Abstract
It is difficult to selectively separate and uptake small amounts of K+ from seawater in the presence of a large amount of Na+. During investigation of the cation-exchange characteristics of inorganic ion exchangers, we have discussed that K⇔ in aqueous solution are strongly held on some synthetic fluorine tetrasilicic micas by a cation-exchange reaction at room temperature.
From among the successfully synthesized micas, sodium ion-exchanged hectorite, Na1/3Mg8/3Li1/3Si4O10F2·H2O (Na+H), and sodium ion-exchanged taeniolite, NaMg2LiSi4O10F2·2H2O (Na+T), were found to be promising. Their removal behaviors of K+ from model aqueous solutions, apractical seawater, and some brines were examined by normal batch methods.
It was found that ⇔ exchange isotherm of Na+T rises steeply and attains plateau above the diagonal line in low-concentration region of K+, which reveals that K+ are extremely preferred to Na+ in the low-concentration region. The order of K+ selectivity was Na+H<<Na+T in the lowcollcentration region. Further, the Na+T was found to selectivity take up a regular amount of K+independent of the concentrations of Na+ and K+ in solution.
It is concluded that Na+T can be utilized in the separation and uptake of K+ from seawater (K+ 370ppm, Na+ 10,600ppm).
