Flotation is the only technique that enables the selective separation of Na and K feldspar minerals from each other. In this study, the flotation separation of Na-feldspar (albite) and K-feldspar (microcline) minerals were investigated in the presence of K+ ion as counter ion. In order to identify the role of K+ ions on the selective separation of feldspar minerals, solubility, adsorption, and desorption of K+ ions from microcline and albite surfaces were independently measured using ion selective electrodes. Adsorption isotherms in feldspars/K ion system were constructed, and the regions representing the ion exchange and ion adsorption delineated. Furthermore, the effect of K+ ions on selective separation of Na and K feldspars was confirmed through zeta potential, solubility, and micro-flotation studies along with adsorption/desorption studies. Our results revealed that K+ ions depressed albite, though the K+ ion acted as counter ion in this system, causing the flotation recovery of albite to sharply decrease compared to that of microcline. The mechanism of selective separation of albite and microcline in the presence of Na+ and K+ ions along with the implications of ion exchange/ion adsorption phenomenon to industrial operations is elaborated in the light of experimental and theoretical data.