Regularities of fluorine leaching from the rocks by organic acids

Abstract

Experiments on fluorine leaching from the rocks (alkaline agpaitic granite, dacite, and feldspathic-quartzy aleurite) by 0.005 M solutions of acetic, tartaric, citric, and oxalic acids were carried out. The previously revealed fact of decrease in the fluorine leaching by organic acids as compared with that by distilled water with an increase in acidity of solutions in the pH range from 6.3 to 3.5 is confirmed. According to the leaching ability in relation to distilled water, organic acids are formed a number: oxalic > citric > acetic ≈ tartaric. It is assumed that decrease in pH leads to sorption of fluorides as a result of the replacement of adsorbed hydroxyl ions. From this point of view, less intensive (compared with distilled water) fluorine leaching in acidic medium can be associated with sorption immobilization of fluoride ions in the solid phase. A positive correlation between amounts of leached fluorine and magnesium indicates the existence of a certain common, as well as not established mechanism for transition of these elements from minerals to aqueous solution.