Preparation of a Montmorillonite-Based Nanoparticle Demulsifier and Its Demulsification Performance for Crude Oil Emulsion.

Using montmorillonite (MMT) as raw material, Fe₃O₄ nanoparticles were loaded on the surface of MMT by a solvothermal method to prepare magnetic montmorillonite (M-MMT). The MMT and M-MMT were functionalized with quaternized chitosan (QC) to obtain nanoparticle (NP) demulsifiers of MMT-QC and M-MMT-QC, respectively. The chemical composition and surface properties of the modified montmorillonite nanoparticles were characterized with scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, zeta potentiometer, and vibrating sample magnetometer, which confirmed the successful preparation of the NP demulsifiers. The demulsification performance of the NP demulsifiers for crude oil-in-water emulsion was evaluated by using bottle tests. The effects of demulsification time, pH, demulsifier dosage, and temperature on the demulsification efficiency were investigated. Results showed that under the condition of 25 °C, 1000 mg/L dosage, and pH 6, the demulsification efficiency of MMT-QC and M-MMT-QC was 98.00% and 98.82%, respectively. In addition, the magnetic NP demulsifier of M-MMT-QC has good recycling performance, with no significant decrease in demulsification efficiency within eight cycles. The demulsification mechanism was revealed and proposed. It is believed that the QC-modified magnetic nanoparticles can firmly combine with the protective film through electrostatic attraction and hydrogen bonds. Under stirring or oscillating conditions, the nanoparticles acquire sufficient kinetic energy to destroy the protective film at the oil-water interface, thereby promoting the oil droplet coalescence and enabling fast oil-water separation at room temperature.