A B S T R A C TThis work investigated the inhibitive effect of citric acid (CA), sodium citrate (SC), and their mixture (CA-SC) on the CaCO 3 scale. The study was carried out using chronoamperometry, impedancemetry, and fast-controlled precipitation methods. The electrochemical study showed that CA provides a slight inhibition of CaCO 3 deposit at a concentration of 70 ppm on stainless steel surface. The use of SC alone inhibits very little the formation of scale. The use of the mixture (50% of CA and 50% of SC) with small concentration led to significant inhibition of the CaCO 3 formation. The deposits formed were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The XRD showed that the intensity of the preferential orientation (1 0 4) corresponding to crystallographic plans of calcite decreases and the SEM demonstrated a decrease in calcite crystal size from 10 to about 2 μm.
International audienceIn this investigation, Mn3O4 spinel-type oxide was synthesized at low temperature using the Pechini process. We employed a sol-gel route, in which a solution of Mn(II) in a mixture of citric acid and ethylene glycol was heated to form a polymeric precursor, followed by annealing at lower temperature. The oxide obtained was identified by X-ray diffraction, scanning electron spectroscopy, and Raman spectroscopy. The results revealed that the formation of Mn3O4 hausmannite structure with a minor secondary phase of MnSO4 occurred at or above 280 A degrees C. The sample powder consisted of fine grains with homogeneous morphology and an average size close to 1 mu m was obtained. This new preparation procedure yielded an electrode oxide which appears to be a promising cathode material for fuel cells and metal-air batteries
The antiscale properties of the aqueous extract of olive (Olea europaea L.) leaves as a natural scale inhibitor for stainless steel surface in Hammam raw water were investigated using chronoamperometry (CA) and electrochemical impedance spectroscopy techniques in conjunction with a microscopic examination. The X-ray diffraction analysis reveals that the scale deposited over the pipe walls consists of pure CaCO calcite. The CA, in accordance with electrochemical impedance spectra and scanning electron microscopy, shows that the inhibition efficiency increases with increasing extract concentration. This efficiency is considerably reduced as the temperature is increased.
The formation of calcium carbonate CaCO3 in water has some important implications in geoscience researches, ocean chemistry studies, CO2 emission issues and biology. In industry, the scaling phenomenon may cause technical problems, such as reduction in heat transfer efficiency in cooling systems and obstruction of pipes. This paper focuses on the study of the glutamic acid (GA) for reducing CaCO3 scale formation on metallic surfaces in the water of Bir Aissa region. The anti-scaling properties of glutamic acid (GA), used as a complexing agent of Ca(2+) ions, have been evaluated by the chronoamperometry and electrochemical impedance spectroscopy methods in conjunction with a microscopic examination. Chemical and electrochemical study of this water shows a high calcium concentration. The characterization using X-ray diffraction reveals that while the CaCO3 scale formed chemically is a mixture of calcite, aragonite and vaterite, the one deposited electrochemically is a pure calcite. The effect of temperature on the efficiency of the inhibitor was investigated. At 30 and 40°C, a complete scaling inhibition was obtained at a GA concentration of 18 mg/L with 90.2% efficiency rate. However, the efficiency of GA decreased at 50 and 60°C.
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