Silicate

The physico-mechanical, chemical and mineralogical characteristics of volcanic glass (perlite) from the Mariovo region (Macedonia) as well as the mineralogical changes that occur during its thermal treatment were investigated to demonstrate its utilization for industrial use. The native perlite was characterized by chemical analysis, X-ray powder diffraction (XRPD), infrared (IR) spectroscopy, thermal analysis (TGA/DTA), scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), and solid- state NMR. The chemical examination suggests that the perlite represents an acidic volcanic rock with a high percentage of SiO2 (72.45%), high in alkali metal oxides (4.21 wt.% K2O, 3.56 wt.% Na2O), with a loss of ignition 3.54 wt.%. Results from the XRPD indicated major amorphous behaviour, with low amounts of feldspars, quartz, and cristobalite. SEM examinations revealed glassy structure with presence of certain pores (dimensions ranging from 50–100 μm). The determined expansion coefficient was 20 times its original volume. XRPD of expanded perlite compared to the native perlite depicted new intensive peaks of cristobalite. SEM and TEM revealed irregular morphology with broken or ragged edges. On the basis of the chemical and mineralogical composition, the studied perlite is classified as an appropriate material suitable as ceramic flux to lower the sintering temperature.

The highly ordered mesoporous silica media, SBA-15, was synthesized and incorporated with iron, aluminum, and zinc oxides using an incipient wetness impregnation technique. Adsorption capacities and kinetics of metal-impregnated SBA-15 were compared with activated alumina which is widely used for arsenic removal. Media impregnated with 10% of aluminum by weight (designated to Al 10SBA-15) had 1.9-2.7 times greater arsenate adsorption capacities in a wide range of initial arsenate concentrations and a 15 times greater initial sorption rate at ph 7.2 than activated alumina. By employing one- and two-site models, surface complexation modeling was conducted to investigate the relationship between the aluminum oxidation states in different media and adsorption behaviors shown by adsorption isotherms and kinetics since the oxidation phase of aluminum incorporated onto the surface of SBA-15 was Al-O, which has a lower oxidation state than activated alumina (Al2O 3). Surface complexation modeling results for arsenate adsorption edges conducted with different pH indicated that the monodentate complex (SAsO42-) was dominant in Al10SBA-15, while bidentate complexes (XHAsO4 and XAsO4-) were dominant in activated alumina at pH 7.2, respectively. In kinetic studies at pH 7.2 ± 0.02, Al10SBA-15 had only a fast-rate step of initial adsorption, while activated alumina had fast- and slow-rate steps of arsenate adsorption. Therefore, it can be inferred that the monodentate arsenate complex, predominant in Al10SBA-15, leads to faster adsorption rates than bidentate arsenate complexes favored with activated alumina. An arsenate adsorption behavior and arsenate surface complexation were thought to be well explained by aluminum oxidation states and surface structural properties of media.

http://www.ncbi.nlm.nih.gov/pubmed/14620839 
http://pubs.acs.org/doi/abs/10.1021/es0343712

We used a green sol-gel synthesis method to fabricate a novel nanoporous copper aluminosilicate (CAS) material. Nanoporous CAS was characterized using X-ray powder diffraction (XRD), field emission transmission and scanning electron microscopies (FE-TEM/FE-SEM), Fourier transform infrared (FTIR) spectroscopy, and optical analyses. The CAS was also evaluated for use as a promising disinfectant for the inactivation of waterborne pathogens. The antimicrobial action and minimum inhibitory concentration (MIC) of this CAS disinfectant were determined against eight microorganisms (Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, Enterococcus faecalis, Candida albicans, and Aspergillus niger). An antimicrobial susceptibility testing of CAS was measured. Results of disc diffusion method pointed out that the diameters of the zone using well diffusion were wider than disc diffusion methods, and the findings also showed that the MIC of the CAS disinfectant against E. coli, S. enterica, and P. aeruginosa was 100 mg/L within 20 min of contact time. Meanwhile, the MIC of the CAS disinfectant was 100 mg/L within 40 min of contact time for the other strains. The efficacy of antimicrobial action (100%) reached within 20 to 40 min against all tested microbes. Herein, the antimicrobial susceptibility testing of CAS disinfectant showed no toxicity for human and bacterial cells. It can be concluded that nanoporous CAS is a promising, economically, and worthy weapon for water disinfection.

