Special Issue "Recent Trends in Phosphate Mining and Beneficiation and Related Waste Management"

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

Deadline for manuscript submissions: closed (30 April 2019).

Special Issue Editors

Prof. Dr. Mostafa Benzaazoua
E-Mail Website
Guest Editor
Reserach Institute in Mining and Environment, University of Quebec (RIME-UQAT), Rouyn-Noranda, Canada
Interests: inorganic industrial and mining wastes; environmental characterization; treatment and recycling of industrial and mining wastes; waste reprocessing; integrated management of mining wastes
Special Issues and Collections in MDPI journals
Prof. Yassine Taha
E-Mail Website
Guest Editor
University Mohamed 6 Polytechnique, Morocco
Interests: inorganic industrial and mining wastes; environmental characterization; treatment and recycling of industrial and mining wastes; waste reprocessing; integrated management of mining wastes
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Phosphate extraction and beneficiation is one of the vital mining industries in the world, especially for the agriculture and food industries. Phosphorus derived from phosphate rock is a vital element of life and an exceptional component in fertilizers. However, high-grade phosphate reserves are known to decrease and the need to explore low-grade ores including waste rocks and tailings to extract apatite minerals is becoming more and more crucial. Also, many streams of waste are continuously produced by the phosphate industry: calcareous and siliceous waste rocks, clayey sludge and phosphogypsum. These wastes are produced in huge volumes reaching a ratio between 5 to 10 tons of waste per each ton of concentrated phosphate. The management of these wastes is becoming a real concern in terms of public concerns and environmental and financial aspects. In addition, phosphate ores are known to contain other critical raw materials (CRM) such as rare earth elements and uranium. The recovery of these vital elements from phosphate wastes may help to develop the needs of the green energy of the future and contribute to the achievement of the sustainable development goals.

Insights related to the following aspects will be included in this Special Issue:

  • Phosphate extraction and beneficiation,
  • Novel phosphate ores
  • Fine characterization of phosphate ores and waste
  • Phosphoric acid production
  • CRM recovery from phosphate ores and wastes,
  • Reprocessing of phosphate wastes
  • Valorization and reuse of phosphate wastes and phosphogypsum

Prof. Dr. Mostafa Benzaazoua
Prof. Yassine Taha
Guest Editors

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Keywords

  • phosphate
  • apatite
  • beneficiation
  • flotation
  • waste rocks
  • phosphogypsum
  • low-grade ores
  • phosphoric acid
  • REE
  • wastes valorization

Published Papers (12 papers)

