Selective flotation of K-feldspar from Na-feldspar in alkaline environment

Abstract

Abstract In this study, a selective flotation process for the separation of K-feldspar from Na-feldspar was developed for the beneficiation of a Norwegian microcline-quartz pegmatite sample. The K-feldspar flotation was performed in alkaline environment (pH 10.5–11.6) with only the addition of NaOH as a modifier and non-ionic Brij58 as a frother, on a fluorine-amine activated bulk feldspar concentrate from the preceding feldspar-quartz separation. The K-feldspar flotation resulted in a K-feldspar concentrate of 14.3% K2O at 77% K-feldspar recovery and K2O/Na2O ratio of 10.4. The NaOH conditioning of the fluorine-amine activated feldspars resulted in rapid desorption of fluorine, and the selectivity of the process was assumed to result from the more rapid desorption of fluorine-amine complexes from the Na-feldspar surface compared to that of the K-feldspar surface. In relation to this, the use of NaOH was found to be superior to that of KOH, the use of DI water was found to be superior to that of tap water, and the introduction of Ca ions was shown to be highly detrimental to the process. In general, the results strongly indicate that the developed process may yield substantially higher K- and Na-feldspar grades and recoveries at fewer flotation operations and lower total chemical consumptions, compared to existing practices on similar mixed feldspar mineral samples.