Moroccan Phosphate Research Articles

Improving phosphorus availability in sewage sludge ash through a novel microwave‐based technology

AbstractThis work is connected with the increasing demand for fertilizers and the associated supply risks and market volatility in the European Union (EU). It highlights the reliance on phosphorus from Moroccan phosphate rocks and the environmental issues stemming from the overuse of phosphate‐based fertilizers. The paper suggests a shift in perspective, viewing waste as a valuable resource. Specifically, it explores the potential of recycling phosphorus from sewage sludge ash, which contains a high phosphorus concentration. The focus is on comparing two methods of phosphorus extraction from sewage sludge ashes: classical wet‐chemical extraction and a new microwave‐based technology. There is an increase in phosphorus bioavailability with the microwave treatment, making it a promising approach for waste management. An initial economic evaluation suggests that the microwave method is highly competitive, especially when compared with wet‐chemical extraction technologies. The resulting material from the microwave treatment is classified as a straight solid inorganic macronutrient fertilizer according to EU regulations.

Occurrence, distribution and fate of iodine during phosphate ore beneficiation process

Numerous beneficiation techniques, such as washing, grinding, flotation, digesting, and calcination, are used to concentrate the minerals found in phosphate rocks, which include apatite, carbonatites, and silicates. Significant iodine levels are often found in phosphate ore minerals, which have a distinctive geochemical occurrence. However, the exact occurrence and distribution of iodine in these minerals are not yet thoroughly understood. A study was carried out to investigate the iodine's distribution, occurrence modes (phases), and release rate in Moroccan phosphate as it undergoes the beneficiation process. The samples underwent a multi-analytical approach combining mineralogical and chemical characterization using ICP-MS, ICP-OES, XRD, elements titration, and Pearson correlation analysis for interelement relationships. Calcination, digestion, and Heavy liquid separation is used to study the fate of iodine. The analysis indicates that iodine is primarily found in fluorapatite, with local concentrations ranging from 35 to 130 ppm. The most enriched grains/zones are associated with fluorapatite, enriched in P2O5, F-. in addition, iodine is positively correlated with its main components, including P2O5, F-, SO3, Na2O, CaO, and REEs. The flotation and heavy liquid separation process used for calcite and silicate removal is acting as an iodine and P2O5 concentrator, given that 99 % of iodine occurs in the apatite phase. However, it has been demonstrated that iodine can be released during the digestion of phosphate rock. Where the initial iodine content is distributed among phosphoric acid, PG, and the gaseous phase, constituting 35 %, 25 %, and 40 %, respectively. Furthermore, the calcination of phosphate rock between 800–1000 °C shows that total iodine is released with gases in I2 form, leading to an increase in the concentration of iodine in the surrounding area. In this regard, an integrated pyrometallurgical process has been proposed for the valorization of iodine as silver iodide. This process involves trapping gaseous iodine in an alkaline solution, followed by precipitation, thereby contributing to the overarching objectives of the circular economy and environmental protection.

Synthesis of High-Purity Hydroxyapatite and Phosphoric Acid Derived from Moroccan Natural Phosphate Rocks by Minimizing Cation Content Using Dissolution-Precipitation Technique.

This study investigates, in the first part, the synthesis and purification of a poorly crystalline hydroxyapatite (HAp) using natural Moroccan phosphate (Boucraa region) as a raw material. Despite its successful preparation, the obtained HAp was contaminated by several metallic cations (mostly Cd, Pb, Sn, Ti, Mn, Mg, Fe, and Al) migrated from the natural rocks during the digestion process, inhibiting HAp application in several sectors. To minimize the existence of these elements, the dissolution-precipitation technique (DP) was investigated as a non-selective purification process. Following the initial DP cycle conducted on the precipitated HAp, the removal efficiency was approximately 60% for Al, Fe, Mg, Mn, and Ti and 90% for Cd and Pb. After three consecutive DP cycles, notable improvement in the removal efficiency was observed, reaching 66% for Fe, 69% for Mg, 73% for Mn, and 74% for Al, while Cd, Pb, and Ti were totally removed. In the second part of this study, the purified HAp was digested using sulfuric acid to produce high-quality phosphoric acid (PA) and gypsum (GP). The elemental analysis of the PA indicates a removal efficiency of approximately 89% for Fe and over 94% for all the examined cations. In addition, the generated GP was dominated by SO3 and CaO accompanied with minor impurities. Overall, this simple process proves to be practically useful, to reduce a broad spectrum of cationic impurities, and to be flexible to prepare valuable products such hydroxyapatite, phosphoric acid, and gypsum.

