Acondicionamento de hidroxiapatita nanoparticulada em sachês biodegradáveis para aplicação como fertilizante mineral
Resumen
In 2013, the portion of the Brazilian
agrarian system in the gross domestic product reached 22.54% according to CEPEA.
The production of agricultural commodities is extremely dependent on imported
fertilizer, as 74.6% of the material used on national soil has foreign origin. In the case
of phosphate fertilizers, the main route for production is by adding sulfuric acid to the
phosphate rock, producing phosphoric acid and calcium sulfate, also known as
phosphogypsum. This is a major environmental problem generator, since large
quantities of by-product are stored without an end use. In order to minimize this issue,
this work aims to examine the release of phosphate by hydroxyapatite (HAP)
solubilization synthesized in the laboratory in order to assess your application as
mineral fertilizer. Since the HAP have low solubility, it was aim at synthesizing a
nanostructured material to aid its dissolution, since this property is, normally,
dependent on the particle size. In order to minimize the effects of leaching of the soil
material were processed blends of biodegradable starch and pectin for the production
of sachets for packaging of HAP particulate as well as the slow release thereof. The
hydroxyapatite used in this study was obtain by wet coprecipitation method followed
by hydrothermal treatment or not. With the use of surfactants and variation in the
hydrothermal treatment time, rod and whiskers morphology materials were obtain. For
characterization of the synthesized samples was using an x-ray diffractometer. The
results from this showed that the particles produced in this study are present in a single
step without the occurrence of undesirable secondary phases. The FTIR and FTRaman confirmed the result obtained by XRD. From the Zeta potential was observed
that the sample of smaller surface area is made more stable in solution than the rest
of the analyzed compounds. It was also observe that increasing the crystallinity of the
material resulted in a lower solubility at neutral pH thereof. The release assay was
repeated at acidic pH, indicating that more acidic conditions lead to higher dissolutions
of samples. From the release tests it was found that the samples had higher solubility
at neutral pH, approximately 4.5 mg L-1 of phosphorus released, were smaller and
less degree of crystallinity. For the larger and more crystalline sample solutions formed
concentrations of at most 1.5 mg L-1. Since the tests made at acidic pH showed that
the samples, regardless of the size and crystallinity presented are easily solubilized.
All solutions obtained showed the phosphorus concentration around 15 mg L-1. Blends
were used to condition the HAP, and chosen to be used in the present work was to
TPS 75: 25 PEC, due to its greater flexibility and greater resistance in solution. The
solubility obtained for the samples contained in the sachet showed high values, even
at pH close to neutral, indicating its potential use.