Sustainable and resource-efficient synthesis of zeolite membranes in a fluoride-free, organic template-free dilute solution

Environmentally friendly and sustainable synthesis technologies hold considerable significance in the manufacturing of high-performance mordenite membranes. Herein, a high-performance mordenite membrane was successfully fabricated on a macroporous tube under fluoride-free and organic template-free conditions, using a highly diluted synthesis solution with a molar composition of H₂O/SiO₂ = 250. This approach eliminated the necessity of fluoride and template agents while reducing chemical usage <i>via</i> a highly diluted solution. The effects of the presence of seed layers and corresponding coating methods and crystallization temperature and time on membrane formation and isopropanol/water separation performance were systematically investigated. Results indicated that high-quality membrane formation was facilitated by a seed layer prepared <i>via</i> variable-temperature hot dip-coating on macroporous tubes. Under optimized preparation parameters, the resulting mordenite membrane achieved a permeation flux of 3.24 kg m^-2 h^-1 and a separation factor exceeding 10 000 in separation of isopropanol dehydration. These findings collectively demonstrate the potential of this fluoride-free, template-free, and diluted-solution approach for producing high-performance mordenite membranes boasting significant environmental and economic advantages.