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

[Display omitted] •Nanofiltration membrane (NFM) was synthesized from fly ash by simple method;•Defects in analcime crystals introduced larger voids and channels;•Super-high flux (330−440 L·m−2 h-1 MPa-1) and rejection rate (> 95 %) for wastewater purification;•Ultra-low fabrication cost of the NFM (∼31.8 $/m2). 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.