Search results for "carbonation"
showing 10 items of 10 documents
On the physico-chemical evolution of low-pH and CEM I cement pastes interacting with Callovo-Oxfordian pore water under its in situ CO2 partial press…
2014
International audience; Abstract Within the framework of geological repositories for radioactive waste, structural concretes must be adapted to the underground chemical conditions. CEM I cement-based materials are characterised by high pH that may produce an alkaline plume in the near-field of the repository. In order to avoid this problem, low-pH cements have been designed. This study compares the physico-chemical behaviour of a low-pH material with a CEM I cement paste, both being subjected to leaching by an aqueous solution. An original experimental setup was designed to reproduce the underground conditions using a specific CO2 regulation device. Under these conditions, the low-pH materi…
Halloysite Nanotubes: Controlled Access and Release by Smart Gates
2017
© 2017 by the authors. Licensee MDPI, Basel, Switzerland. Hollow halloysite nanotubes have been used as nanocontainers for loading and for the triggered release of calcium hydroxide for paper preservation. A strategy for placing end-stoppers into the tubular nanocontainer is proposed and the sustained release from the cavity is reported. The incorporation of Ca(OH) 2 into the nanotube lumen, as demonstrated using transmission electron microscopy (TEM) imaging and Energy Dispersive X-ray (EDX) mapping, retards the carbonatation, delaying the reaction with CO 2 gas. This effect can be further controlled by placing the end-stoppers. The obtained material is tested for paper deacidification. We…
Novel concepts on the recovery of by-products from alkaline pulping
2016
Innovative biorefinery concepts were developed for the separation and utilization of organic materials, especially aliphatic carboxylic acids, lignin, and extractives, which are formed as by-products during wood-based alkaline delignification processes. The partial recovery of sodium as NaOH and aliphatic carboxylic acids from hardwood soda-AQ black liquor was studied via electrodialysis. The lignin was partly (about 59 % of the initial lignin) precipitated from black liquor by carbonation (pH to about 8.5) followed by electrodialysis or H2SO4 (pH to about 2), with subsequent precipitation of more lignin and the liberation of aliphatic acids. The Na2SO4 formed was successfully separated fro…
Laminated carbonate deposits in Roman aqueducts: Origin, processes and implications
2013
Carbonate deposits in Roman aqueducts of Patara and Aspendos (southern Turkey) were studied to analyse the nature of their regular layering. Optical microscopy and electron-backscattered diffraction results show an alternation of dense, coarsely crystalline, translucent laminae composed of bundles and fans of elongate calcite crystals with their c-axes parallel to the long axis, and porous, fine-grained laminae with crystals at near-random orientation. The ?18O and ?13C data show a strong cyclicity and anti-correlation, whereby high and low ?18O values correspond to dense columnar and porous fine-grained laminae, respectively. Geochemical analyses show similar cyclic changes in carbonate co…
Partial Recovery of Aliphatic Carboxylic Acids and Sodium Hydroxide from Hardwood Black Liquor by Electrodialysis
2014
The partial recovery of sodium as NaOH and sodium-free aliphatic carboxylic acids (formic and acetic acids together with various hydroxy carboxylic acids) from alkaline hardwood black liquor (BL, pH about 14) was studied by using electrodialysis (ED). In the first phase, the lignin was partly (about 59% of the initial lignin) precipitated from BL by carbonation (pH to 8.5). Furthermore, the carbonated liquor, mainly containing NaHCO3/Na2CO3 and Na salts of aliphatic carboxylic acids and lignin, was subjected to ED for recovering NaOH and sodium-free aliphatic acids. In the second phase, the carbonated BL was further acidified with H2SO4 (pH to about 2.5) for precipitating more lignin (about…
Microbiological quality of carbonated drinking water produced with in-home carbonation systems.
2005
The microbiological quality of carbonated water produced with tap water in commercial in-home carbonation systems was determined, the results being discussed in the context of the microbiological quality of the tap water used, the properties of the drink makers, and the procedures of preparation and washing of various parts of the appliance. The last-mentioned data were received from each participant of the study by questionnaire. Escherichia coli, coliforms, fecal streptococci and spore-forming sulphite-reducing anaerobes were used as indicators for the hygienic quality of the water. Tap-water samples were collected according to the usual procedure when filling the carbonating bottle, i.e.…
Weathering of gasification and grate bottom ash in anaerobic conditions
2009
Abstract The effect of anaerobic conditions on weathering of gasification and grate bottom ash were studied in laboratory lysimeters. The two parallel lysimeters containing the same ash were run in anaerobic conditions for 322 days, after which one was aerated for 132 days. The lysimeters were watered throughout the study and the quality of leachates and changes in the binding of elements into ash were observed. The results show that organic carbon content and initial moisture of ashes are the key parameters affecting the weathering of ashes. In the grate ash the biodegradation of organic carbon produced enough CO 2 to regulate pH. In contrast the dry gasification ash, containing little org…
Characterization of Hardwood Soda-AQ Lignins Precipitated from Black Liquor through Selective Acidification
2016
In the development of integrated biorefinery process alternatives to produce value-added by-products, various black liquors from sulfur-free pulping processes offer potential feedstocks for recovering their main chemical constituents, lignin and aliphatic carboxylic acids. In this study, lignin fractions were obtained from silver birch (Betula pendula) soda-anthraquinone black liquor by carbonation (pH to about 8.5) or by acidification (pH to about 2) with H2SO4 after carbonation or directly. These fractions were characterized by Fourier transform infrared (FTIR), ultraviolet (UV), energy dispersive X-ray fluorescence (ED XRF), and 13C nuclear magnetic resonance (13C NMR) spectroscopy. In a…
( n ‐Bu 2 Sn) 2 O(CO 3 ): An active, robust and recyclable organotin(IV) for the direct synthesis of linear organic carbonates from carbon dioxide an…
2017
Organotin(IV) compounds are known to promote the direct synthesis of organic carbonates from carbon dioxide and alcohols. In the past, structural studies have highlighted that the carbonato moiety is a recurring ligand of tin species collected during CO2 pressurized reactions. In a mimetic approach and in order to achieve an available and recyclable precursor, the title compound (n-Bu2Sn)2O(CO3) (1) was prepared in a single step by reacting commercial di-n-butyltin dichloride with an aqueous solution of sodium carbonate. Compound 1 was characterized using infrared spectroscopy and thermogravimetric and elemental analyses. Multinuclear NMR investigations in solution were also conducted. Comp…
Risk of failure in existing RC balcony and strength verification under degradation phenomena
2020
Abstract In the present paper, the safety conditions of reinforced concrete (RC) balconies subject to degradation phenomena caused by carbonation, presence of chlorides or water infiltration were examined. After a brief review of the typical damages of balconies occurring with detachments of plaster and bricks expulsion, some cases of collapses of balconies recently occurred were presented. Therefore, a calculation model was proposed for a hand verification of the flexural and shear strength of existing corroded T beams cast in place of lightened RC orthotropic slabs forming the balcony and for the calculus of deflection including slippage of steel bars. Diffused and pitting corrosion on st…