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Purpose Soil diaspore banks of bryophytes are poorly known in tundra grasslands, yet can be important for the maintenance of local bryophyte assemblages. We examined the effects of fertilization and grazing exclusion on above-ground bryophyte assemblages and soil diaspore banks in a tundra grassland. Methods We collected soil diaspore samples and recorded the cover of above-ground bryophytes from a full-factorial experiment with NPK fertilization and grazing exclusion treatments (a Nutrient Network site in NW Finland). Soil diaspore samples were germinated on trays in a greenhouse. We analyzed the compositions of diaspore bank assemblages and of above-ground assemblages and assessed their responses to the experimental treatments. Results The diaspore bank contained c. 50% of taxa found in above-ground assemblages; 26 bryophyte taxa germinated from the diaspore bank, while 40 taxa were found in the above-ground assemblages. These communities had distinct species compositions: the diaspore bank was dominated by Pohlia nutans, while above-ground assemblages were dominated by several species. NPK fertilization and grazing exclusion had negative effects on bryophyte richness and cover in above-ground assemblages, and weaker effects on these responses in the diaspore bank. Conclusion Soil diaspore banks comprise about half of the bryophyte taxa encountered in above-ground assemblages. Bryophyte diaspore banks are more buffered against nutrient enrichment and grazing exclusion than above-ground assemblages, suggesting that diaspore banks may enhance persistence and recovery of local bryophyte assemblages from environmental changes.

The flotation of diasporic bauxite is to separate diaspore (valuable mineral) from aluminosilicate minerals (gangue minerals, mainly including kaolinite, illite and pyrophyllite), and the microscopic interaction force between the two types of minerals and air bubbles determines the separation efficiency. In this paper, based on the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the van der Waals, electrostatic and hydrophobic interaction between particles of the four minerals mentioned above and air bubbles in collectorless solution were calculated first, and then diaspore and kaolinite were taken as examples to analyze the influence of various factors such as electrolyte concentration, mineral particle size, air bubble size, collector type (dodecylamine hydrochloride (DAH) and sodium oleate (NaOL)) and concentration, and pulp pH on the interactions between the particles of valuable mineral and gangue minerals and air bubbles. The results showed that the total extended DLVO interactions between the four minerals and air bubbles were repulsive in most cases in collectorless solution. The increase in electrolyte concentration reduced the interaction force or even changed the direction of the force under certain circumstances. The addition of DAH and NaOL can reduce the adhesion energy barrier of kaolinite-bubble and diaspore-bubble respectively. Each type of minerals exhibited a specific interface interaction response with air bubbles in each collector with different pH values. The research results have theoretical guiding significance for the optimization and directional control of diasporic bauxite flotation conditions.

Electrical conductivities of diaspore (α-AlOOH), δ-AlOOH, and ε-FeOOH were measured by impedance spectroscopy with a frequency range from 10–1 to 106 Hz at pressures from 8 to 20 GPa and temperatures from 500 to 1200 K, well below the dehydration temperatures of these phases at the relevant pressures. For diaspore, the relationship between electrical conductivity and reciprocal temperature can be well fitted by the Arrhenius formula:σ = σ 0 exp ⁡ [ − ( Δ E + P Δ V ) k T ] ,where σ0 is the pre-exponential factor, ∆E is the activation energy, and ∆V is activation volume of 56.0 ± 1.2 S/m, 0.55 ± 0.02 eV, and 1.68 ± 0.12 cm3/mol, respectively. The electrical conductivity of diaspore decreases with increasing pressure ranging from 8 to 12 GPa by a half order of magnitude, whereas the conductivity becomes almost constant in a pressure range above 12 GPa. δ-AlOOH and ε-FeOOH show one and two orders of magnitude higher electrical conductivity than diaspore. Electrical conductivities of δ-AlOOH and ε-FeOOH, which have isostructural CaCl2-type hydroxide structure, show the nearly identical activation enthalpies (0.38 ± 0.01, 0.33 ± 0.05 eV), which are relatively lower than that of diaspore. The dominant conduction mechanism of AlOOH phases can be regarded as proton conduction. The conductivity difference between diaspore and δ-AlOOH attributes to result in the different O1H bond lengths of each phase. The reduction of O1H bond length with increasing pressure could enhance the proton migration by reducing the potential barrier, thereby raising the electrical conductivity. Small polaron conduction may contribute to the conductivity of ε-FeOOH to generate higher conductivity than δ-AlOOH. Furthermore, hydrogen bond symmetrization will also play an important role in the conductivity discrepancy of these hydrous minerals with CaCl2-type hydroxide structure. For subducted sedimentary rocks, polymorphs of AlOOH and FeOOH are representative hydrous phases. Al-rich sediments show conductivity reduction with increasing depth until phase transformation occurs because diaspore represents negative pressure dependence of conductivity. After transformation to δ-AlOOH, the conductivity will jump up around 18 GPa. If ε-FeOOH is stable above 5 GPa in an iron-rich lithology, such as banded iron formation (BIF), a high conductivity zone with positive pressure dependence could be observed to the deep lower mantle.

In the article deals with materials of epistolary which shows position of I.Ogienka (metropolitan Ilariona) to the church question., У статті за матеріалами епістолярної спадщинивисвітлюється позиція І.Огієнка (митрополита Іларіона) у церковному питанні.

Made available in DSpace on 2022-05-01T05:29:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The soil seed bank is the primary source of regeneration in wetlands and has different assessment methods that vary according to the objective of the study. We evaluated the seed bank composition using three methods: seedlings emergence (EME), seedlings emergence with submersion trays in water (SUB) and screening and counting seeds (COU), and finally, we evaluated the applicability of COU to assess seed predation. The abundance and species richness were evaluated for two years at the end of the flood and dry seasons, in the Brazilian Pantanal. The abundance and species richness differed significantly between methods and seasons. The COU method showed the highest richness (84) and abundance (95.023) followed by EME and SUB. The SUB method reflected only the aquatic community. In the flood season, EME and COU methods showed similar species composition. There were no differences between COU and EME + SUB. The main advantage of COU method was the possibility to assess the seed predation, and we detected that Croton trinitatis had 32% of predated seeds. We consider that wetland ecosystems can be sampled by both methods COU and EME + SUB; however, the complete method that can be used for different purposes is COU, also, must be considered the infrastructure and objective of each study. Universidade Estadual Paulista Instituto de Biociências, Avenida 24 A, 1515-Jardim Bela Vista, Universidade Federal de Mato Grosso do Sul Programa de Pós-Graduação em Biotecnologia e Biodiversidade Cidade Universitária, Av. Costa e Silva-Pioneiros Universidade Estadual Paulista Instituto de Biociências, Avenida 24 A, 1515-Jardim Bela Vista

Acanthaceae is a wide spread family with usually capsular fruits, with two valves and explosive dehiscence containing two or more seeds. The morphological features of fruits and seeds are important in the identification at supra especific level, since they vary morphologically. Thus, this study aimed to characterize the morphology of the fruits and seeds of Ruellia furcata. This species is endemic to Brazil and restrict to restinga areas. The collection was carried out with the aid of a gauze type fabric. The fruits were measured in length of the sterile and fertile portion, total length, width, thickness, and retinacula height. The seeds were measured in length, width and thickness. For description, internal and external details were pointed. The fruits and seeds of R. furcata present morphological features that are commonly found in the genus however, its characteristics allow it to be positioned taxonomically and provide an understanding of its dispersion.

