LAYERED DOUBLE HYDROXIDES AS MATRIZES FOR NITRATE SLOW RELEASE FERTILIZERS

Due to the extensive use of nitrogen fertilizers in the agriculture e due to the elevate potential of nitrate leaching, there is a great demand for slow or controlled release fertilizers. Synthetic layered double hydroxides (HDLs) combine the characteristic that qualifies them to be used as matrixes for nitrate slow release fertilizers. The objectives of the present work are focused in the synthesis, characterization and investigation of the slow release of nitrate process in one structure of a HDL containing ions Mg2+ and Al3+ in its structure. The HDL with the formula Mg0,83Al0,17(OH)(2)(NO3)(0,17).0,56H(2)O was synthesized by the co-precipitation method at constant alkaline pH, isolated by centrifugation and dried in an vacuum oven. Measurements of X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and thermal analysis (TGA/DTA) confirmed the obtaining of the compound containing the intercalated hydrated nitrate anions and the proposed formula. The compound was tested for release nitrate NaHCO3 solution buffered to pH 6.5, and distilled water. The representative curves demonstrated two complementary behaviors nitrate release a fast initial and a slow gradual. The compound investigated in this study demonstrates the potential to be used as a matrix for slow release fertilizer nitrate. The compound was submitted to the nitrate release tests using a NaHCO3 solution buffered at pH 6.5 and in distilled water. The obtained curves have shown two complementary events of nitrate release, one fast initial event and another slow and gradual. The compound investigated in the present work has shown a potential to be used as matrix for nitrate slow release fertilizers.