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By P. Zhang, W. D. Xiao

"A process mineralogy study was conducted to guide the development of a process for the extraction of vanadic oxide (V2O5) and aluminum compounds from bone coal and its ash as well as the production of byproducts. Results show that to extract the targeted metals at higher recovery rates, one must find a suitable agent capable of destroying the structure of the mica and breaking down the lattices in which these metal-bearing minerals occur. For such minerals, metal extraction efficiency is usually low if the approach is simply adding an oxidant that cannot destroy the structure. In this research, a byproduct fluosilicic acid (H2SiF6) at 20 percent concentration from an operating phosphate fertilizer plant was found to be powerful and effective for the leaching of vanadium-bearing minerals such as mica. This environmentally friendly process improved the leachability of valuable constituents in the bone coal significantly, with the leaching rate of V2O5 increased to 94 percent, from 83 percent, and that of aluminum oxide (Al2O3) increased to 75 percent, from 40 percent. X-ray diffraction and chemical analyses showed that the structure of mica can be destroyed using fluosilicic acid either alone or in combination with sulfuric acid. Based on the process mineralogy study, a processing flowsheet was tested, which resulted in a final V2O5 powder product with purity of 99.2 percent and an overall recovery rate of higher than 85 percent. The flowsheet consists of leaching, ion exchange and ammonium precipitation. With this process, various byproducts could also be generated, including aluminum fluoride, cryolite, aluminum sulfate, calcium sulfate, ammonium chloride, sodium chloride and cement admixtures.IntroductionVanadium is an important rare metal broadly used in the production of steel alloys and nonferrous alloys as well as in the chemical field as a catalyst. Vanadium-bearing bone coal and clays are abundant in China, and they contain other valuable metals such as aluminum. Bone coal is a type of carbonaceous shale. The vanadium-bearing minerals mainly exist in mica, kaolin, iron oxides, tourmaline and garnet. According to previous studies (Xiao, 2007; Xu, 1989; Xu and Chen, 1991; Ji and Xu, 1991; Chen and Xu, 1992; Xu and Heng, 1992), vanadium occurs from the isomorphous substitution of V3+ for Al3+ or Fe3 + in the crystal lattices of mica, tourmaline, garnet, dolomite and aluminosilicate minerals. In iron oxide and kaolin minerals, vanadium appears as an adsorption form. The isomorphous substitution of vanadium is more stable in tourmaline, garnet and silicate minerals. Therefore, vanadium in bone coal may exist in three phases: vanadium-containing kaolin and oxides, vanadium-containing mica, and tourmaline and garnet (Xu and Chen, 1993; Xu and Zhang, 1993; Xu and Wang, 1994; Feng, et al., 2005; Lin and Fan, 2001)."

Jan 1, 2015

By P. B. Queneau

An operating problem encountered at the Moa Bay operation in Cuba, where nickeliferous laterite ore is processed by sulfuric acid pressure leaching, is the formation of alunite and hematite deposits on the autoclave walls. The AMPX Extractive Research & Development, Inc., metallurgical laboratory (Golden, Colorado) has made substantial improvements in the Moa Bay process in the areas of metal recovery, energy consumption, and feed versatility. One of the advantages of AMAX's process is its ability to treat substantial portions of nickel- and magnesium-rich serpentine while maintaining acid utilization efficiency. The process minimizes scale formation by combining staged acid addition with vigorous agitation and 270°C operation, but does not eliminate scaling. This paper describes how advantage can be taken of MgSO4?XH20 precipitation both to inhibit alunite scaling and to disperse hematite scale within the MgSO4?XH20 matrix. Cooling the autoclave from its 270°C operating temperature down to 180°C takes advantage of the reverse solubility of magnesium sulfate. The magnesium dissolves, liberating entrained hematite, thus providing a means for control of autoclave scale with minimum process disruption.