Работа посвящена изучению высокотемпературного гидрохимического разложения минеральных комплексов диаспор-бемитовых бокситов методом Байера с извлечением макрокомпонентов - алюминия и железа в присутствии металлических восстановителей. Проведены рентгенофазовые исследования, направленные на определение состава и структуры новых соединений в магнетизированном красном шламе. По результатам физико-химических исследований продуктов выщелачивания рекомендованы оптимальные параметры восстановительного выщелачивания бокситов СУБРа, направленные на извлечение алюминия и синтез магнетита. Выявлены закономерности влияния вида металлического восстановителя на морфологию, фазовый состав, размер частиц в красном шламе (КШ). The work is devoted to study of the high-temperature hydrochemical decomposition of mineral complexes of diaspore-bemite bauxites by the Bayer method with the extraction of macro-components-aluminum and iron in the presence of metal reducing agents. X-ray phase studies were performed to determine the composition and structure of new compounds in magnetized spent red mud. Based on the results of physical and chemical studies of leaching products, optimal parameters for reducing leaching of bauxite are recommended, aimed at extracting aluminum and synthesizing magnetite. The regularities of the influence of the type of metal reducing agent on the morphology, phase composition, and particle size in the red mud are revealed.

Interest in gemstones, which have been used as symbols of beauty, wealth and status since prehistoric times, has increased in recent years and taken an important place in many countries. The Menderes Massif is the most important area where bauxite deposits are observed in Turkey. Gemstone quality diaspore crystals are formed only in these deposits. In this study, the mineralogical, geochemical and gemological features of the diaspore formations on the south-western side of the Menderes Massif (Bafa Lake - Milas) were investigated. In field studies carried out in the study area, diaspore crystals were found in the Pınarcık region, located between Bafa Lake and Milas, within metabauxite formations together with chloritoid and muscovite, and in some places were encountered in altered zones close to the metabauxite limestone contact. As a result of petrographic analyses of the wallrock samples, grano-lepidoblastic textured “muscovite-quartzschist”, “quartz-phyllite”, “mica-quartzschist” and lepidoblastic textured “phyllite”, and nematoblastic textured “greenschist-chlorite-epidote fels” rocks were identified. To evaluate the main oxide, traces and rare earth elements on the 28 collected samples, Al2O3-SiO2-Fe2O3 triangular variation was used. According to the classification, the bauxite samples were determined to be in the "ferric bauxite" and "bauxite" areas. As a result of SEM imaging and EDS analyses performed on the samples, it was determined that the samples mainly contained O, Al and Si. K, Na, Fe, Ca and Mg were also found close to these elements. Using Raman Spectroscopy, in the light of matching values obtained from the microscope's own database, it was seen that the samples taken from Pınarcık (PI) region were diaspore, and brucite (Mg(OH)2)) and ugillite (Ca3(Ti, Al, Zr)9O20) minerals were also detected. In addition, FTIR analysis was performed on 4 samples taken from Pınarcık (PI) region and according to the results of their analysis, it was seen that the samples were compatible with standard wavelength references. It was scientifically proven that the samples collected from the region and subjected to facet processing are gemstone quality diaspore crystals with various color variations. This study will make an important contribution to understanding the properties of the gemstone quality diaspore mineral, its formation, and finding similar formations in the region.Diaspore formations in the study area are generally observed as lenticular, brecciated, cracked and pockets in crystallized limestones, bauxite and altered zones with calcite, muscovite and chloritoid minerals. Diaspores are generally observed in the form of sheet around Milas. Increased interest in diaspore crystal, especially in the last 30 years and this study will be important in terms of gaining the deserved value of diaspore crystal which is unique to our country. Since it is likely that new diaspore deposits will be found in the region, further studies are planned on this subject. The data to be obtained will be important in the determination of new diaspore deposits., Tarih öncesi çağlardan beri güzellik, zenginlik ve statü simgeleri olarak kullanılan süstaşlarına olan ilginin son yıllarda artması sonucunda bu konu ülkeler bazında önemli bir yere gelmiştir. Ülkemiz açısından değerlendirildiğinde Menderes Masifi, Türkiye boksit yataklarının yaygın ve en önemlilerinin gözlendiği alanların başında gelmektedir. Süstaşı kalitesindeki diaspor kristalleri ise sadece bu yataklar içerisinde oluşmaktadır. Yapılan bu çalışmada, Menderes Masifi’nin güneybatı kanadındaki (Bafa Gölü - Milas) diaspor oluşumlarının mineralojik, jeokimyasal ve gemolojik özellikleri araştırılmıştır. İnceleme alanında gerçekleştirilen arazi çalışmalarında diaspor kristallerine Bafa Gölü ile Milas arasında yer alan Pınarcık bölgesinde kloritoid ve muskovit ile birlikte metaboksit oluşumları içerisinde yer yer de metaboksit kireçtaşı kontağına yakın altere zonlar içerisinde rastlanmıştır. Yankayaç numunelerinde yapılan petrografik analizler sonucunda grano-lepidoblastik dokulu “muskovit-kuvarsşist”, “kuvars-fillit”, “mika-kuvarsşist” ile lepidoblastik dokulu “fillit” ve nematoblastik dokulu “yeşilşist-klorit-epidot fels” kayaç tanımlamaları yapılmıştır. Derlenen 28 adet numune üzerinde yapılan anaoksit, iz ve nadir toprak element analizleri sonuçlarını değerlendirmek için Al2O3-SiO2-Fe2O3 üçgen varyasyonu kullanılmış ve bu sınıflandırmaya göre, alınan boksit numunelerinin “ferrik boksit” ve “boksit” alanında olduğu belirlenmiştir. Numunelerde yapılan SEM görüntüleme ve EDS analizleri sonucunda numunelerin ağırlıklı olarak O, Al ve Si içerdiği, yakın çekimlerde ise bu elementlere ek olarak K, Na, Fe, Ca ve Mg’nin de varlığı tespit edilmiştir. Raman Spektroskopisi çekim sonucunda mikroskopun kendi veri tabanından alınan eşleşme değerleri ışığında Pınarcık (PI) bölgesinden alınan numunelerin diaspor olduğu görülmüş, bunun yanı sıra brusit (Mg(OH)2)) ve ugilit (Ca3(Ti, Al, Zr)9O20) olduğu tespit edilmiştir. Ayrıca Pınarcık (PI) bölgesinden alınan 4 adet numune üzerinde FTIR analizi yapılmış ve bu analiz sonuçlarına göre numunelerin standart dalga boyu referanslarına istinaden uyumlu olduğu görülmüş ve bölgeden toplanarak fasetlenen numunelerin çeşitli renk varyasyonlarına sahip süstaşı kalitesinde diaspor kristali olduğu bilimsel olarak kanıtlanmıştır. Bu çalışmanın değerli taş niteliğindeki diaspor mineralinin özelliklerinin anlaşılmasına, oluşumuna ve bölgede benzer oluşumların bulunmasına önemli katkılar sağlayacağı düşünülmektedir.İnceleme alanında diaspor oluşumları makro olarak genellikle kalsit, muskovit ve kloritoid mineralleri ile birlikte kristalize kireçtaşları, boksit ve altere zonları içerisinde merceksi, breşik, çatlak ve cepler halinde gözlenmiştir. Diasporlar Milas civarında genellikle levha halinde gözlenmiştir. Özellikle son 30 yıllık süreçte daha önce pek bilinmeyen diaspor mineraline yönelik ilginin artması ve sadece ülkemizde bulunması bu çalışma ile hak ettiği değeri kazanması açısından önemli olacaktır. Yörede yeni diaspor yataklarının bulunması muhtemel görüldüğü için bu konuda daha detaylı çalışmaların yapılması düşünülmekte ve elde edilecek veriler yeni diaspor yataklarının tespitinde önem arz edecektir.

High-iron bauxite, which is a typically unmanageable form of bauxite due to its high contents of iron and diaspore, has not been used by alumina producers. An advanced roasting technique for removing iron from high-iron bauxite, based on static pre-roasting in air and suspension roasting by hydrogen under fluidized conditions followed by magnetic separation was developed in this study. The influences of pre-roasting temperature, suspension roasting temperature, roasting time, and H2 concentration were investigated. The phase transformations of the samples were investigated using X-ray diffraction, vibrating sample magnetometry, field emission scanning electron microscopy, and Brunauer-Emmett-Teller method. After pre-roasting at a temperature of 750 °C for 30 min, diaspore (AlOOH) and goethite (FeOOH) in the raw high-iron bauxite ore were transformed into Al2O3 and Fe2O3, respectively. The optimal suspension roasting conditions were determined to be a roasting temperature of 600 °C with a H2 concentration of 25% for 4 min. The reduction sample was subjected to magnetic separation and a non-magnetic product (aluminum concentrate), with alumina recovery of 80.64% and iron removal of 85.32%, was obtained. Such a non-magnetic product could be used as a raw material for the Bayer process in the alumina production industry, while the magnetic product could be used as a supplementary material for iron ore resources.

