Étude cinétique du dépôt calcomagnésien sur une électrode en Titane et mécanisme de détartrage, comparaison entre la méthode chimique et électrochimique

171 p. ; ill. ; 30 cmL'élévation de la température ainsi la vaporisation partielle de l'eau de mer sont responsables de l'entartrage des évaporateurs et surtout du réchauffeur de saumure de l'unité de dessalement. En effet, les tartres réduisent les sections de passage, dégradent les états de surface et augmentent les pertes de charge et par conséquent les dépenses énergétiques liées à la circulation de l'eau deviennent importantes. Lors de ce travail, nous avons utilisé différentes techniques chimiques et électrochimiques permettant une étude à la fois thermodynamique et cinétique du phénomène d'entartrage dans une eau de mer artificielle.L'étude de l'entartrage par voie électrochimique nous a permis de fixer le potentiel à -1.3 V/Ag-AgCl qui entraine ainsi des dépôts calcomagnésiens riche en CaCO3 et en Mg(OH)2 sur l'électrode en titane. Il a été démontré que la température peut favoriser prioritairement la formation de l'aragonite ou de la brucite en fonction du potentiel appliqué. L'ajout de fortes quantités en ions sulfate présente un effet d'inhibition sur la déposition calcaire, magnésienne et calcomagnésienne.L'utilisation du dégazage contrôlé a montré que la déposition calcaire est affectée par l'augmentation de la concentration en Ca2+. Les ions magnésium inhibent la déposition calcomagnésienne et l'ajout progressif du magnésium rend la surface de l'aragonite secondaire "ballon de rugby" plus striée. Enfin, l'augmentation de la concentration en ions sulfate a permis de diminuer la quantité du dépôt sur le verre alors que sur le titane le nombre de cristaux est plus important dont les tailles sont plus petite

The effect of surface treatments on the electrochemical behavior of titanium alloy in seawater by electrochemical impedance spectroscopy (EIS)

Seawater contains many minerals, dissolved gases, including oxygen O2 cellular organisms, suspended solids and sediments that sometimes impart high turbidity. Chemical and biological characteristics of seawater make it a particularly aggressiv materials in particular titanium. Physico-chemical interactions between a metal material and its environment can lead to corrosion of material. Deterioration of metal due to microbial activity is called biocorrosion or corrosion induced by microorganisms (CIM). Because of its economic and environmental importance, CIM has been extensively over past five decades and several models studies have been proposed to explain the mechanisms biocorrosion observed. Many sectors are a facilities, plant thermal (heat exchangers). Biofilm formation on walls of conduits considerably reduces heat transfer, this is particularly important in case of heat exchanger tubes. We noted that electrode moves corrosion potential to more cathodic values. And more, the short stay of titanium in natural seawater, corrosion potential varies around - 250 mV/Ag/AgCl, and then it reaches less cathodic values to longer residence time. Electrochemical impedance measurements showed the presence of one loop relative to the capacitive charge transfer phenomenon of metal/passive layer. Keywords: Natural seawater, Titanium, OCP, Electrochemical impedance spectroscop

Recuperation of silver from wastewater of miroiterie of thenia (Algeria)

In Algeria, the nonexistence of silver mines makes it particularly rarer than its classification among the precious metals imposes its metal recuperation. The objective of this study is electrodeposition of silver ions of sludge from wastewater of miroiterie of SOMIVER Thenia. The process applied in this case is electrolysis of sludge formed in a glass cell containing two electrodes: a cathode made of aluminum and a graphite anode. An adjustable continue current source capable of delivering from 1 to 10 Amps, this causes the cathode reaction electrodeposition of silver. Therefore, we lead to precede by comparison determinations under the effect of weight of cathode. Its weighing before and after electrolysis, and weight difference, means that amount of silver accumulated. Second, we determined the characteristics of sludge by electrochemical aluminum interface (OCP linear voltammetry and electrochemical impedance spectroscopy) before and after electrolysis, this is made possible by Potentiostat PGZ 301. In the electrolysis of silvering solution it has proved that low currents from 0.5 to 4 A can get a good yield of deposit silver where ∆m increases linearly with increasing intensity of electrolysis current for a period of 30 minutes. By against, for electrolysis currents higher than 4 A we recorded decrease in the amount of silve

Study of the antideposit effect of 2-Hydroxy-4-methylbenzylphosphonic acid

The scale inhibitor, 2-hydroxy-4-methylbenzylphosphonic acid (HMBP) appears efficient for desalination plants of sea water. A concentration of 26.5 ppm (131 μmol/L) prevents the calcareous magnesium deposits. The anti-scale effect of this inhibitor is achieved by chronoamperometry at imposed potential and complex impedance. SEM allows observation of the calcareous magnesium deposits with and without inhibitor 2-hydroxy-4-methylbenzylphosphonic acid (HMBP

Verification of Levich law. determination of hydrogen currents accoring to temperature and polarization potential during calcareous deposition

The complexity of calcareous deposits processes in a marine environment results in simultaneous effects of the following parameters: temperature, polarization potential, interfacial pH, chemical composition, etc.. The comprehension of these processes implies studies in artificial seawater and a follow-up of the parameters by voltamperometry and chronoamperometry. Calcareous deposits electrochemically are very often used to follow up the evolution of scale deposition in desalination circuits. Again, the scale formation is brought about by electrochemical reduction of dissolved oxygen. The hydroxyl ions formed on the metallic surface engender a rise of interfacial pH which causes calcareous deposition (CaCO3 and Mg(OH)2). This reaction goes with reaction of hydrogen evolution which could disrupt the formed deposit. A study is carried out in a solution of seawater ASTM without calcium and without magnesium (so that the deposit will not be formed) on a titanium rotating disk electrode monitored between 300 and 1000 rpm. Study shows that Levich criterion is checked for the four values of selected potential on the diffusion plateau and a very cathodic polarization potential and a high temperature favors hydrogen current rat

Transition-metal complexes of N,N′-di(4-bromophenyl)-4-hydroxycoumarin-3-carboximidamide: synthesis, characterization, biological activities, ADMET and drug-likeness analysis

International audienc

Crystal structure, Hirshfeld surface and reactivity of novel ligand-L-AT1 derived from dehydroacetic acid: intermolecular interactions with SARS-Cov-2/main protease

International audienceThe crystals of new ligand, namely (3E)-6-methyl-3-{1-[(pyridin-3-ylmethyl) amino] ethylene}-2H-pyran-2, 4(3H)-dione) (L-AT1), were synthesized using the evaporation solution technique. Single-crystal X-ray diffraction and physico-chemical characterization (ATR, proton and carbon-13 NMR and UV-Visible) of L-AT1 were reported. In addition, Hirshfeld surface analysis (HSA) of the solid compound, structure optimization, Mulliken and NBO charges, global indices of reactivity, local reactivity descriptors and molecular electrostatic potential (MEP) of the ligand were investigated theoretically. XRD analysis showed that L-AT1 crystallizes in the triclinic space group P-1 and the structure was stabilized through hydrogen bonds. HAS revealed that H horizontal ellipsis H (46.5%) and O horizontal ellipsis H (25.7%) contacts are in control of crystal stacking. The energy gap (4.679 eV) and reactivity descriptors indicate the stability of L-AT1. The Mulliken and NBO charges showed that the protons have a positive charge and the heteroatoms exhibit negative charges. The Fukui function and MEP study revealed that the heteroatoms are the most reactive sites for an electophilic attack on the ligand. Molecular docking simulation shows that the significant binding affinity of L-AT1 with SARS-CoV-2/Mpro is due to the formation of high number of hydrogen bonds