Natural Phosphates Characterization and Evaluation of their Removal Efficiency of Methylene Blue and Methyl Orange from Aqueous Media

This study evaluated the capacity of a rock phosphate for the adsorption of organic dyes methylene blue MB and methyl orange MO in aqueous solution, in order to minimize the impact of these dyes on the environment. The physicochemical characterization of natural phosphates (NP) shows that its mineralogy is carbonate-fluorapatite, calcite and quartz, as demonstrated by X-ray diffraction. An infrared (IR) analysis completed the structural study by confirming the characteristic bands of a carbonated fluorapatite type B. The influence of adsorbent dose, pH, initial concentration and temperature of the dye solution on adsorption onto NP was studied. The experimental results show that MB is adsorbed almost entirely at an adsorbent dose of 1 g/L and at a more basic pH and that the Langmuir model describes its isotherm well. For MO, adsorption is performed at acidic pH, such that discoloration reaches 60% at pH 4 and NP adsorbent dose of 10 g/L. The maximum adsorbed amounts of MB (pH=9) and MO (pH=4) were found to be 9.54 and 1.09 mg/g, respectively. The kinetic data were analyzed to show that the pseudo-second-order model seems to be the most appropriate to describe the adsorption dynamics of both dyes on the naturel phosphate. The thermodynamic results show that the adsorption is endothermic for MB and exothermic for MO. So, rock phosphate shows a good potential as a sorbent for cationic dyes removal from wastewater.

Middle Ordovician Upwelling-Related Ironstone of North Wales: Coated Grains, Ocean Chemistry, and Biological Evolution

Middle Ordovician phosphatic ironstone of the Welsh Basin provides new insight into the paleoenvironmental significance of ironstone and Ordovician ocean chemistry. Deposition occurred in a back-arc basin along the southern margin of Avalonia as the Rheic Ocean opened to the south. Ironstone is interpreted to have accumulated as part of an aggradational parasequence on a storm-dominated shelf with coastal upwelling. This parasequence has a laminated pyritic mudstone base that grades upward into variably bioturbated mudstone and coated grain-rich, intraclastic ironstone, which is overlain in turn by cross-stratified grainstone composed entirely of coated Fe grains. A coarser clastic parasequence composed of more proximal lithofacies rests conformably above and suggests the contact between the two parasequences is a maximum flooding surface marking the onset of highstand conditions. Lithofacies associations suggest that sustained coastal upwelling created a wedge of nutrient-rich, ferruginous seawater on the middle shelf that stimulated high surface ocean productivities. Large, coated Fe grains (granule size) composed of discontinuous and concentric carbonate fluorapatite, hematite, and chamosite cortical layers record fluctuations in pore water Eh that are interpreted to have been related to changes in upwelling intensity and intermittent storm reworking of the seafloor. Results support an emerging model for Ordovician ironstone underpinned by the development of ferruginous bottom water that was periodically tapped by coastal upwelling. Expanding, semi-restricted seaways such as the Rheic Ocean were ideal locations for the ponding of this anoxic, hydrothermally enriched seawater, especially during the early Paleozoic when the deep ocean was variably and inconsistently oxygenated. The coincidence of ironstone depositional episodes with graptolite diversification events suggests that, in addition to Fe, the sustained supply of upwelling-related P may have driven the radiation of some planktonic ecosystems during the Great Ordovician Biodiversification Event. Concomitant minor extinctions of benthic trilobites occurred as these ferruginous waters impinged on the shelf.

CALCULATION OF THE VALUES OF THERMODYNAMIC FUNCTIONS OF THE SULFURIC ACID DECOMPOSITION OF THE PHOSPHORITE CONCENTRATE OF THE RIVAT DEPOSIT OF TAJIKISTAN

В статье обобщены полученные результаты лабораторных исследований и расчета значений термодинамических функций процесса сернокислотного разложения фосфоритного концентрата месторождения Риват. Установлен минералогический состав концентрата рентгенофазовым анализом. Показано, что основной составной частью концентрата является карбонат-фторапатит. В ходе исследования показано, что повышение температуры неблагополучно влияет на сернокислотное разложение концентрата и оно протекает самопроизвольно при комнатной температуре. The article summarizes the results of laboratory studies and calculation of the values of thermodynamic functions of the process of sulfuric acid decomposition of phosphorite concentrate from the Rivat deposit. The mineralogical composition of the concentrate was determined by X-ray phase analysis. It is shown that the main constituent of the concentrate is carbonate - fluorapatite. In the course of the study, it was shown that an increase in temperature adversely affects the sulfuric acid decomposition of the concentrate and it proceeds spontaneously at room temperature.