In this study, a diaspore sample is evaluated as a dual source of alumina and potash. The thermal treatment of diaspore with sodium hydroxide yielded alumina and potash values. Microwave heating resulted in enhanced diffusion with improved precipitate purity and recovery with a significant reduction in reaction time. The thermal treatment precipitate comprises alumina purity of 48% with a recovery of 49%. The mechanical milling route yields optimal conditions of 8 h milling followed by acid leaching in 2 M HCl at 50°C for 1 h with ~ 70% and 45% potash and alumina extraction, respectively. The dissociation of the muscovite structure is crucial for high extraction values, and milling time was found to be the significant factor. The milling route at optimal conditions yielded an alumina precipitate with ~ 89% purity with a surface area of 104.6 m2/g and a sylvinite-rich solution, which can be used in fertilizer application.

Nicht zuletzt durch den Klimawandel und sich verändernde Anbaumethoden im Ackerbau breitet sich die neophytische Unkrautart Datura stramonium in Deutschland weiter aus. Als Spätkeimer profitiert die Art in landwirtschaftlichen Kulturen davon, dass dann Unkrautregulierungsmaßnahmen bereits abgeschlossen sind und sie sich dann dementsprechend gut entwickeln kann. Kenntnisse zur Samenbildung, zum Keimverhalten sowie zur Samenüberdauerung der Art sind für eine integrierte Bekämpfung notwendig. Um den Einfluss des Samenalters auf die Keimung der Samen zu untersuchen, wurde ein Keimtest mit Diasporen 16 verschiedener Jahrgänge aus dem Zeitraum 1973 bis 2019 durchgeführt. Ermittelt wurde die kumulative Keimrate und der KR50-Wert (Zeitpunkt an dem 50 % der Gesamtkeimrate erreicht sind). Parallel dazu wurde bei 10 der 16 geprüften Jahrgänge ein Triphenyltetrazoliumchlorid-Test durchgeführt, um auf diese Weise die Keimfähigkeit der Populationen im Labortest mit der generellen Lebensfähigkeit der Diasporen zu vergleichen. Die Ergebnisse dokumentieren eine lange Überlebensdauer der Samen, was bei der Bekämpfung der Art berücksichtigt werden muss., Not least due to climate change and changing cultivation methods in agriculture, the neophytic weed specie Datura stramonium continues to spread in Germany. As a late germinating weed, the specie benefits in agricultural crops from the fact that weed control measures have often already been completed and it can then develop accordingly well. Knowledge of seed formation, germination behaviour and seed persistence of the species is necessary for integrated control. To investigate the influence of seed age on seed germination, a germination test was carried out with diaspores of 16 different vintages from the period 1973 to 2019. The cumulative germination rate and the KR50 value (time at which 50% of the total germination rate is reached) were determined. In parallel, a triphenyltetrazolium chloride test was carried out on 10 of the 16 vintages tested in order to compare the germination capacity of the populations in the laboratory test with the general viability of the diaspores. The results document a long survival time of the seeds, which need be taken into account when controlling the species., Tagungsband: 30. Deutsche Arbeitsbesprechung über Fragen der Unkrautbiologie und -bekämpfung, p. 173

The karst bauxites of the Parnassos-Ghiona Unit (Greece) are hosted within Upper Jurassic to Late Cretaceous carbonate rocks. Three bauxite horizons are intercalated within shallow water limestones. They are named B1, B2 and B3 from bottom to top. In this study we present the characteristics of the B3 horizon (Cenomanian-Turonian) sampled in Agia Anna, Variani and Shila 1 underground mines. The bauxite ore has a prevailing oolitic texture. Diaspore, boehmite, hematite and goethite are the major mineral components of the analyzed samples. Kaolinite, rutile and anatase are common minor phases. Pyrite occurs in a small number of samples. Ilmenite, rutile, chromite, zircon, baddeleyite and serpentine are common detrital minerals. Authigenic minor minerals are mostly represented by REE-phosphates, barite, and gypsum. The presence of pyrite and diaspore suggests that after a first stage of additional in situ weathering and bauxitization, the deposits were affected by early diagenetic reducing conditions (allowing the formation of pyrite) and significant diagenesis, resulting in diaspore formation. This three-stages genesis is reflected in complex correlations between major, minor and trace elements. The occurrence of detrital chromite and serpentine in the bauxite reflects mafic parental rocks. The mafic component likely originated from the ophiolite suites exposed in the vicinity of the Parnassos-Ghiona bauxites.

In single crystals of orthorhombic alpha-AlOOH, known also as mineral diaspore, χ(3)-nonlinear lasing by stimulated Raman scattering (SRS) and Raman-induced four-wave mixing (RFWM) is investigated. Picosecond pumping at 1.064 µm wavelength produces a broadband Stokes and anti-Stokes frequency comb with up to 25 SRS- and RFWM-generated emission lines. All observed Stokes and anti-Stokes lasing components in the visible and near-IR are identified and attributed to a single SRS-promoting vibration mode with ωSRS ≈ 445 cm−1. The first Stokes steady-state Raman gain coefficient in the visible spectral range is estimated to a value not less than 0.36 cm GW−1.

The thermoelasticity and stability of diaspore (α-AlOOH, Al1.002Fe0.003OOH) were investigated in this study by in situ synchronous X-ray diffraction (XRD) and Raman spectroscopy methods at high pressure and high temperature conditions. The results indicate that diaspore is stable within the pressure and temperature (P-T) region examined in this study. With increasing pressure, the Raman peaks move toward the high wave number direction, the intensity of the Raman peaks increases, and the vibration mode of diaspore changes linearly. Pressure-volume data from in situ high-pressure XRD experiments were fitted by the third-order Birch-Murnaghan equation of state (EoS) with the zero-pressure unit-cell volume V0 = 118.15 (4) Å3, the zero-pressure bulk modulus KV0 = 153 (2) GPa, and its pressure derivative K'V0 = 2.4 (3). When K'V0 was fixed at 4, the obtained KV0 = 143 (1) GPa. The axial compressional behavior of diaspore was also fitted with a linearized third-order Birch-Murnaghan EoS, showing slight compression anisotropy with Ka0 = 137 (5) GPa, Kb0 = 169 (7) GPa and Kc0 = 178 (6) GPa. In addition, the temperature-volume data from in situ high-temperature XRD experiments were fitted by Fei’s thermal equation with the thermal expansion coefficients αV = 2.7 (2) × 10–5 K−1, αa = 1.13 (9) × 10–5 K−1, αb = 0.77 (5) × 10–5 K−1, and αc = 0.85 (9) × 10–5 K−1 for diaspore, which shows that diaspore exhibits slightly anisotropic thermal expansion. Furthermore, in situ synchrotron-based single-crystal XRD under simultaneously high P-T conditions indicates that the P-T stability of diaspore is up to ∼10.9 GPa and 700 K. Combined with previous results, we infer that diaspore can be subducted to ∼390 km under cold subduction conditions based on existing experimental data and is a good candidate for transporting water to the deep Earth.

Seed dispersal plays critical roles in determining species survival and community structures. Since the dispersal is biologically under maternal control, it is hypothesized that intraspecific variation of dispersal potential and associated traits of seeds (diaspores) should be influenced by maternal habitat quality. We tested this hypothesis by examining the effects of maternal environmental light condition on morphological traits and descending performance of nearly 1800 wind-dispersed samaras collected from maple species Acer palmatum. Results showed that samaras produced by trees from shaded microhabitats had greater dispersal potential, in terms of slower terminal velocity of descent, than those produced in open microhabitats. This advantage was largely attributed to morphological plasticity. On average, samaras produced in shaded microhabitats, as compared to those produced in open habitats, had lower wing loading by only reducing weight but not area. In allometric details, in the large size range, samaras from shaded microhabitats had larger areas than those from open microhabitats, in the small size range, samaras from shaded microhabitats had wider wings. These findings suggest that greater dispersal potential of samaras in response to stressful maternal light environment reflected an active maternal control through the morphological allometry of samaras.

