Analysis of Structural Modifications of Phlogoptite from Bahia/Brazil as an Alternative Source of Potassium in Agriculture

Resumo

Brazil has an enormous agricultural potential, but crop yields can be hampered by the lack of some
nutrients in soil. Potassium is one of the main macronutrients needed for plant development. The low
content of potassium available in soil makes it necessary to apply fertilizers, mainly imported. In order
to promote the development of the sector, phlogoptite rock was studied, from Pindobaçu region, Bahia,
which contains 8.26% of K2O in its chemical composition. Two structural modification methods were
applied. The first was the samples calcination with 10% w/w of CaO at different temperatures. The second
involved mechanochemical activation by 10% of CaO for 30, 60 and 90 min followed by calcination
at different temperatures. In both cases, the samples were submitted to extraction tests with citric acid
0.1 mol.L-1. At the end of the tests, it was observed an increase in the nutrient solubility, going from
0.450 g.L-1 in the unprocessed rock to 4.14 g.L-1 in the sample calcined at 1,200 °C after addition of 10%
w/w of CaO and to 25.1 g.L-1 in the sample subjected to mechanochemical activation for 90 minutes with
10% w/w of CaO, calcined at 1,000 °C.