REE-Rich Turonian Phosphates in the Bohemian Cretaceous Basin, Czech Republic: Assessment as Source of Critical Elements and Implications for Future Exploration

Numerous phosphate occurrences are located in the Bohemian Cretaceous Basin (BCB) of the Czech Republic, within the Cenomanian–Turonian sequences. Small phosphate occurrences have been reported in the Upper Cenomanian, Lower Turonian, and Upper Turonian marine glauconitic siliciclasts. The phosphates are generally <1 m thick, present as phosphatized hardgrounds, nodules, coprolites, skeletal remains, phosphatized shells, peloids, sponges, and tube-fills, associated with black mudstone and other siliciclasts. Only recently the critical elements have been highlighted in these phosphates. The present study covers eight of these occurrences and provides information on petrography, mineralogy, and chemical composition of major elements, trace elements, and stable isotopes. The phosphate mineralogy is comprised of carbonate-fluorapatite, associated with quartz, glauconite, smectite, kaolinite, and pyrite. Most of the phosphates are rich in organic matter. The phosphate chemistry is dominated by P2O5, CaO, F, Na2O, SO3, and CO2. Minor amounts of SiO2, Al2O3, K2O, and MgO are found, related to quartz and alumino-silicate impurities. Evidence of fossil microbial structures is revealed. The indices derived from rare earth elements (REE) indicate phosphogenesis at various redox conditions, ranging from anoxic to oxic, whereas the carbon stable isotopes of the apatite suggest generally reducing conditions. The critical and other valuable elements found in these Mid-Cretaceous phosphates include P2O5 (18.9–26.76 wt. %), F (1.67–3.25 wt. %), REE (325–1338 ppm), Y (74–368 ppm), and U (10.4–37.9 ppm). The investigation of the Turonian phosphate occurrences show that those located at the base of the Bílá Hora Formation (earliest Turonian) are the most persistent in the southern margins of the BCB, and found in localities extending for about 200 km. They were developed at the onset of the Early Turonian global transgression and are strata-bound to the base of the Bílá Hora Formation. Future exploration for marine sedimentary phosphorites should focus on thicker and better developed deposits at the base of the Turonian sediments as the main target.

Geochemical Assessment and Mobility of Undesired Elements in the Sludge of the Phosphate Industry of Gafsa-Metlaoui Basin, (Southern Tunisia)

The raw phosphates in the Gafsa-Metlaoui phosphate basin are valorized by wet processes that are performed in the laundries of the Gafsa Phosphates Company (CPG, Gafsa, Tunisia) to reach market grades (>28% P2O5). This enrichment process allows the increase of P2O5 content by the elimination of the coarse (>2 mm) and fine (<71 µm) fractions. Mineralogical analysis has shown that all the investigated materials (raw phosphate, marketable phosphate, coarse waste, and fine waste) from the laundries of M’Dhilla-Zone L and Redeyef are both composed of carbonate fluorapatite, carbonates, quartz, gypsum, clays, and clinoptilolite. Chemical analysis shows that Cr, Cd, Zn, Pb, and U are concentrated in the fine wastes and associated with the clay–phosphate fraction. The rare earth elements are more concentrated in both raw and marketable phosphates. Drilling and sludge-water analysis, along with leaching tests conducted on the fine wastes, showed that, due to phosphate industry, cadmium, fluorine, and sulfate contributing to the pollution of water resources in the region, pollution is more conspicuous at M’Dhilla.

Rippite, K2(Nb,Ti)2(Si4O12)O(O,F), a New K-Nb-Cyclosilicate from Chuktukon Carbonatite Massif, Chadobets Upland, Krasnoyarsk Territory, Russia

