High Gradient Magnetic Separation Research Articles

Spatial magnetic force and magnetic energy density analysis of microsphere medium in high gradient magnetic fields: A 3D simulation

Abstract High gradient magnetic separation technology is the key technology for green and efficient separation and purification of mineral resources. Existing studies are vague about the division of the attraction and repulsion zones of the medium, and there are fewer explorations of the effect of various conditions on the attraction zones. In this work, a novel method for calculating the magnetic force is derived, which provides an accurate calculation of the 3D magnetic force. The attraction and repulsion zones are divided clearly by analyzing the relationship between the spatial angle of the spherical medium and the magnetic force density per unit volume, with the magnetic force density per unit volume tangent to the spherical surface as the dividing line. The attraction and repulsion zones are divided by β = 30°~35°, and the attraction region accounts for 45%~50% of the total space volume. Furthermore, the influence of different conditions on the attraction zone is studied. It was found that the zone of attraction decreases as one moves away from the spherical medium, which results in an ellipsoid with the effective zone of attraction of the spherical medium having the magnetic field direction as its long axis. The attraction region increases from 45.49% to 49.87% of the space occupied with increasing the relative permeability of the spherical medium. It does not affect the proportion of the attraction zone in space by changing the background magnetic field and the size of the spherical medium, but it will change the depth of the magnetic force. It provides a theoretical basis for the design of high-efficiency magnetic media, and gives a reference for further improving the selection effect of high gradient magnetic separation technology on fine and weak magnetic particles.

A simulation on field distribution and particle capture characteristics in a multi-wire PHGMS system

ABSTRACT In the development history of high gradient magnetic separation (HGMS), the introduction of pulsating flow was extremely important, it successfully solved the problem of matrix clogging and allowed continuous and stable operation in the industry. However, the current pulsating HGMS (PHGMS) theory remains inadequately understood. In this paper, a 2D simulation model was established in COMSOL Multiphysics to reveal the magnetic field characteristics, flow field distribution, and particle capture dynamics in a PHGMS system. Quantitative comparisons were carried out between single-wire and multi-wire systems in the presence and absence of pulsation flow. The simulation results indicated that due to the coupled effect of neighboring magnetic wires in matrix, the magnetic field strength around an individual magnetic wire would slightly drop while the flow field velocity would increase. The introduction of pulsating flow could increase the peak value of fluid velocity and give particles a chance to move up and down. The analysis of particles travels length and capture probability indicated that the recovery for fine particles might be improved by increasing the strength of pulsating flow. This study provided a novel strategy for the highly efficient recovery of fine, weakly magnetic materials.

Study on the influence of high permeability magnetic iron on energy consumption reduction in high gradient magnetic separator

The green processing of weakly magnetic iron ore is inseparable from high-intensity and high-gradient magnetic separator (HGMS), which is one of the most energy-intensive magnetic separation equipment. Iron (Fe) armor serves as the key primary structure for enhancing magnetic field conduction efficiency within the magnetic system. The order of magnetic properties of commonly used magnetic yoke materials is: ordinary carbon structural steel < Q235 steel < DT4 electrical pure iron. But the utilization cost of DT4 electrical pure iron is the highest, especially the magnetic properties of DT4C super electrical pure iron are unstable and the yield is low. On the basis of ordinary pure iron materials, this article has developed a new type of 411 pure iron (411) upon controlling the levels of harmful elements, while increasing the concentration of beneficial elements.intensity Furthermore, through the utilization of magnetic field simulation software, the impact of 411 on the background magnetic field intensity of HGMS was analyzed. The results indicated that the newly developed 411 pure Fe exhibited a coercivity of 24.07 A/m, a saturation magnetization intensity of ∼ 1.69 T, a maximum relative magnetic permeability of 24.38 × 10-3H/m, demonstrating superior magnetic properties in comparison with Q235 and DT4C. When using 411 pure iron as the magnetic yoke material, the background magnetic field intensity of the HGMS can be increased by 6.85 % − 14.64 % compared with using DT4C super pure iron under the same excitation current conditions. The magnetic yoke with better magnetic conductivity will enhance the magnetic field utilization efficiency of the magnetic system, a reduce the excitation energy consumption, and improve the sorting performance of HGMS.

