INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Glyphosate and its metabolitos adsorptions on clay
Autor/es:
TORRES SANCHEZ, ROSA M; GENET, M; DOS SANTOS AFONSO M
Lugar:
Aveiro Portugal
Reunión:
Congreso; Euroclay 2007; 2007
Resumen:
Glyphosate,
(PMG) is the most employed herbicide around the world. After application a
significant amount reaches the soil due to the different treatment methods and
weather conditions. PMG is adsorbed onto the soil components such as clays,
organic matter, oxides and humic substances. PMG metabolites are aminomethylphosphonic
acid (AMPA), methylphosphonic acid (MPA) and sarcosine (SAR).
Montmorillonite (M), develops high specific surface and a net surface charge
having at least two available types of adsorption surface. PMG forms inner-sphere
complexes with several metals such as Al+3 and Fe+3 and iron oxides surfaces. Both, PMG and M have negative net charge at all pH
evaluated, so no electrostatic attractive phenomena is associated with PMG-M
interaction. Some parameters as
particle morphology (SEM), pzc, size particle, TG and specific surface area
were measured to characterize the clay. Electrophoretic mobility and size
particle of a treated sample with PMG was evaluated due to the enormous changes
in M stability suspension in presence of PMG. Multisite isotherms were found
for adsorption indicating that almost two types of specific adsorption sites
are present in clay surface. DRX and XPS analysis of PMG, AMPA, MPA and SAR
adsorbed onto M were made to determine the interlayer role and the structure of
surface complexes formed during the adsorption processes. In all the cases the d(001) parameter shifted
to lower values of 2q which indicate the
clay expansion due to ligand incoming into the interlayer space. The =NH2+,
=NH and P2p surface speciation were calculated from XPS results.
Physicochemical parameters related with adsorption process are reported for all
sample at all measured conditions.