Abstract
In this work, the effect of layer charge density of Na-montmorillonite (Na-MT) and carbon chain length of alkyl ammonium on the structure and gel property of organo-montmorillonite (organo-MT) was studied by using X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric (TG) analysis, contact angle test, molecular dynamics (MD) simulation, and gel apparent viscosity determination experiment. The results of XRD show that Na-MT with lower layer charge density is easier to swell after intercalation of alkyl ammonium, and the basal spacing of organo-MT increases with the increase of carbon chain length. The results of FTIR show that the absorption bands at 2924 cm−1 and 2853 cm−1 shift towards low frequency region with the increase of carbon chain length, and the absorption bands at 515 cm−1 and 463 cm−1 move towards high frequency region when the layer charge density increases. The mass loss of organo-MT evidently increases with the increase of layer charge density of Na-MT or carbon chain length of alkyl ammonium. The contact angle test results are well in line with the TG data and reveal that alkyl ammonium with longer carbon chain can significantly improve the hydrophobicity of organo-MT. MD simulation indicates that, when the layer charge density is low, the distribution of alkyl ammonium gradually changes from parallel double layers to partially inclined distribution with the increase of carbon chain length, but when the layer charge density is high, the distribution of alkyl ammonium gradually changes from three layers into four layers. The test results of the apparent viscosity of the gel formed by organo-MT in xylene show that the apparent viscosity of organo-MT gel is negatively correlated with the layer charge density of Na-MT and positively correlated with the carbon chain length of alkyl ammonium.
Highlights
IntroductionMontmorillonite (MT) is a kind of typical phyllosilicate clay mineral and is rich in nature
Montmorillonite (MT) is a kind of typical phyllosilicate clay mineral and is rich in nature.Its structure is an octahedral sheet sandwiched by two tetrahedral layers [1,2]
The effect of layer charge density of Na-MT and carbon chain length of alkyl ammonium on the structure and gel property of organo-MT was systematically studied by using many characterization techniques
Summary
Montmorillonite (MT) is a kind of typical phyllosilicate clay mineral and is rich in nature. In order to expand the application of MT in industry, organo-MT is synthesized by intercalating surfactant into interlayer space of natural MT [11] In this way, interlayer distance of MT obviously increase and new sorption sites can be formed [12], besides, inorganic cation can be exchanged by surfactant, which results in that the surface property of MT converts from hydrophilic to hydrophobic. Large amounts of works on the organic modification of MT have been done, but to our knowledge, there is no systemic comparative study about the effect of layer charge density of Na-MT and carbon chain length of alkyl ammonium on the structure and gel property of organo-MT. The research results of this work can bring new insights into the influence mechanism of layer charge density of MT and carbon chain length of alkyl ammonium on the structure and gel property of organo-MT, which can pave the way to apply organo-MT in industry
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