High Intensity Magnetic Separation Research Articles

Iron Removal from Low-Grade Pyrophyllite Ore by Microwave Irradiation and Dry Magnetic Separation

Owing to its unique properties, pyrophyllite is an economical alternative to many minerals in different applications. The presence of iron-bearing minerals in Saudi pyrophyllite hampers its industrial uses. The aim of this study was to examine the removal of iron from Saudi low-grade pyrophyllite ore using two approaches. The first approach involves dry high-intensity magnetic separation, whereas the second approach involves microwave pretreatment of the ore before dry magnetic separation. For the first approach, the studied operating parameters were roll speed; feed rate, field intensity, and feed particle size. For the alternative approach, microwave treatment followed by dry magnetic separation, the microwave irradiation time and the magnetic field intensity were studied. The results show that the combined microwave treatment and dry separation method could provide high-purity pyrophyllite for filler industries. Microwave irradiation for 30 min was optimal to change impurity phases (i.e., pyrite, hematite) into ferromagnetic phases in microwave-treated pyrophyllite samples. At a magnetic field intensity of 2000 Gauss, the 30 min microwave-irradiated pyrophyllite sample achieved an iron recovery of 11.2% in non-magnetic fractions, with a removal efficiency of 89% with an alumina recovery of 91.31%.

Economic heavy minerals in the stream sediments of wadi Shaàb, southern coast of the Red Sea, Egypt; characterization and upgrading for investigation of their potential recovery

The southern coast of the Red Sea is one of the most promising areas for the occurrence of economic minerals. Therefore, studying the characterization and evaluation of these minerals in the Wadi Shaàb Quaternary sediments and investigating their ability to concentrate and physically separate using economical and ecofriendly techniques is the main goal of this work. The results showed that the representative sample contains an average of 0.06% ilmenite, 0.08% zircon, 0.07% rutile, 0.07% leucoxene, 0.008% cassiterite, 0.004% xenotime, 0.0004% monazite, 0.022% almandine garnet, and 0.46% magnetite. The recovery of economic heavy minerals was applied using a combination of wet-gravity technique via shaking table and magnetic separation using high intensity magnetic separator. The results demonstrated the success of gravity separation in raising the grade from 7.63% to 45.03% in a yield of 13.74% out of the original sample, and also valuable metallurgical recoveries that greater than 89% for tabling multi-stages (rougher and scavenging) was obtained. Concentrated mineral fractions of magnetite, ilmenite, almandine, heavy silicates, and the non-magnetic fraction bearing zircon and rutile were obtained using a high intensity magnetic separator at different ampere range

Chemical and mineralogical characterization to define parameters for comminution, aiming at granulometric adequacy in rock rich in feldspars extracted in Pedra Lavrada-PB

The demand for high purity feldspars with low contaminant content, especially for use in the manufacture of porcelain tiles and white crockery, poses a challenge for processing the ore. Due to the need for very low iron levels, less than 0.15%, operations must be more complex, costly and capable of providing a high purity final product. To this end, it is necessary to employ mineralogical and technological characterization to understand the ore and plan the operations of the processing plant. A sample of rock rich in feldspars collected in an extraction in the municipality of Pedra Lavrada/PB was studied, aiming to identify the chemical composition and release spectrum using XRD and SEM techniques. Aliquots were subjected to preparation, granulometric classification and high-intensity wet magnetic separation steps. The results indicate that the rock has high concentrations of feldspars, quartz and a significant content of magnetite and hornblende. The physical release of magnetic mineral phases occurs below 0.104mm, and fragmentation operations must be designed with this grain size standard in mind. Magnetic separation, with mass recovery of 14.01% in relation to the feed, satisfactorily guaranteed a reduction in the concentration of magnetic minerals in the ore

Comprehensive Study on Mineral Processing Methods and Mineral Technical Economics of Manganese Ore in Chongqing Chengkou.

Chongqing Chengkou manganese deposit is a large carbonate-type manganese deposit in the upper reaches of the Yangtze River, located in Gaoyan Town, Chengkou County, Chongqing. In order to improve the recovery rate of low-grade manganese ore and concentrate grade index, achieve efficient utilization of mineral resources, and sustainable development of Gaoyan manganese ore deposit in Chengkou, Chongqing, China, in this paper, by means of optical microscope analysis, high-resolution X-ray tomography technology, three-dimensional image analysis technology, X-ray diffraction analysis, X-ray fluorescence spectrum analysis, and technical and economic analysis, the occurrence state and process mineralogy of manganese are studied, and the technical and economic analysis of flotation, high-intensity magnetic separation, and gravity separation are carried out. It provides a reference for other mining enterprises to choose the most suitable beneficiation method according to the specific mineral species.

