Stability of Mica, KFeldspar and Apatite in Water, Organic Matters and Citric Acid

Abstract

The short term stability of mica, feldspar and apatite in different geochemical conditions were tested in the laboratory. Different proportions of powdered minerals (<125 µm) were mixed with (1) organic matter with water, (2) water and (3) 2% citric acid. The mixtures were kept under room conditions with controlling the moisture content. The water soluble ionic concentrations of each mixture were measured and their variations with the time were studied. The study revealed that the dissolution of minerals is controlled by mineralogical characteristics of them and the chemical nature of solutions. Both mica and feldspar release higher values of potassium compared to other ions when they are in water or in moist organic matter. Feldspar is stable whereas mica and apatite are significantly unstable in the citric acid. However, mica releases considerably higher amount of iron in the acidic media (pH-2-3). The dissolution of apatite and K-feldspar is low when mineral mixtures contain biotite. Biotite mica and apatite have high potential to use as fertilizers for crops growing in acidic soils