Enhancing Hygiene and Technical Properties of Ceramic Tiles through Moroccan Phosphate Additives

This study offers a simple solution to manufacture ceramic tiles with good technical and hygienic properties. This solution consists of integrating the phosphate product from Morocco in the industrial formulation of ceramic tiles, to produce materials in compliance with the criterion of the ISO standard. For phosphate products, three grades were studied: HG-high grade, MG-medium grade, and LG-low grade. The results show that for materials containing these additives, there is both an effect of the concentration and type of additive on technical and hygienic properties. The mechanical property is improved when the incorporated component was richer in P2O5. Only the use of HG-high grade and MG-medium grade as an additive at least 15% makes it possible to satisfy the mechanical requirement. The anti-biofilm effect of natural phosphate (PN) as an additive to manufacture ceramic tiles is confirmed, it may prevent bio adhesion and biofilm formation at almost 75% for the HG-high grade and MG-medium grade. This solution could interest professionals and all users who care about the state of hygiene of their ceramic materials sensible to the formation of biofilm, like orthopaedic implants, swimming pool tile…etc.

Utilization of Crop Residues and Solubilizing Bacteria to Enhance the Dissolution of Moroccan Phosphate Rock

Phosphorus is essential for plant growth, but its availability in soils is limited due to low solubility of phosphate compounds. This study evaluated the combined effects of crop residues (CR) and phosphate-solubilizing bacteria (PSB) on the dissolution of Moroccan phosphate rock. Pot experiments were conducted for 60 days using different doses of MPR (450 kg/ha, 300 kg/ha, and 150 kg/ha), rice and maize crop residues, and a PSB consortium from a rice paddy field. Parameters such as pH, bacterial count, and phosphorus content were measured. The pH increase was significantly higher under the T3 treatment (CR + PSB) with pH 8.26 to 8.58, followed by T1 (CR alone) with pH 7.73 to 8.1, T2 (PSB alone) with pH 7.4 to 7.91, and T0 (control) with pH 7.27 to 7.67. The number of PSB was highest under the T3 treatment (1238.5 x 10-6 to 2081.1 x 10-6 bacteria/g dry matter), followed by T1 (127.2 x 10-6 to 249.03 x 10-6 bacteria/g dry matter) and T2 with 1.7 x 10-6 to 44.6 x 10-6 bacteria/g dry matter, regardless of the MPR dose. Phosphorus solubilization was 35% to 62% with PSB alone (T2), 72% to 88.5% with CR alone (T1), and over 83.98% when both CR and PSB were combined (T3). This increase was more pronounced with higher MPR doses (300 to 450 kg/ha). Incorporating PSB and crop residues as biofertilizers is a viable strategy for enhancing phosphate rock dissolution and improving soil fertility in agricultural systems.

Phosphate δ13Corg chemostratigraphy from the Gantour basin, Morocco: A proof of concept from the K–Pg transition to mid-Thanetian

