Siliceous Earth Research Articles

Greensand formation, siliceous earth deposition and coastal metal drawdown in the Danubian Cretaceous Basin (Bavaria, Germany)

The Late Cretaceous epoch was characterized by extreme greenhouse climates and widespread glaucony formation in shallow marine settings. However, in the Danubian Cretaceous Basin (DCB, Bavaria, SE-Germany), contemporaneous shallow marine deposition of glauconitic sandstones of the Regensburg Formation in the eastern and the glaucony-free Neuburg Siliceous Earth deposits of the Wellheim Formation in the western parts of the basin during Cenomanian–early Turonian times is puzzling. An integrated approach of sedimentology, stratigraphy, mineralogy and geochemistry reveals that the striking lithological and mineralogical differences can be attributed to the geological structure of the hinterland and the nature of element input: in the eastern DCB, deeply chemically weathered granites and gneisses of the Bohemian Massif were leached due to the warm climate and high precipitation rates as indicated by high values of the modified Chemical Index of Alteration (CIXrev). Elements crucial for glaucony formation (K, Fe, Si, Al) were amply supplied by rivers, fueling a shallow marine glaucony factory. Slightly reducing conditions and a temporally increased primary productivity further promoted favorable conditions for geologically fast shallow water glaucony authigenesis. In the western DCB, in contrast, a hinterland consisting of karstified Upper Jurassic carbonates devoid of essential elements for glaucony formation and a lack of significant fluvial input inhibited shallow marine glaucony formation. Furthermore, we suggest that the depositional environment of the Neuburg Siliceous Earth was affected by submarine discharge of silica-rich groundwater resulting in intense early diagenetic silicification. Additionally, our geochemical data provide the first evidence of a trace metal drawdown during Oceanic Anoxic Event 2 (approx. 94 Ma) in shallow water/coastal settings in Germany, as shown in very low V/Al, Ni/Al, Cu/Al and As/Al ratios, much lower than the average shale and upper continental crust.

Chemical and Structural Comparison of Different Commercial Food Supplements for Silicon Uptake

Various food supplements for silicon uptake were compared in terms of their structures and chemical compositions. In particular, we analyzed the silanol group content, which can be an indicator of the uptake of the siliceous species in the human body. We analyzed the commercial products Original Silicea Balsam®, Flügge Siliceous Earth Powder, Pure Colloidal Silicon, and BioSil® by applying various methods such as FTIR, 29Si NMR, and TGA. The Si-OH group content of the samples containing pure silica was the highest for the Original Silicea Balsam followed by the Pure Colloidal Silicon. The siliceous earth powder revealed the lowest content of such groups and the densest structure. BioSil® contained a considerable concentration of organic molecules that stabilized orthosilicic acid. The study may help to understand the silicon uptake behavior of different food supplements depending on their chemical structure.

Chemical, Microbial Quality, and Risk Assessment due to Toxic Metal Contamination of Egusi (Citrullus colocynthis L.) Powder Sold in Selected Ghanaian Markets.

The present study was undertaken to investigate the physicochemical and microbiological qualities of melon seed powder sold in some open Ghanaian markets. Twenty-five samples of powder were collected randomly from each of four major markets and analyzed for moisture, pH, total ash, acid insoluble ash, and free fatty acids (FFA) using standard methods. The microbial population was determined using the pour plate method. Melon seed powder samples had a neutral pH (6.9-7.3) and contained significant amounts of ash (0.1-0.6%). Acid insoluble ash of powder from one market was high (0.6%) and possibly indicate contamination with siliceous earth material. FFA ranged between 4.1 and 11.6% for powder from the four markets. Levels of lead were higher (0.4-0.8 ppm) than other metals such as cadmium (0.02 ppm) and copper (0.3-0.6 ppm). HQ values >1 were recorded for Pb, implying a greater risk of toxicity to consumers. Counts for aerobic bacteria, fecal coliforms, and yeast and molds were in the range of 3.2-4.4, 1.6-4.0, 1.4-2.8, and 1.1-3.2 log CFU/g correspondingly for these organisms. E. coli was not detected in any of the melon seed powder samples analyzed. This study highlights the need for proper handling of melon seed during processing, storage, and distribution, to safeguard its quality for consumers.