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Research

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Open AccessArticle
Rare Earth Element Recovery from Acidic Extracts of Florida Phosphate Mining Materials Using Chelating Polymer 1-Octadecene, Polymer with 2,5-Furandione, Sodium Salt
Minerals 2019, 9(8), 477; https://doi.org/10.3390/min9080477 - 06 Aug 2019
Abstract
To meet the growing global demand for rare earth elements (REEs), nontraditional mining sources of these metals are being investigated. Phosphate ore and phosphate mining wastes have been identified as possible alternative sources to REEs. In this study, REEs were extracted from Florida [...] Read more.
To meet the growing global demand for rare earth elements (REEs), nontraditional mining sources of these metals are being investigated. Phosphate ore and phosphate mining wastes have been identified as possible alternative sources to REEs. In this study, REEs were extracted from Florida phosphate mining materials using mineral and organic acids. The REEs were then recovered at high efficiencies using a chelating polymer, 1-octadecene, polymer with 2,5-furandione, sodium salt. At pH 1.5, the chelation polymer effectively bound nearly 100% of the rare earth elements extracted from the solids. Overall extraction and recovery yields were between 80% for gadolinium and 8% for praseodymium from amine tailings, between 70% for terbium and 7% for praseodymium from phosphogypsum, between 56% for scandium and 15% for praseodymium from phosphate rock, and between 77% for samarium and 31% for praseodymium from waste clay. These results suggest that this chelating polymer efficiently recovers rare earth elements from acidic extracts of phosphate mining waste products. Full article
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Open AccessArticle
Geochemical Characteristics of Dolomitic Phosphorite Containing Rare Earth Elements and Its Weathered Ore
Minerals 2019, 9(7), 416; https://doi.org/10.3390/min9070416 - 08 Jul 2019
Cited by 2
Abstract
In order to provide a good theoretical guidance for the development and utilization of weathered phosphorite resources, we investigated the geochemical and mineralogical characteristics of primary and weathered phosphorites. The analysis of trace elements showed that the primary ore has hydrothermal sedimentation effect [...] Read more.
In order to provide a good theoretical guidance for the development and utilization of weathered phosphorite resources, we investigated the geochemical and mineralogical characteristics of primary and weathered phosphorites. The analysis of trace elements showed that the primary ore has hydrothermal sedimentation effect in the later stage, the weathered ore has obvious residual enrichment and the phosphate ore belongs to clastic lithologic phosphate rock. In addition, through leaching test method, it was shown that rare earth elements are present in fluorapatite in the form of isomorphic substitution, and the proportion of rare earth elements adsorbed on clay and other minerals was likely to be between 2% and 3%. The light rare earth elements are relatively enriched in both primary and weathered phosphorite, and Ce and Eu have obvious negative anomalies. The primary phosphorite is a dolomitic phosphorite containing rare earth elements, which are naturally enriched by weathering, and its weathered ore has obvious residual enrichment, while the deposit was characterized by normal marine sedimentation and hydrothermal action. Full article
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Open AccessArticle
A Comparative Study of Different Columns Sizes for Ultrafine Apatite Flotation
Minerals 2019, 9(7), 391; https://doi.org/10.3390/min9070391 - 28 Jun 2019
Abstract
The desliming operation to discharge ultrafine particles less than 20 µm prior to concentration by flotation is a common practice in phosphate ores beneficiation plants. The first industrial application for the beneficiation of the phosphate material with particle sizes <44 µm in Brazil [...] Read more.
The desliming operation to discharge ultrafine particles less than 20 µm prior to concentration by flotation is a common practice in phosphate ores beneficiation plants. The first industrial application for the beneficiation of the phosphate material with particle sizes <44 µm in Brazil was in the Araxá plant concentrator in the beginning of the 1980s. This work shows the comparative flotation results with two different phosphate slime samples (<40 µm) obtained from the Copebras (CMOC International) industrial plant located in Catalão (Goiás state, Brazil), considering a circuit with rougher/cleaner configuration with different columns sizes, as follows: Circuit 1 (rougher—4” diameter column; cleaner—2” diameter column) and circuit 2 (rougher—6” diameter column; cleaner 4” column). The results indicate that better flotation apatite recovery results were achieved for the circuit with higher size columns (6” and 4”). The results can be explained by the application of a cavitation tube in the rougher stage in the 6” column. The improved flotation performance can be attributed to increased probabilities of collision and attachment and the reduced probability of detachment by the small size bubbles generated by the cavitation tube in comparison with the bubbles produced by the porous tube of the 4” column flotation. Full article
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Open AccessArticle
Durability Evaluation of Phosphogypsum-Based Cemented Backfill Through Drying-Wetting Cycles
Minerals 2019, 9(5), 321; https://doi.org/10.3390/min9050321 - 26 May 2019
Cited by 1
Abstract
In this study, the durability of phosphogypsum (PG)-based cemented backfill was investigated by drying-wetting cycles to explore deterioration of its strength and the release of impurities. The leachates in this test were composed of deionized water, 5% Na2SO4 solution, 5% [...] Read more.
In this study, the durability of phosphogypsum (PG)-based cemented backfill was investigated by drying-wetting cycles to explore deterioration of its strength and the release of impurities. The leachates in this test were composed of deionized water, 5% Na2SO4 solution, 5% NaCl solution, and a range of sulfuric acid solutions with pH values of 1.5, 3, and 5. After drying-wetting cycles, unconfined compressive strength (UCS), visual deterioration, porosity, microstructure and concentrations of phosphate and fluoride in the leachates were measured. The results showed that both saline and acidic solutions could lead to strength reduction of PG-based cemented backfill under different deterioration mechanisms. The mechanical damage of salinity was caused by micro-cracking and degradation of C–S–H. However, the H+ broke the backfill by dissolving hydration products, leaving the conjunctures between PG particles weakened. Furthermore, the environmental impact was investigated by measuring the concentration of phosphate and fluoride in the leachates. In acidic solutions, the release of phosphate and fluoride was greatly enhanced by H+. Compared to the great strength deterioration in saline leachates, the concentration of phosphate and fluoride were similar to that of deionized water, indicating that saline solutions had little impact on the release of hazardous impurities. Full article
