4 research outputs found
Hydrogen barrier coatings and liners for steel pipelines
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Identification et caractĂ©risation de la formule inhibitrice dâun extrait vĂ©gĂ©tal pour le blocage de la rĂ©action germination-croissance du carbonate de calcium : ModĂ©lisation des dĂ©pĂŽts
This Work focuses on the development of a new green inhibitor âParonychia Argentea extract â for reducing calcium carbonate scale formation on metallic surfaces. The effects of temperature on the efficiency of the inhibitor were investigated. Its antiscaling properties have been evaluated by chronoamperometry method and electrochemical impedance spectroscopy (EIS). The calcareous layers were characterized by scanning electron microscopy observations and X- ray diffraction rays. A complete scaling inhibition was obtained with a concentration of 108 ppm of green inhibitor for mineral water at 20°C. However, its efficiency decreases at 50°C. Electrohydrodynamic impedance spectroscopy was performed to elucidate the layer nature at the interface metal/ inhibitor/ solution. Furthermore, the effect of the inhibitor on oxygen limiting current was studied by linear voltammetry. For a better data processing and understanding the nucleation-growth process, it appeared interesting to investigate experimentally and theoretically the kinetics and the mass transfer phenomena at mineral potable water solution/ carbon steel interface. The model developed in this work predicts within a good accuracy the relative contributions of 3-D growth to the nucleation-growth process of calcium carbonate at disk electrode.Lâobjectif de cette thĂšse a Ă©tĂ© dâĂ©valuer lâefficacitĂ© dâun nouvel inhibiteur vert sur lâentartrage en remplacement des inhibiteurs chimiques classiques, Ă base de phosphonates nĂ©fastes pour lâenvironnement. Pour ce faire, nous avons suivi par chronoampĂ©romĂ©trie, lâĂ©volution du recouvrement par CaCO3 dâune Ă©lectrode en acier, en absence et en prĂ©sence dâinhibiteur vert. Lâeffet de la tempĂ©rature et de la vitesse dâagitation a Ă©tĂ© testĂ© sur cet inhibiteur. Les impĂ©dances Ă©lectrochimiques (SIE) ont Ă©tĂ© utilisĂ©es pour Ă©tudier la cinĂ©tique de formation de CaCO3. Les dĂ©pĂŽts obtenus ont Ă©tĂ© caractĂ©risĂ©s par microscopie Ă©lectronique Ă balayage (MEB) et par diffractomĂ©trie de rayons X (DRX). Lâinhibition totale de lâentartrage est obtenue en prĂ©sence de 108 ppm dâinhibiteur en solution Ă 20°C, Par contre, il perd son efficacitĂ© Ă 50°C. Des analyses complĂ©mentaires en spectroscopie dâimpĂ©dance Ă©lectrohydrodynamique ont Ă©tĂ© effectuĂ©es sur une Ă©lectrode en acier pour mettre en Ă©vidence le caractĂšre de couche poreuse Ă l'interface mĂ©tal/inhibiteur/solution. Par ailleurs, lâeffet de lâinhibiteur sur le courant limite de diffusion de lâoxygĂšne a Ă©tĂ© Ă©tudiĂ© par voltammĂ©trie linĂ©aire. Pour mieux comprendre le phĂ©nomĂšne de germination/ croissance du CaCO3, nous avons Ă©tudiĂ© la cinĂ©tique et le transfert de matiĂšre Ă lâinterface solution/mĂ©tal en prĂ©sence et en absence d'inhibiteur. Le modĂšle Ă©laborĂ© dans ce travail prĂ©dit dans une bonne prĂ©cision les contributions relatives de la croissance 3-D dans le processus de nuclĂ©ation-croissance des cristaux de CaCO3
Nucleation-growth process of calcium carbonate on rotating disk electrode in mineral potable water
International audienceThis paper presents numerical simulation for interpretation of chronoamperometric experimental curves of nucleation-growth process of calcium carbonate on rotating disk carbon steel electrode. The simulation based on finite element resolution was carried out to solve the convective-diffusion equation in order to calculate dioxygen gradient concentration at the electrode which allows the limiting current diffusion determination at various rotation speeds in the presence and absence of calcium carbonate. Methodology used in this paper opens a new way for chronoamperometric curve interpretation through analytical expression determination of lateral and vertical crystal growth rate on carbon steel, kL and kV, respectivel
Synthesis and Characterization of Egg Shell (ES) and Egg Shell with Membrane (ESM) Modified by Ionic Liquids
International audienceEgg shell (ES) is a biological macromolecule mainly containing calcite embedded in proteins and polysaccharides, while shell membrane predominantly contains proteins. Thus ES with membrane (ESM) possesses richer protein contents than ES. In the present work, ES and ESM have been separately modified using mono-and di-cationic imidazolium ionic liquids, [C 5 mim + ][Br-] (IL) and [Bis-(PhCH 2 MIm) + ][2Cl-] (DIL). Thus four modified products have been obtained namely ES-IL, ES-DIL, ESM-IL and ESM-DIL. In order to determine physico-chemical modifications of the ES due to the interactions with the ionic liquids, the structural, spectroscopic and thermal properties of all products were investigated by means of XRD, FTIR and TG/DTA. The IR spectra display significant changes in the 1400-1550 and 2800-3100 cm-1 regions confirming the insertion of IL and DIL into the ES and ESM layers. Furthermore, the XRD results indicate that this modification process influence the crystal structure of the ES. Thermal analysis suggests that the chemical modification increases the thermal stability of the ES and ESM. It has also been ascertained that presence of proteins in the shell membrane is responsible for increasing thermal stability in the order ES < ESM < ES-IL < ESM-IL < ES-DIL < ESM-DIL