title: Water treatment residues as accumulators of oxoanions in soil. Sorption of arsenate and phosphate anions from an aqueous solution.
abstract: Here we report a survey addressed to determine, at different pH values (pH 4.0, 7.0 and 9.0), the ability of two different water treatment residues, a Fe-based (Fe-WTR) and an Al-based (Al-WTR), to accumulate arsenate and phosphate anions from an aqueous solution and to define the mechanism which regulate the sorption of these anions. Fe-WTR showed a greater As(V) and P(V) sorption capacity respect to Al-WTR at all the pH values investigated, in particular at pH 4.0. The greater capacity of the Fe-WTR to accumulate phosphate at pH 4.0 seems to be linked to the higher content of manganese ions compared to Al-WTR, which can give rise, with phosphate ions, to the formation of MnHPO4 precipitates. Sequential extraction of As(V)- or P(V)-WTRs suggested that the main mechanism governing the sorption of both two anions likely involve the formation of inner-sphere surface complexes [Fe/Al-O-As(P)]. Such a coordination mode was supported by the FT-IR spectra that exhibit well resolved band at 865cm(-1) and 1040cm(-1) attributable to ν(As-O) or ν(P-O) stretching vibration, respectively.
authors.affiliation: Dipartimento di Agraria, Sezione di Scienze e Tecnologie Ambientali e Alimentari, University of Sassari, Viale Italia 39, 07100 Sassari, Italy. Electronic address: castaldi@uniss.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Castaldi
authors.affiliation: Dipartimento di Agraria, Sezione di Scienze e Tecnologie Ambientali e Alimentari, University of Sassari, Viale Italia 39, 07100 Sassari, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Mele
authors.affiliation: Dipartimento di Agraria, Sezione di Scienze e Tecnologie Ambientali e Alimentari, University of Sassari, Viale Italia 39, 07100 Sassari, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Silvetti
authors.affiliation: Dipartimento di Agraria, Sezione di Scienze e Tecnologie Ambientali e Alimentari, University of Sassari, Viale Italia 39, 07100 Sassari, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Garau
authors.affiliation: Dipartimento di Agraria, Sezione di Scienze e Tecnologie Ambientali e Alimentari, University of Sassari, Viale Italia 39, 07100 Sassari, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Deiana
mesh_terms: D000327:Adsorption; D001149:Arsenates / Q000302:isolation & purification*; D011232:Chemical Precipitation; D010710:Phosphates / Q000302:isolation & purification*; D012987:Soil / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D018508:Water Purification
chemical_list: D001149:Arsenates; D010710:Phosphates; D012987:Soil
keywords: Adsorption isotherms; Arsenate and phosphate; FT-IR spectroscopy; Fe- and Al-WTRs; Sequential extraction