Defective analcime/geopolymer composite membrane derived from fly ash for ultrafast and highly efficient filtration of organic pollutants.

Nanofiltration membranes (NFMs) are of great interest for water purification attributed by their excellent performance, while the high fabrication cost greatly limits their use. Herein, an ultra-low-cost zeolite-based NFM was developed by a simple hydrothermal method using fly ash as the raw material and used for the high-efficiency filtration of organic pollutants from wastewater. The as-obtained zeolite membrane was composed of crystalline analcime (ANA) type zeolite and amorphous geopolymer (GP) composite. Benefiting from the defects introduced large cavities and microporous channels in ANA, the ANA/GP composite membrane with a thickness of ∼60 μm exhibited permeation rates as high as 340-440 L/(m2·h·MPa), and the rejection rates are up to 97 % towards methylene blue. Moreover, the fabrication cost of the ANA/GP membrane is only $31.8/m2, far lower than the reported efficient NFMs. The development of the ANA/GP-NFM paves the way for developing commercially applicable membranes for organics separation and water purification.