A Novel Technology for the Recovery and Separation of Cassiterite- and Iron-Containing Minerals from Tin-Containing Tailing

Tin-containing tailing is classified as a solid waste, but it possesses valuable resources such as tin and iron. Tin-containing tailing exhibits a fine distribution and compact symbiosis of cassiterite- and iron-containing minerals. Therefore, it is difficult to recover and separate cassiterite- and iron-containing minerals using traditional mineral processing methods. The study proposed a novel technology involving pre-concentration, reduction roasting, and magnetic separation for the treatment of tin-containing tailings with a tin grade of 0.14% and an iron grade of 12.79%. The classification pre-concentration method was achieved using a combination of shaking tables, suspension vibration cone separators, and high-gradient magnetic separation with a magnetic field strength of 1.4 T. The discarded tailings ratio reached 73.56%. The gravity pre-enriched concentrates and magnetic pre-enriched concentrates underwent reduction roasting to facilitate the conversion of hematite and goethite into magnetite, respectively. The optimal conditions for reduction roasting of the gravity pre-enriched concentrate were a 10% lignite dosage, a roasting temperature of 650 °C, and a holding time of 80 min. The optimal conditions for reduction roasting of the magnetic pre-enriched concentrate were a 8% lignite dosage, a roasting temperature of 750 °C, and a holding time of 100 min. The reduction roasted products were treated using magnetic separation with a magnetic field strength of 0.16 T. Finally, a tin-rich middling with a tin grade of 2.93% and a recovery ratio of 70.88%, as well as an iron concentrate with an iron grade of 61.95% and a recovery ratio of 68.08% were obtained. The study achieved efficient recoveries of tin and iron from tin tailings, thereby presenting a novel approach for the utilization of resources in the tailing.

Mechanism analysis of enhanced desulfurization of pulverized coal through high-gradient magnetic separation with microwave radiation

Dry high gradient magnetic separation technology is a low-carbon green technology. It can be embedded in a power plant to remove coal pyrite with a high-efficiency magnetic separator and remarkable magnetic properties difference between coal pyrite and coal matrix. This study selected the microwave radiation method to improve the magnetic properties difference and carried out a desulfurization experiment with a self-developed high-gradient permanent magnetic separator using the tapered iron auxiliary magnetic pole. The results demonstrate that the pyrite content and specific magnetic susceptibility increase with the decrease in particle size. The desulfurization rate did not change significantly at 25 °C. The coal sample began to appear in the thermal reaction at 450 °C, and the pyrite can become a strong magnetic property pyrrhotite. The desulfurization rate can achieve 58.70 % at 700 °C, and is equivalent to the wet washing index, due to the supply of high magnetic field force. The dynamic characteristic response of magnetic particles becomes more obvious with short time adsorption, and the probability of carrying non-magnetic particles is reduced. This study demonstrates that the high-gradient magnetic separation technology of pulverized coal enhanced by microwave irradiation is feasible.

Hematite tailings to high-purity silica: Mechanistic studies and life cycle assessment analysis

This study aimed to recover high-purity silica from hematite tailings (HTs) using superconducting high-gradient magnetic separation (S-HGMS) technology. This process involved converting silica into a silicone-rich concentrate and subsequently employing a fluorine-free mixed acid to leach the silicon-rich concentrate to remove impurities and achieve refinement and purification. The optimization of the S-HGMS process was conducted using the "Box-Behnken Design" method, resulting in the following optimal conditions: a pulp concentration of 50 g/L, a magnetic velocity ratio of 0.076 T s/m, and a pulp velocity of 500 mL/min. These conditions yielded a silica grade range of 61.905% in the HTs to 91.818% in the silicon-rich concentrate, with corresponding recovery rates of 53.031%. Under the optimized leaching process, this resulted in an increase in the silica content from 91.818% in the silicon-rich concentrate to 99.938% in high-purity silica. Additionally, by analyzing the production process of 1 kg of high-purity silica from HTs using the process LCA method, environmental hotspots were identified, and corresponding solutions were proposed. This approach is vital for efficient utilization of HTs as a resource. This process has low energy consumption and is environmentally friendly, enabling the reduction of hematite tailings. It has a wide range of applications and offers substantial economic benefits, rendering it a promising candidate for industrial applications.