Investigation of physicochemical characterization and magnetic enrichment of iron ore from Sidi Maarouf deposit

The establishment of a new metallurgical complex in Bellara, located in El-Milia in the Jijel region, is geographically advantageous due to its proximity to the Sidi Maarouf deposit (Algeria). This proximity has been a fundamental motivation for the completion of the current study. The object of research is the quality of iron products from Sidi Maarouf. The research is aimed at developing a treatment process aimed at improving the quality of iron products from Sidi Maarouf, while reducing the impurities of quartz and clay present in this ore. This approach will be based on an approved technological treatment scheme, implemented through an experimental approach to ensure reliable results that meet the requirements of the steel industry. The problem issue revolves around the difficulties encountered in the production of steels due to the natural characteristics of the raw material. In the absence of a physico-chemical characterization of the Sidi Maarouf iron ore deposit, samples taken undergo a series of thorough analyses, including microscopic examinations, X-ray diffraction (XRD), as well as additional chemical analyses using X-ray fluorescence (XRF). The identified minerals are predominantly composed of hematite in terms of iron. As for the gangue, it is mainly composed of calcite and quartz. Through to the pre-treatment process involving washing, we have successfully removed lightweight particles, resulting in a concentrate containing dense particles. This approach was crucial in achieving satisfactory results during the high-intensity dry magnetic separation. As a result of the research it is shown that the enrichment of the Sidi Maarouf iron ore through high-intensity dry magnetic separation, a final concentrate was obtained with a Fe2O3 content exceeding 67 %, along with a significant reduction in silica impurities to 0.92 % and alumina to 0.77 %. It was concluded that this concentrate, derived from the -1+0.5 mm fraction and obtained under a current intensity of 12 A, meets the requirements of the steel industry. Following the work carried out, it is found that the methods of valorization of iron ore through mineralogical processes consistently require a high level of efficiency and performance in terms of equipment and characterization of the products obtained. In the future, iron ore processing will be conducted using innovative methods, integrating advanced technologies to enhance its characteristics while adopting environmentally friendly practices.

Staged magnetic concentration of complex rare earth ores containing niobium and zirconium

ABSTRACT The Balzhe rare earth deposit, located in Inner Mongolia, China, is a complex deposit that also contains niobium and zirconium. However, it remains undeveloped. One notable challenge is the low grades of the main valuable minerals, including xinganite, zircon, niobite, ilmenorutile, pyrochlorite, eschynite, monazite, and bastnaesite. These minerals are either weakly magnetic or associated with ilmenite, a paramagnetic mineral. To overcome this, a high-intensity magnetic method can be employed to separate these valuable minerals from the gangue minerals, thereby generating enriched products to lower the cost of the following flotation. In this study, the first step involved utilizing a high-intensity magnetic separation to enrich particles in different size fractions. It was observed that the size fraction of −0.5 + 0.02 mm was particularly suitable for effective separation. Subsequently, staged magnetic pre-concentration was conducted to obtain products with varying specific magnetization coefficients. To optimize the applied magnetic field intensity, a combination of a high-intensity magnetic separator and a superconducting magnetic separator was employed at different magnetic induction intensities. This proposed technique not only reduces reagent costs but also enhances the operational efficiency of subsequent flotation processes. By implementing this approach, it is anticipated that the Balzhe rare earth deposit can be effectively processed, overcoming the challenge of low-grade valuable minerals. This would contribute to improved economic viability and operational efficiency in the extraction of rare earth elements, niobium, and zirconium from the deposit.