Jan 1, 1984

By Matthew S. Sanchez, Richard J. Lee, Matthew D. Zock, Drew R. Van Orden

"Current Environmental Protection Agency (EPA) risk models and asbestos fiber counting techniques for monitoring airborne exposures treat all fibers as being equivalent and ignore the effect of dimension on toxicity. While this may have been appropriate when modern analytical methods were not available, the measurement world is now fully capable of making the appropriate distinctions. The importance of width as a determinant of carcinogenicity has been recognized for nearly 30 years within the published literature. Stanton,1 in a landmark study of a suite of fibrous materials, found that durable mineral fibers with widths less than 0.25 mm and lengths longer than 8 mm were causally associated with the induction of tumors. Pott,2 in a later study, postulated a fiber toxicity model that agreed reasonably well with the Stanton findings, but extended the concept to include varying toxicity as a function of length and width. Wylie et al.3 reanalyzed samples used by Davis et al.4 and found that tumor generation was strongly and inversely correlated with fiber width. Crump5 testified increasing fiber length was correlated with disease occurrence. Lippman6 reviewed a number of studies and suggested that mesothelioma was closely associated with long, thin fibers. Berman et al.7 published a risk model, which found that disease was correlated almost exclusively with fibers longer than 40 mm and width less than 0.25 mm. Recently, Loomis et al.8 reanalyzed textile mill samples and found that aspect ratios greater than 40:1 were highly correlated with disease. Incorporation of width into risk models has been limited by the availability of data from operating asbestos plants and, in particular, the observation of an asbestos plant for which there is no observable mesothelioma. There have been only limited studies published on the dimensions of asbestos fibers, with a few serving as the primary references in other literature.9_13 A rare opportunity to collect detailed concentration and dimensional data of airborne crocidolite from an operating asbestos-cement plant using modern analytical procedures arose, providing a chance to supplement the existing literature on airborne fiber dimensions. The asbestos-cement plant is located in the eastern end of Cochabamba, Bolivia along Highway 4. Cochabamba is a relatively large city located in the Andes Mountains, approximately 250 km southeast of the capital La Paz. The city sits in a valley that runs east-west with mountains to the north and south. The crocidolite used in the products made at this facility is mined in central Bolivia, approximately 75 km northwest of Santa Cruz. The crocidolite is a fibrous magnesioriebeckite 14 (blue asbestos). Crocidolite fibers from Bolivia were the subject of prior reports suggesting the fibers are generally longer and thicker than crocidolite from Australia or South Africa.9 At the cement plant, the run-of-mine crocidolite was first pulverized using a hammer mill and then sieved on vibratory sieves to produce fibers of limited size ranges for use in the cement. The sieved crocidolite is mixed with other components, including recycled cement product, to produce a slurry that is vacuum filtered into sheet form. The sheets are then manually molded into a corrugated shape, air dried, and sawed (using circular saws) to accepted dimensions. The sawed sheets are cured in soaking pits for 28 days before being shipped to the consumer. Prior to shipping, the sheets are finished by a light hand sanding followed (at customer request) by applying one or more coats of paint. A detailed description of the cement plant and the industrial hygiene results can be found in Van Orden et al.15"

Jan 1, 2012

By K. V. K. Prasad

Stochastic simulation has been routinely used for performing risk and sensitivity analyses in a variety of fields. The commonly used means of generating the simulations has been the Monte Carlo approach which usually employs a Simple Random Sampling (SRS) scheme of the variable distributions. This method is prone to sample clustering and requires a large number of samples to represent the distribution faith-fully. This can become problematic for simulating complex processes where it is impossible to run an arbitrarily large number of replicate simulations. The Latin Hypercube Sampling (LHS) method uses a stratified sampling approach which assures representation of the input distributions for any given number of samples. In this paper the LHS and SRS approaches are compared using a petroleum resource estimation example.

Jan 1, 1993

By Meisam Ghiasi, Mohammadreza Khalesi, Mahmoud Abdollahy

In the current research, isothermal experiments of kinetic analysis were performed at different temperatures (800–1050 °C) and particle sizes (885 to 10,763 μm) to investigate the calcination kinetics of high-purity limestone. Thermal analyses were carried out in a zirconia crucible, 1 cm in height, for different temperatures and particle sizes. The reaction rate coefficients were varied in the 2.2 × 10−5-1.62 × 10−3-m0.6.s−1 range. Moreover, various isothermal kinetic analysis methods were applied to assess the decomposition mechanism and the calcination function governing the process. The modified shrinking core model was found as the best representation of the high-purity limestone kinetic data. The activation energy was evaluated using the Arrhenius curve, and an average value of 86 kJ.mol−1 was obtained.

Sep 15, 2020

By Y. Wang

Wet magnetic separation methods for recovering hematite and chromite fines and ultrafines are investigated in this paper. These methods include wet high intensity and high gradient magnetic separations, carrier or "piggy-back" magnetic method, magnetic field-induced aggregation and magnetic seeding. This investigation indicates that wet magnetic separation is more efficient for fines and ultrafines whereas other methods can be used to enhance the particle aggregation and/or the magnetic response. The magnetic behaviour of these minerals with respect to magnetizing field, particle size and temperature is also presented.