The Late Cretaceous–early Paleogene interval is globally associated with transient to long-term changes in the stable carbon isotopic composition of marine carbonates (δ13Ccarb). Based on biostratigraphic reconstruction, this critical period of Earth's history is thought to coincide with the deposition of world heritage Paleocene phosphate deposits (phosphorites) in northwestern Morocco. However, the detailed stratigraphy of the Gantour basin, one of the most important Moroccan phosphate deposits, has not yet been constrained. For instance, the former “Montian” Stage has been used to tentatively approximate the Danian, whereas the succeeding Selandian Stage remains to be identified. Here, we develop a detailed organic carbon isotopic (δ13Corg) curve from phosphorus-rich horizons of the western Gantour sedimentary sequence in an attempt to constrain their stratigraphic placement and depositional age model. Upsection, these strata host long-term negative and positive δ13Corg trends that tend to correlate with global δ13Ccarb records of the Cretaceous–Paleogene and mid-Thanetian transitional boundaries. The data support the presence of Danian and Selandian rocks in the Gantour basin, which are succeeded by strata containing characteristic signatures of the well-known Cenozoic δ13C maximum at 58–57.5 Ma (the Paleocene Carbon Isotope Maximum). Our results shift the previously proposed Cretaceous–Paleogene transition in the Gantour basin further down into the older sediment C2M layer without interfering with recorded massive biological turnover in faunal diversity and abundance. Moreover, the refined stratigraphy suggests that the deposition of the Gantour phosphorites spanned ∼8.5 Myr. Our results confirm the utility of δ13Corg chemostratigraphy for dating and correlating phosphate-bearing deposits of the Tethyan province. They have important implications for deciphering Paleocene phosphogenesis, the co-evolution of associated vertebrate groups, and for prospecting phosphorus-rich mineral deposits.

Fired brick production using phosphogypsum and phosphate mining waste

The main objective of this study is to propose advanced solutions for recycling phosphogypsum (PG) in the construction industry. In Morocco, PG has been produced in large quantities (around 20 million tons) by a series of phosphoric acid manufacturing plants for many years. To address this issue, fired bricks were created using PG and red clay (RC), a waste material from Moroccan phosphate mines. The pressed brick samples were dried at 105 °C and then fired at temperatures between 900 and 1100 °C for 2–5 h. The PG, RC, and sintered briquettes were characterized and analyzed through thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), physical properties and response surface methodology (RSM). The Toxicity characteristic leaching procedure test (TCLP) was also conducted on the raw materials and the fired brick samples to assess contamination risk. At all temperatures, the addition of PG results in a microstructure with high porosity that significantly impacts the mechanical characteristics. Despite this, the mechanical and physical performance of the fired brick samples meet the required standards. The TCLP test results did not detect any release of contaminants. The samples fired at 1056 °C for 4.5 h with a PG content of 40% demonstrate optimal conditions, exhibiting a notable bending strength of 13.15 MPa, a moderate density, and minimal water absorption. These findings indicate a promising and sustainable future trend in the construction industry by incorporating PG in fired brick production, providing a viable solution for waste management. Furthermore, comparing the results with previous works highlights the significant improvements achieved in terms of meeting industry standards and minimizing contamination risks associated with the utilization of mine wastes in fired bricks.

Impacts of U.S. countervailing duties on phosphate fertilizers

AbstractCountervailing duties are a trade policy instrument by which importing governments tax imports that are found to benefit from foreign subsidies. Thus, in effect, these duties attempt to remedy market distortions generated by foreign subsidies by further distorting market mechanisms. On March 11, 2021, the U.S. International Trade Commission issued duties ranging between 19.97% and 47.05% on Moroccan phosphate imports upon finding that Moroccan exports had been receiving unfair government subsidies. In this research, we estimate the impacts of these duties on U.S. diammonium phosphate and triple superphosphate fertilizers, as well as long‐run downstream prices of five U.S. row crops with the largest phosphate usage. Using these results, we assess the implications for gross receipts in the U.S. fertilizer industry and gross margins for American farmers. We also calculate the implied change in expenditure for agricultural end users. We find that the countervailing duties have increased U.S. phosphate fertilizer prices by approximately 34% over counterfactual levels. This corresponds to an expected downstream price response ranging from around 10% for corn, cotton, and sorghum to between 1% and 4% for soybeans and wheat. This market distortion generates a $23 billion increase in gross receipts for a concentrated domestic fertilizer industry while shrinking gross margins for American farmers by 2% and 8% and increasing agricultural user expenditures by approximately $10.84 billion.

