Nanopartículas de ocorrência natural em latossolo vermelho: caracterização
Carregando...
Arquivos
Data
2017-08-15
Autores
Maltoni, Kátia Luciene [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Resumo
De ocorrência comum nos solos, as nanopartículas desempenham importante papel
em processos relacionados à gênese, aos ciclos biogeoquímicos dos elementos, ao
transporte e biodisponibilidade de elementos químicos e, em alguns casos, o destino
final de nutrientes e contaminantes naturais ou antropogênicos dos solos. A percepção
de que estes minerais tem seu tamanho em escala nano pressupõe superfície
específica elevada, o que pode aumentar a adsorção de fósforo, carbono, em algumas
situações de arsênio, entre outros compostos e ânions. Para estudar estas partículas
é necessário separa-las do solo, o que foi feito, com sucesso, a partir de uma
sequência de processos de dispersão e centrifugação. O mapeando químico deste
material realizado com MET e EDX, mostrou coincidência em vários mapas da
presença do P associado à ocorrência dos óxidos de Fe e Ti, particularmente Hematita
e Anatásio. A partir dos dados do DRX foi possível calcular o tamanho dos cristais de
caulinita e hematita do material < 100 nm e na fração argila, isto é, < 2000 nm, 16,6 e
25,7 nm respectivamente. Para hematita as medidas foram 13,3 e 21,3 nm na fração
nano e na fração argila respectivamente. O anatásio e a gibbsita só apareceram na
fração entre 2000 e 100 nm, no DRX. Importante destacar que mesmo em escala
nanométrica os óxidos de ferro, no caso a hematita apresentam estrutura interna bem
definida. A distribuição do P, considerando as nanopartículas mostrou associação com
óxidos de Fe e Ti, o que merece ser melhor avaliado.
Naturally occurring in soils, nanoparticles play an important role in processes related to genesis, biogeochemical cycles of the elements, transport and bioavailability of chemical elements and, in some cases, the final destination of nutrients and natural or anthropogenic contaminants of soils. The perception that these minerals have their size at nano scale presupposes high specific surface, which can increase the adsorption of phosphorus, carbon, in some arsenic situations, among other compounds and anions. To study these particles it is necessary to separate them from the soil, which has been successfully done from a sequence of dispersion and centrifugation processes. The chemical mapping of this material performed with TEM and EDS showed a coincidence in several maps of the presence of P associated with the occurrence of Fe and Ti oxides, particularly Hematite and Anatase. From the XRD data it was possible to calculate the size of the kaolinite and hematite crystals of the material <100 nm and in the clay fraction, that is <2000 nm, 16.6 and 25.7 nm, respectively. For hematite the measurements were 13.3 and 21.3 nm in the nano fraction and in the clay fraction respectively. Anatase and gibbsite only appeared in the fraction between 2000 and 100 nm, on XRD. It is important to note that even in nanometric scale the iron oxides, in the case the hematite has a well defined internal structure. The distribution of P, considering the nanoparticles, showed an association with Fe and Ti oxides, which deserves to be better evaluated.
Naturally occurring in soils, nanoparticles play an important role in processes related to genesis, biogeochemical cycles of the elements, transport and bioavailability of chemical elements and, in some cases, the final destination of nutrients and natural or anthropogenic contaminants of soils. The perception that these minerals have their size at nano scale presupposes high specific surface, which can increase the adsorption of phosphorus, carbon, in some arsenic situations, among other compounds and anions. To study these particles it is necessary to separate them from the soil, which has been successfully done from a sequence of dispersion and centrifugation processes. The chemical mapping of this material performed with TEM and EDS showed a coincidence in several maps of the presence of P associated with the occurrence of Fe and Ti oxides, particularly Hematite and Anatase. From the XRD data it was possible to calculate the size of the kaolinite and hematite crystals of the material <100 nm and in the clay fraction, that is <2000 nm, 16.6 and 25.7 nm, respectively. For hematite the measurements were 13.3 and 21.3 nm in the nano fraction and in the clay fraction respectively. Anatase and gibbsite only appeared in the fraction between 2000 and 100 nm, on XRD. It is important to note that even in nanometric scale the iron oxides, in the case the hematite has a well defined internal structure. The distribution of P, considering the nanoparticles, showed an association with Fe and Ti oxides, which deserves to be better evaluated.
Descrição
Palavras-chave
Cerrado, Hematita, Caulinita, Fósforo, MEV, HR-MET, Raio-X, Savannah, Hematite, Kaolinite, Phosphorus, SEM, HR-TEM, X-ray