Jan 1, 1993

By D. R. Wilburn

This summary of international mineral exploration activities for the year 2013 draws upon information from industry sources, published literature and U.S. Geological Survey (USGS) specialists. The summary provides data on exploration budgets by region and mineral commodity, identifies significant mineral discoveries and areas of mineral exploration, discusses government programs affecting the mineral exploration industry and presents analyses of exploration activities performed by the mineral industry. Three sources of information are reported and analyzed in this annual review of international exploration for the year 2013: 1) budgetary statistics expressed in U.S. nominal dollars provided by SNL Metals & Mining (SNL) of Halifax, NS, Canada (formerly Metals Economics Group (MEG); 2) regional and site-specific exploration activities that took place in 2013 as compiled by the USGS; and 3) regional events that affected exploration activities, including economic, social and political conditions, that were derived from published sources and unpublished discussions with USGS and industry specialists. Commodity and regional compilations are presented in this summary. Because multiple sources are used to develop commodity and regional compilations, reported statistics may vary depending on the source and type of data that are being reported. The SNL data summarize planned company budgets for worldwide exploration activities in 2013 for 20 nonfuel mineral commodities based on surveys returned by companies primarily focused on precious metals (gold, platinum-group metals and silver), base metals (cobalt, copper, lead, molybdenum, nickel, tin and zinc), bulk commodities (coal, iron ore, phosphate and potash), and specialty commodities (diamond, lithium, niobium, rare-earth elements, tantalum and uranium). Information on uranium exploration activities was included in the MEG overview for the first time in 2007. MEG included data on the commodities lithium, niobium, phosphate, potash, rare-earth elements and tantalum for the first time in 2010 because of the increased topical significance of these commodities. Since 1999, companies with exploration budgets of $100,000 and greater were included in the MEG and SNL compilations. SNL budget estimates exclude aluminum, coal, and oil and gas. Budget estimates for iron ore have been compiled since 2011 but reported separately. The post-1999 budget surveys by MEG and SNL cover at least 90 percent of world?s reported nonferrous, nonfuel mineral exploration budgets; the 2013 survey is reported by SNL to cover an estimated 95 percent of these budgets. The 5 percent that is not covered is accounted for by companies that chose not to participate in the SNL survey, private companies that do not publish their budget data, and government-funded exploration activities.

By Wm. Terry Siemer

Abstract. The value of industrial rocks and minerals produced in New Mexico in 1978 exceeded 227 million. 1e state ranked first in the nation in production of potash and perlite and was a leader in pumice production. Other commodities with sizable production in New Mexico include barite, caliche, clay, dimension stone, fluorspar, gypsum, humate, limestone, mica, salt, sand and gravel, scoria, and silica sand Non metallic resources are distributed throw out the state, but development and exploitation is concentrated in western and southeastern New Mexico. The value of industrial rocks and minerals within the state grew about 9 percent to more than $227 million in 1978. Continued growth, however, depends on continued demand, exploration, and development.

Jan 1, 1980

By Santosh Kumar Ray, DEBASHISH MISHRA, Niroj Kumar Mohalik, SOMU MANDAL, Jai Krishna Pandey, Asfar Mobin Khan

Coal is a low-cost and high-calorific-value fuel. The coal mining industry worldwide has been suffering from severe accidents due to coal dust explosion hazards since its inception. Statistically, it was observed that 12,489 fatalities had occurred in 104 reported mining accidents from coal dust explosions during 1900–2020. There are numerous methods for detection, prevention, and control of coal dust explosions in mines. The underground mining environment is unpredictable and has an array of variables. These undulating factors make it difficult to prevent or control the coal dust explosion hazard. However, coal mining is done aggressively throughout the world, especially in developing countries as coal is a major source of thermal energy used in power plants contributing to about 38% (IEA, (2019), World Energy Outlook, IEA, Paris https:// www. iea. org/ repor ts/ world- energy- outlo ok- 2019.) of world electricity. Worldwide, coal dust explosibility studies are carried out in experimental mines, laboratories, and simulations. The complexity, lack of proper infrastructure, and unavailability of laboratory equipment sometimes make it difficult to study coal dust explosibility. The authors have discussed in detail and proposed that the CFD modelling can be a viable option for studying and evaluating coal dust explosibility.