Zirconia Enrichment of Zircon from Arikya, Nasarawa State, Nigeria, by Magnetic and Gravity Separation Processes for Use as Reinforcing Agent in Composite Formulation

Acceptable zircon for composite formulation in the aerospace industry requires that the mineral contains a minimum of 65% zirconia (ZrO2). Despite having vast deposits of zircon, Nigeria’s aerospace industry has historically relied primarily on imported mild steel tubes for solid rocket motor cases (SRMCs) construction, resulting in three major challenges: low strength-to-weight ratio, pressure, and temperature containment. In this study, the Arikya zircon deposit located in northern Nigeria was investigated with the aim of upgrading low-grade zircon ore using magnetic and gravity separation processes for use in composite formulation for SRMCs. The dry high-intensity magnetic separator (DHIMS) produced a ZrO2 grade of 52.48%, recovery of 57.99%, and an enrichment ratio of 0.78 with a separation efficiency of 0.56, while the air-floating separator (AFS) generated the highest of 65.52% ZrO2 grade with 70.81% recovery and enrichment ratio of 1.25 with a separation efficiency of 0.25. The ZrO2 content increased from 40.77 to 65.52% after beneficiation. Iron oxide and titanium dioxide contaminants at 0.73 and 0.83% were reduced to 0.66 and 0.54%, respectively, while the specific gravity increased from 4.4 to 4.6 g/cm3. The ZrO2 content and specific gravity were improved to the minimum standard specified for zirconia-reinforced composite application and competed effectively with industrially/globally accepted zircon. These results demonstrated the efficacy of combining DHIMS and AFS to upgrade the low-grade zircon ore from Arikya, Nasarawa State.

Optimizing the removal of iron oxide from Egyptian feldspar ore

The demand for feldspar as a raw material for various industrial applications continuously increases. Feldspar is a primary raw material in manufacturing ceramics, glass, fillers, welding electrodes, and enamel. Feldspar is often associated with iron oxide, which decreases its economic value and hinders its industrial application. The present work aimed at reducing iron oxide content in Egyptian feldspar ore from the Wadi Zerabi locality. Ball milling was used for preparing feldspar feed of size -250+45µm. Carpco dry high-intensity magnetic separation followed by acid leaching processes were carried out in order to decrease the iron contamination and increase the feldspar content. A Box-Behnken statistical design was used to optimize the magnetic separation results. From a feldspar feed containing 1.40% Fe2O3, a non-magnetic concentrate of 0.25% Fe2O3 was obtained. The Fe2O3 removal reached up to 82% with a high yield as the % weight of non-magnetic feldspar reached up to 97.5%. The leaching process further reduced the iron oxide content down to 0.19 %. Also, the feldspar whiteness was improved from 65.17% in the original ore to 85.60% in the leached product.

A novel pneumatic dry high-intensity magnetic separator for the beneficiation of fine-grained hematite

This study focuses on the development of a novel pneumatic dry high-intensity magnetic separator (PDHIMS) (maximum magnetic induction of 2 T) to enhance the efficiency of separating hematite ore fines. Force analysis of the novel separator demonstrated that it can potentially reduce the lower size limit of hematite dry beneficiation from 58 μm to 10 μm. A series of experiments of mixed samples, such as hematite–quartz/feldspar/chlorite/augite indicated that PDHIMS is successful in achieving highly selective separation of hematite particles fine to 13 μm, overcoming the slime coating of −13 μm quartz particles on the surface of −150 + 38 μm hematite particles, and improving the separation efficiency between hematite and poorly intergrown particles (or magnetic gangues). Energy dispersive spectrometer (EDS) and microscopic imaging of the concentrate confirmed that −13 μm particles form stable aggregates and cannot be disrupted by the employed aerodynamic field in PDHIMS, resulting in a notable entrapment of quartz particles within the concentrate. Lastly, the induced roll magnetic separators (IRMS) with gravity feed and airflow feed were selected as the objects compared with the PDHIMS. The comparison revealed that PGHIMS exhibits a marked superiority in eliminating slime coatings from coarser magnetic products.

The Use of Flotation and High-Intensity Magnetic Separation to Improve Feldspar Concentrate Quality

The Use of Flotation and High-Intensity Magnetic Separation to Improve Feldspar Concentrate Quality