Silicon powder production from organosilicon waste by a beneficiation-metallurgy combination process

A large amount of waste contact is produced in the preparation of organosilicon monomer. The current researches are mainly focused on copper extraction, with little attention paid to silicon. Moreover, the large accumulation of decoppered residue from organosilicon waste causes environmental pollution and resource waste. In this study, a novel beneficiation-metallurgy combination process was developed for the extraction of silicon from decoppered residue, which was defined as high gradient magnetic separation followed by roasting and acid leaching. The results showed that high gradient magnetic separation was effective in separating silicon from metallic impurities. Under the optimum conditions, the removal efficiencies of metallic impurities are more than 80 %. Fe content in the non-magnetic product can be further reduced to 0.82 % by cleaning. The non-magnetic products obtained by a roughing-cleaning process are subjected to roasting and acid leaching experiments. Under the optimum conditions, the removal efficiency of C and O can reach 94.26 % and 96.32 %, respectively. The final silicon powder product meets the standard of "YS/T1109–2016", which can be reused in the production of methylchlorosilane. This process is suitable for large-scale treatment of decoppered residue and is simple enough to help solve the problem of large-scale output of organosilicon waste.

Enhancing PHGMS performance for recovery of ultra-fine ilmenite from tailings

In southwest China, the Panzhihua area annually produces about 80 million tons of tailings with a TiO&lt;sub&gt;2&lt;/sub&gt; grade of around 5.0%, which causes serious waste of titanium resources as well as environmental and safety issues. The ilmenite contained in these tailings is ultra-fine in size, so it is difficult to recover under the regular operating conditions of pulsating high gradient magnetic separation (PHGMS). In this study, an SLon-100 PHGMS separator was applied to concentrate an ultra-fine titanium tailing under a wide range of operating conditions. The experimental results indicated that a combination of high pulsating frequency, large pulsating stroke, and low feed velocity was favorable for the highly efficient recovery of ultra-fine ilmenite from the tailings. The TiO&lt;sub&gt;2&lt;/sub&gt; grade in the optimal concentrate was enhanced from 4.33% to 13.64%, at a recovery of 66.55% and an enrichment ratio of 3.15 through a one-stage PHGMS process. The size analysis of the optimal concentrate showed that the TiO&lt;sub&gt;2&lt;/sub&gt; recovery in -25+18 µm and -18+10 µm fractions exceeded 70%. To further understand this PHGMS performance, the optimal ultra-fine ilmenite and larger-size ilmenite concentration conditions were compared. This study provides a valuable reference in the PHGMS operation for recovering ultra-fine weakly magnetic minerals, including ilmenite.

Effect of eddy currents on metal fine particles in high gradient magnetic separation using a superconducting magnet

Abstract Dry high gradient magnetic separation is one of the key technologies expected in removing magnetic metal fine particles as contaminations in the production process of various powders. However, the effect of eddy currents on such metal fine particles in dry high gradient magnetic separation has not been adequately explored in previous research. In order to understand this phenomenon more comprehensively, we conducted particle trajectory simulations using a finite element analysis with numerical methods and actual magnetic separation experiments to investigate the influence of eddy currents on magnetic separation efficiency. The results show that for both paramagnetic and diamagnetic metal particles, eddy currents can favourably influence the capture efficiency. Furthermore, these effects depend on the particle size, electrical conductivity, and the rate of change in the magnetic field. Therefore, by taking eddy currents into account, magnetic separation systems can be better optimized and their performance further improved.

