Djebel Onk Research Articles

Assessment of metallic trace elements contamination in a mining area of the processing of Djebel Onk phosphate ore (Algeria)

Research relevance. Phosphate mining activities are one of the main sources of contamination by heavy metals since they harmfully affect the soil and lead to the degradation of the ecosphere. Research aim. This study aims at characterizing and evaluating the metallic contamination of soils in the vicinity of the Djebel Onk mine in the town of Bir El Ater (Wilaya of Tébessa) in eastern Algeria, and particularly focusing on estimating the spatial variability of this contamination and the extent of the contaminated area. Methodology. The physicochemical characteristic (pH) was determined by pH-meter, whereas AAS was used for the determination of heavy metals (Pb, Cu, Zn, Cd) in the examined soil Research results. The results reveal that soils that are close to the mine site studied and even those that are far away are heavily contaminated with heavy metals — lead (Pb), zinc (Zn), copper (Cu) and cadmium (Cd); the results also point out to a high variability of concentrations not only between sampling sites but also within the same mine site. The analysed soil pollution index is generally high even for soils sampled downstream more than 30 km from the mine site, whereas it is extremely high on the surface of the tailings slopes, underlining the fact that tailings are considered perennial sources of heavy metal contamination in their current state. Conclusion. The unhealthy area affected by metal pollution from mining sites in the Djebel Onk is very large as a result of the dispersion, by wind and water transport, of residual pollutants from the mine wastes abandoned on site. Remediation measures must be put into place to immobilize the pollutants and limit their spread to the environment Keywords: Soil contamination, Algeria, heavy metals, phosphate mine, pollution index.

Trace metal elements in phosphate rock wastes from the Djebel Onk mining area (Tébessa, eastern Algeria): A geochemical study and environmental implications

Algeria is one of the phosphate-rich countries where many deposits are found in the Tébessa region which are currently being mined from the Kef Essenoun quarries. The processing of run-off-mine, to increase P2O5 grads in the commercial product, includes the use of wet and dry procedures which in turn leads to the production of large amounts of wastes. The present study focuses on tracking the amount of trace metal elements (TMe) in the phosphate rock wastes resulting from the processing of phosphate run-of-mine. The representative samples of solid rejects and sludge wastes from both processing ways were collected and analysed using SEM and FTIR to characterise the materials, whereas ICP-AES and ICP-MS were used to determine major and TMe compositions, respectively. The results showed that the analysed wastes are P-enriched (P2O5 = 20 wt% - 27 wt %) together with similar mineralogy such as natural phosphorites (carbonate fluor-apatite), but they displayed an enhancement in matrix phases. Moreover, the overall tendency showed that the concentrations of TMe are relatively increased with a decrease in grain size diameter where higher contents of V, Cr, Co, Ni, Cu, Zn, As, Zr, Nb and Cd have been recorded in sludge and fine fraction from the wet way process (Rw −0.08 mm) when compared to other samples. The fine fractions generally contain the matrix that enhances almost all of TMe except for Sr and U which are hosted in apatite. Risk assessment of TMe showed that both raw phosphorites and their wastes, as all worldwide sedimentary phosphorites, yield some hazardous TMe exceeding the standards for soils (e.g., U, Cd, Cr, Mo, V and Tl). Hence, owing to the waste exposure and mobilisation of the finest particles by wind and rainfall, these hazardous metals could have harmful effects on the environment as well as human health.