Molecular force plays an important role in the interaction between collector and minerals, which directly reflects the intrinsic reason for the selectivity and collection of the collector to minerals. In this work, the interaction forces between sodium oleate (NaOL) and minerals (kaolinite and diaspore) were directly characterized by atomic force microscopy (AFM) combined with EDLVO theory. The results show that after interacting with NaOL, the zeta potentials of kaolinite and diaspore were more negative, and the hydrophobicity of minerals increased. EDLVO calculation results indicate that electrostatic repulsion dominated the interaction forces between mineral particles, and the van der Waals interaction energy, electrostatic interaction energy, and hydrophobic interaction energy increased after NaOL treatment. AFM measurements show that the NaOL collector increased the attraction force of diaspore-diaspore and kaolinite-kaolinite particles, and the increase in attraction force for diaspore-diaspore particles was larger than in kaolinite particles, which was consistent with the EDLVO results. The adhesion force between the NaOL collector and the diaspore surface was larger than in kaolinite, confirming the fact that NaOL had better collection and selectivity for diaspore than kaolinite. This work improves understanding of the interaction mechanisms between NaOL collector, diaspore, and kaolinite minerals.

Corundum primary deposits in Greece occur in four locations: Paranesti in Drama and Gorgona in Xanthi, both belonging to the wider Rhodope Massif, as well as, Ikaria island and Kinidaros in Naxos island, both belonging to Attic-Cycladic Massif. Eight samples were examined with spectroscopic methods (FTIR, UV-Vis, EDXRF) in order to better characterize these four primary deposits: two pink sapphires from Paranesti, a pink and a blue sapphire from Gorgona, two blue sapphires from Ikaria and three blue sapphires from Kinidaros. Under the microscope, all samples present characteristics linked to post-crystallization deformation, decreasing their gem quality. The FTIR absorption spectra of all samples present in different relative intensities, bands of boehmite, diaspore, goethite, mica and/or chlorite inclusions and CO2 in fluid inclusions. Boehmite and diaspore inclusions are most likely epigenetic. In the UV-Vis spectra, the pink color of the samples is linked with Cr3+ absorptions and the blue color with absorptions due to Fe2+-Ti4+ intervalence charge transfer. EDXRF analyses in the studied samples show relatively high titanium and iron concentrations that are related with mineral inclusions. Gallium is slightly variable in samples from different regions, also, different colored samples from Gorgona present diverse gallium content.

La divisione dei saperi in discipline-disciplinate, così come si è costituita attraverso la divissione del lavoro dell’era industriale, articolata in facoltà, dipartimenti, curricula ecc., si dissolve nell’aria di pixel. La costellazione concettuale del saggio si basa sull’indisciplina metodologica. La ricerca in campo materiale e immateriale, analogico e digitale mescola concetti chiave: sincretismi culturali, polifonie narrative, soggettività onnipresente, diaspore inquiete, meta-feticismi. L’etnografo si muove dislocato, attento ai minimi dettagli nei fluenti panorami alterati; così impara ad osservarsi durante la ricerca. Nel corso del metodo riflessivo, il ricercatore si scopre parte della ricerca e l’incongruenza dialettica soggetto/oggetto. A divisão do conhecimento em disciplinas-disciplinadas, tal como foi estabelecida pela divisão do trabalho da era industrial, dividida em faculdades, departamentos, currículos etc., se dissolve no ar de pixels. A constelação conceitual do ensaio é baseada na indisciplina metodológica. A pesquisa no campo material e imaterial, analógico e digital mistura conceitos-chave: sincretismos culturais, polifonias narrativas, subjetividade ubíqua, diásporas inquietas, meta-fetichismos. O etnógrafo se move deslocado, atento aos menores detalhes nas paisagens que fluem; assim, aprende a se observar durante a pesquisa. No processo do método reflexivo, o pesquisador se descobre parte da pesquisa e a inconsistência dialética sujeito/objeto. The division of knowledge into disciplined-disciplines, as established by the division of labor in the industrial age, divided into faculties, departments, curricula, etc., dissolves in the air of pixels. The conceptual constellation studied is based on methodological indiscipline. Research in the material and immaterial, analog and digital fields mixes key concepts: cultural syncretisms, narrative polyphonies, ubiquitous subjectivity, restless diasporas, meta-fetishisms. The ethnographer moves around, attentive to the smallest details in the flowing landscapes; thus, learning to observe itself during the research. In the process of the reflective method, the researcher discovers part of the research and the subject/object dialectical inconsistency.

Milling corundum nanoparticles High-purity corundum (α-Al 2 O 3 ) nanoparticles could enable applications such as more stable catalyst supports or precursors for high-strength ceramics. Milling of corundum only produces micrometer-scale particles, and direct synthesis from other aluminum oxides that would be likely starting materials, such as γ-Al 2 O 3 , fails because of the high activation barrier for converting the lattice structure of these cubic close-packed oxides. Amrute et al. show that ball milling of boehmite, γ-AlOOH, created ∼13-nanometer-diameter corundum nanoparticles of high purity through a mechanically induced dehydration reaction and by the effect of milling impacts on the surface energy of the particles. Science , this issue p. 485

Plant dispersal mechanisms rely on anatomical and morphological adaptations for the use of physical or biological dispersal vectors. Recently, studies of interactions between the dispersal unit and physical environment have uncovered fluid dynamic mechanisms of seed flight, protective measures against fire, and release mechanisms of explosive dispersers. Although environmental conditions generally dictate dispersal distances, plants are not purely passive players in these processes. Evidence suggests that some plants may enact informed dispersal, where dispersal-related traits are modified according to the environment. This can occur via developmental regulation, but also on shorter timescales via structural remodelling in relation to water availability and temperature. Linking interactions between dispersal mechanisms and environmental conditions will be essential to fully understand population dynamics and distributions.

With the rapid development of China's aluminum industry and the depletion of high-quality bauxite resources, technology for the clean and efficient utilization of non-traditional bauxite resources has become the focus in related fields. The alumina-to-silica mass ratio of low-grade high-iron sedimentary bauxite from Yunnan, China is 2.65; diaspore and goethite coexist in this bauxite. To enhance the utilization efficiency of bauxite, the hydrometallurgy process of the “calcification-carbonation method” (CCM) had been proposed, and the research results indicated that the addition of lime promoted the transformation of the goethite phase significantly, and the replacement ratio of Al in goethite decreased from 16.02% to 12.15% for a calcification temperature of 200 °C. The Gibbs free energy for the generation of Ca3(Fe0.87Al0.13)2(SiO4)1.65(OH)5.4 decreases gradually with an increase in the reaction temperature, and an excessive decomposition temperature in the carbonization process is not conducive to the decomposition of the garnet phase. The calcification reaction is controlled by diffusion and chemical reaction, and the activation energy in the temperature range from 220 to 260 °C (determined using a high-pressure DSC) is 38.4 kJ/mol; it is 19.6 kJ/mol in the temperature range from 260,276.8 °C. Fe completely dissociates from hydrogarnet upon carbonization, and the main silica-containing phases in the digested slag are unreacted hydrogrossular and calcium silicate. The CCM enhanced the recovery ratios of Al2O3 and Fe from high-iron diasporic bauxite by ~20% and 10%, respectively, compared with those in the Bayer process, and the Na content decreased to lower than 0.1% in the CCM slag; this can be used as cement raw material directly. Thus, the clean and efficient utilization of low-grade high-iron sedimentary bauxite was achieved using the CCM.

