title: Sorption of arsenite and arsenate on ferrihydrite: effect of organic and inorganic ligands.
abstract: We studied the sorption of As(III) and As(V) onto ferrihydrite as affected by pH, nature and concentration of organic [oxalic (OX), malic (MAL), tartaric (TAR), and citric (CIT) acid] and inorganic [phosphate (PO(4)), sulphate (SO(4)), selenate (SeO(4)) and selenite (SeO(3))] ligands, and the sequence of anion addition. The sorption capacity of As(III) was greater than that of As(V) in the range of pH 4.0-11.0. The capability of organic and inorganic ligands in preventing As sorption follows the sequence: SeO(4) ≈ SO(4) < OX < MAL ≈ TAR < CIT < SeO(3) ≪ PO(4). The efficiency of most of the competing ligands in preventing As(III) and As(V) sorption increased by decreasing pH, but PO(4) whose efficiency increased by increasing pH. In acidic systems all the competing ligands inhibited the sorption of As(III) more than As(V), but in alkaline environments As(III) and As(V) seem to be retained with the same strength on the Fe-oxide. Finally, the competing anions prevented As(III) and As(V) sorption more when added before than together or after As(III) or As(V).
authors.affiliation: Dipartimento di Scienze del Suolo, della Pianta, dell'Ambiente e delle Produzioni Animali, Università di Napoli Federico II, Via Università 100, 80055 Portici, Napoli, Italy.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
authors.forename: Massimo
authors.initials: M
authors.lastname: Pigna
authors.forename: Vincenza
authors.initials: V
authors.lastname: Cozzolino
authors.forename: Antonio G
authors.initials: AG
authors.lastname: Caporale
authors.forename: Antonio
authors.initials: A
authors.lastname: Violante
mesh_terms: D000327:Adsorption; D001149:Arsenates / Q000302:isolation & purification*; D018053:Arsenites / Q000302:isolation & purification*; D005290:Ferric Compounds / Q000737:chemistry*; D007287:Inorganic Chemicals; D008024:Ligands; D009930:Organic Chemicals
chemical_list: D001149:Arsenates; D018053:Arsenites; D005290:Ferric Compounds; D007287:Inorganic Chemicals; D008024:Ligands; D009930:Organic Chemicals; C092844:ferric oxyhydroxide; C015001:arsenite; C025657:arsenic acid