Extraction of rare earth elements from waste products of phosphate industry

Rare earths are critical elements in our modern societies and the ever-increasing demand raises fears of supply risks in the coming years. This work dealt with the feasibility of extracting rare earth elements (REEs) from an industrial waste product from the exploitation of phosphate ores of “Djebel Onk” in Tébessa eastern region of Algeria. The solid residue was first leached at room temperature with three different inorganic acids (HNO3, H2SO4 and H3PO4) at various concentrations and leaching times. It was possible to recover almost 100% of La, Ce, Eu, Gd and Y with HNO3 3 N in 24 h. However, only about 10% of Yb were leached. The leachates were further treated with two organophosphorous extractants, trioctylphosphine oxide (TOPO) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) at various concentrations in chloroform. A virtually total extraction of Eu, Gd, Y and Yb was achieved with TOPO at 0.3 M. The extraction efficiency of light rare earth elements (LREEs), La and Ce, was only 38 and 55%, respectively. Very good selectivities between heavy rare earth elements (HREEs), and LREEs as well as between medium rare earth elements (MREEs) and LREEs were obtained but TOPO was unable to selectively separate HREEs from MREEs. Although D2EHPA led to lower REEs extraction efficiency than TOPO, it showed interesting performance for the selective separation of REEs into three fractions corresponding to LREEs (La and Ce), MREEs (Eu and Gd) and HREEs (Y and Yb).

Characterization of crude and calcined phosphates of Kef Essennoun (Djebel Onk, Algeria)

Rock phosphate is the fundamental component for the manufacture of phosphoric acid and phosphate fertilizers. The aim of this study is to predict how sample preparation of Kef Essennoun phosphate responds to heat treatment and to estimate the purity of the raw and calcined phosphates. The influence of temperature (600–900 °C) was evaluated. The evolution of thermal treatment and the characterization of the Kef Essennoun ore (Djebel Onk mine, Algeria) were carried out by various analytical techniques including X-ray diffraction (XRD), wavelength-dispersive X-ray fluorescence, Fourier-transform infrared spectroscopy, thermogravimetric analysis/differential thermal analysis, and scanning electron microscopy (SEM). The results showed that the raw phosphate is a mixture of six phases, of which carbonate hydroxyapatite [Ca10(PO4)3(CO3)3(OH)2] is the dominant phase. With heat treatment, at 700 °C, a fluorapatite [Ca5(PO4)3F] phase appeared, as confirmed by XRD analysis, with good crystallization indicated by SEM. The P2O5 content was increased from 28.389% in raw phosphate to 31.085% in the calcined product. The dissolution of the calcined phosphate at 900 °C was completed by HNO3 acid attack, and occurred rapidly at ambient temperature. The results show that the production of phosphoric acid by Ca5(PO4)3F was more easily achieved with optimized consumption of the acid attack.

Development of new composite cement based on waste rocks from Djebel Onk phosphate deposit (Tebessa-Algeria)

Development of new composite cement based on waste rocks from Djebel Onk phosphate deposit (Tebessa-Algeria)

Comprehensive REE + Y and sensitive redox trace elements of Algerian phosphorites (Tébessa, eastern Algeria): A geochemical study and depositional environments tracking

The Algerian sedimentary phosphorites of marine origin are located mainly in the Tébessa region, which is part of the Eastern Saharan Atlas. These phosphorites are hosted by Paleocene-Eocene series and crop out in two main sedimentary areas: the northern sites (Djebel El Kouif, Djebel Dyr and Djebel Tazbant) and the southern sites, which include the Djebel Onk commercial world-class ore deposits that are represented in this study by the Kef Essenoun sector. This study reports a detailed investigation of these phosphorites at a regional scale and is aimed to characterizing the evolution of their depositional environments. Field and laboratory works consist of a systematic sampling of outcrops, petrographical (OM and SEM-EDS), mineralogical (XRPD) and chemical (major, trace and rare earth elements by ICP-MS) analyses associated with a PCA statistical treatment. The time-wise evolution of the depositional environments was constrained based on rare earth elements (REE) and selected redox sensitive element proxies, such as Ce, Eu, Y, Mn, U and V.The results show that the phosphorites have a granular fabric with variable grain sizes. The grains can contain micro-remains and impurities related to their origin, which was most often fecal pellets. Carbonate fluor-apatite is the main mineral phase in these phosphorites, where P2O5 contents show large variations between different outcrops (average from 18.39 to 30.16 wt%). A marked evolution of depositional environments is observed in their vertical trends from sub-reduced and sub-oxic in the lower beds to rather oxic conditions in the upper layers. This evolution shows a significant shift along the sedimentary profiles reflecting more open connection to Tethyan seawater towards younging trend. These results contrast remarkable changes of depositional conditions during Paleocene–Eocene transition.

