Search results for " Carbonate"
showing 10 items of 381 documents
Phosphorus recovery by struvite crystallization in WWTPs: Influence of the sludge treatment line operation
2010
Phosphorus recovery by struvite (MgNH(4)PO(4).6H(2)O) crystallization is one of the most widely recommended technologies for treating sludge digester liquors especially in wastewater treatments plants (WWTP) with enhanced biological phosphorus removal (EBPR). In this paper, phosphorus recovery by struvite crystallization is assessed using the rejected liquors resulting from four different operational strategies of the sludge treatment line. Phosphorus precipitation and recovery efficiencies of between 80-90% and 70-85%, respectively, were achieved in the four experiments. The precipitates formed were mainly struvite, followed by amorphous calcium phosphate and, in some experiments, by calci…
Isotopic composition of cattle pancreatic stones: biological and geochemical implications.
1977
Latitudinal variations of the O18/O16-ratios of carbonate and phosphate of cattle pancreatic stones parallel a similar pattern of oxygen isotope values in rain water. C13/C12-ratios were virtually identical for the 7 cases studied. Isotopic measurements of mammalian hard tissues may be used for studying short-term climatic variations through Quaternary.
Amorphous polyphosphate/amorphous calcium carbonate implant material with enhanced bone healing efficacy in a critical-size defect in rats
2016
In this study the effect of amorphous calcium carbonate (ACC) microparticles and amorphous calcium polyphosphate (polyP) microparticles (termed aCa-polyP-MP) on bone mineral forming cells/tissue was investigated in vitro and in vivo. The ACC particles (termed ACC-P10-MP) were prepared in the presence of Na-polyP. Only the combinations of polyP and ACC microparticles enhanced the proliferation rate of human mesenchymal stem cells (MSCs). Gene expression studies revealed that ACC causes an upregulation of the expression of the cell membrane-associated carbonic anhydrase IX (CA IX; formation of ACC), while the transcript level of the alkaline phosphatase (ALP; liberation of orthophosphate from…
Nonenzymatic Transformation of Amorphous CaCO3 into Calcium Phosphate Mineral after Exposure to Sodium Phosphate in Vitro: Implications for in Vivo H…
2015
Studies indicate that mammalian bone formation is initiated at calcium carbonate bioseeds, a process that is driven enzymatically by carbonic anhydrase (CA). We show that amorphous calcium carbonate (ACC) and bicarbonate (HCO3 (-) ) cause induction of expression of the CA in human osteogenic SaOS-2 cells. The mineral deposits formed on the surface of the cells are rich in C, Ca and P. FTIR analysis revealed that ACC, vaterite, and aragonite, after exposure to phosphate, undergo transformation into calcium phosphate. This exchange was not seen for calcite. The changes to ACC, vaterite, and aragonite depended on the concentration of phosphate. The rate of incorporation of phosphate into ACC, …
Aqueous two-phase system cold-set gelation using natural and recombinant probiotic lactic acid bacteria as a gelling agent
2016
The present study aimed to entrap probiotic lactic acid bacteria (LAB) in a sodium alginate and sodium caseinate aqueous two-phase gel system. The natural acidifying properties of two therapeutic probiotic LAB were exploited to liberate calcium ions progressively from calcium carbonate (CaCO3), which caused the gelation of the co-existing phases. Bi-biopolymeric matrix gelation of GDL/CaCO3 or LAB/CaCO3 was monitored by dynamic rheological measurements, and the final gels were characterized by frequency dependence measurements and confocal laser scanning microscopy. Weak to strong gels were formed with an elastic modulus G' from 10 to 1.000Pa, respectively. After cold-set gelation of our sy…
Calcifying phytoplankton standing stocks in the North Pacific from the R/V Kilo Moana cruise KM1712
2022
This dataset compiles the CaCO3 standing stocks of living coccolithophores (mg/m³), of detached coccoliths (mg/m³) and the integrated CaCO3 standing stocks of coccolithophores (mg/m²). The samples were collected in the North Pacific between Hawaii and the Gulf of Alaska during the R/V Kilo Moana cruise KM1712 in August 2017, with rosette Niskin bottles equiped with CTD (Sea-Bird SBE 9) at different depths throughout the photic zone including the deep chlorophyll maximum. To estimate the CaCO3 contribution by coccolithophore assemblages in each sample, we carried out the transformation of coccospheres in number of coccoliths, following the estimates by Yang and Wei (2003), and then we adopte…
Integrated annual calcium carbonate production of planktic calcifiers in the North Pacific from the R/V Kilo Moana cruise KM1712
2022
This dataset compiles the estimates of annual CaCO3 production, including the upper and lower limits of the estimates, for the 4 planktic calcifying groups considered in the study, the pteropods (mg/m²/yr), the heteropods (mg/m²/yr), the foraminifers (mg/m²/yr) and the coccolithophores (mg/m²/yr). The estimates derived from the living standing stocks of these 4 groups of organisms collected in the North Pacific between Hawaii and the Gulf of Alaska during the R/V Kilo Moana cruise KM1712 in August 2017. R code was used to calculate the integrated annual CaCO3 production for the different organisms, including the upper and lower limits (Gray, 2022).
Monitoring the whiting phenomenon in Lake La Cruz (Cuenca, Spain)
2020
[EN] In the present study, a five-year follow-up was performed by remote sensing of the calcium carbonate precipitation in La Gitana karstic lake also known as La Cruz (located on the province of Cuenca, Spain). The important role that calcium carbonate precipitation plays in the ecology of the lake is well known for its influence on the vertical migrations of phytoplankton, the concentration of bioavailable phosphorus and, therefore, the eutrophication and quality of the waters. Whiting take place between the months of July and August, and it can be studied at this time through its optical properties, with the main objective of offering updated data on a phenomenon traditionally studied an…
Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives
2012
2,3,6,7,10,11-Hexahydroxytriphenylene of good quality and purity can be obtained via anodic treatment of catechol ketals and subsequent acidic hydrolysis. The electrolysis is conducted in propylene carbonate circumventing toxic and expensive acetonitrile. The protocol is simple to perform and superior to other chemical or electrochemical methods. The key of the method is based on the low solubility of the anodically trimerized product. The shift of potentials is supported by cyclic voltammetry studies.
The influence of various synthesis methods on the catalytic activity of cerium oxide in one-pot synthesis of diethyl carbonate starting from CO2, eth…
2013
Different synthesis methods such as homogeneous precipitation at room temperature and supercritical water (T > 647 K and P > 22.1 MPa) were employed for cerium oxide preparation. Additionally, deposition of ceria on silica mesoporous material, SBA-15, was carried out. The obtained materials were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physisorption, X-ray photoelectron spectroscopy and CO2 temperature programmed desorption. Considerable variations in physico-chemical properties of the resulting materials were observed. The catalytic activities of pristine cerium oxide and ceria loaded on SBA-15 support were…