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Open AccessArticle
Phosphate Mine Tailing Recycling in Membrane Filter Manufacturing: Microstructure and Filtration Suitability
Minerals 2019, 9(5), 318; https://doi.org/10.3390/min9050318 - 24 May 2019
Cited by 1
Abstract
Ceramic membrane filters based on industrial by-products can be considered to be a valorization alternative of phosphate mine tailings, even more so if these ceramic membranes are used in the industrial wastewater treatment due to their good mechanical, chemical, and thermal resistance. The [...] Read more.
Ceramic membrane filters based on industrial by-products can be considered to be a valorization alternative of phosphate mine tailings, even more so if these ceramic membranes are used in the industrial wastewater treatment due to their good mechanical, chemical, and thermal resistance. The depollution of textile industry rejections with this method has not been studied in detail previously. In this work, ceramic membrane filters have been manufactured from natural clay and phosphate mine tailings (phosphate sludge). Blends of the abovementioned materials with a pore-forming agent (sawdust, up to 20 wt. %) were investigated in the range 900–1100 °C using thermal analysis, X-ray diffraction, scanning electron microscopy, and mercury porosimetry. Ceramic properties were measured as a function of firing temperature and sawdust addition. Filtration tests were carried out on samples with advantageous properties. The results showed that gehlenite together with diopside neoformed from lime decomposed carbonates and breakdown products of clay minerals, while calcium phosphate derived from partial decomposition of fluorapatite. Both quartz and fluorapatite resisted heating. The results of the experimental design showed that the variations of physical properties versus processing factors were well described by the polynomial model. Filtration results are quite interesting, allowing these membranes to be used in industrial effluent treatment. Full article
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Open AccessArticle
Rare Earth Occurrences in Streams of Processing a Phosphate Ore
Minerals 2019, 9(5), 262; https://doi.org/10.3390/min9050262 - 30 Apr 2019
Abstract
Rare earth elements (REEs) are defined as lanthanides with Y and Sc. Rare earth occurrences including the REE-bearing phases and their distributions, measured by rare earth oxides (REOs), in the streams of processing a phosphate ore were determined by using MLA, the mineral [...] Read more.
Rare earth elements (REEs) are defined as lanthanides with Y and Sc. Rare earth occurrences including the REE-bearing phases and their distributions, measured by rare earth oxides (REOs), in the streams of processing a phosphate ore were determined by using MLA, the mineral liberation analysis and EPMA, the electron probe microanalysis. The process includes an apatite ore beneficiation by flotation and further processing of the beneficiation concentrate with sulfuric acid. Twenty-six, sixty-two and twelve percent of the total REOs (TREO) contents from the ore end up in the products of beneficiation tailings, phosphogypsum (PG) and phosphoric acid, respectively. Apatite, allanite, monazite and pyrochlore are identified as REE-bearing minerals in the beneficiation process. In the beneficiation tailings, the REEs are mainly distributed in monazite (10.3% TREO), apatite (5.9% TREO), allanite (5.4% TREO) and pyrochlore (4.3% TREO). Gypsum, monazite, apatite and other REE-bearing phases were found to host REEs in the PG and the REEs distributions are 44.9% TREO in gypsum, 15.8% TREO in monazite, 0.6% TREO in apatite and 0.6% TREO in other REE-bearing phases. Perspectives on the efficient recovery of REEs from the beneficiation tailings and the PG are discussed. Full article
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Open AccessArticle
Valorization of Phosphate Mine Waste Rocks as Materials for Road Construction
Minerals 2019, 9(4), 237; https://doi.org/10.3390/min9040237 - 17 Apr 2019
Abstract
The road construction sector is a worldwide high consumer of natural aggregates. The use of unusual industrial by-products in road techniques can contribute to the conservation of non-renewable natural resources and the reduction of wastes produced by some industries. Phosphate waste rocks could [...] Read more.
The road construction sector is a worldwide high consumer of natural aggregates. The use of unusual industrial by-products in road techniques can contribute to the conservation of non-renewable natural resources and the reduction of wastes produced by some industries. Phosphate waste rocks could be considered as potential alternative secondary raw materials in road construction. The use and valorization of these wastes is currently limited according to the Moroccan guide for road earthworks (GMTR). The guide has classified these materials as waste products, which consequently, cannot be used in road construction. However, phosphate waste rocks are sedimentary natural rocks which have not been subjected to any transformation other than mechanical fragmentation. The goal of this paper is to discuss key-properties of various phosphate mine waste rocks (PMWR) to be used as road materials. Samples were taken from different stockpiles in the phosphate mine site of Gantour in Morocco. The different waste rocks samples were characterized in terms of their physical, geotechnical, chemical, mineralogical and environmental properties using international testing norms. The obtained results showed that the studied PMWR presented satisfying characteristics; the specific (particle) density: ρs > 26 kN/m3, Los Angeles abrasion: 45% < LA < 58%), methylene blue value MBV < 1 g/100g, organic matter: OM < 1% and plasticity index: PI < 20%. All PMWR were confirmed as possessing the requested geotechnical properties to be used as materials for embankments. Moreover, leaching tests showed that none of them released any contaminants. In field application, these materials have been also successfully used in in situ experimental pilot testing. Therefore, the PMWR have to be classified in the category of natural aggregates that are similar to conventional materials. Full article