Adhesion abilities and biosorption of Cd and Mg by microorganisms - first step for eco-friendly beneficiation of phosphate ore

Chemical reagents used in traditional mineral processing can be toxic and hazardous for the environment. Therefore, the use of biotechnological methods is becoming increasingly important. Great hopes are being placed in the use of microorganisms for bio-beneficiation of raw materials. However, assessment of adhesion abilities of bacteria onto minerals surface as well as biosorption of metals are essential steps before designing final process of each ore beneficiation. The main aim of this work was an investigation of biosorption of Cd and Mg, as well as adhesion abilities of five microorganism species with minerals included in the natural mixture of phosphate ore form Djebel Onk, Algeria. The ore, due to its unique composition, created conditions for adhesion of all five tested microbial strains onto apatite surface during incubation at pH 3. Moreover, Rhodococcus erythropolis CD 130, Pseudomonas fluorescens and Escherichia coli adhered distinctly onto apatite surface during incubation at pH 7. Incubation lasting 20 min at pH 4-6 created the most favorable conditions for biosorption of metals by B. subtilis and adhesion of cells. In case of C. albicans, biosorption of metals as well as adhesion of cells onto the mineral surface were more effective after longer time and in a wider pH range.

Characterization and homogenization of Bled El-Hadba phosphate ore, case of Djebel Onk (Algeria)

Characterization and homogenization of Bled El-Hadba phosphate ore, case of Djebel Onk (Algeria)

Glauconite-bearing sedimentary phosphorites from the Tébessa region (eastern Algeria): Evidence of REE enrichment and geochemical constraints on their origin

Rare earth element (REE) analyses are reported on glauconite-bearing phosphorites from northeastern Algeria. These rocks of Paleocene-Eocene age are located in the Eastern part of the Saharan Atlas, where two localities were investigated: the Djebel El Kouif in the north and the Kef Essenoun in the south. The latter belongs to the world-class Djebel Onk mining deposit. Petrographic examination indicates that phosphorite from the main layer of the Kef Essenoun deposit has a significant abundance in glauconite grains, while their occurrence in the Djebel El Kouif is restricted to the basal levels. In both deposits, glauconite grains are richer in REEs than other co-existing particles (pellets, coprolites, enameloid and dentine of marine fish teeth), but the glauconites of the Kef Essenoun deposit exhibit significantly higher REE concentration (min = 654 ppm, max = 1760 ppm, average = 1146 ppm) than those of Djebel El Kouif deposit (min = 543 ppm, max = 623 ppm, average = 584 ppm). The whole-rock REE concentrations also show substantial differences between the two deposits and the REE enrichment in the Kef Essenoun main sub-layer is more likely the result of the high glauconite content. PAAS normalized-REE patterns of the glauconite grains display similar patterns between the northern and southern localities with weak negative Ce anomalies and slight middle REE enrichments. On the other hand, the pellets and whole phosphorite grains from the northern deposit indicate a REE source from oxic-suboxic seawater, whereas those from the Kef Essenoun deposit exhibit slight middle REE enriched patterns with weak negative Ce anomaly suggesting a different environment of deposition (i.e. a tendency to reduced conditions). These geochemical results along with previous petrographic studies confirm the allochthonous character of the main phosphorite sub-layer in Kef Essenoun, where winnowing, transport and re-deposition of previously deposited phosphorites resulted in high accumulation and formation of glauconite grains. The glauconitization process of fecal pellets happened in two stages and was controlled by semi-confined micro-environments. This can explain the abundance of glauconite grains in the phosphorites from Kef Essenoun deposit and their restricted occurrence in the basal levels of the Djebel El Kouif outcrop.