Tungsten tailings issues and reprocessing solutions

This paper aims to provide an overview of tungsten (W) tailings properties, detrimental impacts of these tailings, approaches to mitigate these impacts, and a presentation of methods to reprocess them to capture their economic value. Since W is widely used in a variety of industries, it has been extensively mined since the 19th century, and the mining continues to generate significant volumes of tailings. Recent data show that global W production stands at 84 kt per year, and more than 100 Mt of W tailings exist containing over 100 kt of WO3. The tailings contain variable amounts of valuable products and deleterious environmental substances. Some of the contained metals are in great demand for the energy transition. However, these tailings usually contain FeS2/Pyrrhotite and FeAsS minerals, which, when exposed to air and water, can produce acid mine drainage. As such, W tailings may pose environmental and human health risks. Globally, the reprocessing of W tailings presents a potential resource that can be regarded as a paradigm of sustainability and circular economy. Flotation, enhanced gravity separation, and wet high-intensity magnetic separation have been reported to be the common approaches to reprocessing W tailings. However, W processing presents particular difficulties owing to complex material properties, such as fine particle size, surface weathering, similarity in surface properties exhibited by gangue materials (fluorite, apatite, calcite), low concentrations of the elements of interest, and poor mineral liberation.

Investigation of particle capture by grooved plates with elliptic teeth for high intensity magnetic separation

Horizontal ring high intensity magnetic separators adopting grooved plates with right angle teeth present superiority on recovering ultrafine weakly magnetic materials. Being limited by saturation magnetization of magnetic iron yoke, optimizing magnetic field characteristics of grooved plates is a potential way for further improving separation efficiency. In this study, elliptic teeth were designed and optimized for grooved plates in horizontal ring separators. Magnetic field characteristics and particle capture performance of elliptic teeth plates were investigated and compared with conventional plates theoretically and experimentally. Magnetic field force and particle capture cross section area of elliptic teeth plates increased with increasing aspect ratio. Elliptic teeth plates with aspect ratio λ > 1.5 presented larger high magnetic field force region and particle capture cross section area than conventional plates. Particle capture experiments with pure and actual hematite ore indicated that elliptic teeth plates with aspect ratio of 2 and 3 had better particle capture performance and separation efficiency than conventional plates, which was in consistence with theoretical analyses. Elliptic teeth plates presented better magnetic field characteristics and had good application prospect in horizontal ring high intensity magnetic separators.

Upgrading silica rock quality by using attrition scrubbing and magnetic separation techniques

The study was carried out to produce high-purity silica sand used for glass making. Generally, all grades of silica sands are comparable in their chemical composition except for iron oxide (Fe2O3) content, which is slightly rigid and its concentration varies for different applications. The objective of this work was to increase silicon dioxide (SiO2) content to at least 99.5% and to reduce iron oxide content to less than 0.015% using attrition scrubbing and magnetic separator technique for the purification process. Gravimetric analysis was carried out on the original sample to determine SiO2 content, and minor elements of Fe2O3 quantification using ultraviolet–visible (UV–VIS). A complete chemical and phase analysis were carried out on the raw sample and post-treatment samples. Field Emission Scanning Electron Microscopy (FESEM) was also employed for morphological and mineral phase identification. In this analysis, 70% of solid percent in pulp was used. The optimization of the scrubbing process was performed by studying the effect of using distilled water and citric acid at various concentrations of 0.25 M, 0.5 M, and 0.75 M. The processing time and rotational speed were kept constant at 20 min and 1250 rpm, respectively. The scrubbed silica rocks were then deslimed and dried before being subjected to a wet high intensity magnetic separator (WHIMS) with a magnetic field intensity of 3A, 5A, and 7A. According to this research work, more than 99.5% of SiO2 content and less than 0.015% of Fe2O3 content was achieved although using only distilled water in the scrubbing process. The optimum consumption of citric acid was 0.5 M in the acidic scrubbing process.

Magnetic separation for arsenic and metal recovery from polluted sediments within a circular economy

Several metals and metalloids (e.g., As, Cd, Cu, Pb, Zn) are toxic at low concentrations, thus their presence in sediments can raise environmental concern. However, these elements can be of economic interest, and several techniques have been used for their recovery and some of them have been widely applied to mining or to industrial soils, but not to sediments. In this work, wet high-intensity magnetic separation (WHIMS) was applied for As, Cd, Cu, Pb and Zn recovery from polluted sediments. A composite sample of 50 kg was taken in the Avilés estuary (Asturias, North Spain) with element concentrations above the legislation limits. Element distribution was assessed using wet-sieving and ICP-MS analysis, revealing that the 125–500 μm grain-size fraction accounts for the 62 w% of the material and that element concentration in this fraction is lower than in the other grain size fractions. Subsequently, WHIMS was applied at three different voltage intensities for the 125–500 μm and <125 μm fractions, revealing excellent recovery ratios, especially for the coarser material. Furthermore, magnetic property measurements coupled to microscopy analysis revealed that the success of the technique derives from concentrating metal-enriched iron oxides particles (ferro- and para-magnetic material) in a mixture of quartz and other minerals (diamagnetic particles). These results indicate the feasibility of the magnetic separation for metal and metalloid recovery from polluted sediments, and thus offer a double benefit of coastal area restoration and valuable material recovery in the context of a circular economy.