Making a synthetic zeolite from a residue of bauxite washing

A zeolite synthetic of NaA type is generally prepared by mixing the alumina and silicate-containing materials (alkali alumino hydro-silicates). The used raw materials include the amorphous solids such as metakaolin, siliceous earth, coal ash, kimberlite waste, alumina trihydrate [Al(OH)3], bauxite, and aluminum metal. Residue of bauxite washing retains a fine texture and contains significant alumina and silica content, namely 30-36% Al2O3 and 10-15% SiO2. Both components are required for making the zeolite NaA . In this research, the zeolite NaA was made by extracting the alumina from residue of bauxite washing with caustic soda, and followed by reacting it with a water glass after through the flushing and washing process. The composition of zeolite NaA is as follows: 33.87% SiO2, 27.63% Al2O3, 16.31% Na2O, and 22.18% H2O with Na96Al96Si96O384.216H2O or Na12(AlO2)12(SiO2)12.27H2O as its mineral composition.

A novel approach in blending natural rubber latex with siliceous earth nanoparticles

Siliceous earth (SE), a kind of volcanic ash, was formed more than 100 million years ago with a special crystal structure and morphology. In this work, SE was first used as filler to blend with natural rubber (NR) latex, and then an improved process was employed to build up a kind of sacrificial bond to prepare NR composites with SE loadings 0–10 per hundred rubber (phr). X-ray diffractometry, Fourier-transform infrared spectroscopy and scanning electron microscopy were employed to determine the structure and morphologies of NR composite films. Furthermore, to investigate the effect of SE loading on mechanical properties of films, tear and tensile tests were applied. The NR latex, reinforced with 2–10 phr SE nanoparticles, showed 14.9–38.1% improvement in tensile strength and 109.2–345.3% improvement in 500% modulus when compared to pure NR film. The tensile strength and tear strength of NR composite films reached 34 MPa and 55 N/mm, respectively, when 6 phr SE was added. The results of thermogravimetric analysis indicated that thermal decomposition temperature of the NR composite films increased with increase in SE loading. The results of Mooney–Rivlin equation and Lorenze–Park equation showed that stronger filler/rubber interfacial interactions exist between SE particles and NR molecular chains. The improvement of NR properties was resulted from good filler–polymer interactions and uniformly dispersed SE particles.

The different reinforcing behavior between siliceous earth nanoparticles and silica on natural rubber

The reinforcing behaviors of siliceous earth (SE) nanoparticles and silica on natural rubber (NR) were compared. SE employed in this work was formed by volcanic eruptions 100 million years ago and mainly consists of SiO2 (∼80%), Al2O3 (∼14%), and K2O (∼4%) and is composed of low quartz and illite in crystal structure and with a special flaky and laminated morphology. The effects of SE slurry with different filler loading of 30, 40, 50 per hundred parts of rubber (phr), and 40 phr silica(S-40) were investigated. Mechanical properties were measured, and the results show that 300% modulus, elongation at break, tensile, and tear strength of SE/NR are all higher than those of S-40. Combination results of tensile properties and rubber process analyzer (RPA), the rubber–filler interaction parameter (I) was calculated and the results show the value of I increase slightly with SE loading, while obviously higher than that of S-40. But the results of dynamic mechanical analysis and bound rubber content show that S-40 has obviously lower tan δ and higher bound rubber content, which indicate that there exists stronger rubber–filler interaction between silica and NR. The seemingly conflicting results imply that the effect of the two fillers on the NR network structure should be different. The special morphology of SE can help them to distribute more evenly in the NR matrix, making it less likely to form particle networks and providing very strong filler–rubber interaction, while showing higher average rubber–filler interaction and results in better mechanical properties of SE/NR composites.