Enhancing Recovery of Ultra-Fine Magnetite from Low-Iron-Grade Cyanidation Tailings by Optimizing Flow Field Parameters of Low-Intensity Magnetic Separation (LIMS)

The characteristics of iron minerals in cyanidation tailings with a low iron grade were determined via chemical composition analysis, iron phase analysis, and mineral liberation analysis (MLA). The results showed that the cyanidation tailings contained 15.68% iron, mainly occurring in the form of magnetite (19.66%) and limonite (79.91%), in which 16.52% magnetite and 65.90% limonite particles were fully liberated. Most ultra-fine magnetite grains were adjacent and wrapped with limonite to form complex intergrowths, which resulted in low-efficiency magnetite recovery in low-intensity magnetic separation (LIMS) and adversely affected the downstream high-gradient magnetic separation (HGMS) process. Thus, in this work, the optimization of the flow field was proposed to enhance the separation of ultra-fine magnetite from the cyanidation tailings using pilot-scale LIMS separation, and the controllable parameters (including feed flow, separation gap, drum rotating speed, and solid weight) affecting ultra-fine magnetite capture were investigated. Under optimized conditions, a high-grade magnetite concentrate assaying 63.31% Fe with 86.46% magnetite recovery was produced, which, respectively, increased by 0.76% and 15.22%, compared with those obtained from industrial production. In addition, from the flow dynamics simulation, it was found that the magnetite particles in the −6 µm ultra-fine fraction were lost much more easily than those of coarser fractions due to the relatively enhanced hydrodynamic drag force acting on the particles compared with the magnetic force. However, this loss would be effectively reduced with the regulation and control of the flow field. The iron recoveries in the −16~+6 µm and −6 µm fractions of magnetite concentrate increased by 3.66% and 4.42%, respectively, under optimized hydrodynamic conditions. This research outcome provides a valuable reference for the economic and effective utilization of iron resources from such solid wastes.

S-HGMS coupling with alkali precipitation for the scale inhibition in recirculating cooling water with high hardness: Performance, mechanism and field application

Recirculating cooling water (RCW) contains various scale-forming ions, such as Ca2+ and Mg2+, which tend to form the hard scale in the heat transfer process. In this study, a novel method via superconducting high-gradient magnetic separation (S-HGMS) coupling with alkali precipitation for scale inhibition in RCW was proposed, which could achieve efficient removal of total hardness (91.64 %). The scale inhibition mechanism of the S-HGMS coupling is attributed to the increase of ionic hydration shell thickness and the formation of hydrogen bonds, enhancing the solubility of scale-forming ions and diminishing their nucleation rate. Furthermore, this coupling induces a crystalline transformation from recalcitrant calcite to looser aragonite, contributing to the separation of scale from the pipe wall. Significantly, the proposed method was implemented in the field application by establishing a pilot-scale system with a capacity of 800–1000 L/h, which realized a stable reduction in the total hardness of the RCW from 1270 mg/L to below 127 mg/L at a magnetic flow ratio of 0.05 T·s/m. Moreover, the heat exchanger surface scaling was effectively controlled after 71 days of continuous treatment. This study helps promote the industrial application of S-HGMS technology for scale inhibition in high-hardness water.

Comparative investigation on capture characteristics of chalcopyrite and hematite in PHGMS process

Pulsating high-gradient magnetic separation (PHGMS) is a promising method of separating chalcopyrite from other minerals with similar floatability. However, the capture characteristics of chalcopyrite in PHGMS process remains poorly understood. In this study, the difference in the capture capacity of chalcopyrite and hematite, a typical weak magnetic mineral, was theoretically compared. The effects of the key operating parameters, i.e., magnetic induction, slurry flow rate, and magnetic wire diameter, on the capture difference of chalcopyrite and hematite were investigated through experimental verification. The comparison results showed that chalcopyrite shared similar capture trend with hematite. The capture mass weight of the matrix decreased with an increase in the pulsating frequency, slurry flow rate, and magnetic wire diameter, but it increased with improved magnetic induction. However, chalcopyrite exhibited an obviously smaller capture mass weight due to its lower susceptibility, which required a higher magnetic induction, slower flow rate, lower pulsating frequency and smaller matrix diameter for high efficient recovery of chalcopyrite. This study provides a reference for the PHGMS of separating chalcopyrite from typically applied weakly magnetic minerals by PHGMS process.