Jun 29, 2022

By J. Baz-Dresch

A custom-designed shotcrete system, consisting of an 8-m3 (10-cu-yd) transit mixer and a shotcrete spray boon carrier, is used by a two-man crew to transport and place up to 25 m3 (32 cu-yd) of steel fiber reinforced, dry, silica fume shotcrete per 11-hour shift. Shotcrete is custom blended by a local supplier and delivered predampened. Mix design and quality control are performed with a computer program that develops and graphs a properly balanced mix based upon the materials sieve analyses.

Jan 1, 1992

By G. A. Munoz

Gold leaching of an auriferous pyrite ore from the Portovelo deposit in Ecuador indicates that noncyanide leaching systems, such as thiocyanate and thiourea, are not as effective as the traditional cyanide system. For example, whereas approximately 95% of the gold can be leached from the ore with cyanide, only about 50% gold dissolution can be achieved with a thiocyanate leaching system. Electrochemical measurements indicate that gold is not cathodically protected by pyrite in these systems. Based on the results of preliminary diagnostic experiments, it appears that gold dissolution in thiocyanate and thiourea systems is limited by passivation due to the formation of either elemental sulfur or sulfur compounds on the gold surface.

Jan 1, 1999

By D. C. Torre

Ever since the early '60's there have been efforts to develop and produce reliable continuous haulage systems capable of taking the full output of a continuous miner and transporting it, in one continuous flow, from the face to the tipple. The majority of the continuous haulage systems which have been most successful to date were placed in operation in the early '70's and were all of the bridge conveyor type, usually consisting of bridges and mobile bridge carriers attached at the inby end to the continuous miner and at the outby end to the panel conveyor itself. These successful bridge conveyor type continuous haulage systems were, and continue to be, either of the belted or chain type. Undoubtedly, the most successful belt type continuous haulage systems are those manufactured and marketed by the Long-Airdox Company. Until early 1977, the most successful chain conveyor type haulage systems were manufactured and marketed by Jeffrey Mining Machinery Division. In 1977, Long-Airdox reentered the market with a chain type system to complement its belted system. I say "reentered" because the original bridge type continuous haulage system was introduced to the coal mining industry in the early '60's by the old Long Company, a predecessor of the current Long-Airdox Company, and those original units were of the chain conveyor type.

Jan 1, 1981

By Manoj Khandelwal, Minghui Liu, Jian Zhou, Kun Du

The waste rock and tailings backfill into the mined-out areas are the most effective method for solving the environmental pollution and surface disasters for nonferrous metals mines. In practice, the success and availability of backfill operations are dependent on the slurry fluidity and the strength properties of cement backfill. The transport of the slurry through the pipeline to the designated backfilling area relies on its eximious flow properties, while the appropriate strength of the filling body ensures the safe operation of the stope. In this paper, the effects of cement and aggregate types on the slurry fluidity and strength characteristics of cemented backfill are studied in detail, which are often ignored in other pieces of literature. Diffusivity is used as an indicator to evaluate the slurry fluidity. Various slurries whose concentrations ranging from 70%, 73%, 75%, 78%, and 80% are made with different aggregate ratios and cement-sand ratios are tested. It has been shown that slurry fluidity is inversely related to its concentration, but 78% is the “stopping point” for the deterioration of fluidity. The addition of rod-milled sand improves or worsens the cemented backfill (CB) strength depending on the amount of rob-milled sand. The uniaxial compression experiment results on 216 CB specimens produced by different combinations of influencing variables showed that CB specimens made from cement with superior mechanical properties have a higher uniaxial compressive strength (σucs). It has been also found that the effect of aggregate ratio on the CB strength is not singular, but works in conjunction with the curing time and the cement-sand ratio. The longer the curing time and the higher the cement content, the higher the CB’s σucs. To avoid the time-consuming and costly problem of obtaining the strength of the CB from indoor experiments, an SVR model capable of predicting the uniaxial compression strength of CB specimens is proposed, which is optimized by genetic algorithm (GA) and particle swarm optimization (PSO) algorithm. The results of the three performance indexes (MAPE, MSE, and R2) show the superior performance of the GA-SVR and PSO-SVR models and the agreement of the predicted results with the experimental results, which indicate that these two models can accurately predict the σucs of CB.

