Cation clay reactions

Formation damage caused by clay migration may be observed when the injected brine replaces the connate water during operations such as water-flooding, chemical flooding including alkaline, and surfactant and polymer processes. These effects can be predicted by a physicochemical flow model based on cationic exchange reactions when the salinity decreases [1665]. Other models have also been presented [345,1245]. 

Cationic clays have also been used as supports for Cu. Cu-doped alumina-pillared montmorillonites have been employed in the oxidation of toluene and of xylenes with H2C>2. The pillaring and the Cu exchange are performed under acidic conditions at pH 2 and 3.5, respectively. It is unclear whether the Cu2+ remains fully associated with the clay in the presence of H2O2, which is itself acidic. Moreover, the reactions are unselective mixtures of ring-hydroxylated and side chain-oxidized products are obtained (180). 

H. Laudelout, R. van Bladel, G. H. Bolt, and A. L. Page, Thermodynamics of heterovalent cation exchange reactions in a montmorillonite clay, Trans. Faraday Soc. 64 1477 (1968). 

Cation exchange in soils or clay minerals involves replacement of a given cation on a given mineral surface by another cation. Exchange equations are commonly used to evaluate ion availability to plant roots and/or release of metals to soil water (e.g., heavy metals to groundwater or surface water). There are two major types of cation-exchange reactions in soil systems—homovalent and heterovalent cation exchange. 

Diquat and paraquat are readily adsorbed from aqueous solutions by soil particles 40, 41, 42, 43, 44, 45, 46, 47), montmorillonite (30, 41, 48, 49, 50, 51, 52, 53, 54, 55, 56), kaolinite 41, 50, 52, 53, 54, 55), vermiculite 29, 30, 49,56), biotite 29, 30), muscovite 29, 30), phlogo-pite (29), muck 46, 48, 51), and cation exchange resins 48, 57). Only small or insignificant amounts were adsorbed by charcoal and anion exchange resins 48, 51, 53). The compounds were adsorbed to cation exchange substances through cation exchange reactions for diquat by clay minerals (Equation 1). 

The layered silicate nanoparticles are usually hydrophilic and their interactions with nonpolar polymers are not favorable. Thus, whereas hydrophilic polymers are likely to intercalate within Na-activated montmorillonite clays [24-29], hydrophobic polymers can lead to intercalated [23,30-32] or exfoliated [33] structures only with organophilized clays, i.e., with materials where the hydrated Na+ within the galleries has been replaced by proper cationic surfactants (e.g., alkylammonium) by a cation exchange reaction. The thermodynamics of intercalation or exfoliation have been discussed [34-37] in terms of both enthalpic and entropic contributions to the free energy. It has been recognized that the entropy loss because of chain confinement is compensated by the entropy gain associated with the increased conformational freedom of the surfactant tails as the interlayer distance increases with polymer intercalation [34,38], whereas the favorable enthalpic interactions are extremely critical in determining the nanocomposite structure [39]. 

In their search for the development of PBFnano-composite materials, Hsu et al. prepared organically modified Montmorillonite MMT (m-MMT) by a cation-exchange reaction between Na+-Montotrillonite (Na+-Mont) clay and an ammonium salt of dodecyl-amine [46]. This MMT was used as a nanofiller in... 

Table 4.3 Equilibrium constants of cation exchange reactions between clay minerals and aqueous solution (Lerman 1979)...

The clay organophilization step was performed through the cationic exchange reaction between protonated adducts and clay and was investigated from FTIR spectra as shown in Fig. 2. The analysis of FTIR spectra (Fig. 2a) shows that there... 

Jlassi, K., A. Mekki, M. Benna-Zayani, A. Singh, D. K. Aswal, and M. M. Chehimi. Exfoliated clay/polyaniline nanocomposites through tandem diazonium cation exchange reactions and in situ oxidative polymerization of aniline. RSC Adv. 4, 2014 65213-65222. 

An extension of the relative simple formulation used in SCMs for surfaces with permanent eharges (see Section II.B.l) has been published recently [84]. A fictitious surface species (X ) was defined and hypothetical complexation reactions on site X were written, and thus cation-exchange reactions of permanent negative layer charges were easily incorporated into such model. The model showed not only to fit satisfactorily all of the experimental data of transition metal adsorption on montmorillonite but also to explain specific features of adsorption on clays compared to oxides. 

Usuki et al. (1993) introduced MMT nanoclay modification by studying the cation-exchange reaction of MMT nanoclays with an amino acid solution. It was found that the interlayers of MMTs were modified by an amino acid to produce new clay-intercalated stmctures. The typical case can be represented by the addition of modified MMTs on nylon 6 matrices for better clay dispersion with the reduction of molecular weight (MW) of nylon 6/clay nanocomposites (Usuki et al., 1993). A new network was further established between nylon 6 and MMT interlayer surfaces with the aid of ammonium cations. 

Identification of Clay Minerals Through Clay Complexes. Basic dyestuffs are adsorbed by clay minerals by a cation exchange reaction. It has been found that clay mineral-dye complexes exhibit characteristic thermograms that can be used to identify clay minerals. Certain... 

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