Potassium Release Kinetics from K-Feldspar in Comparison with Muscovite as Influenced by Different Extractants

In Iran, no research has yet been performed on potassium release from feldspar in comparison with that from muscovite. The objective of this research was to compare potassium release kinetics of these minerals as influenced by organic and inorganic extractants using successive extraction method. The experiment was carried out in a completely randomized design with a factorial combination. Treatments consisted of three kinds of K-bearing minerals (Muscovite, and Yazd and Ward feldspars), three extractants including CaCl2, oxalic and citric acids of 0.01 M concentration and 6 times of extraction (1, 2, 8, 24 and 48 hours). The results indicated that the potassium release from muscovite was 6-8 times higher than that from feldspars. The type of extractant significantly affected potassium release. Potassium release by organic extractants was 2.5-3 times higher than that by CaCl2 as an inorganic extractant. Different kinetic equations showed that power function, parabolic diffusion and first order equations adequately described K release whereas Elovich equation did not. Among the three equations, power function equation was selected as the best model describing K release from the minerals. Based on the selected kinetic equations, it seems that potassium release from K-bearing minerals is controlled by diffusion process.