Silicate Solubilization and Plant Growth Promoting Potential of Rhizobium Sp. Isolated from Rice Rhizosphere

Silicon is a beneficial plant nutrient with a vital role in maintaining plant growth and enhancing tolerance to both biotic and abiotic stresses. The polymeric insoluble silica present in soils is solubilised during weathering to release monosilicic acid into the soil solution which is the bioavailable form of silicon absorbed by plants. In the present study, a silicate solubilizing bacterial isolate IIRR-1 from rhizopshere soil of rice was characterized for its potential to release soluble silica from insoluble inorganic (Ca, Al, K and Mg) silicates and biogenic materials like diatomaceous earth, siliceous earth, rice husk and rice straw. Incubation studies revealed the ability of the isolate to colonise and grow on all insoluble silicates leading to increased release of silica (12.45–60.15% over control) into culture media by the process of acidolytic (pH 4.5) dissolution of silicates. The isolate, besides possessing additional mineral (P, K and Zn) solubilising capacities, also exhibited phytostimulatory behaviour by producing IAA (0.95 + 0.14 μg IAA /μg bacterial cell protein) and ACC deaminase activity (2.52 + 0.73 μg α ketobutyrate /μg bacterial cell protein/24 h) that modulates the ethylene levels in plant. Furthermore, the isolate successfully colonized rice seedling roots and improved seedling vigour by 29.18% as compared to uninoculated control. The isolate identified as Rhizobium sp. has the potential to be employed as a plant beneficial bacterium for accelerating the weathering process and increasing the rhizosphere available silica concentration.

The Use of Untreated Neuburg Siliceous Earth as Filler for High-Density Polyethylene

The Use of Untreated Neuburg Siliceous Earth as Filler for High-Density Polyethylene

Mineralogical and Micromorphological Diagnostics of Pedogenesis on Intermediate and Mafic Rocks in the Northern Taiga of the Timan Range

Mineralogical, micromorphological, and physicochemical characteristics of soils developed on the outcrops of intermediate and mafic rocks in the central part of the Timan Range under northern taiga vegetation are discussed. These soils have been classified within the order or iron-metamorphic soils of the new Russian soil classification system and as Hyperskeletic Leptosols (Humic) in the WRB system. The in situ accumulation of nonsilicate iron compounds (ferrugination) controlled by the specific features of iron-rich parent rocks is the major process in these soils. In dependence on the composition of parent material, the direction of its modern weathering, the character of plant litter, the degree of its biological transformation, and the presence of features attesting to the mobility of silicate plasmic material, these soils are subdivided into two types: rzhavozems on colluvium of mafic rocks with some admixture of siliceous morainic fine earth and organic rzhavozems on the eluvium of mafic rocks with a predominance of specific polycrystalline aggregates of iddingsite and bowlingite (saponite) representing supergene postmagmatic pseudomorphs after pyroxenes and olivine with the initially different iron contents.

River-fed wetland palaeovegetation and palaeoecology at the HWK W site, Bed I, Olduvai Gorge

Palaeolandscape studies are an essential tool for understanding adaptation and use of plant- and water-related affordances by hominins. A number of high-resolution palaeolandscape analyses have been carried out at Olduvai Gorge (northern Tanzania) over the last two decades but none have focused on the Tuff ID-IE stratigraphic interval (1.83–1.84 Ma). At locality HWK W, this interval presents earthy facies, including siliceous earth, earthy claystone, sandy earth, and earthy sandstone facies varieties, which are rare for Bed I. These facies have been interpreted at other stratigraphic levels to represent densely vegetated wetlands. Additionally, the HWK W site has yielded quantities of fossil bone and tools eroding to the surface. Within the Tuff ID-IE interval, and during regression periods of Palaeolake Olduvai, fluvial and wetland facies were deposited. During this period, the phytoliths and plant macrofossils show that the vegetation was dominated by palms, associated with a mix of C3 and C4 grasses as well as sedges. The variation in phytolith types within these facies implies a locally diverse palaeoenvironmental micro-mosaic, with stacked transgressive sequences, varying from vegetated fluvial channels to vegetated levées and then backswamp subenvironments. Diatoms are particularly rich at Trench T155 and are associated with sponge spicules, indicating the presence of freshwater palaeowetlands with clear water. The extensive diatom valve fragmentation and the differences among trenches suggest that the diatom depositional environment was a heterogeneous river-fed palaeowetland or a vegetated fluvial channel affected by periodic droughts. A diverse fauna was recovered, comprising autochthonous hippopotamus and crocodile elements as well as herbivores drawn to the freshwater resource. Oldowan lithic artifacts were also recovered and some bone was processed through percussion and cutting by early hominins, likely Homo habilis. Overall, the first landscape reconstruction undertaken at HWK W locality during the Tuff ID-IE interval shows a dynamic and richly vegetated area that would have provided hominins with fresh water, scavengeable carcasses, as well as with edible plant affordances (palm fruits, starch-rich rhizomes from sedges and Typha). The presence of palms suggests the area supported a diversity of trees, affording hominins refuge from predators.