Coupling effect between magnetic wires and its influence on high gradient magnetic separation performance

High gradient magnetic separation (HGMS) is effective for the separation of weakly magnetic minerals, and this method is achieved through the use of matrix, which is made of huge numbers of rod wires. So that the coupling effect of magnetic field and flow field between wires has a marked effect on the HGMS performance. In the investigation, the coupling effect between magnetic wires and its influence on high gradient magnetic separation performance were theoretically described and simulated using COMSOL Multiphysics. It is found that the magnetic field round a wire would be affected by the neighboring wires, and then a coupling effect of magnetic field between wires was produced, increasing the magnetic induction intensity on the upstream and downstream of wire surface. And the coupling effect of flow field could increase the slurry velocity at the regions of the wire surface with azimuth angles of 0° and 90°, which is beneficial for the selective capture of wire. These simulated results were basically validated with the experimental separation, using an innovative Magnetic Capture Analysis Method. It is found that the wire spacing has significant effect on the coupling effect of magnetic wires, and a critical spacing for wires could achieve an excellent coupling effect, which is beneficial for the improvement of HGMS performance. This investigation contributes to improve HGMS performance in concentrating fine weakly magnetic ores.

Increase in Recovery Efficiency of Iron-Containing Components from Ash and Slag Material (Coal Combustion Waste) by Magnetic Separation

This article presents the results of research aimed at optimizing the process of recovery of valuable components from ash and slag waste from thermal power plants. In this work, both experimental and theoretical studies were carried out to substantiate the use of magnetic separation methods for ash and slag waste processing. Ash and slag wastes were chosen as an object of research due to the presence of valuable components such as iron, aluminum, etc., in them. The research results showed that the method of magnetic separation, including high-gradient magnetic separation, can be effectively used in ash and slag waste processing. As a result, the topology of a magnetic beneficiation technological scheme has been proposed to obtain high-value-added products such as high-magnetic iron minerals, low-magnetic iron minerals, and aluminosilicate microspheres. By using magnetic separation in a weak magnetic field, magnetic microspheres containing high-magnetic iron minerals associated with intermetallics, ranging in size from 20 to 80 µm, were recovered. In the second stage of magnetic separation (high-gradient magnetic separation), an iron ore product with an iron content of 50% with a recovery of 92.07% could be obtained. By using scanning electron microscopy, it was found that the main part of microspheres, which contain low-magnetic iron minerals and aluminosilicates, with sizes from 2 to 15 microns, was recovered in the magnetic fraction. This paper proposes a new approach to the enrichment of ash and slag materials using magnetic separation, which will increase the efficiency of their processing and make the process environmentally sustainable.

Enhancing the separation of refractory weakly magnetic minerals with magnetic fluid in high gradient magnetic separation: Conversion of competing capture to mechanical entrainment

Due to serious competing capture of magnetic gangue minerals in high gradient magnetic separation (HGMS), combined separation processes which commonly have defects of long flowsheets and high energy consumption are applied to processing refractory weakly magnetic ores. High gradient magnetic separation coupling with magnetic fluid (HGMSCMF) is proved effective in eliminating competing capture and presents great potential in recovering refractory magnetic minerals, but the enhancing mechanism and particle capture relations among magnetic valuable minerals, magnetic gangue minerals and nonmagnetic minerals still remains unclear. In this study, particle capture and separation behaviors of minerals with different magnetic characteristics in HGMS and HGMSCMF were comprehensively investigated through pure and artificial mixed ore experiments using ilmenite, augite and quartz. Captured mass of augite was quite low and could hardly increase with increasing applied induction while that of ilmenite maintained a high level and increased with increase of applied induction even under high MnCl2 concentration. Results of artificial mixed ore experiments and numerical simulation of particle capture presented that separation characteristics of ilmenite-augite mixed ore gradually approached to that of ilmenite-quartz mixed one, indicating the conversion of competing capture to mechanical entrainment for high selectivity in HGMSCMF.

