INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Factors affecting the sorption/desorption of arsenic on/from synthetic nanomaterials
Autor/es:
A. VIOLANTE; M. PIGNA; R.M. TORRES SÁNCHEZ; M. DOS SANTOS AFONSO
Lugar:
Mar del Plata, Argentina
Reunión:
Congreso; V Congreso Iberoamericano de Fisica y Quimica Ambiental; 2008
Institución organizadora:
UNSAM, UBA, SiFyQA
Resumen:
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Sorption/desorption
reactions on/from inorganic sorbents control the concentration of arsenic in
solution and influence its mobility and toxicity. These reactions are affected
by many factors, such as pH, nature of the sorbents and presence and
concentration of organic and inorganic ligands. In natural systems, dissolved
organic and inorganic ligands may compete with arsenic for adsorption sites on
mineral surfaces, facilitating its potential mobility.
We studied
the sorption/desorption of arsenate and arsenite on/from synthetic
nanomaterials such as metal oxides (ferrihydrite, non crystalline aluminum
hydroxide, mixed iron-aluminum oxide), double layered hydroxides (anionic clays),
pillared clays and iron exchanged clays as affected by pH and presence of
inorganic (phosphate, sulfate, selenate, selenite) and organic ligands (oxalate,
citrate, malate, tartrate).
Arsenate
was adsorbed much more than arsenite on nanomaterials containing aluminum,
whereas almost similar amounts of arsenate and arsenite were fixed on the sorbents
containing iron. Anionic clays and iron oxides were the nanomaterials which
showed the highest capacity to adsorb arsenic. The presence of foreign ligands
prevented arsenic sorption. Phosphate, selenite, citrate, tartrate malate and
oxalate inhibited (in the order listed) the sorption of arsenic or promoted its
desorption, whereas sulfate and selenate had a negligible effect in preventing
adsorption or in replacing arsenic previously sorbed onto the minerals. The
sorption of arsenic was strongly influenced by the order of addition of organic
and inorganic ligands and arsenate or arsenite on the sorbents. For example, we
have found that phosphate prevented arsenate sorption onto selected sorbents
much more when added before arsenate than when added as a mixture or after
arsenate.
Finally,
the effect of selected anions in promoting arsenate or arsenite desorption from
the sorbents under investigation was studied. The desorption of arsenic was
affected by the surface properties of the sorbents, the nature and
concentration of the inorganic or organic ligands, pH, surface coverage and
residence time of arsenic onto the surfaces of the nanominerals.