Feb 3, 2022

By M. E. Hinkle

Concentrations of He, CO2, and O2 in soil gases were measured regularly for more than a year at a site near Golden, Colorado. Samples were collected from a hollow probe at 0.75-m depth and from a plastic hemisphere on the ground surface. Soil temperature, air temperature, percent humidity, And barometric pressure were also measured. Soil moisture was measured only indirectly as amount of rain or snowfall. Higher concentrations of CO2 in both the 0.75-m and surface samples correlated with higher soil and air temperatures, which suggests that CO2 was produced by bacteria. Lower concentrations of helium in both the 0.75-m and surface samples correlated with higher soil and air temperatures. Rain and snowfall appear to affect helium concentrations. Carbon dioxide concentrations were lowest when snow lay on the ground for extended periods of time. No correlation was seen between barometric pressure or percent humidity and concentrations of He, CO2, or O2 at 0.75-m depth or at the ground surface. No correlation, either positive or negative, was seen between concentrations of CO2 and O2.

Jan 1, 1988

By Mahaboob Basha Shaik, Shakuntala Tudu, Indrajit Paul, Chandra Sekhar, Neha Gupta, Amit Kumar, Srinivas Dwarapudi, Arvind Kumar Patel

In this study, the effect of colemanite and calcined colemanite (CC) addition on the properties of iron ore pellets is studied. The pellets are prepared in a lab without and with 0.2% colemanite and varying amounts of CC from 0 to 1.0 wt%in steps of 0.2%. A reference pellet is prepared under typical plant conditions, and the properties of the reference pellet are considered as the base value for improving the cold compressive strength (CCS) while maintaining the other parameters at an acceptable limit without altering the pellet. The study also aims to provide a detailed characterization of colemanite and calcined colemanite to better understand their behaviour during firing. The lab-scale results show that the CCS of pellets made with 0.2% colemanite was reduced by 222 points (60%) as compared to the reference pellets due to crack formation during firing. The results show an improvement in the CCS of the indurated pellets with CC dosage up to 0.4%, and decreasing strength is noted thereafter. It is observed that the swelling index increases with the increase in calcined colemanite dosage. To simulate plant conditions, reference pellets and pellets with optimized CC dosage were fired in a plant furnace.

Oct 16, 2020

By T. Brozell

"Communities near sand mines and processing facilities in Wisconsin have raised concerns regarding possible exposure to ambient respirable (PM4) crystalline silica. Fenceline PM4 (particulate matter captured with a 50 percent cut size of 4 micrometers aerodynamic diameter) crystalline silica concentration data were compiled at Fairmount Santrol Inc., Mathy Construction Inc. and U.S. Silica facilities. The long-term average PM4 crystalline silica concentrations ranged from 0.05 to 0.45 micrograms/m3 when sample values below the limit of quantification were treated as zeros. All of the long-term average concentrations were less than 20 percent of the Minnesota Department of Health’s and California Office of Environmental Health Hazard Assessment’s PM4 crystalline silica chronic reference exposure level of 3.0 micrograms/m3. The measured concentrations were consistently within the local background concentration range.Air Control Techniques P.C. compiled the sampling data using Thermo Fisher Scientific Inc. Partisol 2000i PM2.5 samplers meeting the requirements of 40 CFR Part 50, Appendix L. These samplers were adapted to capture particulate matter with a 50 percent cut size of 4 micrometers. The use of polyvinyl chloride filters allowed for crystalline silica X-ray diffraction analysis by NIOSH Method 7500. The combined use of adjusted PM2.5 filter-based samplers with Method 7500 crystalline silica analyses provided for a highly sensitive limit of quantification of 0.31 micrograms/m3 of PM4 crystalline silica.BackgroundIn 2005, the California Office of Environmental Health Hazard Assessment (OEHHA, 2005) adopted a 70-year chronic reference exposure level (REL) for PM4 (particulate matter having aerodynamic diameter of 4 micrometers or less) crystalline silica. The REL was extrapolated from occupational hygiene epidemiological studies, essentially all of which were based on in-plant PM4 crystalline silica measurements. No well-established ambient sampling technique for PM4 crystalline silica was available at the time that OEHHA adopted its REL. The personal samplers used for the National Institute for Occupational Safety and Health (NIOSH) Method 0600 in-plant sampling of employee exposure were designed for concentrations higher than ambient levels. The limit of quantification (LOQ) of PM4 crystalline silica on NIOSH 0600 filters was too high for the effective sampling of ambient air."