Rippite K2(Nb,Ti)2(Si4O12)(O,F)2, a new K-Nb-cyclosilicate, has been discovered in calciocarbonatites from the Chuktukon massif (Chadobets upland, SW Siberian Platform, Krasnoyarsk Territory, Russia). It was found in a primary mineral assemblage, which also includes calcite, fluorcalciopyrochlore, tainiolite, fluorapatite, fluorite, Nb-rich rutile, olekminskite, K-feldspar, Fe-Mn–dolomite and quartz. Goethite, francolite (Sr-rich carbonate–fluorapatite) and psilomelane (romanèchite ± hollandite) aggregates as well as barite, monazite-(Ce), parisite-(Ce), synchysite-(Ce) and Sr-Ba-Pb-rich keno-/hydropyrochlore are related to a stage of metasomatic (hydrothermal) alteration of carbonatites. The calcite–dolomite coexistence assumes crystallization temperature near 837 °C for the primary carbonatite paragenesis. Rippite is tetragonal: P4bm, a = 8.73885(16), c = 8.1277(2) Å, V = 620.69(2) Å3, Z = 2. It is closely identical in the structure and cell parameters to synthetic K2Nb2(Si4O12)O2 (or KNbSi2O7). Similar to synthetic phase, the mineral has nonlinear properties. Some optical and physical properties for rippite are: colorless; Mohs’ hardness—4–5; cleavage—(001) very perfect, (100) perfect to distinct; density (meas.)—3.17(2) g/cm3; density (calc.)—3.198 g/cm3; optically uniaxial (+); ω = 1.737-1.739; ε = 1.747 (589 nm). The empirical formula of the holotype rippite (mean of 120 analyses) is K2(Nb1.90Ti0.09Zr0.01)[Si4O12](O1.78OH0.12F0.10). Majority of rippite prismatic crystals are weakly zoned and show Ti-poor composition K2(Nb1.93Ti0.05Zr0.02)[Si4O12](O1.93F0.07). Raman and IR spectroscopy, and SIMS data indicate very low H2O content (0.09–0.23 wt %). Some grains may contain an outermost zone, which is enriched in Ti (+Zr) and F, up to K2(Nb1.67Ti0.32Zr0.01)[Si4O12](O1.67F0.33). It strongly suggests the incorporation of (Ti,Zr) and F in the structure of rippite via the isomorphism Nb5+ + O2− → (Ti,Zr)4+ + F1−. The content of a hypothetical end-member K2Ti2[Si4O12]F2 may be up to 17 mol. %. Rippite represents a new structural type among [Si4O12]-cyclosilicates because of specific type of connection of the octahedral chains and [Si4O12]8− rings. In structural and chemical aspects it seems to be in close with the labuntsovite-supergroup minerals, namely with vuoriyarvite-(K), K2(Nb,Ti)2(Si4O12)(O,OH)2∙4H2O.

Ultrahigh-Temperature Sphalerite from Zn-Cd-Se-Rich Combustion Metamorphic Marbles, Daba Complex, Central Jordan: Paragenesis, Chemistry, and Structure

Minerals of the Zn-Cd-S-Se system that formed by moderately reduced ~800–850 °C combustion metamorphic (CM) alteration of marly sediments were found in marbles from central Jordan. Their precursor sediments contain Se- and Ni-enriched authigenic pyrite and ZnS modifications with high Cd enrichment (up to ~10 wt%) and elevated concentrations of Cu, Sb, Ag, Mo, and Pb. The marbles are composed of calcite, carbonate-fluorapatite, spurrite, and brownmillerite and characterized by high P, Zn, Cd, U, and elevated Se, Ni, V, and Mo contents. Main accessories are either Zn-bearing oxides or sphalerite, greenockite, and Ca-Fe-Ni-Cu-O-S-Se oxychalcogenides. CM alteration lead to compositional homogenization of metamorphic sphalerite, for which trace-element suites become less diverse than in the authigenic ZnS. The CM sphalerites contain up to ~14 wt% Cd and ~6.7 wt% Se but are poor in Fe (means 1.4–2.2 wt%), and bear 100–250 ppm Co, Ni, and Hg. Sphalerite (Zn,Cd,Fe)(S,O,Se)cub is a homogeneous solid solution with a unit cell smaller than in ZnScub as a result of S2− → O2− substitution (a = 5.40852(12) Å, V = 158.211(6) Å3). The amount of lattice-bound oxygen in the CM sphalerite is within the range for synthetic ZnS1−xOx crystals (0 < x ≤ 0.05) growing at 900 °C.

Flotation Studies on Low-Grade Phosphate Rock of Tarnawai, District Abbottabad, KPK Province, Pakistan

A low-grade siliceous sedimentary phosphate rock assaying 22.05% P205 was upgraded by double float (direct and reverse) technology. The rock contains collophane (carbonate fluorapatite) as the valuable phosphate mineral along with siliceous, carbonaceous and clay minerals. A process was developed which yielded a high-grade phosphate concentrate with improved recovery rate. The developed process consists of three parts. The first part includes wet grinding of ore to liberation point followed by separation of fines (slimes) by cone classifier. The finely ground deslimed ore was floated by direct anionic flotation using oleic acid collector to get rougher phosphate concentrate. It was cleaned once using additional quantity of reagents. In the second part, the fines generated during grinding operation were floated by column flotation to recover phosphate values. The cleaned concentrate and column concentrate were mixed together and washed thoroughly with hot water to remove the attached reagents. The final part comprises of cationic flotation of combined phosphate concentrate with fatty amine collector to float away quartz and silicates and to leave behind phosphate values. The grade of final phosphate concentrate was found to be 32.85% P205 with an overall recovery of 88.14%. The concentrate obtained meets the specifications of fertilizer and acid grade.