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.