Mechanical properties of polyethylene filled with treated neuburg siliceous earth

Mechanical properties of polyethylene filled with treated neuburg siliceous earth

Mechanical properties of siliceous earth/natural rubber composites

Siliceous earth (SE), which has a special morphology and structure, was selected as filler of natural rubber (NR) and mechanical properties of compounds were analyzed. Two processes were employed to prepare SE/NR compounds described as mechanical mixing method and latex method, respectively. Cure characteristics, mechanical properties of the vulcanizates prepared from the masterbatches were compared with those prepared by mechanical mixing method. X‐ray diffraction results of NR/SE vulcanizations indicated that mechanical mixing above the latex process facilitated the intercalation of NR into the galleries of SE. The results of mechanical properties show that SE has good reinforcing properties on NR both by latex or mechanical mixing process. By comparison, H samples show slightly higher crosslink density, tensile strength, 300% modulus, and lower elongation at break than M sample in same loading. But in the aspect of dynamic properties there exist obviously difference between latex and mechanical mixing process. Rubber processing analyzer (RPA) results showed that uncured M samples showed obviously higher storage modulus than that of H samples. The heat build‐up of M30 is much lower than that of H30. These behaviors indicated better dynamitic properties when the masterbatches prepared by the predispersing method was utilized. POLYM. ENG. SCI., 58:1043–1052, 2018. © 2017 Society of Plastics Engineers

A Comparative Investigation of Rice Husk Ash and Siliceous Earth as Reinforcing Fillers in Dynamically Cured Blends of Epoxidized Natural Rubber (ENR) and Thermoplastic Polyurethane (TPU)

The present work aimed to develop epoxidized natural rubber/thermoplastic polyurethane thermoplastic vulcanizates (ENR/TPU TPVs) having some specific properties, i.e., good processability and dynamic properties, and excellent heat and oil resistances. A comparative study on the effects of rice husk ash (RHA) and commercial siliceous earth (SE) as reinforcing fillers on alteration and enhancement of TPV properties was performed. It was found that the RHA-filled ENR/TPU TPVs showed an improvement of thermoelastic properties with outstanding thermal resistance relative to the pure TPU. This might be attributed to the synergistic effects of the dispersed vulcanized ENR domains and the RHA particles in the TPVs. Furthermore, the RHA-filled ENR/TPU TPVs had rather similar performance, processability and physical properties to the SE-filled ENR/TPU TPV. This indicates that the RHA has great potential as a filler in thermoplastic vulcanizates, in particular with ENR that is a renewable green resource.

Landschaftsgeschichte der südlichen Fränkischen Alb und Lagerstätten der Neuburger Kieselerde (Exkursion H am 21. April 2017)

Landschaftsgeschichte der südlichen Fränkischen Alb und Lagerstätten der Neuburger Kieselerde (Exkursion H am 21. April 2017)

The effect of epoxidized natural rubber on mechanical properties of siliceous earth/natural rubber composites

Siliceous earth (SE) is a kind of mineral consisting of lamellar kaolinite, muscovite (aluminum silicate) and corpuscular silica. Natural rubber (NR) composites containing NR as matrix, epoxidized natural rubber (ENR) as compatibilizer and SE as filler were produced by latex coagulating process and cured using a conventional sulfuric system. Monsanto measurements have shown that the ENR accelerates the vulcanization reaction and gives rise to a marked increase of the torque. The results of physico-mechanical properties of NR vulcanizates show that, when SE modified by silane coupling agent and in the meanwhile adding 4 phr of ENR as compatibilizer, maximum tensile strength, elongation at break, reinforcing index (M300/100) of NR/SE vulcanizates were obtained. The dynamic-mechanical properties exhibit the addition of ENR can enhance wet grip characteristics and reduce rolling resistance by lowering tan δ values at 60 °C and increasing tan δ values at 0 °C of NR compounds. The overall results show that properties of SE-reinforced NR substantially improved by adding ENR as compatibilizer. The addition of silane coupling agent and combining an appropriate amount of ENR would be better choice to improve the properties of NR/SE compounds.