Removal of Iron from Pyrite-Rich Coal Refuse by Calcination and Magnetic Separation for Hydrometallurgical Extraction of Rare Earth Elements

In the metallurgical extraction of rare earth elements (REEs), the ratio of contaminant ions to REEs in the leachate dictates the cost and operational efficiency of the downstream processes. The current study investigated the potential iron contamination removal from the feed to the hydrometallurgical process by calcination followed by magnetic separation. The 2.20 specific gravity sink fraction of Baker coal seam coarse refuse was pulverized to finer than 180 μm, calcined at various temperatures, and separated into magnetic and non-magnetic fractions using a wet high-intensity magnetic separator at different field strengths. The untreated feed, calcined products, and their subsequent magnetic and non-magnetic fractions were subjected to acid leaching tests with 1.2 M sulfuric acid at 75 °C and 1% w/v solids concentration. The recovery of light and heavy rare earth elements (LREEs and HREEs, respectively) along with the concentration of common contaminant ions (Al, Ca, and Fe) were measured as output variables. The weight percent of magnetic material was maximized at approximately 29% by calcination at a temperature of 400 °C. Magnetic removal of this fraction using a field strength of 1.15 Tesla resulted in the rejection of 81% of the iron. Leaching of the magnetic fraction provided significantly higher Fe recovery relative to untreated feed material and the non-magnetic fraction. The non-magnetic fraction was subsequently calcined at 600 °C to dehydroxylate the clays and released the REE minerals in the same manner as the treatment of the original coarse refuse material. A comparison of the leachate elemental concentrations resulting from the leaching of both the calcined non-magnetic and original coarse refuse showed only a slight reduction in the iron content from the non-magnetic material. This finding combined with the REE loss in the magnetic fraction resulted in the conclusion that the magnetic removal step was unfavorable.

Optimization of magnetic separation of hematite contained in the depressed product from vazante mine s zinc ore flotation

The mining industry has seen a significant decline in mill feed grade in recent years, resulting in an ongoing build-up of materials not recovered at the mineral processing plants whose economic value has not yet been determined. Tailings dams have been the preferred method of disposal of such materials. However, recent dam breach events and the growing demand for mineral goods have enhanced the appeal of a more effective use of mined materials to prevent tailings accumulation and reduce social and environmental impacts, in line with the environmental, social and governance (ESG) principles that most companies have adopted. Different techniques can be used to recover economically valuable minerals contained in such materials, among which magnetic separation stands out for reasons of cost, production capacity, and recent developments of new equipment and matrices for wet high-intensity magnetic separators. The outcome includes gains in capacity, grade, and recovery yield. This paper assessed the use of a matrix developed by the company Gaustec, called BigFlux, in the magnetic separation of depressed product from the flotation process at Nexa Resources’s Vazante mine. Laboratory-scale magnetic separation tests were conducted using standard and an optimized matrix. For a 59% iron concentrate, the metallurgical recovery using such optimized matrix reached 72.6%, up 4% from the figure resulting from the use of the standard matrix, thus indicating that the use of the optimized matrix can improve the magnetite recovery process of the studied material.

RECOVERY OF CHROMITE FROM ENRICHMENT PLANT TAILING

In this study, experimental studies have performed to recover chromite from Eskiköy-Sivas chromite concentrator which is owned Bilfer Madencilik ve Turizm A.Ş. Mineralogical and liberation measurement studies were performed, and it was decided to grind the feed to 100% finer than 300 µm.&#x0D; Gravity concentration and wet high intensity magnetic separation (WHIMS) tests were performed. After grinding to -300 µm, -38 µm fraction which cannot be recovered efficiently was removed. The studies were conducted on 300+100 µm and -100+38 µm fractions. After the beneficiation tests, it was determined a circuit consists of spiral concentrator and shaking tables could produce a concentrate containing 48% Cr2O3 from the tailings having 6,54 % Cr2O3, with a 56% recovery.

