Cation-Intercalated Clay-Based Two-Dimensional Membranes for Effective Desalination and Molecule Sieving

Montmorillonite (MMT) is known as an ion-exchangeable material, and cations between MMT nanosheets are easily exchanged by other cations. In this work, Ca 2+, Fe 3+, and Al 3+ intercalated two-dimensional MMT membranes were developed by ion exchange of pristine MMT membranes (Na + -MMT), and their ion and dye removal abilities were investigated. The d -spacings of hydrated Fe 3+ intercalated MMT membrane (Fe 3+ -MMT) and Al 3+ intercalated MMT membrane (Al 3+ -MMT) were decreased compared with hydrated Na + -MMT membrane due to the stronger electrostatic attraction between Fe 3+ /Al 3+ and negatively charged MMT nanosheets. Ion and dye sieving performances were improved significantly after the intercalation of Ca 2+, Fe 3+, and Al 3+ into MMT membranes. Al 3+ -MMT membrane with a thickness of 1.17 μm could exclude 94% of Na +, and its ion sieving performance remained stable during a 120-h ion sieving experiment. Moreover, the rejection rate for rhodamine B (RB) reached 94% using an Al 3+ -MMT membrane with a thickness of 500 nm, and a water permeance of 73 L m –2 h –1 bar –1 was achieved. The excellent ion and dye sieving performances make it promising in the application of desalination and nanofiltration.