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Open AccessArticle
Utilisation of Water-Washing Pre-Treated Phosphogypsum for Cemented Paste Backfill
Minerals 2019, 9(3), 175; https://doi.org/10.3390/min9030175 - 12 Mar 2019
Cited by 4
Abstract
Recycling phosphogypsum (PG) for cemented paste backfill (CPB) has been widely used at phosphate mines in China. However, the impurities in PG prolong the setting time and reduce the uniaxial compressive strength (UCS), limiting the engineering application of PG. This paper aims to [...] Read more.
Recycling phosphogypsum (PG) for cemented paste backfill (CPB) has been widely used at phosphate mines in China. However, the impurities in PG prolong the setting time and reduce the uniaxial compressive strength (UCS), limiting the engineering application of PG. This paper aims to investigate the feasibility of treated PG (TPG) washed repeatedly using deionised water (DW) for CPB. A water-washing pre-experiment was first conducted to find the proportion with the least DW demand and the effects of water-washing on ordinary PG (OPG). Then, based on the PG:DW ratio obtained from the pre-experiment, the properties of the OPG-based CPB (OCPB) and TPG-based CPB (TCPB) were tested using slump tests, UCS tests, and microstructural analysis. The results show that (1) after 11 water-washings at the PG:DW ratio of 1:1.75, the pH of the supernatant (pH = 6.328) meets the requirements of Chinese standard GB 8978-1996. (2) Water-washing improves the particle gradation quality of PG and removes the soluble impurities adsorbed at the surface of PG crystals. (3) The initial slump values of TCPB are 0.19–1.15 cm higher than that of OCPB, furthermore, the diffusivity values of TCPB are better than the performance of OCPB, with 0.61–1.68 cm of superiority. (4) The UCS values of TCPB are up to 0.838 MPa, 1.953 MPa, and 2.531 MPa, after curing for 7, 14, and 28 days. These are 0.283 MPa, 0.823 MPa, and 0.881 MPa higher than that of OCPB, respectively. It can be concluded that water-washing pre-treatment greatly improves the workability and mechanical property of PG-based CPB. These results are of great value for creating a reliable and environmentally superior alternative for the recycling of PG and for safer mining production. Full article
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Open AccessArticle
Radioactivity of Five Typical General Industrial Solid Wastes and its Influence in Solid Waste Recycling
Minerals 2019, 9(3), 168; https://doi.org/10.3390/min9030168 - 09 Mar 2019
Abstract
The level of radionuclides is an important index for the preparation of building materials from industrial solid waste. In order to investigate the radiological hazard of five kinds of typical general industrial solid wastes in Guizhou, China, including fly ash (FA), red mud [...] Read more.
The level of radionuclides is an important index for the preparation of building materials from industrial solid waste. In order to investigate the radiological hazard of five kinds of typical general industrial solid wastes in Guizhou, China, including fly ash (FA), red mud (RM), phosphorus slag (PS), phosphogypsum (PG), and electrolytic manganese residue (EMR), the radiation intensity and associated radiological impact were studied. The results show that concentrations of 238U, 235U, 232Th, 226Ra, 210Pb, and 40K for different samples vary widely. The concentration of 238U was both positively correlated with 235U and 226Ra, and the uranium contents in the measured samples were all of natural origin. The radiation levels of PG, EMR, EMR-Na (EMR activated by NaOH), and EMR-Ca (EMR activated by Ca(OH)2) were all lower than the Chinese and the world’s recommended highest levels for materials allowed to be directly used as building materials. The values of the internal and external illumination index (IRa and Iγ, respectively) for FA and RM were higher (IRa > 1.0 and Iγ > 1.3 for FA, IRa > 2.0 and Iγ > 2.0 for RM). The radium equivalent activity (Raeq), indoor and outdoor absorbed dose (Din and Dout, respectively), and corresponding annual effective dose rate (Ein and Eout) of RM, PS, and FA were higher than the recommended limit values (i.e., 370 Bq/kg, 84 nGy/h, 59 nGy/h, 0.4 mSv/y, and 0.07 mSv/y, respectively), resulting from the higher relative contribution of 226Ra and 232Th. The portion of RM, FA, and PS in building materials should be less than 75.44%, 29.72%, and 66.01%, respectively. This study provides quantitative analysis for the safe utilization of FA, RM, PS, PG, and EMR in Guizhou building materials. Full article
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Open AccessArticle
The Beneficiation Processes of Low-Grade Sedimentary Phosphates of Tozeur-Nefta Deposit (Gafsa-Metlaoui Basin: South of Tunisia)
Minerals 2019, 9(1), 2; https://doi.org/10.3390/min9010002 - 20 Dec 2018
Abstract
The enrichment of the low-grade-phosphate ore of the Tozeur-Nefta deposit was investigated using scrubbing-attrition, ball grinding and anionic/cationic reverse flotation in order to separate phosphate-rich particles from their gangue. The choice of the beneficiation process was based on the petrographic, mineralogical and chemical [...] Read more.
The enrichment of the low-grade-phosphate ore of the Tozeur-Nefta deposit was investigated using scrubbing-attrition, ball grinding and anionic/cationic reverse flotation in order to separate phosphate-rich particles from their gangue. The choice of the beneficiation process was based on the petrographic, mineralogical and chemical analyses. The petrographic and mineralogical studies have revealed the abundance of phosphatic (carbonate-fluorapatite-CFA) particles) coupled with carbonates (calcite, dolomite,) and silicates (quartz, illite, kaolonite) that constitute the (endo/exo) gangue of these ores. Chemical analysis has demonstrated that the raw phosphate sample contains low amounts of P2O5 (12.0%) and MgO (4.9%) and high amounts of CaO (40.7%) and SiO2 (20.5%). Microscopic observation/counting has shown that the release mesh occurs in the 71–315 μm size. Scrubbing-attrition, grinding and reverse flotation methods were applied to the +71μm fraction. Scrubbing-attrition tests of the 71–315 μm fraction have helped to improve the P2O5 grade to 15.5%. Ball-grinding tests were used to reduce the coarse fraction +315 μm. Grounded materials were sieved to 71–315 μm and combined with the scrubbed fraction in the flotation feed. Reverse-flotation tests of the phosphate-rich fraction (71–315 μm) have helped to improve the P2O5 grade to 27.1%, with a recovery rate of 92.4%. Full article
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Review