Low-grade diasporic bauxite in central Guizhou Province, China, contains Li that can be exploited and utilized. In this paper, several methods were used to determine the main chemical components in low-grade diasporic bauxite, which were Al2O3, SiO2 and TiO2, and the main minerals were diaspore, boehmite, kaolinite, illite and anatase. Independent Li minerals were not found. According to chemical phase analysis, Al mainly exists in diaspore, boehmite, kaolinite, and illite, while Li mainly exists in clay minerals along with a small amount in diaspore and boehmite. Li is inferred to be mainly ionically connected to the external hydroxyl group of kaolinite and the interlayer of illite; and partially occupies the site of missing hydrion in the diaspore and boehmite crystals.

Kaolinite is one of the main associated minerals (gangue) in the processing of diasporic bauxites. Sulfuric acid pretreatment has been shown to have an improving effect on kaolinite-diaspore flotation separation, but the mechanism underpinning this effect is not well known. This study reports the surface chemistry of acid-treated kaolinite and diaspore in the presence of flotation reagents (sodium hexametaphosphate (SHMP) as a depressant and dodecylamine hydrochloride (DAH) as a collector) using X-ray photoelectron spectroscopy (XPS) analysis and zeta potential determinations. Quantitative XPS analysis revealed that the Al/Si atomic ratio on the kaolinite surface was reduced after the acid treatment. Compared with natural kaolinite, acid-treated kaolinite showed weakened adsorption properties for SHMP. Consequently, there was an enhanced DAH adsorption on the acid-treated kaolinite. High-resolution XPS analysis showed formations of “unsaturated Al” components on the diaspore surface after the acid treatment, which were ready to interact with phosphite groups of SHMP to depress diaspore in kaolinite flotation. Zeta potential studies also confirmed extended SHMP adsorption on acid-treated diaspore in comparison with the natural mineral. These findings form a firm knowledge for interpreting the application of kaolinite and diaspore in many adsorption studies, including the efficient separation between kaolinite and diaspore.

We analysed the surface anisotropy of Taraxacum officinale cypselae, without their pappus, microscopically and biomechanically. A scanning electron microscope was used for visual analyses. We then measured the angle, at which cypselae start to slide from tilted substrates of different roughness and compared cypselae sliding along their structure with those sliding against their structure. Finally, forces during pushing cypselae into the soil and pulling them out were measured with a force transducer moved by a micromanipulator. The cypselae had a ribbed surface pattern with apically pointing spines, plenty of scale-like structures and small protuberances. In general, the angle at which cypselae started to slide-off from an inclined surface increased with increasing roughness of the inclined surface, but this did not hold for cypselae sliding along their structure and for the glass surface. The angles at which the cypselae started to slide were on all but the glass surface significantly higher for cypselae sliding against the structure compared to cypselae sliding along the structure. Pull-out forces were higher when pulling cypselae out of the soil against their structure compared to pulling along their structure. Anisotropic structures hinder cypselae from being drawn from soil by wind.

The Arbanos bauxite deposit is located in the Iran-Himalayan karst-type bauxite belt and about 25 km northeast of Bukan city, northwestern Iran. The bauxite ores occur as layers and lenses along the contact of the carbonate (limestone and dolomite with intercalations of shale) of the Ruteh Formation (Upper Permian) and dolomite of the Elika Formation (Triassic). Hematite, kaolinite, and diaspore are the major rock-forming minerals in the ores, accompanied by lesser amounts of chlorite, montmorillonite, chamosite, siderite, goethite, boehmite, calcite, rutile, anatase, zircon, and quartz. Mass balance calculations indicate that the distribution of Ni, V, and Cr is controlled by the iron oxyhydroxides, whereas the distribution of Ba and Sr is controlled by kaolinite. The bivariate diagrams of the Sm/Nd versus the conservative elemental indices such as TiO2/Al2O3, Al2O3/Hf, Al2O3/Nb, and Nb/Ta reveal that the shale of the Ruteh Formation is the most plausible parent rock for the bauxite ores. The factor analysis method indicates that the paleo-environmental changes, soil redox state, and water activity in the pedogenic environments played a fundamental role in distribution of the major, minor, and trace elements.

The Semirom karst type clayey bauxite is located in the Zagros zone, a part of the Irano-Himalayan belt, and occurs between the Sarvak and Ilam Formations. The Albian to Cenomanian limestone bedrock of the Sarvak Fm is a part of a platform ramp environment including clay bearing components. Diaspore, boehmite, kaolinite, and hematite are the major ore-forming minerals. Elemental mobility determinations reveal that Th and the critical metals Co, Ni, and Cr are enriched in the bauxitic horizons relatively to the Upper Continental Crust. Further, only one sample is outlier for more than one critical metal (Cr, Co, Ni, and Ga) likely recording a specific event during bauxitization. The outlier is enriched in Ni, Co, Ga, and Th, is depleted in Cr, and shows a large positive Ce anomaly (Ce/Ce∗ = 3.03). The outlier may record an event characterized by more acidic and oxidizing conditions and may have a regional relevance. R-mode factor analysis suggests that Cr and Co are likely adsorbed onto oxy-hydroxides probably in horizons also concentrating secondary phosphates hosting HREE and Th. Nickel is instead likely adsorbed onto titanium oxides which concentrate in the pool of highly insoluble detrital phases also including zircon whereas diaspore and boehmite are important in controlling both Ga and LREE. The low contents of Ni and Cr associated to the Semirom clayey bauxite exclude a provenance from a mafic protolith. Further, most of the samples have Eu/Eu∗ values close to those observed in the Sarvak Fm marly limestone, suggesting that the clayey component within the underlying limestone acted as protolith. The oxygen and hydrogen isotopic composition of the kaolinite-rich separates from the Semirom deposit indicates temperature never lower than 30 °C, supporting the idea of the Zagros basin close to the equator during the Cenomanian-Turonian under a warm and humid tropical climate with heavy rainfall.

The Poci bauxite deposits in western Henan, China, are hosted in the lower member of Upper Carboniferous Benxi Formation, unconformably overlying upon the paleokarst surface of the Ordovician Majiagou Formation. The orebodies comprise a high-grade bauxite horizon (characterized by the association of diaspore-illite-anatase) and a basal iron-rich horizon (diaspore-goethite-hematite-illite-anatase), sandwiched between the overlying clayey layer (illite-diaspore-goethite-anatase) and the underlying clayey layer (illite-diaspore-microcline-goethite). Geochemical investigations reveal that Rb, Cs, Ba, Cu, Zn are depleted, while B, Ga, Bi, V, Sc, Zr, Hf, Nb, Ta, W, U and Th are enriched in bauxite horizons. B is highly enriched in bauxite ores and clays (contents 176–1061 ppm) and positively associated with SiO2, indicating B is mainly hosted in clay components, e.g. dominantly illite, which are considered a mixture of authigenic minerals transformed from kaolinites during diagenesis and unaltered detrital minerals. Mass change calculations reveal that Hf, Zr, Nb, Ta, U, Th, Sc, Cr, and Ga are stable relative to TiO2 during the bauxitization process, indicating these elements are mainly associated with anatase and diaspore. The bauxite horizons and the underlying clays are more enriched in total REE contents (ΣREEs) and display more intense LREE/HREE fractionation than the overlying clays. Provenance analysis shows that parental materials of Poci bauxites were mainly derived from felsic-dominated igneous rocks along the southern margins of the North China Craton, with minor contribution from siliciclastic sedimentary rocks and argillaceous components of underlying carbonates. A conceptual model is proposed for the formation and evolution of Poci bauxites. Uplift caused by the North Qinling orogenesis along the southwestern margin of NCC led to the formation of karstic topography, allowing aluminum-rich source materials to be transported to the low karst plain and transformed into incipient bauxites under hot and humid tropical conditions. When the platform was submerged, Fe2+ ions were released from Fe/Al oxides/hydroxides under the reducing conditions associated with bacteria activity in an organic-rich environment, and redeposited as pyrites and siderites, generating a high-grade bauxite horizon and an iron-rich bauxite horizon. This marine modification resulted in further aluminum enrichment of bauxite ores.

