Accumulation and mobilization of arsenate by Fe(III) polyions trapped in a Ca-polygalacturonate network.
The role of Fe(III) stored at the soil-root interface in the accumulation of arsenate and the influence of citric acid on the As(V) mobility were investigated by using Ca-polygalacturonate networks (PGA). The results indicate that in the 2.5-6.2 pH range Fe(III) interacts with As(V) leading to the sorption of As(V) on Fe(III) precipitates or Fe-As coprecipitates. The FT-IR analysis of these precipitates evidenced that the interaction produces Fe(III)-As(V) inner-sphere complexes with either monodentate or bidentate binuclear attachment of As(V) depending on pH. In the 3.0-6.0 pH range, As(V) diffuses freely through the polysaccharidic matrix that was found to exert a negligible reducing action towards As(V). At pH 6.0 citric acid is able to mobilize arsenate from the As-Fe-PGA network through the complexation of the Fe(III) polyions that leads to the release of As(V).
Deiana
Salvatore
S
Dipartimento di Scienze Ambientali Agrarie e Biotecnologie Agroalimentari, Università di Sassari, V.le Italia 39, 07100 Sassari, Italy. sadeiana@uniss.it
Deiana
Luca
L
Premoli
Alessandra
A
Senette
Caterina
C
D000327:Adsorption; D001149:Arsenates / Q000493:pharmacokinetics*; D018053:Arsenites / Q000493:pharmacokinetics; D002118:Calcium / Q000737:chemistry; D019343:Citric Acid / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D010368:Pectins / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D012987:Soil
D001149:Arsenates; D018053:Arsenites; D005290:Ferric Compounds; D012987:Soil; D019343:Citric Acid; D010368:Pectins; C015001:arsenite; C025657:arsenic acid; D002118:Calcium; C003181:polygalacturonic acid