Performance evaluation of PHGMS technology for superfine chalcopyrite-molybdenite separation

Chalcopyrite (CuFeS2) and molybdenite (MoS2) as typical sulfide minerals are very easy for co-flotation in practice, but their mutual separation consumes a large quantity of flotation reagents, particularly for superfinely associated chalcopyrite and molybdenite as encountered in most porphyry copper deposits. Pulsating high gradient magnetic separation (PHGMS) was effectively applied for pre-concentration of relatively coarse chalcopyrite ore, therefore in this work, its feasibility for separation of superfine chalcopyrite from molybdenite was firstly attempted, with the separation performance under key operating parameters elucidated via a SLon-100 cyclic PHGMS separator in separating a primary superfine chalcopyrite-molybdenite co-flotation concentrate, which assays 8.12 % Cu and 20.00 % Mo, with − 23 μm superfine fraction weighting 79.14 %. The separator achieved a high-selective separation under optimized conditions, producing a copper concentrate of 19.12 % Cu and 6.60 % Mo at 70.90 % Cu recovery, with the Cu content and Mo recovery in the molybdenum concentrate reduced to 3.38 % and reaching 90.88 %, respectively. It was found that low feed weight and velocity, fine matrix, high magnetic induction, and a gentle pulsation were required for producing the effective separation; and the chalcopyrite above 11.4 μm was sufficiently recovered into the copper concentrate, while the high-sufficient recovery for those below 11.4 μm remains a challenge to be overcome, due to its extremely weak magnetic force subjected. This detailed investigation provided a requisite understanding for industrializing the PHGMS technology for fine chalcopyrite-molybdenite separation.

Enhancing magnetism and magnetic separation of ultrafine chalcopyrite from talc through surface oxidation treatment

Magnetic separation has been proposed to greenly separate chalcopyrite and talc several decades ago, due to their extremely similar floatability of minerals. However, this approach was not achieved initially due to the inadequately magnetic induction of traditional magnetic separation, and fine particle size of chalcopyrite. Currently, the development of highly magnetic induction technology provides strong feasibility for this separation. In this work, we employed pulsating high-gradient magnetic separation (PHGMS) with highly magnetic induction (1.8T) to separate chalcopyrite and talc, and found that the PHGMS achieves a good separation of chalcopyrite from talc. But the chalcopyrite recovery decreased with the decrease of its particle size, and thus surface oxidation treatment was attempted to increase the magnetism and magnetic capture of ultrafine chalcopyrite. As a result, an increment of approximately 10 % was observed in the recovery of ultrafine chalcopyrite post-oxidation. As verified by the superconducting quantum interference device measurements, the oxidized ultrafine chalcopyrite exhibited a significant increase in the saturation magnetisation intensity, remanent magnetisation and coercivity values. Such magnetism enhancement is a result of the formation of paramagnetic Fe(III)–O–OH structures on the oxidized chalcopyrite surface, in terms of X-ray photoelectron spectroscopy and Mössbauer spectroscopy investigations. Furthermore, the density functional theory revealed that the formation of Fe(III)–O–OH structures caused a substantial increase in the magnetic moments of iron ions in antiferromagnetic chalcopyrite. These findings may extend the application of magnetic separation, and facilitate the flotation of ultrafine chalcopyrite from other minerals, at significantly reduced reagents use, and productive and environmental costs.