Propyl gallate (propyl 3, 4, 5-trihydroxybenzoate; PG) was introduced as a new type of collector for diasporic bauxite flotation. The flotation performance of PG for diaspore and kaolinite was evaluated by comparing PG with sodium oleate (NaOl) as a typical collector through micro flotation tests. The results indicated that PG had higher collection ability for diaspore than for kaolinite at 15 mg/L and pH 7–9. Compared with NaOl, PG also exhibited higher selectivity for diaspore against kaolinite. Analyses of zeta potentials, adsorption amount, Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectra (XPS) revealed that PG adsorbed onto diaspore surfaces through chemical adsorption and hydrogen bonding, whereas PG hardly adsorbed onto kaolinite surfaces. Specifically, PG chelated with Al atoms on the diaspore surfaces by forming five-member rings through its ortho oxygens. These findings indicated that PG could be adopted as a novel collector for diaspore flotation and the activated phenolic hydroxyl groups also offered new insights for the development of flotation collectors.

This lecture text presents features of the fascinating mineral corundum and its gem varieties, ruby and sapphire. The geologic occurrences of its varieties and the best-known world localities are presented in detail. The mineralogy and crystallography of corundum, as well as its occurrence forms, are discussed. The origin of their colour varieties and their usage are described, in addition to their important physical characteristics. Applications in the watch and laser industries and as an abrasive material, among others, are included. The ruby variety from dolomite marble in North Macedonia exhibits the unique optical phenomenon known as diasporescence–the inclusion of diaspore crystals in the corundum matrix. This phenomenon affects the parting of corundum crystals and influences their colour, density and hardness. Therefore, special attention is paid here to morphological and physical characteristics of the Macedonian gem corundum.

Submitted by Jeferson Carlos da Veiga Rodrigues (jveigar@unisinos.br) on 2021-03-08T16:47:26Z No. of bitstreams: 1 GIliandro Goncalves Silva_.pdf: 3174753 bytes, checksum: e77e89377becb8298e2f9839426a24a6 (MD5) Made available in DSpace on 2021-03-08T16:47:26Z (GMT). No. of bitstreams: 1 GIliandro Goncalves Silva_.pdf: 3174753 bytes, checksum: e77e89377becb8298e2f9839426a24a6 (MD5) Previous issue date: 2121-02-19 CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior A ampla distribuição geográfica de algumas espécies sesseis ou com baixa capacidade de auto locomoção que habitam sistemas aquáticos continentais isolados sempre foi um enigma ecológico. A dispersão passiva através de um vetor de transporte é a principal explicação para entender a dispersão entre áreas úmidas e neste processo as aves aquáticas desempenham um papel de destaque. Ao contrário de outras regiões biogeográficas, na região Neotropical os estudos sobre a dispersão promovida por aves aquáticas são escassos. Nesta tese são apresentados estudos abordando a importância das aves aquáticas para a dispersão de plantas, invertebrados e peixes na região neotropical. Foram realizadas coletas de dados em campo e experimentos ex situ. Em relação aos diásporos de plantas, foi possível identificar que a dispersão depende da interação entre a espécie de ave e a estação do ano. Ainda sobre plantas, comprovou-se que uma angiosperma inteira (Wolffia columbiana) sobrevive à passagem pelo trato digestivo de cisnes e marrecas, representando um meio dispersão até então não conhecido para plantas. Em relação aos invertebrados, a dispersão promovida por aves está associada à espécie de ave, não sendo encontrado efeito da estação ou do peso das amostras. Por último, foi comprovado que ovos de peixes-anuais (Rivulidae) continuam seu desenvolvimento e eclodem mesmo após serem ingeridos e expelidos por uma ave, representando uma forma de dispersão desconhecida para vertebrados. Nesta tese é demonstrado que a endozoocoria promovida por aves é fundamental para compreender a dinâmica de dispersão de organismos aquáticos em áreas úmidas neotropicais. The wide distribution of freshwater species sessile or with low locomotion capacity inhabitants isolated continental aquatic systems has always been an ecological puzzle. Passive dispersal through a transport vector is the main explanation for understanding the dispersal among these wetlands, and waterbirds play an important role in this process. In the Neotropical region, studies on the dispersal promoted by waterbird are scarce. In this thesis, studies are presented addressing the importance of waterbird for the dispersal of plants, invertebrates and fish in the neotropical region. Field data collections and ex situ experiments were carried out. Regarding plant diaspores, it was possible to identify the dispersal depends on the interaction between the bird species and the season. Still on plants, it was proved that an entire angiosperm (Wolffia columbiana) survives the passage through the digestive tract of two species of Anatidae, representing a dispersal mode previously unknown. On invertebrates, the dispersal promoted by birds is associated with the bird species, with no effect of the season or sample weight. Finally, it has been proven that killifish (Rivulidae) eggs continue their development and hatch even after being ingested and expelled by a bird, representing an unknown dispersal means to a vertebrate. In this thesis, it is demonstrated that the endozoochory promoted by waterbirds is fundamental to understand the dispersal dynamics of aquatic organisms in neotropical wetlands.

Silicate minerals (such as kaolinite) are common gangues in diaspore type bauxite, which are easy to be mudding and adhered to the diaspore surface in the flotation system, thus affecting the flotation recovery. Fluid flow enhancement with agitation is one of the more effective ways to improve the dispersion of aluminum–silicate minerals and reduce flotation entrainment. Whether high shear agitation could also change the surface properties of mineral particles was investigated through dispersion experiment of diaspore and kaolinite slurry in this paper. The results show that a high turbulence environment was beneficial to enhance the mass transfer of reagents and change the surface properties of mineral particles. With the increase of stirring strength, the contact angle and zeta potential of two minerals were increased at the same dispersant dosage, and the dispersion of two minerals was further improved.

International audience; The dissolution rates of Green Monster Mine epidote at temperatures of 25, 100 and 200 °C, and over the pH range 2–11, were determined from far-from equilibrium experiments performed in both batch and mixed-flow reactors. Epidote dissolution rates based on silicon release decrease with increasing pH to pH ∼ 8, then increase in response to further pH increases. The apparent relative metal release rates from epidote at chemical steady-state were found to vary with pH and temperature, in part due to secondary phase formation. At 100 and 200 °C, Al is preferentially released relative to Si at alkaline pH, but preferentially retained by the solid at 2

Using an effective collector is often the key to improving the flotation recovery of valuable mineral concentrates. China’s diaspore-type bauxite is a refractory ore, since silicate minerals, such as kaolinite, are often closely embedded with diaspore. Propyl gallate (PG) is an effective and novel collector of diaspore. Detailed flotation behaviors of diaspore and kaolinite with PG and traditional collector sodium oleate (NaOL) were investigated in this work. The effects of stirring speed, aeration volume, slurry pH, and collector dosage on the flotation recovery of the two minerals were discussed. The results show that, compared with the traditional collector NaOL, PG had better collection and selectivity for diaspore since the collector PG could increase the hydrophobic difference of diaspore and kaolinite than NaOL. Under the optimal flotation conditions: 1600 r/min of stirring speed, 60 mL/min of aeration volume, 60 mg/L of PG dosage, and slurry pH 9, the flotation recovery of diaspore and kaolinite are 88.5% and 23.4%, respectively.

© Copyright © 2020 Cavanagh, Morgan and Godfree. Seed dispersal is a vital part of a plant’s life cycle that enables progeny to reach new sites suitable for burial and establishment. Awns are characteristic of many grass species and enable diaspores to self-disperse. Little is known, however, about the role of different awn morphologies in dispersal or burial. The objective of this study was to investigate the influence of awn morphology on diaspore surface dispersal and burial among representative Australian Poaceae. Surface dispersal, burial and microsite selectivity of diaspores were compared across 30 grass species and ten awn morphological types using laboratory and natural simulation experiments. The presence of an awn significantly facilitated surface dispersal and burial of diaspores, with awn length and hygroscopic activity being positively related to both surface dispersal and burial depth. Geniculate (once-bent) and bigeniculate (twice-bent) awns were the most efficient at surface dispersal. Burial efficiency, however, was influenced by microsite conditions; a surface obstruction increased burial for almost all awn types, while falcate (curved)-awned species were effective at burying without such objects. This study indicates that awn morphologies likely play different functional roles in the success of Australian grass progeny.

