Synthesis and characterization of K-phillipsite (K-PHI) membrane for potassium extraction from seawater

摘要

K-phillipsite (K-PHI) membrane was synthesized on the outer surface of a porous α-alumina tubular support by seeded hydrothermal synthesis using tetrabutylammonium bromide (TBAB) as template. The synthetic sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). The separation factors (α) of the sample to K~+ were researched using the mixed K~+-Na~+, K~+-Ca~(2+), K~+-Mg~(2+) solutions and simulated seawater as testing media, respectively. The synthetic membrane which is mainly composed of Si, Al, K, Na and O is typical K-PHI structure. The K-PHI membrane on the tubular support is defect-free and the thickness of the membrane is about 20 μm. The separation factors (α) of the sample to K~+ in the mixed K~+-Na~+ K~+-Ca~(2+), K~+-Mg~(2+) solutions are 18.1, 32.1 and 118.4, respectively. And the average separation factor of K~+ relative to Na~+ in simulated seawater is α_(K~+/Na~+) = 15.7. Therefore the sample has preference selectivity to K~+ and can be used as a potential inorganic membrane for potassium extraction from seawater.