Influence of the modification method on the surface adsorption of stearic acid by natural calcite (original) (raw)
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SURFACE PROPERTIES OF NATURAL CALCITE FILLER TREATED WITH STEARIC ACID
In order to obtain hydrophobic material, the water suspension of natural limestone with the high content of calcite (>95 %), was treated with different amounts (0.5-4 %) of stearic acid dissolved in chloroform. Thermal analysis showed that at lower initial concentrations of stearic acid (up to 2 %), surfactant molecules are chemisorbed on calcite surface, while at higher initial concentrations acid molecules are additionally physisorbed on mineral surface. XRPD analysis of starting calcite as well as two modified products with 1.5 and 3 % of stearic acid indicated that modification of calcite surface with both amounts of stearic acid, did not cause any changes in the structure of calcite mineral. It was confirmed that long chain stearic acid, in presence of water, alters the calcite surface to strongly hydrophobic, where reaction between stearic acid and Ca 2+ ions occurs. Thus, the chemisorption of stearic acid on the calcite surface is responsible for retaining the lower surfactant layer on a charged surface while hydrophobic bonding causes formation of the upper surfactant layer. The optimal amount of stearic acid needed to cover the calcite surface with a monolayer of organic molecules lies between 1.5 % and 2 %.
Mechanism of stearic acid adsorption to calcite
Powder Technology, 2013
This paper presents the interpretation of binding mechanism of stearic acid for calcite surface in two modification methods. In the "dry" method, a surface dissociation of stearic acid is assumed where H + ion goes to a surface carbonate ion and stearic ion is chemisorbed on primary surface center of −Ca + ion which is only available for chemisorption. The structure of adsorbed layer indicates chemisorption of stearate, but due to steric effects, and the oblique or gauche conformation of hydrocarbon chains. A part of surface − Ca + centers can be blocked, which is explained by the result that physical adsorption dominates over 1.5%. In the "wet" method, by adding stearic acid, at concentration above the critical concentration of micelle formation in base solution, micelles are formed, and on the other side free stearic acid molecules or molecules from developed micelle dissociate. The resulting stearic ions can be chemisorbed on primary centers of −Ca + ions or participate in ion exchange with OH − ions from secondary surface centers. With increasing adsorption density, the adsorbed ions and molecules, due to interactions of hydrocarbon chains, and thickness of double electrical layer, achieve a vertical orientation and keep the trans-conformation of hydrocarbon chains.
International Journal of Current Research and Academic Review
Surfactant adsorption at rock-fluid interface is fundamental to wettability alteration that is relevant to enhanced oil recovery process but the extent of this adsorption can also impact the economic viability of the surfactant application in the process. In this paper, adsorptions of two biologically generated surfactants (rhamnolipid and greenzyme) on carbonate and sandstone rock surfaces have been studied and reported. The rocks' main components and physicochemical makeup were determined with the use of X-ray diffraction and scanning electron microscopy. The compositional analyses of sandstone and carbonate rocks show the dominant components as quartz and calcite respectively. From the adsorption investigations, rhamnolipid tends to show higher surface activity than greenzyme. It also shows stronger affinity for sandstone rock surface than carbonate while greenzyme shows stronger affinity for carbonate surface. Furthermore, decrease in adsorptions of rhamnolipid and greenzyme with increase in temperature and decrease in salinity was observed in all the systems. Finally, the adsorption models suggest rhamnolipid adsorption process to be mono-layer in nature, while greenzyme adsorption tends to be monolayer at low adsorption and heterogeneous at high adsorption.
Effect of fatty acids, water composition and pH on the wettability alteration of calcite surface
Journal of Petroleum Science and Engineering, 2006
Fatty acids in presence of water film alter calcite surface to oil-wet. The wettability alteration is dependent on the structure of the fatty acids, water composition and pH. Long chain fatty acid (stearic acid), strongly adsorbs onto the calcite surface from boil phaseQ (n-C 10 ) in oil/water/calcite system as indicated by contact angle measurements. On the other hand, short chain fatty acid (heptanoic acid) adsorbs on the calcite surface to a lesser extent, which agrees with bTraube's ruleQ.
