smaller than that of the longitudinal-field HGMS. Consequently, research on the optimization of the matrix box for improving the processing capacity is essential. This work investigates the optimization of the matrix box for the SSS® HGMS to enhance the ilmenite separation efficiency and processing capacity. The results show that the matrix’s influence on separation performance is primarily influenced by the diameter of the rod matrix, the filling ratio, the depth of the matrix in the direction of slurry flow, and the ore unloading efficiency. Ilmenite pre-concentration tests are carried out using a test sample ore from Panzhihua, China. Pilot-scale validation research is carried out. The test results indicate that the depth of the matrix box should not be considerably thick, as an excessive number of layers increases the capture zone, but simultaneously reduces the unloading efficiency. The depth of the matrix box should neither be considerably thick nor particularly thin, as this would result in low processing capacity. Meanwhile, the segmented multi-layer matrix box should be used to balance the capturing and unloading performance. Finally, an optimal double-layer matrix ring is applied to the industrial transverse-field HGMS, and its inner and outer rings are equipped with matrix boxes with ϕ3 mm and ϕ2 mm rods, respectively, which improves its pre-concentrate efficiency and processing capacity. The concentrate indexes of the transverse-field HGMS is achieved with a TiO2 grade of 18.01% and a recovery of 87.28%, which is better than the separation indexes of the longitudinal-field HGMS. Full article
(This article belongs to the Special Issue Advances in the Theory and Technology of Physical Separation)
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23 pages, 10122 KiB  
Article
Effect of the Cross-Sectional Geometry of the Mixed Particle Zone on the Spiral Separation Process and Its Structural Optimization
by Shuling Gao, Qian Wang, Xiaohong Zhou, Chunyu Liu, Yanbai Shen and Baoyu Cui
Minerals 2024, 14(12), 1251; https://doi.org/10.3390/min14121251 - 9 Dec 2024
Cited by 1 | Viewed by 654
Abstract
Cross-sectional geometry is of significance in determining the flow characteristics and the particles separation in spiral concentrators. The effects of the cross-sectional geometry within the mixed particle zone on the secondary flow and the separation process of hematite and quartz particles with a [...] Read more.
Cross-sectional geometry is of significance in determining the flow characteristics and the particles separation in spiral concentrators. The effects of the cross-sectional geometry within the mixed particle zone on the secondary flow and the separation process of hematite and quartz particles with a size of 89.5 μm were investigated via a computational fluid dynamics (CFD) approach. The optimization of the line segment slopes was conducted using response surface methodology (RSM). The results indicate that the peak radial fluxes and average radial velocities of the secondary flow are positively correlated with the corresponding line segment slope. The independent adjustment of line slopes in regions I and II, and the interaction of line slopes in regions I and III, influence the separation efficiency of hematite and quartz particles significantly. The separation performance of the experimental spiral concentrator with a cross-sectional profile of the optimized line segments for a feed of hematite and quartz with a size range of −100 + 75 μm is remarkably improved by nearly 5%. This study provides insights for the cross-section design of spiral concentrators for the effective separation of coarse-grained hematite and quartz. Full article
(This article belongs to the Special Issue Advances in the Theory and Technology of Physical Separation)
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18 pages, 7739 KiB  
Article
Study on the Preparation of High-Quality Quartz and Its Mechanism by Combining Pretreatment with Metallurgy
by Hongjun Huang and Ning Zhang
Minerals 2024, 14(12), 1229; https://doi.org/10.3390/min14121229 - 2 Dec 2024
Viewed by 911
Abstract
As a strategically important resource with stable properties, high-purity quartz plays a crucial role in various fields such as high-purity quartz crucibles, semiconductors, and electronics. Currently, the availability of high-quality quartz resources is gradually diminishing, and there are no high-quality quartz deposits in [...] Read more.
As a strategically important resource with stable properties, high-purity quartz plays a crucial role in various fields such as high-purity quartz crucibles, semiconductors, and electronics. Currently, the availability of high-quality quartz resources is gradually diminishing, and there are no high-quality quartz deposits in some areas, making the improvement of low-quality quartz essential. This study focuses on the quartz sand produced through river dredging in Yueyang. The detected SiO2 content is 92.31%, which enables the secondary utilization of waste resources and provides significant environmental benefits. In this study, the iron oxide removal efficiency achieved through magnetic separation pretreatment can reach 87.24%. Following flotation, calcination, and leaching processes, high-purity quartz products with a total impurity content of less than 100 ppm were successfully obtained. In addition, the factors affecting magnetic separation and calcination effect were studied, and the process parameters for reference were obtained. The mechanism of microwave impurity removal was investigated using SEM, TG-MS, and in-situ XRD, demonstrating the feasibility of producing high-purity quartz from low-quality quartz. Full article
(This article belongs to the Special Issue Advances in the Theory and Technology of Physical Separation)
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16 pages, 3757 KiB  
Article
Preconcentrating Ultrafine Ilmenite Tailings Using a Laboratory-Scale Reflux Classifier
by Zhenqiang Liu, Zhenhua Su, Bing Liu, Yuhua Wang, Yuxin Zhang, Xuqun Zhong, Kangkang Chen, Xiaoxing Hu and Dongfang Lu
Minerals 2024, 14(11), 1125; https://doi.org/10.3390/min14111125 - 7 Nov 2024
Viewed by 864
Abstract
China is rich in reserves of titanium, but a large amount of titanium resources is lost in the ultrafine tailings, and it is challenging to treat the ilmenite contained in ultrafine ore. The reflux classifier (RC), a novel gravity concentration technology, has been [...] Read more.
China is rich in reserves of titanium, but a large amount of titanium resources is lost in the ultrafine tailings, and it is challenging to treat the ilmenite contained in ultrafine ore. The reflux classifier (RC), a novel gravity concentration technology, has been applied in the preconcentration of ultrafine ilmenite in this study. During this process, the feasibility of using RC for preconcentration of ultrafine ilmenite was explored through theory and conditional experiments. After one-stage preconcentration using RC, the ultrafine ilmenite ore with a TiO2 grade of 8.77% can be concentrated into a product with a TiO2 grade of 20.3% and a recovery rate of 82.8%. The tailings grade is as low as 2.44%, and the yield reaches 62.6%. The separation efficiency achieves 50.0%. Experimental results demonstrate that utilizing RC for the preconcentration of ultrafine ilmenite can avoid the influence of weakly magnetic gangue and achieve better results compared to a magnetic separator. Therefore, RC offers a more effective and affordable method for preconcentrating ultrafine ilmenite ore. Full article
(This article belongs to the Special Issue Advances in the Theory and Technology of Physical Separation)
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