Molecular simulation of electrokinetics of montmorillonite surface coated with hexadecyltrimethylammonium cations
Q Zhao and SE Burns, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 516, 354-361 (2017).
Organoclays are effective sorbent component for nonionic species in slurry or drilling fluid. The surface electrokinetics controls the behaviors of suspended organoclay particles in a system mixed of water, colloidal particle and electrolytes. This study presents a molecular dynamics simulation to illustrate the structure and kinetics of organic surfactant coating, inorganic ions and water near montmorillonite surfaces. The simulated system contained approximately 10,000 atoms and was run as long as 15 ns, to ensure that both the size and time scale of the simulated system are large enough. The results were analyzed quantitatively to address the species distribution near the clay surface; and the difference of electrical potential near base and surfactant-modified montmorillonite surfaces. Simulation results indicated the organic coating could effectively shield the layer charges of the clay and also alter the alignment of water molecules near the clay surface. Consequently, the organoclay particles tend to have lower "effective charges" and less negative surface electrical potentials, in agreement with previous zeta-potential measurements. (C) 2016 Elsevier B.V. All rights reserved.
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