Preparation of high-purity SiO2 by S-HGMS coupled with mixed-acid leaching: A case study on hematite tailings from Ansteel, China

Hematite tailings (HTs) are rich in silica and are used as replacements for fine aggregates in the preparation of construction materials. However, there is scope for a more effective utilization of the valuable elements present in HTs. In this paper, a process for preparing high-purity SiO2 using HTs procured from Ansteel (China) is proposed. HTs were treated using the superconducting high-gradient magnetic separation (S-HGMS) technology, where the silica as part of the nonmagnetic fraction was obtained in the form of a high-silica concentrate, which was then subjected to mixed-acid leaching to dissolve impurities to achieve refined purification. The optimum process conditions for S-HGMS were determined, and the response surface methodology was applied to optimize the process parameters of the mixed-acid leaching process. The process indicators of the mixed-acid leaching step included the leaching time, leaching temperature, and molar ratio of the mixed acids. The optimum process conditions for S-HGMS were as follows: the magnetic strength-to-velocity ratio in the weak magnetic separation stage was set to 0.034 T·s/m whereas it was maintained at 0.076 T·s/m in the strong magnetic separation stage; the pulp concentration was 40 g/L, the pulp velocity was 500 mL/min, and the dispersant concentration was 1 mg/g. Under these conditions, the high-silica pulp was processed. The corresponding SiO2 grade increased from 71.788 % to 95.260 %, and its recovery and yield reached 56.330 % and 42.450 %, respectively. The SiO2 content in the sample increased from 95.260 % to 99.961 %. Further, the mechanisms of the S-HGMS and mixed-acid leaching were revealed. The proposed process is environmentally friendly and operationally inexpensive. It can reduce the amount of HTs by 42.450 %, and the obtained high-purity silica product has high economic value and good industrialization prospects.

Recent advances in the marketing, impurity characterization and purification of quartz

Due to its stable physical and chemical properties and its abundance in nature, quartz is widely employed in industrial and high-tech applications. However, the presence of diverse types and states of impurities in quartz ores from different geological formations poses a challenge in the process of purifying high-purity quartz, leading to wastage of raw materials and escalated costs. This study presents the socio-economic applications of quartz, scrutinizes the formation and separation mechanisms of impurities in quartz ores from a mineralogical perspective, examines the obstacles faced in quartz purification, explains the current state of development, and provides a technical summary of quartz purification. The analysis reveals that lattice impurity elements and various types of inclusion impurities are the principal factors affecting the purity of quartz. Various green separation techniques are applied based on the composition of the quartz minerals and the state of the impurities. Standard practices may involve physical pre-treatment such as scrubbing, ultrasonic crushing, and electromagnetic pulse cracking, followed by rough cleaning through color separation, superconducting high gradient magnetic separation, and flotation, and chemical pre-treatment (high-temperature or microwave roasting with chloride doping, and ammonium sulfate thermal crushing combined with water quenching to remove gas-liquid inclusions from quartz minerals). Finally, finishing processes such as fluorine-free and catalytic hot-pressure acid leaching or microbiological purification treatment with filamentous or Aspergillus fungi are used to obtain high-purity silica sand with an anticipated purity of about 99.99%.

SPIONs Magnetophoresis and Separation via Permanent Magnets: Biomedical and Environmental Applications

Superparamagnetic iron oxide nanoparticles (SPIONs) have emerged as cutting-edge materials, garnering increasing attention in recent years within the fields of chemical and biomedical engineering. This increasing interest is primarily attributed to the distinctive chemical and physical properties of SPIONs. Progress in nanotechnology and particle synthesis methodologies has facilitated the fabrication of SPIONs with precise control over parameters such as composition, size, shape, stability, and magnetic response. Notably, these functionalized materials exhibit a remarkable surface-area-to-volume ratio, biocompatibility, and, most importantly, they can be effectively manipulated using external magnetic fields. Due to these exceptional properties, SPIONs have found widespread utility in the medical field for targeted drug delivery and cell separation, as well as in the chemical engineering field, particularly in wastewater treatment. Magnetic separation techniques driven by magnetophoresis have proven to be highly efficient, encompassing both high-gradient magnetic separation (HGMS) and low-gradient magnetic separation (LGMS). This review aims to provide an in-depth exploration of magnetic field gradient separation techniques, alongside a comprehensive discussion of the applications of SPIONs in the context of drug delivery, cell separation, and environmental remediation.