Organic-rich Albian deposits as the origin of hydrocarbon-contaminated phosphates, southeastern Constantine Basin, Algeria

The southeastern Constantine Basin, from its phosphatic layers (Djebel Onk, Bled El Hadba, Negrine) and its hydrocarbon resources, constitutes a promising area for mining and oil research of northern Algeria. The presence of organic matter (OM), micro-organisms and phosphate particles in the Upper Albian deposits would correspond to layers of source rock for hydrocarbons. The facies characterizing this stage correspond to marine deposits of which OM related to the formation of these hydrocarbons in a relatively reducing environment. Such layers, with TOC rates varying from 0.50% to 11.53%, seem comparable to Paleocene-Eocene phosphatic layers, and thus economically exploitable with an average content of P2O5 of 16%. A stratigraphic, structural and paleogeographic overview are based on geochemical and petrographic data. Such data were analyzed and indicate that Albian layers are at the origin of a phosphate layer with organic support, e.g. radiolarians and diatoms, covered by a sedimentation inducing hydrocarbon production. They are found at subsurface among the Upper Cretaceous sedimentary pile, as it can be mentioned in several oil exploration wells. This is related to their lower location compared to the northern part of the basin where the Upper Cretaceous formations are eroded, suggesting maturation temperatures much higher southwards, and thus corroborating the link with burial sedimentary levels.

Dissolution of Djebel Onk phosphate ore using sulfuric acid

The purpose of this study is to compare the P205 recovery of two phosphate rocks obtained by sulfuric acid attack. These phosphate rocks with different chemical composition, are extracted from the same deposit (Djebel Onk, Algeria). Experience shows that, for the two phosphate rocks, the reaction is faster during the first 20min. For both phosphates, the P205 recovery remains almost stable after 40min of reaction. But when the phosphates are attacked by 70wt% of concentrated H2SO4, this rate is about 96%.By optimizing the reaction parameters, we managed to get a high decomposition of phosphates. Therefore, the maximum P205 recovery are, respectively, 96.19% for the first phosphate (65.38% BPL) and 94.46% for the second phosphate (53.75% BPL). These maximum values are obtained when the following parameters are used: (1) Sulfuric acid concentration: 96wt%; (2) Reaction time:50min; (3) Stirring speed: 200rpm; (4) Phosphate particle size: 88μm (−170mesh).The production of phosphoric acid or the SSP (single superphosphate) requires prior knowledge of the effect of some parameters on the performance of the reaction; hence, the importance of this work for the fertilizer industry as it helps to have an idea about the behavior of this type of phosphate rock at its dissolution by sulfuric acid.

Mapping underground cracks using 2D electrical resistivity tomography: the case of the landslide of Kef Essenoun phosphate deposit, Djebel Onk (northeast of Algeria)

The landslide of Kef Essenoun phosphate deposit (northeast of Algeria) occurred on September 2007, when a large mass of rocks detached from the rock mass scale and filled almost entirely the pit (the career). Recently, new cracks oriented N–S and NE–SW with large sizes have appeared in several places near a slide area and even in the alignment of the 2007 slide area. To understand the nature of the deformations recently observed at the surface, and to favor safety measures that can be implemented rapidly, it is essential to obtain maximum information on the deep structure of underground cracks and areas of weakness. Electrical resistivity imaging or tomography (ERT) is well suited for characterizing the bedrock surface thanks to the ability of the technique for detecting resistive features as well as discriminating subtle resistivity variations. For the present investigation, a Wenner transect was conducted through a visible crack area near the landslide area. The electrode spacing was 2 m and the length of the transect was about 60 m. In this case study, the survey results suggest that ERT is a cost-effective tool that can easily be deployed to gather valuable subsurface data and to aid in the detecting and mapping of underground cracks and other subsurface cavities.