Jan 1, 2015

By M. J. Hrebar

In the summer of 1990, a study was conducted to document large tractor (i.e., Caterpillar Dl1N) utilization in surface coal mining. The tractors were found to be utilized as primary production machines and in combination systems with blast casting and draglines and blast casting and excavator/truck systems. In addition, dozers were used to prebench ahead of a primary dragline system. The study also established ranges and averages for Dl1N operating costs and mechanical availability. Based on simulated production of various tractor dozing applications, the potential for low cost coal stripping was suggested (Hrebar, 1991). A follow-up study, also funded by Caterpillar Inc., was conducted in the summer of 1991 to determine actual production rates in two dozer stripping applications. These actual production rates would then serve as a foundation for estimates of stripping costs. This paper presents the results of the studies in a contour and a cast application.

Jan 1, 1992

By Sandeep Kumar Jeripotula, Govinda Raj Mandela, Aruna Manglapady

Dumper operators are frequently exposed to whole body vibration (WBV) in surface mines. Surface mining activities involve the amalgamation of comparatively high intensity of vibration and extended exposure durations. Efficient risk reduction mandates knowing of important phases of a task that poses a threat to health of dumper operators. So far in India very limited studies have been reported on WBV exposure with regard to surface mines. This paper evaluates WBV of dumper operators based on ISO 2631-1:1997 Standards and European Union (EU) Directive 2002 for different phases of job cycle. Six dumpers were considered for this study and the vibration measurements were made for all the four phases of the job cycle by placing the triaxial accelerometer on the operator’s seat-surface and at the seat-back, independently. The findings of the study revealed that the haulage task (loaded travel and empty travel) remains the chief contributor to vibration exposure according to seat-surface and seat-back measurements. Maximum frequency weighted root mean square (RMS) of 1.12 m/s2 and 1.09 m/s2 were reported for empty travel task for seat-surface and seat-back measurements, respectively. For seat-surface measurements based on RMS, Z axis remains as the dominant axis of vibration for all the dumpers during haulage task, whereas for seat-back measurements, the dominant axis varies between X and Y. Exposure action value (EAV) based on RMS has exceeded the threshold value of 0.5 m/s2 for all the dumpers during loaded travel and empty travel for seat-surface as well as for seat-back measurements.

By Myles E. Robinson

During the last decade there were pronounced changes in the competitive pattern of the fossill fuels It is proposed to trace these trends and describe inter-fuel competition, first as it relates to the economy as a whole and then more specifically to examine competition of the fossil fuels as these share the electric utility market. Table 1, Competitive Fuels and Water Power Used in the United States, 1950-1959, shows the growth in the consumption of coal, oil, gas and water power 'during the past decade. Uses which are not directly competitive among the fuels, such as tractor fuel, carbon black, and consumption of petroleum products in the making of synthetic rubber, have been excluded from these statistics. The experience of the three fossil fuels in competition since 1950 shows natural gas expanding more rapidly, than oil by roughly twice as much, 219.0 percent' compared to 124.1 percent growth in B.t.u.s of oil consumed in the ten-year period. Percentagewise, water power little more than held its own, and coal, including anthracite, actually decreased more than one-fifth.

Jan 1, 1961

By Fahimeh Dehghani, Louis Ackah, Tathagata Ghosh, Justin Godbold, Jia Liu, Meisam Peiravi, Manoj Mohanty, Azam Baharlouei

Primary economical deposits of rare-earth elements (REEs) are exhausting all over the world, and it has become necessary to find new sources and methods for their extraction. In addition, increasing the application of REEs in modern technological society has increased its demand globally. One of the important movements to compensate for the future shortages of critical metals is the recovery of REEs from recyclable materials. This paper presents a review of the classification and extraction methods, as well as general applications of REEs with emphasis on secondary sources such as coal and coal byproducts, iron ore tailings, apatite, and phosphate byproducts. An overview of the current state of knowledge on the various methods of REE beneficiation and extraction is covered. These methods include physical separation, as well as hydrometallurgical and bio-hydrometallurgical techniques. The application of these REE extraction techniques for enhanced recovery has been driven primarily by the unique industrial application of these important elements. This paper further explores the existing and potential environmental challenges associated with REE extraction. The authors have presented a wide array of literature, in-depth discussion of the subject, and a succinct summary of processes and relevant case studies.

Sep 23, 2020