Surface pretreatment on minerals prior to flotation was proved to increase the selectivity of separation process. Organic acid pretreatment of low-grade diasporic-bauxite was conducted, and the effects of oxalic acid on bauxite flotation were investigated in this work. The oxalic acid pretreatment mechanisms were studied by adsorption measurements, zeta potential testing, XPS analysis, and ICP analysis. The flotation results showed that the oxalic acid treatment could significantly improve Al2O3 recovery from 75.39% to 81.88% and decrease SiO2 recovery from 53.26% to 47.30%. The adsorption capacity of diaspore for sodium oleate (NaOL) increased by 8.50%, while that of kaolinite decreased by 11.72%. XPS analysis revealed that oxalic acid treatment improved the relative contents of unsaturated Al at diaspore surface beneficial to the adsorption of NaOL. While the relative contents of Al at kaolinite surface was decreased due to the Al dissolution revealed by ICP results. Zeta potential analysis indicated that oxalic acid changed the surface property of minerals favorable for the selective adsorption of NaOL on diaspore surface rather than kaolinite surface. These findings provided a promising direction for surface pretreatment of low-grade bauxite using oxalic acid for the improvement of the flotation desilication.

The pyrophyllite-rich ferruginous (PRF) bauxites in northwestern Iran from the Irano–Himalayan karst belt are deposited on the paleokarst of the middle Permian carbonate sequence of the Ruteh Formation. They were selected from the lowermost part of weathered profiles from 9 karst bauxite deposits, belonging to different stratigraphic positions. These bauxite deposits share similar mineralogical and geochemical features. Powder-XRD analyses show that the bauxites consist of diaspore, hematite, and pyrophyllite, with lesser amounts of goethite, rutile, anatase, illite, and clinochlore. Among minor constituents, single crystals, such as monazite, florencite, and zircon, were detected by SEM–EDS analyses. The positive Ce anomaly of the PRF bauxites (1.0–2.2), the relevant depletion of mobile elements, and values of the La/Y ratio (1.0–3.2) indicate that the PRF bauxites formed in a well-drained environment, characterized by a prevailing alkaline environment, promoting the stability of Fe (oxyhydr)oxides. The mineralogical composition of the PRF bauxites affects the distribution of trace elements: the redox-sensitive trace elements Ni, Cr, Co, Ce, U, and V are probably controlled by Fe (oxyhydr)oxides, whereas most of high field strength elements, such as critical metals Hf and Nb, are hosted in the pool of resistant minerals. Gallium co-varies with Al2O3, indicating this critical trace metal is distributed by diaspore. Phosphate-bearing minerals probably played an efficient role in concentrating light (LREE: La Sm) and heavy (HREE: Eu Lu plus Y) rare earth elements during the generation of the PRF bauxites. The mineralogical control on the distribution of LREE and HREE, coupled with the preferential complexation of HREE in an alkaline environment clearly affect the (La/Yb)ch and (LREE/HREE)ch fractionation ratios. Based on the Th Zr and TiO2–Zr binary diagrams, the concentration of trace elements Zr, Cr, and Ga, bivariate plots of Ta (ppm) versus Al2O3 (wt%) and TiO2 (wt%), and the discriminant function 3 against discriminant function 4 variation diagram, basalt rocks within carbonate bedrocks of the Ruteh Formation have considered to be a probable provenance for the PRF bauxites, similar to some bauxite deposits from the Mediterranean-type karst bauxite belt of different ages, especially northern and northwestern Iran and western India.

Aiming at the effective utilization of the abundant high-alumina iron ores with low iron grade, the influence of alumina concentration and type on high-temperature characteristics was clarified based on the analyses of eight typical iron ores. The results indicate that high-temperature characteristics of iron ores in various alumina types are different. Higher Al2O3 concentration is deleterious to assimilability and liquid phase fluidity, but the influence extent of each alumina type is substantially different. Kaolinite (Al2O3&middot, 2SiO2&middot, 2H2O) contributes to correspondingly better assimilability, followed by hercynite (Fe(Fe, Al)2O4), gibbsite (Al(OH)3), diaspore (AlO(OH)), and free state alumina (Al2O3) in turn. Diaspore promotes relatively higher liquid phase fluidity, followed by kaolinite, free state alumina, and hercynite, while gibbsite possesses the maximum adverse impact. Kaolinite and hercynite are more beneficial to form dendritic or acicular silico-ferrite of calcium and alumina (SFCA) with high strength due to the better reactivity, and gibbsite and diaspore lead to more formation of relatively lower strength lamellar or tabular SFCA, while free state alumina is preferable to form disseminated SCFA with rather poorer strength. Kaolinite and hercynite are the most desirable alumina types for sintering rather than free state alumina.

The major type of bauxite in China is low-grade diasporic bauxite, which is mainly composed of diaspore and kaolinite. Separation of silicate minerals by flotation technology can meet the requirements of Bayer process, but Na+, K+ and Cl− deriving from mineral dissolution and entrainment in flotation water will inevitably mix in the flotation slurry, which will affect the flotation of bauxite. The results of flotation show that NaCl and KCl have little effect on the flotation of diaspore, but NaCl has a beneficial effect on kaolinite flotation. It may be attributed to the ion size order Na+ < K+ < Cl−. Na+ has the ability to enter the layer spacing of kaolinite due to its smaller size, which increases the zeta potential and the dipole-dipole force between kaolinite and sodium oleate, therefore improving the flotation of kaolinite. In addition, Na+ has “salt effect” on the anionic collector, which also promotes the flotation of kaolinite. This study may have some reference significance to the industry flotation of diasporic bauxite.

The wild boar is an omnivorous animal that disturbs the top soil layer by foraging (rooting). In some regions of Europe seasonal fluctuations in rooting have been observed. Wild boars not only eat plants, but also strongly modify their habitat. In the Białowieża Forest wild boar most frequently visit oak−hornbeam forests growing on fertile soil. On sites where the forest floor is covered with dense vegetation germination of seeds is difficult, and wild boar rooting can promote the removal of diaspores from deeper layers of the soil seed bank. The aim of this study was to assess the impact of wild boar rooting on the soil seed bank in a natural oak−linden−hornbeam forest. Observations were carried out on permanent plots in the strictly protected zone of the Białowieża National Park. Samples of the soil seed bank were taken from plots which showed varying intensities of wild boar rooting (frequency and average percentage of exposed ground surface). Areas to be sampled were selected on the basis of archival data. Research was conducted by the seedling emergence method during two vegetation seasons. Altogether, 7985 seedlings of 67 taxa germinated from 240 soil samples. The highest number of germinated seedlings and species were found in the highly rooted plots. In all the series dominant species was Urtica dioica. In the soil seed bank 19 species of anemochory germinated, and accounted for 27.5% of all species present in the seed bank of all series. Permanent wild boar rooting increased the species richness in the soil seed bank and increased the amount of species with higher light requirements., Sylwan 164 (8): 676-682

Sodium oleate (NaOL), as an important collector, has been extensively applied in oxide and silicate mineral flotation. The quantitative determination has to be analyzed for investigating its adsorption mechanism on the mineral surface. In this study, a novel method of Gas Chromatography Mass Spectrometry (GCMS) was proposed to precisely and stably measure NaOL concentration in diaspore and kaolinite flotation pulp through methyl esterification pretreatment. Compared with Total Organic Carbon (TOC) analyzer and High Performance Liquid Chromatography (HPLC), this method can avoid systematical and manual operation error effectively, benefitting from the internal standard application of heptadecanoic acid. The obtained linear relevance coefficient is 0.99902 and the standard deviation of adsorption results on the diaspore and kaolinite is much smaller than that of TOC and HPLC.