Graphene-Oxide-Grafted Natural Phosphate Support as a Low-Cost Ceramic Membrane for the Removal of Anionic Dyes from Simulated Textile Effluent

A novel natural phosphate/graphene oxide (GO) composite membrane was successfully fabricated using two steps: (i) silane chemical grafting and (ii) dip-coating of a GO solution. First, the low-cost disk ceramic support used in this work was fabricated out of Moroccan natural phosphate, and its properties were thoroughly characterized. The optimized ceramic support was sintered at 1100 °C following a specific heat treatment based on thermogravimetric analysis (TGA) and differential thermal analysis (DTA); it exhibited a permeability of 953.33 L/h·m2·bar, a porosity of 24.55%, an average pore size of 2.45 μm and a flexural strength of 22.46 MPa. The morphology analysis using SEM showed that the GO layer was homogenously coated on the crack-free Moroccan phosphate support with a thickness of 2.8 μm. The Fourier transform infrared spectrometer (FT-IR) results showed that modification with silane could improve the interfacial adhesion between the GO membrane and the ceramic support. After coating with GO on the surface, the water permeability was reduced to 31.93 L/h·m2·bar (i.e., by a factor of 142). The prepared GO/ceramic composite membrane exhibited good efficiency in the rejection of a toxic azo dye Congo Red (CR) (95.2%) and for a simulated dye effluent (87.6%) under industrial conditions. The multi-cycle filtration tests showed that the rejection rate of CR dye remained almost the same for four cycles. Finally, the flux recovery was also studied. After 1 h of water cleaning, the permeate flux recovered, increased significantly, and then remained stable.

Phosphate and potash solubilizing bacteria from Moroccan phosphate mine showing antagonism to bacterial canker agent and inducing effective tomato growth promotion.

Most agricultural soils are facing limited phosphorus availability that challenges modern agriculture. Phosphate solubilizing microbia (PSM) has been explored extensively as potential biofertilizers for plant growth and nutrition, and harnessing phosphate rich areas could provide such beneficial microorganisms. Isolation of PSM from Moroccan rock phosphate led to the selection of two bacterial isolates, Bg22c and Bg32c, showing high solubilization potential. The two isolates were also tested for other in vitro PGPR effects and compared to a non-phosphate solubilizing bacterium Bg15d. In addition to phosphates, Bg22c and Bg32c were able to solubilize insoluble potassium and zinc forms (P, K, and Zn solubilizers) and produce indole-acetic acid (IAA). Mechanisms of solubilization involved production of organic acids as demonstrated by HPLC. In vitro, the isolates Bg22c and Bg15d were able to antagonize the phytopathogenic bacteria Clavibacter michiganensis subsp. michiganensis, causal agent of tomato bacterial canker disease. Phenotypic and molecular identification by 16S rDNA sequencing demonstrated delineation of Bg32c and Bg15d as members of the genus Pseudomonas and Bg22c as member of the genus Serratia. The two isolates Bg22c and Bg32c were further tested either alone or in a consortium and compared to the non-P, K, and Zn solubilizing Pseudomonas strain Bg15d for their efficacy to promote tomato growth and yield. They were also compared to treatment with a conventional NPK fertilizer. Under greenhouse conditions, Pseudomonas strain Bg32c remarkably improved the growth of whole plant height, root length, shoot and root weight, number of leaves and fruits, as well as fruit fresh weight. This strain also induced stomatal conductance enhancement. The strain also improved total soluble phenolic compounds, total sugars, protein, phosphorus and phenolic compounds contents compared to the negative control. All increases were more pronounced in plants inoculated with strain Bg32c in comparison with control and strain Bg15d. The strain Bg32c could be considered a potential candidate for formulation of a biofertilizer in order to improve tomato growth.

Valorization of Moroccan Phosphate Sludge Through Isolation and Characterization of Phosphate Solubilizing Bacteria and Assessment of Their Growth Promotion Effect on Phaseolus vulgaris

Valorization of Moroccan Phosphate Sludge Through Isolation and Characterization of Phosphate Solubilizing Bacteria and Assessment of Their Growth Promotion Effect on Phaseolus vulgaris

Geochemical and mineralogical characterization of phosphogypsum and leaching tests for the prediction of the mobility of trace elements.