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Open AccessReview
A Review on Comprehensive Utilization of Red Mud and Prospect Analysis
Minerals 2019, 9(6), 362; https://doi.org/10.3390/min9060362 - 13 Jun 2019
Abstract
Red mud (RM) is a by-product of extracting of alumina from bauxite. Red mud contains high quantities of alkali-generating minerals and metal ions, which can cause significant environmental damage. Many valuable components such as rare-earth elements, Al, and Fe, in RM are difficult [...] Read more.
Red mud (RM) is a by-product of extracting of alumina from bauxite. Red mud contains high quantities of alkali-generating minerals and metal ions, which can cause significant environmental damage. Many valuable components such as rare-earth elements, Al, and Fe, in RM are difficult to be utilized owing to their particle size and alkalinity. Thus, developing an economical and efficient technology to consume a large amount of RM can efficiently solve RM disposal issues. This paper systematically reviews the comprehensive utilization methods for reducing RM environmental pollution and divides the comprehensive utilization of RM into three aspects: the effective extraction of valuable components, resource transformation, and environmental application. Based on resource, economic, and environmental benefits, the development of new technologies and new processes with market competitiveness, environmental protection, and ecological balance should be the prerequisite for the low-energy, low-pollution, low-cost, and high-efficiency comprehensive utilization of RM. The direction of future research to solve RM disposal issues is also suggested. Full article
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Open AccessReview
Review on Beneficiation Techniques and Reagents Used for Phosphate Ores
Minerals 2019, 9(4), 253; https://doi.org/10.3390/min9040253 - 25 Apr 2019
Cited by 1
Abstract
Phosphate ore is an important raw material for manufacturing fertilizers and phosphorous chemical products. While most of the phosphate resources cannot be directly treated as feed stock due to the low grade of P2O5 and high content of impurities. In [...] Read more.
Phosphate ore is an important raw material for manufacturing fertilizers and phosphorous chemical products. While most of the phosphate resources cannot be directly treated as feed stock due to the low grade of P2O5 and high content of impurities. In order to obtain a qualified phosphate concentrate, the beneficiation of the low-grade phosphate ore is, hence, of great necessity. Many beneficiation techniques can be employed to upgrade the P2O5 grade of phosphate ores based on their characteristics in chemical composition and texture. The flotation process is most widely applied to balance the P2O5 recovery ratio and cost. In this review, the dominant techniques for the beneficiation of phosphate ores are introduced. Moreover, the factors that affect the flotation of phosphate ore, including the properties of mineralogy, flotation reagents (depressants and collectors) and flotation medium, were systematically analyzed. Full article
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