On the Coating of Precipitated Calcium Carbonate with Stearic Acid in Aqueous Medium
Langmuir, 2010
A series of experimental precipitated calcium carbonates (PCCs) coated with commercial stearic acid (stearin), with the coating amount of stearin added to the PCC particles ranging from 3 to 13.5 wt %, were prepared in aqueous medium and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR and TGA results indicated that only calcium stearate is present without any free stearic acid left on the surface of the produced PCCs. It was also found that the calcium stearate formed on the coated surface is partially chemisorbed and partially physisorbed. Interestingly, the surface coverage of the chemisorbed stearate, determined by the DSC technique in about 3.25 wt %, was much lower than the theoretical full monolayer coverage (4.17 wt %) for the same set of particles. This result was confirmed by determining the amount necessary to cover the filler with a full monolayer of surfactant by means of a dissolution method where the amount of dissolved surface agent, after the coating reaction, was measured by gas chromatography (GC). In other words, a complete chemisorbed monolayer on the surface cannot be reached, even in the presence of an amount of stearate ions far in excess compared to those required by the stoichiometry. This can be explained by considering that the coating in aqueous medium is quite different from solvent or dry coating, since the process is controlled by micelle adsorption, followed by the collapse of micelles into double or multiple layers during the drying stage.
Influence of sulfate ions on the interaction between fatty acids and calcite surface
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006
The effect of sulfate ions on adsorption/displacement of long chain fatty acids onto/from calcite surface is investigated. The fatty acids used in this work are stearic acid (SA), oleic acid (OA) and 18-cyclohexyl-octadecanoic acid (CHOA). The main methods are thermogravimetric analysis for determining the extent of surface modification and vapour adsorption isotherm to evaluate the wetting behaviour. An appreciable reduction of adsorbed amount of fatty acids is observed in presence of sulfate ions. This is interpreted by the high affinity of the sulfate ions for the active sites of the calcite. In addition, they modify the calcite surface to a negative charge, as indicated by zeta potential measurements, hence reducing the availability of the active sites for carboxylate ions. The ability of sulfate ions to displace the pre-adsorbed fatty acids from the calcite surface is also demonstrated. It is mostly related to the molecular structure of the fatty acids, where the percentage of displacement by 0.1 M sulfate is found to be 7 and 10 for stearic acid and oleic acid, respectively. This work shows that the sulfate ions changed the wettability of calcite to more water-wet as indicated by water vapour adsorption isotherms. .no (A.A. Hamouda). fatty acids, and second part, the ability of sulfate ions to displace pre-adsorbed fatty acids.
A fundamental understanding of the interactions between mineral surfaces and amphiphilic surface modification agents is needed for better control over production and uses of mineral fillers. Here, we controlled the carboxylic acid layer formation conditions on calcite surfaces with high precision via vapour deposition. The properties of the resulting carboxylic acid layers were analyzed using surface sensitive techniques such as atomic force microscopy (AFM), contact angle measurements, angle resolved X-ray photoelectron spectroscopy (XPS) and vibrational sum-frequency spectroscopy. A low wettability was achieved with long hydrocarbon chain carboxylic acids, such as stearic acid. The stearic acid layer formed by vapour deposition is initially patchy, but with increasing vapour exposure time, the patches grow and condense into a homogeneous layer with a thickness close to that expected for a monolayer as evaluated by AFM and XPS. The build-up process of the layer occurs more rapidly ...
Adsorption of anionic and cationic polymers on porous and non-porous calcium carbonate surfaces
Applied Surface Science, 1994
The adsorption of anionic and cationic polymers onto calcium carbonate surfaces was studied by ellipsometry. Sodium polyacrylate was observed to both adsorb on and promote dissolution of polished limestone surfaces in 5 mM CaSO 4 solution at pH 10.3. It was not possible to differentiate between the two processes when they occurred simultaneously. Cationic starch adsorbed on the limestone surfaces at low concentrations and caused mineral dissolution at higher concentrations. The adsorbed amount of starch was higher on surfaces which were first made porous by partial dissolution than on freshly polished surfaces. Surfaces created by cleavage of Iceland spar calcite were quite stable against dissolution and the amount of starch adsorbed determined by ellipsometry agreed well with the adsorbed mass determined from batch adsorption experiments on ground calcite.
Reaction of Calcite With Surfactant-Based Acids
Proceedings of SPE Annual Technical Conference and Exhibition, 2006
... 9. Nasr-El-Din, HA, Al-Mohammed, A., Al-Shurei, AA, Merwat, NK, Erbil, MM, and Samuel, M.: Matrix Stimulation of Water Disposal ... AlKattan, M., Oelkers, E., Dandurand, J., Schott, J.: An Experimental Study of Calcite and Limestone Dissolution Rates as a Function of pH from ...