Phosphoric acid manufacturing generates large amounts of phosphogypsum (PG); a by-product generally disposed in the surface or evacuated in the seawater without any pretreatment. Phosphogypsum may host non-negligible amounts of valuable elements such as rare earth elements (REEs), which are critical elements on the global market. Surface disposal of PG may be a sustainable option to allow further processing in order to recover valuable elements. However, surface disposal exposes PG to atmospheric conditions (e.g., water, oxygen) which may increase their reactivity and accelerate the release rate of chemical species. This study aims to evaluate the trace element release rate from PG at atmospheric conditions. The studied PG samples were collected from a Moroccan phosphate treatment plant. The samples were characterized for their (i) chemical composition using inductively coupled plasma optical emission spectrometry (ICP-OES) for major elements and inductively coupled plasma mass spectrometry (ICP-MS) for trace elements; (ii) mineralogical composition by X-ray diffraction (XRD), scanning electron microscope equipped with energy-dispersive spectrometer (SEM-EDS), laser-induced breakdown spectroscopy (LIBS), and the mineral chemical composition was analyzed by electron probe microanalyzer (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS); and (iii) chemical species release rate using leaching tests over 24h at 25 and 60°C. Chemically, the PG samples were mainly composed of Ca (23.03-23.35 wt.%), S (17.65-17.71 wt.%), and Si (0.75-0.82 wt.%), and non-negligible amounts of trace elements: REE (344-349ppm), Cd (3.5-7.4ppm), U (9.3-27.4ppm). Mineralogically, the PGs are mainly formed by gypsum (94.2-95.9 wt.%) and quartz (1.67-1.76 wt.%). In terms of chemical species release, the PGs showed a higher reactivity at 60°C compared to room temperature with a higher release rate at the beginning of the leaching tests. Quantitatively, the PG samples released 3.57-4.11µg/L/day of REE, 3.18-17.29µg/L/day of U, and 1.67-5.49µg/L/day of Cd. Based on the leaching results, we concluded that the trace elements (e.g., U, Cd, REE) are incorporated in PG crystal lattice, which may explain their low concentrations in the leachates. Consequently, total digestion of PG matrix is required to solubilize REE.

Development of WEF-P Nexus based on product-supply chain: A case study of phosphorous fertilizer industry in Morocco

The aim of this study was to analyze various sustainability strategies for phosphate and phosphorous fertilizer production systems from the perspective of their holistic impacts on water, energy, and CO2 emissions. The study was conducted using the Water-Energy-Food (WEF) Nexus Tool 2.0, adapted to include the phosphate industry (WEF-P tool). It assesses the scenarios based on priorities identified by the Moroccan phosphate industry, such as the environmental impact of transporting phosphate rock by train and phosphate slurry by pipeline and increased desalinated water use. Results show that each scenario's sustainability can be assessed in terms of phosphate production, processes, resource (water and energy) availability, and CO2 emissions in mining and manufacturing areas. The analytical methodology of the tool is based on an integrated supply chain and life cycle assessment, which includes the production flows linking mining phosphate and manufacturing phosphorous fertilizers and their water and energy supply systems. Field surveys were used to identify the supply chain and estimate the relationships between production and resource consumption in each process. The tool is a decision-support platform that produces sustainability indices for multiple scenarios of resource allocation (water and energy) and CO2 emissions, allowing stakeholders to compare potential outcomes and formulate decisions based on their understanding of the actual trade-offs involved.

Flotation Tendency Assessment Through DOE: Case of Low-Grade Moroccan Phosphate Ore

Flotation Tendency Assessment Through DOE: Case of Low-Grade Moroccan Phosphate Ore

Rheological behaviour modelling of phosphoric acid produced from Moroccan phosphate rocks

ABSTRACT Rheological behaviour of the industrial phosphoric acid is considered as one if not the most important factor that affects the performance and profitability of phosphoric acid production in wet process facilities. This work is focused on studying and modelling the rheological behaviour of phosphoric acid produced from the Moroccan sedimentary phosphate rocks. The phosphoric acid is produced at different P2O5 concentrations, ranging from 18% P2O5 up to 54% P2O5. The rheograms experimentally elaborated under a range of temperature from 22°C to 80°C, allowed us to determine the rheological behaviours and the appropriate models for these acids. The recorded results indicate that the Herschel–Bulkley model fits all the acids perfectly under the different conditions, with regression coefficient R 2 greater than 99.3% and mean absolute error of less than 0.142. Furthermore, we managed to develop a mathematical model that describes the apparent viscosity of this acid in terms of P2O5 concentration and temperature. The model obtained presents a regression coefficient of 79.26% and a mean absolute error of 4.111.