A comparative study of rice husk ash and siliceous earth as reinforcing fillers in epoxidized natural rubber composites

Rice husk ash (RHA) and siliceous earth (SE) were compared as alternative reinforcing fillers in epoxidized natural rubber (ENR) vulcanizates. The effects of RHA and SE on processability, curing characteristics, mechanical, thermal and morphological properties, and thermoelastic behavior of vulcanizates were studied, in the presence and absence of bis(triethoxysilylpropyl) tetrasulfide (TESPT) silane coupling agent. The results indicated that the RHA offers processing advantages over the commercial SE. The filled ENR vulcanizates without TESPT provided higher tensile strengths than the unfilled ENR vulcanizates, but had lower elongations at break. This is attributed to physical interactions between filler particles and rubber matrix, which affects the reinforcement by the filler. The modification of filler surfaces with TESPT resulted in further improved properties of the rubber vulcanizates. This is attributed to the coupling of polymer matrix and filler particles via TESPT linkages that increased the polymer–filler interactions. It was also found that the RHA filler, a renewable resource, exhibited similar reinforcement to the conventional SE. This indicates that the RHA has great potential as a reinforcing filler that can substitute for conventional SE in polymer composites. POLYM. COMPOS., 39:414–426, 2018. © 2016 Society of Plastics Engineers

Characterization of porous glass-ceramic material as absorber of electromagnetic radiation

Investigations of a foam glass-ceramic material synthesized from raw siliceous earth material by the two-stage method at temperatures below 950°C have demonstrated the improvement of its physic mechanical properties in comparison with foam glass synthesized from glass cullet. This material actively interacts with microwaves and can be used for the development of protective screens reducing the adverse effect of microwaves on biological objects, anechoic chambers, and rooms with low level of electromagnetic background noise. Spectra of the transmission and absorption coefficients and of the complex dielectric permittivity for frequencies in the range 26-260 GHz are presented. The observed effects demonstrate the existence of regions with partial and total reflection arising on the glass-pore boundary and of the microwave interaction with ultradisperse carbon particles that remain after foaming with incomplete frothier transition from the soot to the gas phase.

Electrophysical Characteristics of a Foam Glass Crystal Material

Investigations of a foam glass crystal material synthesized from raw siliceous earth material by the two-stage method at temperatures below 950°С have demonstrated the improvement of its physicomechanical properties in comparison with foam glass synthesized from glass cullet. This material actively interacts with microwaves and can be used for the development of protective screens reducing the adverse effect of microwaves on biological objects, unechoic chambers, and rooms with low level of electromagnetic background noise. Spectra of the transmission and absorption coefficients and of the complex dielectric permittivity for frequencies in the range 26–260 GHz are presented. The observed effects demonstrate the existence of regions with partial and total reflection arising on the glass–pore boundary and of the microwave interaction with ultradisperse carbon particles that remain after foaming with incomplete frother transition from the soot to the gas phase.

360 Dose-response relationship between a particular form of cryptocrystalline silica and the incidence of silicosis

ObjectivesIt has been known for centuries that crystalline silica induces silicosis. However, there are different entities of crystalline silica. Siliceous earth is a worldwide unique blend of amorphous and cryptocrystalline...

Erratum

In the article “Effects of Azodicarbonamide and Vulcanization Methods on Acrylonitrile-Butadiene Rubber/Polyvinyl Chloride Foam Properties” (Vol. 86, No. 1, pp. 86-95) by P. Suriyachai et al. (1), the following correction is made to Table 1. “Kaolin” in the left column (line 8) should be changed to “Neuburg Siliceous Earth (Silitin N82)” and “Hoffmann Mineral, Neuberg, Germany” in the second column (line 8) should be changed to “Hoffmann Mineral GmbH, Neuburg an der Donau, Germany”.