期刊
ACS APPLIED MATERIALS & INTERFACES
卷 13, 期 42, 页码 49964-49973出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c14602
关键词
demulsification; oil-water separation; anion exchange; MOFs; dynamic process
资金
- National Natural Science Foundation of China [U1862111]
- Major Science and Technology Projects of Sichuan Province [2020ZDZX0008]
- Cheung Kong Scholars Program of China
- Graduate Scientific Research Innovation Foundation of SWPU [2019cxzd012]
This study proposed a phosphate-mediated anion exchange strategy to fine-tune the surface charge of a metal-organic framework, MIL-100(Fe), for effective demulsification of cationic surfactant-stabilized emulsions. The phosphate-exchanged MIL-100(Fe) exhibited enhanced demulsification efficiency by capturing the surfactant and causing irreversible deformation of emulsion droplets. The research highlighted a promising approach to deal with cationic surfactant-emulsified oily wastewater and revealed the fundamental demulsification process.
Demulsifying ionic surfactant-stabilized emulsions remains an emerging issue due to the stringent electrostatic barriers. In this work, a phosphate-mediated anion exchange strategy was proposed to fabricate a metal-organic framework, MIL-100(Fe), with adjustable surface charge for effective demulsification toward a cationic surfactant-stabilized emulsion. By adjusting the pH of the phosphate precursor solution, the surface charge of MIL-100(Fe) can be fine-tuned. At pH 3.0, the phosphate-exchanged MIL-100(Fe) with the zeta potential decreasing from 21.4 to 6.1 mV exhibited a significant enhancement of the demulsification efficiency (DE) from 35 to 91%. Further elevating the pH to 9.0 results in the zeta potential of the phosphate-exchanged MIL-100(Fe) to be reversed to -2.0 mV, and the DE can be optimized to 96% within 5 min. The demulsification mechanism was systematically explored based on the zeta potential, distribution of the surfactant, viscoelastic modulus evaluation, and morphological characterization of the emulsion in combination with monitoring of the dynamics process of demulsification. It was found that the phosphate-exchanged MIL-100(Fe) captured by the emulsion can lead to the release of the surfactant and heterogenization of the interfacial film, causing the elasticity of the emulsion to decrease and the irreversible deformation of emulsion droplets. Consequently, the destabilized emulsion could be subjected to the effective demulsification either by the fusion pathway mediated by the phosphate-exchanged MIL-100(Fe) or direct rupture. This work emphasized a facile and promising approach to deal with the cationic surfactant-emulsified oily wastewater and disclosed the fundamental demulsification process.
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