The local structure about Fe(II) and Fe(III) in silicate melts was investigated in-situ using iron K-edge X-ray absorption near-edge structure (XANES) spectroscopy. An aerodynamic levitation and laser heating system was used to allow access to high temperatures without contamination, and was combined with a chamber and gas mixing system to allow the iron oxidation state, Fe3 +/ΣFe, to be varied by systematic control of the atmospheric oxygen fugacity. Eleven alkali-free, mostly iron-rich and depolymerized base compositions were chosen for the experiments, including pure oxide FeO, olivines (Fe,Mg)2SiO4, pyroxenes (Fe,Mg)SiO3, calcic FeO-CaSiO3, and a calcium aluminosilicate composition, where total iron content is denoted by FeO for convenience. Melt temperatures varied between 1410 and 2160 K and oxygen fugacities between FMQ – 2.3(3) to FMQ + 9.1(3) log units (uncertainties in parentheses) relative to the fayalite-magnetite-β-quartz (FMQ) buffer. Remarkably, XANES pre-edge peak areas imply mean Fe-O coordination numbers (nFeO) close to 5 in all cases, with only a slight tendency toward higher values in the most iron rich melts, suggesting an intermediate role for both Fe(II) and Fe(III) in terms of network formation. End member coordination numbers for Fe(II)-O and Fe(III)-O are estimated to be similar, having means (and standard deviations) of 5.0(2) and 4.9(1), respectively. As such, the preference for ferric iron to occupy lower coordination sites than ferrous is weak, in contrast to published behavior in some alkali-rich systems, which may explain the larger published viscosity variations with Fe3 +/ΣFe in alkali-, compared to alkaline earth-iron silicates. Temperature effects on nFeO are inferred to be small based on the melt data, as well as by comparison to glasses formed on quenching. Positive shifts of the pre-edge peak centroids observed in many cases on quenching are attributed to rapid oxidation enabled by the stirring of the melt droplets by the levitation gas jet. Fe3 +/ΣFe values were estimated from XANES pre-edge peaks using published calibrations and compared to semi-empirical thermodynamic model calculations and Mössbauer measurements on quench products. Whilst showing positive correlation, the comparisons highlight the limitations involved in applying XANES calibrations and models for Fe3 +/ΣFe derived from measurements on glasses, to high temperature basic melts. Fe3 +/ΣFe varies from approximately zero up to about 65% in the high temperature melts and 75% in the glasses.

Resumo Este estudo visou avaliar sazonalmente e espacialmente o silicato dissolvido nas águas superficiais de dois rios com características físicas similares, porém com diferentes níveis de interferências antropogênicas. Os resultados mostraram que em períodos de estiagem a água superficial de locais de baixa profundidade pode apresentar concentrações elevadas, demonstrando que a circulação estuarina é determinante nas flutuações deste nutriente na camada superficial, ainda que o mesmo seja abundante no ambiente. A sinalização de processos erosivos por este parâmetro é mais evidente em períodos chuvosos. Abstract This study aimed to evaluate seasonally and spatially the dissolved silicate in surface waters of two rivers with similar physical characteristics, but with different levels of anthropogenic interference. In dry season the surface water in shallow sites can represent high concentrations, proving that the estuarine circulation is very influential in the concentrations of dissolved silicate on surface. The dissolved silicate as an indicator of erosion becomes more evident during rainy periods.

Objetivou-se verificar a eficiência de silicato de alumínio na composição do substrato para produção de mudas de Corymbia citriodora. O delineamento adotado foi o inteiramente casualizado com
cinco tratamentos e oito repetições. A composição do substrato consistiu de moinha de carvão, esterco bovino, casca de eucalipto e substrato comercial. Foram acrescidos nos tratamentos 0 (testemunha), 5, 10, 15 e 20% de silicato de alumínio. O índice de qualidade de mudas, altura, diâmetro do coleto, massa seca e fresca da raiz, área foliar média e total e relação entre massa seca da raiz e massa seca da parte aérea não foram influenciados. Para massa seca e fresca da parte aérea as testemunhas foram superiores 2,5953 e 4,9323 g, respectivamente. Porém a adição de 12,2% apresentou ganhos crescentes no número de folhas. O silicato de alumínio para produção de mudas de C. citriodora surge como potencial alternativa de destino deste resíduo.