The fate of phosphorus (P) in the eco-system is strongly affected by the interaction of phos- phates with soil components and especially reactive soil mineral surfaces. As a consequence, P immobilization could occur which eventually leads to P inefficiency and thus unavailability to plants with strong implications on the global food system. A molecular level understanding of the mechanisms of the P binding to soil mineral surfaces could be a key for the development of novel strategies for more efficient P application. Much experimental work has been done to understand P binding to several reactive and abundant minerals especially goethite (α-FeOOH). On the other hand, atomistic modeling of the P-mineral molecular systems using molecular dynamics (MD) simulations is emerging as a new tool which provides more detailed information regarding the mechanisms, nature, and strength of these binding processes. The present study characterize the binding of the most abundant organic phosphates in forest soils, inositol hexaphosphate (IHP) and glycerolphosphate (GP), to the 100 diaspore (α-AlOOH) surface plane. Here, different molecular models have been introduced to simulate typical situations for the P-binding at the diaspore/water interface. For all models, quantum mechanics/molecular mechanics (QM/MM) based MD simulations have been performed to explore the diaspore–IHP/GP–water interactions. The results provide evidence for the formation of monodentate (M) and bidentate (B) motifs for GP and M and as well as two monodentate (2M) motifs for IHP with the surface. The calculated interaction energies suggest that GP and IHP prefer to form the B and 2M motif, respectively. Moreover, IHP exhibited stronger binding than GP with diaspore and water. Further, the role of water in controlling binding strengths via promoting of specific binding motifs, formation of H-bonds, adsorption and dissociation at the surface, as well as proton transfer processes is demonstrated. Finally, the P-binding at the 100 diaspore surface plane is weaker than that at the 010 plane highlighting the influential role of the coordination number of Al atoms at the top surface of diaspore.

Sodium oleate (NaOl), a collector in diaspore flotation, has been widely used for more than 30 years, while its low selectivity becomes an issue under today's process requirement. This study introduced tert dodecyl mercaptan (TDM) together with NaOl as a mixed collector to improve selectivity in diaspore flotation. We found that using the mixed collector of NaOl/TDM (total concentration 0.1 mM, the molar ratio 8:2 of NaOl: TDM) at pH = 9–10 significantly effectively separated diaspore and kaolinite. Comparing the recovery of Al2O3 and the ratio of Al2O3 to SiO2 (A/S) treated by NaOl/TDM (pH = 9) and NaOl (pH = 10), the Al2O3 recovery and A/S in concentrate for NaOl/TDM are 7.5% and 2.2 higher than that for NaOl in mixed mineral flotation. Also, surface tension measurements, Zeta potential measurements and Fourier Transform Infrared (FTIR) spectra analysis were used to examine its selectivity from a flotation mechanical perspective. Surface tension measurements show that mixed collector NaOl/TDM has stronger surface activity and hydrophobic association than NaOl. The results of Zeta potential measurements and FTIR spectra analysis indicate that NaOl and TDM can selectively co-adsorb diaspore through physical adsorption. Moreover, the adsorption of TDM promotes the adsorption of NaOl on diaspore. However, when NaOl/TDM treats on kaolinite together, TDM can hardly adsorb on mineral surface, nor can it promote the adsorption of NaOl.

In-situ single-crystal and powder X-ray diffraction (XRD) experiments were performed on diaspore at high temperatures. The powder XRD experiments showed that the dehydration reaction from diaspore to corundum occurs between 703 and 733 K. The in-situ single-crystal XRD measurements of diaspore could successfully determine the cell parameters, fractional atomic coordinates and anisotropic displacement parameters at high temperatures, i.e., from 295 to 698 K. Temperature variations in the cell parameters indicate that thermal expansion of the a-axis is a little higher than those of the b-axis and the c-axis. However, the axial thermal expansivity is not as anisotropic as was previously suggested. The results of structure refinements indicate that such lattice expansion behavior is the result of thermal expansion of the tunnels through O2–H···O1 hydrogen-bond separation in the diaspore structure. To the best of our knowledge, this is the first time that the thermal expansion of diaspore has been investigated at an atomic level by in-situ single-crystal XRD experiments at high temperatures.

The active sites of mineral surfaces play an important role in many industrial processes, such as mineral flotation and dewatering. This paper was aimed to investigate the effect of Al- and Si-active sites on the mineral crystal faces exposed to water on the electrokinetic properties, surfactant adsorption, and floatability of diaspore and kaolinite, which are, respectively, the valuable and gangue minerals in the processing of diasporic bauxite ores. Specifically, the acid treatment was used to change the physicochemical properties of diaspore and kaolinite minerals for their selective flotation. Microelectrophoresis method was used to determine the zeta (surface) potential of diaspore and kaolinite particles before and after the acid treatment as a function of pH. The change in the surface potential was analyzed applying the theory on the electrical double layers at the solid-solution interface. The proton donor–acceptor reactions occurring simultaneously on amphoteric alumina or/and silica sites of diaspore and kaolinite were considered. The mass balances were applied to link the surface active sites with the minerals charge and potential. Comparing the modeling with the experimental data revealed the significant decrease in the Al-active sites and increase in the Si-active sites by the acid treatment. Single mineral flotation and surfactant adsorption tests of diaspore and kaolinite before and after the acid treatment were carried out using sodium hexametaphosphate (HMP) and dodecylamine hydrochloride (DAH) as a depressant and a collector, respectively. After the acid treatment, the adsorption density of depressant on both diaspore and kaolinite decreased due to the reduced density of Al-active sites on the minerals surfaces. The changes of collector adsorption capacity and floatability of diaspore were very small while those of kaolinite were significantly increased. These changes were caused by decreasing the density of Al-active sites (covered by HMP and thereby preventing DAH adsorption) on both diaspore and kaolinite and increasing the density of Si-active sites of kaolinite (not covered by HMP and thereby facilitating DAH adsorption). The results clearly indicated that the acid treatment was shown to be conducive to changing the active Al- and Si-sites on diaspore and kaolinite and thereby improving their flotation separation.

Bayer Process-derived red mud produced in China can be classified into three types according to chemical composition: high-iron diaspore red mud, low-iron diaspore red mud, and gibbsite red mud. The specific chemical and mineral compositions of three such typical Bayer-derived red mud samples have been characterized by XRF, ICP-MS, XRD, and SEM. These results, for example, indicate that GX (a high-iron diaspore red mud) contains more than 1015 μg/g lanthanides, 313 μg/g yttrium, 115 μg/g scandium, and 252 μg/g niobium and that HN (a low-iron diaspore red mud) has a high content of lithium (224 μg/g), whereas SD (a gibbsite red mud) possesses a very low valuable trace element content, except for gallium (59.4 μg/g). A sequential extraction procedure was carried out to assess the leachability of valuable trace elements in these three red mud samples. Applying the extraction procedure, 60% of the yttrium in GX and 65% of the lithium in HN could be extracted which would be of interest for trace metal recovery.

Desulfurization is a critical problem in the efficient exploitation of high-sulfur bauxite resources. This study synthesized a novel thioether-containing hydroxamic acid (2-BTHA) by click-esterification-hydroxylamine oximation for flotation separation of pyrite from diaspore. DFT calculations indicated the functional groups of 2-BTHA were hydroxamate and thioether groups. Flotation results demonstrated 2-BTHA can effectively separate pyrite from diaspore under weak acidic conditions without adding vulcanizing agent. The UV-absorbance and surface energy tests explained introducing a thioether group improved the adsorption of Fe2+ on the collector, thus reducing its surface energy, hydrophilic index and free energy of bubble-mineral interaction, conducive to selective flotation. Zeta potential, infrared spectrum analyses and XPS further proved 2-BTHA could chemically adsorb on pyrite rather than on diaspore. It mainly reacted with pyrite surface Fe to form Fe-S bonds and five-membered hydroxamate-(O, O)-Fe rings. This research provides a potential multi-functional collector for green and efficient utilization of high-sulfur bauxite.

The Bayer process is a conventional method for refining bauxite in the production of alumina. The Al/Si ratio in bauxite before feeding to the process must be enriched to more than eight by reducing impurities (mainly aluminosilicates). Therefore, diasporic bauxite ores (Al/Si