Highly variable content of fluorapatite-hosted CO32−in the Upper Cretaceous/Paleogene phosphorites (Morocco) and implications for paleodepositional conditions

Phosphorus (P) usually occurs as microcrystalline minerals of carbonate fluorapatite (CFA) in sediments of upwelling-related areas. The Upper Cretaceous/Paleogene marine sedimentary rocks in Morocco host the world's largest economic reserves in phosphorus, which were deposited on the eastern passive margin of the central Atlantic Ocean. However, a full petrographic, mineralogical and geochemical characterization of the Moroccan phosphate minerals is yet to be determined. Here, we use optical and scanning electron microscopies, X-ray diffraction, and infrared spectroscopy, in combination with a microprobe analyzer to document carbonate (CO32−) substitutions in CFA from two distinct phosphate basins and their possible implications for paleoenvironmental conditions. The Moroccan phosphorus-rich deposits predominantly comprise porous phosphatic peloids and coated grains with a maximum size of 500 μm, which in turn consist of high-density nano- to micron-sized rod-shaped and sphere-like crystallites. Bulk and in situ analyses reveal heterogeneous CO32−content in CFA at the regional- and grain-scale. Fourier transform infrared spectra indicate that CO32−accommodates only in the phosphate site within the fluorapatite structure, as found in other natural phosphate minerals. Bulk CO32−variations in CFA between phosphate basins, ranging from 1.97 to 8.24%, are likely related to depositional conditions – and thus of supersaturation with respect to CFA – during mineral formation, transport, and redeposition. Moreover, some phosphatic coated grains have revealed alternations of CO32−-rich and CO32−-poor CFA laminae, pointing out local differences in CO32−concentrations in sediment pore waters. Interestingly, the change in shape and diminution in size of CFA crystallites caused by high content of CFA-hosted CO32−could have possibly increased the intragranular porosity, highlighting an underestimated role of CO32−on grain morphology. Considering the higher solubility of CO32−-rich CFA than fluorapatite, the application of such phosphate rocks from specific Moroccan areas as rock phosphate powders may be of deep interest for long-term soil fertilization. These results further evidence the importance of studying phosphorites for economic, environmental, and scientific interests.

Investigation of bacterial diversity using 16S rRNA sequencing and prediction of its functionalities in Moroccan phosphate mine ecosystem

Native plants in extreme environments may harbor some unique microbial communities with particular functions to sustain their growth and tolerance to harsh conditions. The aim of this study was to investigate the bacterial communities profiles in some native plants and samples of the Moroccan phosphate mine ecosystem by assessing the percentages of taxonomic identification using six hypervariable regions of the 16S rRNA. The rhizosphere of the three wild plants in the Moroccan phosphate mine is characterized by interesting bacterial diversity including Proteobacteria (62.24%, 71.15% and 65.61%), Actinobacteria (22.53%, 15.24%, 22.30%), Bacteroidetes (7.57%; 4.23%; 7.63%), and Firmicutes (5.82%; 1.17%; 2.83%). The bulk phosphate mine samples were dominated by Actinobacteria with average relative abundance of 97.73% that are different from those inferred in the rhizosphere samples of the native plants. The regions V3, V4 and V67 performed better in the taxonomic profiling at different taxonomic levels. Results indicated that both plant genotype and mainly soil conditions may be involved in the shaping of bacterial diversity. Such indication was also confirmed by the prediction of functional profiles that showed enrichment of many functions related to biological nitrogen fixation in the rhizosphere of native plants and the stress related functions in the bulk phosphate mine in comparison with the wheat rhizosphere samples.

