Comprehensive Characterization of the Structure and Gel Property of Organo-Montmorillonite: Effect of Layer Charge Density of Montmorillonite and Carbon Chain Length of Alkyl Ammonium

• Main Authors: Jun Qiu, Dongliang Liu, Yueting Wang, Guowei Chen, Shan Jiang, Guoqing Li, Yaqi Wang, Wenxin Wang, Peng Wu, Xiaodong Liu, Guifang Wang, Xianjun Lyu
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Minerals
• Subjects: montmorillonite; layer charge density; alkyl ammonium; carbon chain length
• Online Access: https://www.mdpi.com/2075-163X/10/4/378

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.