Modified Phillipsite as a Novel Ion-Exchanger for Potassium Extraction from Seawater

Abstract

Template-free preparation of phillipsite as a novel K⁺ ion-exchanger was studied systematically by hydrothermal synthesis. The alkalinity, dosage of water glass, dosage of H₂O, aging time, reaction temperature and time of hydrothermal synthesis were discussed in detail. The optimized material obtained about phillipsite through the synthesis and testing methods was performed. The K⁺ ion-exchange capacity and selectivity coefficient were tested. The molar composition for preparing high performance phillipsite obtained was 2K₂O:18SiO₂:Al₂O₃:510H₂O by optimizing synthetic conditions. The K⁺ ion-exchange capacity of phillipsite was 57.3 mg/g in seawater. The K⁺ selectivity coefficient was 88.6 in an equimolar K⁺ and Na⁺ mixed solution. Phillipsite can selectively capture K⁺ over other ions, and therefore can be used for potassium extraction selectively from seawater. Phillipsite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The XRD pattern indicated that the synthetic zeolite was phillipsite. The phillipsite particles exhibited cross-like shape and the average particle size was about 2.5 μm. The synthetic phillipsite was mainly consisted of Si, Al, K and O elements.