Contrasting preservation in pycnodont fishes reveals first record of regurgitalites from the Upper Cretaceous (Maastrichtian) Moroccan phosphate deposits

Isolated jaw elements (vomers, prearticulars, premaxillae) of pycnodont fishes (Actinopterygii: Pycnodontiformes) occur frequently within the Moroccan Oulad Abdoun phosphate assemblages, although their taphonomy has remained unstudied. Recent collecting has identified two conflicting taphonomies: unetched (unaltered) and etched. Three etched jaw specimens of Phacodus punctatus Dixon, 1850 display severe pitting, corrosive marking and enamel discolouration characteristics on the bone and teeth, strongly inferring them to be regurgitalites. Regurgitalites are fossilised remains of partial or undigested skeletal elements that have been ejected from the mouth of the producer. Taphonomy of these etched specimens is attributed to partial transport through the gut of a larger vertebrate where they were partially digested before being regurgitated orally. Different macropredators in the assemblage are scored on their physiological capabilities of being the producer, with a large mosasaur like Prognathodon being the most plausible culprit. Regurgitalites are previously unreported in the formation, further adding to our understanding of the complex trophic food webs in the latest Cretaceous of Morocco. The elusive form and function of the characteristic dental ‘pits’ in the genus Phacodus are additionally investigated using thin section petrography and scanning electron microscopy (SEM).

Development and Validation of an Analytical Method for Determination of Al, Ca, Cd, Fe, Mg and P in Calcium-Rich Materials by ICP OES.

Four procedures based on closed-vessel microwave-assisted wet digestion with different oxidative reagents, including HNO3 (P1), HNO3 + H2O2 (P2), aqua regia (P3) and Lefort aqua regia (P4), for preparation of calcium (Ca)-rich materials prior to determination of total concentrations of Al, Ca, Cd, Fe, Mg and P by inductively coupled optical emission spectrometry (ICP OES) were compared. It was found that digestion with Lefort aqua regia (P4) provided the best results for all examined elements, i.e., precision of 0.30–4.4%, trueness better than 2%, recoveries of added elements between 99.5–101.9%, and limits of detection within 0.08–1.8 ng g−1. Reliability of this procedure was verified by analysis of relevant certified reference materials (CRMs), i.e., Natural Moroccan Phosphate Rock—Phosphorite (BCR-O32). Additionally, selection of appropriate analytical lines for measurements of element concentrations, linear dynamic ranges of calibration curves and matrix effects on the analyte response were extensively investigated. Finally, the selected procedure was successfully applied for routine analysis of other Ca-rich materials, i.e., CRMs such as NIST 1400 (Bone Ash), CTA-AC-1 (Apatite Concentrate Kola Peninsula) and NCS DC70308 (Carbonate Rock), and six natural samples, such as a dolomite, a phosphate rock, an enriched superphosphate fertilizer, pork bones, pork bones after incineration, and after steam gasification.

Recycling of marls from phosphate by-products to produce alkali-activated geopolymers

During open-pit mining operations of phosphates, huge volume of rocks by products are accumulated and deposited in the mine site. The aim of this paper is to investigate the use of marls as an only aluminosilicate precursor to produce alkali-activated geopolymers. Marls from Moroccan phosphate basins are composed of carbonates, quartz and clays. Raw marl was dried, grinded and calcined at 750 °C. After the heat treatment, the calcined powder was activated using a strong alkali solution, which is a mixture of sodium hydroxide and sodium silicate with a ratio of 0.5. The physical and chemical properties of raw and calcined marls were analyzed using TGA, BET, Pycnometer, particle size analyzer, XRF, XRD, FTIR and SEM. Furthermore, elaborated geopolymers were characterized after 7 and 120 days of curing at ambient temperature using XRD, XRF, TGA, SEM and the mechanical behavior was tested by measuring the compressive strength. The results showed the formation of both; C-A-S-H (Calcium aluminum silicate hydrate) and N-A-S-H (Calcium aluminum silicate hydrate) gels with a compressive strength of 38 MPa confirming that marls from phosphate extraction by-products could be used as a source for the elaboration of geopolymers.