Swelling Phenomena of the Nonswelling Clay Induced by CO₂ and Water Cooperative Adsorption in Janus-Surface Micropores

Abstract

With the development of microscopy and sensor techniques, it becomes evident that nonswelling clays show swelling behavior under CO 2 − water mixture environments at high pressures and temperatures. The examples include Illite, muscovite, and kaolinite-rich rock samples. Here, we investigated the underlying mechanisms of kaolinite swelling induced by CO 2 and water using molecular simulations and low-pressure gas adsorption experiments. The results suggest the cooperative adsorption behavior of CO 2 and water on contact with kaolinite micropores, which have distinct wettabilities on the two adjoining interlayer surfaces. Even if clay-bound water exists, CO 2 can enter the micropores to induce swelling. The measured micropore volume, simulated equilibrium stable interlayer distance with pure water, and that with CO 2 −water mixture were used in the swelling estimation, which shows good agreement with our experiments. The CO 2 and water molecule distributions inside the interlayer micropores verify the importance of the wettabilities of the kaolinite surfaces in this cooperative adsorption behavior. The result extends the traditional understanding of the swelling mechanism, i.e., cation hydration and subsequent osmotic processes. In addition to earlier observations of kaolinite swelling behavior with potassium acetate, our study indicates the significance of the subtle balance of the noncovalent interactions between CO 2 , water, and the kaolinite Janus surfaces.

Methane Hydrate Formation in the Salty Water Confined in Clay Nanopores: A Molecular Simulation Study

“…Kaolinite is a 1:1 type dioctahedral aluminosilicate, which is formed by an octahedral aluminum−oxygen (gibbsite) layer and a tetrahedral silicon−oxygen (siloxane) layer. 57 The gibbsite surface has many hydroxyl groups and show strong affinity for water and salt ions, 58 while the siloxane surface is distributed with silicon−oxygen rings and may show some affinity for CH 4 . The lattice parameters and atom coordinates of the kaolinite crystal structure were taken from the American Mineralogist Crystal Structure Database.…”

Complex Coupled Effects of Seawater Ions and Clay Surfaces on CH4 Hydrate Formation in Kaolinite Janus-Nanopores and Bulk Solution

“…38 A kaolinite sheet was constructed by cutting 49 kaolinite unit cells (7 × 7 × 1). It is noted that a kaolinite sheet has Janus surfaces, 39 that is, one hydrophilic gibbsite surface with the presence of many hydroxyl groups and one relatively hydrophobic siloxane surface. Thus, a Janus double-nanopore model can be constructed by three layers of kaolinite sheets with specific orientations: as shown in Figure 1, the upper nanopore was hydrophilic nanopore (Pgg) with two gibbsite surfaces facing the solution, while the lower nanopore was hydrophobic nanopore (Pss) with two siloxane surfaces facing the solution.…”

Data-Driven Experimental Design of Rheological Clay–Polymer Composites

“…16−18 A typical formulation of a rheological agent is composed of a liquid phase (water, oil, or emulsion) and a clay-based solid phase. The latter may refer to pure clay minerals, 16 organoclays, 19 or multicomponent formulations which incorporate clays, 20,21 polyacrylic or cellulosic polymers, 8,22,23 surfactants, 24 salts, 24 or hydroxides. 25 Among clays, smectites have been intensively studied for their swelling properties and high cation exchange capacity.…”

“…Bentonite-based rheological agents are extensively used to prevent dangerous architectural operations during oil and gas extraction or install underground pipelines, cables, and service conduits through noninvasive horizontal directional drilling operations. − A typical formulation of a rheological agent is composed of a liquid phase (water, oil, or emulsion) and a clay-based solid phase. The latter may refer to pure clay minerals, organoclays, or multicomponent formulations which incorporate clays, , polyacrylic or cellulosic polymers, ,, surfactants, salts, or hydroxides . Among clays, smectites have been intensively studied for their swelling properties and high cation exchange capacity. , However, palygorskites and sepiolite are also suitable as thixotropic agents and viscosity controllers. , The exceptional performance of clay-based rheological agents is typically evaluated by the yield point and the plastic and apparent viscosity.…”