Mineral and Chemical Characterization of Magnetic and Non - Magnetic Products Obtained from Dry Magnetic Enrichment of Lignite Coals

The mineral and chemical composition of magnetic (tailing fraction) and non – magnetic (clean coal fraction) products from the dry magnetic separation of coal samples with high ash and sulfur contents obtained from Çanakkale Çan lignite (S1) and Manisa Kula Pabuçlu lignite (S2) were investigated in this study. The feasibility of the dry magnetic separation technique for the separation of the minerals from the coal matrix was identified as the function of coal types and particle sizes. The separation technique depends on coal fragments being weakly diamagnetic, while most of the minerals present in the coal are weakly to moderately paramagnetic. Three particle sizes (coarse-, medium-, and fine-sized) of feed lignite and their magnetic and non-magnetic fractions were separated and characterized. The influence of coal type on the magnetic separation efficiency was determined by the recovery of tailing fractions obtained from S1 and S2 lignites. The particle sizes of S1 lignite were quite lower than S2 lignite. When the fine-sized lignite samples from S1 and S2 were used, the recovery of tailing fractions was the highest compared to other sizes. The mineral compositions of S2 lignite include typically mica, smectite (clay mineral), gypsum, kaolinite (clay mineral), pyrite, quartz, and plagioclase. The results showed that the Permroll High-Intensity Magnetic Separation method for high calorific value and low ash content at the medium-sized particle was more efficient for the S2 lignite sample than the S1 lignite sample.

Separation characteristics of dry high-intensity drum magnetic separator

Dry high-intensity drum magnetic separator (DHIDMS) has been effectively used for the utilization of low-grade iron ores, thus an in-depth investigation on the separation characteristics of the DHIDMS separator would contribute to its design and practical operation. A numerical model was established to describe the particles motion in the DHIDMS process, on which the motion trajectories of siderite and quartz particles were simulated in the high and low magnetic field areas above the magnet surface, to reveal their dynamic behaviors; and the effects of two dominant operating parameters affecting the trajectory of particles, i.e., particle size and drum rotation speed, on the separation performance of a pilot-scale DHIDMS separator were investigated for a siderite ore. Simulation analysis indicates that the motion trajectories of the siderite and quartz particles are obviously different from each other in the high magnetic field area, but they generate negligible diversities in the low magnetic field area. In addition, in the high magnetic field area, the particle size and drum rotation speed significantly affect the distance between the motion trajectories of siderite and quartz particles, thereby affecting the separation selectivity of the DHIDMS separator. Experimental investigations indicate that, the feed particle size and drum rotation speed have definitely significant effects on the separation selectivity of the separator in the high magnetic field area; meanwhile, there is no separation selectivity for iron minerals in the low magnetic field area, thus deteriorating the recovery rate of iron concentrate. These results are basically consistent with the simulation analysis. This investigation has provided a general reference for the optimum design and operation of DHIDMS separator.

Separation of pyritic sulfur from ultrafine coal by pyrolysis & wet high magnetic separation

ABSTRACT Coal plays a major role in the economic development of many countries, especially in metallurgical industries and conventional power generation plants. The removal of sulfur from coal has recently become even more critically important. Existence of sulfur compounds in coal limits its industrial applications due to environmental as well as technical problems. Thus, high sulfur coal is usually upgraded by desulfurization through physical, chemical, and biotechnological processes. In this study, lowering of pyritic sulfur took place after thermal treatment at 500–700°C (pyrolysis) using a wet high-intensity magnetic separation process. The samples were subjected to size reduction to −25 µm and characterized with X-ray diffraction (XRD), proximate and ultimate analysis, and differential thermal analysis (DTA). Then, the experiments were performed based on central composite rotatable design (CCRD) and response surface methodology (RSM) after thermal treatment of coal containing 3.30% total sulfur. Statistical analysis was performed to examine the significance of the effect of different operating parameters. A maximum sulfur rejection of 90.10% with the lowest sulfur content of 0.59 was obtained at 8.38% solid concentration, 4.59 g/min feed rate, and 7810 gauss magnetic field intensity. The confirmation tests at the optimum conditions produced 0.54–0.56% total sulfur with 90.25–92.33% sulfur rejection.