Tests of Adsorption of Amino-acids on the Natural Phosphate of the El Hadba Layer, Djebel Onk, Algeria

Adsorption tests were carried out in static mode, on natural phosphate samples both in a raw state and after processing. Various techniques of analyses were used (i) to characterize the material adsorbing on the granulo-chemical and thermo-mineralogical levels, (ii) to evaluate the performances of the process of adsorption used in relation to the existing mineralogical species, in phosphatic and gangue elements, (iii) to evaluate incubation condition in ions PO43-, carboxylate grouping and steric obstruction effect on lateral chains of adsorbates. This effect is significantly affected by the composition of the incubation medium. Thus, the fractions low in phosphate ions appeared definitely more effective. The adsorption isotherms highlight a good correlation between experimental points and values predicted by Temkin model, confirming the influence of interactive effects on the used adsorbates. Study of the mechanisms of adsorption and the transfer mode of matter was carried out using the linear shape of the isotherm models, their respective correlation coefficients, the speed constants and the diffusion coefficients for the kinetic models based on reaction and diffusion.

Trace Elements of Kef Es Sennoun Natural Phosphate (Djebel Onk, Algeria) and how they Affect the Various Mineralurgic Modes of Treatment

Trace elements in particles of the phosphate ore and their behaviour in the various mineralurgic modes of processing were studied to: (i) locate the importance of these contents according to granulometry, their association with the existing mineralogical species, and (ii) check if the enrichment operations applied are compatible with a kind of processing. We used several methods of preconditioned analyses to (i) define the optimal meshes of release of the phosphatic elements and gangue minerals, (ii) identify the raw material mineralogical phases, the major elements chemical composition, their distribution into particle-size classes, and their thermal behaviour. X-ray fluorescence and ICP-MS allowed to identify 30 REE and transition metals. We obtained significant differences in the particle shapes, especially the fine ones and in the mineralurgic modes of treatment used, where the floatation processing is prevailing. A close relation between trace elements and various minerals (apatite, dolomite and silicates), through operations of substitution, is evidenced.

Kinetical Study of the Decomposition of Djebel ONK Phosphates by Nitric Acid

Abstract The development of industrial processes designed to produce efficient fertilizers is nowadays of great importance, particularly in the field of farming. One way of producing phosphate fertilizers is by reacting phosphate rocks with nitric acid. In the present work, the kinetics of this reaction has been studied using phosphate mineral from the Djebel Onk mine (Algeria) and measurements of the conversion of P2O5 have been carried out by gravimetry. The effects of various operating parameters, such as the reaction time, the reaction temperature, the nitric acid concentration and the size of the particle have been studied. The experimental conditions have been optimized and global kinetic data such as the reaction rate constant and the activation energy have been determined.

The use of three physico-chemical methods in the study of the organic matter associated with the sedimentary phosphorites in Djebel Onk Basin, Algeria

The study of the organic matter (OM) associated with the phosphate ore of Kef Essennoun deposit (Djebel Onk mining basin, Algeria) was with a view to determine the decomposition degree of the OM within the pellets and the matrix, and the conditions of diagenesis. The sedimentary phosphates of this deposit are constituted of sub-rounded, phosphate-rich grains (pellets) dispersed in a surrounding, much poorer than pellets in P, matrix (or gangue). The survey of the OM associated with both pellets and matrix used several types of analyses: scanning electron microscopy (SEM), scanning electron microscope with energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The results show the OM, dispersed approximately homogeneously, in the form of large flat particles, within the gangue and within the phosphatic pellets in the form of small particles. The O/C ratio showed that the OM is more oxidised in the matrix than within the pellets. The oxidation increased with the phosphatisation rate of the pellets and more with the carbonation rate of the matrix, but it decreased with the silicification degree in the siliceous carbonated matrix. Two major functional classes were distinguished within pellets: aliphatic and oxygenated ones, the latter being fundamentally present in humic OM. The presence and abundance of these humic compounds in pelletal phosphorites are known from the 1980s and considered as witnessing a formation of apatite in a strictly closed environment, inside the pellet.