Thalassiosira allenii (Takano) türünün fosfor ve silikattan nasıl etkilendiğini daha iyi anlamak için büyüme hızları üzerinde 6 farklı reaktif PO4 ve 6 farklı reaktif Si konsatrasyonunun etkileri araştırılmıştır. T.allenii türü, İzmir Körfezi-Kuzey Ege-Türkiye’den izole edilerek, f/2 zenginleştirme ortamında, sürekli-aydınlık periyotta ve kesikli kültür sisteminde inkübe edildi. Türün büyümesi eksponensiyel büyüme fazı takip edilerek Chl a (µgl-1) olarak ölçüldü, elde edilen verilerin istatistiksel analizi en küçük kareler metoduyla yapıldı. Her bir nütrient için hesaplanan Ks ve µmax değerleri sırasıyla: PO4 için Ks= 0.544 µM-PO4-P ve µmax= 0,972 gün-1, Si için -Ks=0,615 µM Si ve µmax=0,989 gün-1 olarak bulundu. T.allenii türü, PO4-P sınırlı gelişim gösterirken, silikat sınırlayıcılığı tespit edilememiştir. Bu sonuçlar, özellikle evsel kirletici yükün yoğun olduğu ve Si değişimlerininin sık yaşandığı kıyısal sularda T.allenii türünün aşırı alg çoğalmalarında yeralma yeteneğine sahip olduğunu göstermektedir.
In order to better understand the effect of phosphorus and silica on Thalassiosira allenii (Takano), the effects of 6 different concentrations of reactive PO4 and 7 different concentrations of reactive Si were investigated. T.allenii was isolated from İzmir Bay-Northern Aegean Sea-Turkey and incubated in a f/2 enrichment medium under constant light in a batch culture system. The growth rate of the species was measured as Chl a (mg/l) by monitoring the exponential growth phase. The statistical analysis of the obtained data was performed by utilizing the method of least squares. Half saturation constant (Ks) and maximum spesific growth rate (µmax) values estimated for phosphorus and silica were obtained as follows: Ks=0,55 µM PO4-P and µmax=0,847 day-1 for phosphorus, -Ks=0,615 µM Si and µmax=0,989 day-1 for silica. This results shows that T.allenii species has ability to take a great role on algal blooms in coastal waters which particularly domestic pollution load intense and changes of Si frequently experiencing.

The upper 35 m of a thick (≤175 m) Early Jurassic North Mountain Basalt flow at KcKay Head contains 25 cm thick differentiated layers that are separated by 130 cm sections of basalt. The lower layers are mafic, pegmatitic, and contain thin (2 cm), fine-grained…

The inclusion of small amounts of copper is often reported to enhance the mechanical and biointegrative performance of bioceramics towards tissue engineering applications. In this work, 3D scaffolds were additively manufactured by robocasting of precipitation derived copper doped diopside. Compositions were chosen in which magnesium sites in diopside were substituted by copper up to 3 at.%. Microstructure, mechanical performance, bioactivity, biodegradability, drug release, biocompatibility, in vitro angiogenesis and antibacterial activity were studied. Results indicate that copper is incorporated in the diopside structure and improves materials’ fracture toughness. Scaffolds with > 80% porosity exhibited compressive strengths exceeding that of cancellous bone. All compositions showed bioactivity and drug release functionalities. However, only samples with 0–1 at.% copper substitution showed favorable proliferation of osteogenic sarcoma cells, human umbilical vein endothelial cells and fibroblasts, while larger amounts of copper had cytotoxic behavior. In vitro angiogenesis was significantly enhanced by low levels of copper. Copper-containing materials showed anti-Escherichia coli activity, increasing with copper content. We show that across multiple indicators, copper substituted diopside of the composition CaMg0.99Cu0.01Si2O6, exhibits high performance as a synthetic bone substitute, comparing favorably with known bioceramics. These findings present a pathway for the enhancement of bioactivity and mechanical performance in printable bioceramics.