Magnetic properties of the Bled El Hadba phosphate-bearing formation (Djebel Onk, Algeria): Consequences of the enrichment of the phosphate ore deposit

To improve the enrichment of the Thanetian marine phosphate ore deposit from the quarry of Bled El Hadba (Djebel Onk, Algeria) before its exploitation, we first conducted a joint study using different techniques for comparison. These studies reveal that magnetic minerals play a significant role within the matrix of the central productive unit which is squeezed between two other units. Magnetic separation procedures show that there are some positive correlations between magnetic susceptibility and grain size fraction (80–250 μm). These dolomite-rich fractions are more clearly separated. Different tools were used to characterize the magnetic minerals (X-ray, microprobe, differential scanning calorimetry, thermogravimetric and thermomagnetic analyses). They show correlations between magnetic phases and the presence of associated magnetic minerals within the matrix or included in the phosphate ore deposit. They enabled us to distinguish a series of magnetic minerals (magnetite, hematite, maghemite, goethite, ilmenite, pyrite, iron–titanium oxide and titanium oxide sulphate) and to determine that Fe and Ti are prevalent in the separated fractions, following the same variation as Mg. The phosphorous (phosphate) rate is higher in the non-magnetic material, especially in the layers that are rich in dolomitic carbonates (upper and lower units), which could be trapped within the dolomitic matrix, while Magnesium (dolomite) is more important in the magnetic fraction. The separation of phosphate elements and dolomite carbonates is effective and therefore the ore can be enriched through magnetic procedures. Comparison between products enriched by magnetic separation, flotation and calcination showed important differences, chemically, economically and technically speaking.

Typology of Phosphate Ores in Deposits of the Djebel Onk Mining Basin (Eastern Algeria)

Typology of Phosphate Ores in Deposits of the Djebel Onk Mining Basin (Eastern Algeria)

Caracterisation physico-chimique du minerai de phosphate de Bled El Hadba — Tebessa

Abstract Physico-chemical characterization of the phosphate ore of Bled El Hadba-Tebessa. Algeria, with the layers of Djebel Onk, located in the east of the country, has important phosphate reserves. With the aim of developing its phosphate output , the Ferphos company has planned to put in exploitation the layer of Bled El Hadba which is within 14 kilometers of the treatment plant of Djebel Onk, close the algero-tunisian border. This layer is the object of detailed attention because of important lithochemical variations which result in an enrichment in carbonates (dolomite) and a reduction in abundance of phosphate grain in the lower and upper parts. This thus makes it possible to distinguish three main layers: summital, principal and basal. A characterization of the ore was carried out to determine the mineralogical and chemical characteristics and the dimensions of main minerals. The physicochemical studies which were undertaken by various methods of qualitative and quantitative analyses (DRX, FX, ATG…etc), should allow, on the one hand, to better define a plan of exploitation of the layer, so as to obtain mixtures of raw materials wich must satisfy as much as possible the quality indices required by industry and, on the other hand, to propose suitable methods of treatments for phosphate ore enrichment by the elimination of the undesirable matters.

Étude de la Cinétique de Décomposition des Phosphates de Djebel Onk Par l'Acide Nitrique

AbstractThe development of industrial processes designed to produce efficient fertilisers is nowadays of great importance, particularly in the field of farming. One way of producing phosphate fertilisers is by reacting phosphate rocks with nitric acid. In the present work, the kinetics of this reaction has been studied using phosphate mineral of the Djebel Onk mine (Algeria) and measurements of the conversion of P2O5 have been carried out by gravimetry. The effects of various operating parameters such as the reaction time, the reaction temperature, the nitric acid concentration and the size of the particle have been studied. The experimental conditions have been optimised and global kinetic data such as the reaction rate constant and the activation energy have been determined.