Binding ability of arsenate towards Cu2+ and Zn2+: thermodynamic behavior and simulation under natural water conditions. Issue 8 (16th July 2020)

• Record Type: Journal Article
• Authors: Giuffrè, Ottavia; Aiello, Donatella; Chillè, Donatella; Napoli, Anna; Foti, Claudia
• Is Part Of: Environmental science. Volume 22:Issue 8(2020)
• Page Start: 1731
• Page End: 1742
• Publication Date: 2020-07-16
• Subjects: Environmental monitoring -- Periodicals; Biological monitoring -- Periodicals; Environmental chemistry -- Periodicals; 363.7363
• DOI: 10.1039/d0em00136h
• Languages: English
• ISSNs: 2050-7887

Abstract

Abstract : The purpose of this study is obtaining reliable thermodynamic data for arsenate complexes and a consistent speciation model for applications in natural waters. Abstract : A study on the sequestering ability between arsenate, AsO4 3−, and Cu 2+ and Zn 2+ in aqueous solution is reported. The results of the elaboration of potentiometric data include only species with 1 : 1 metal to ligand ratio for Cu 2+ –arsenate system, namely CuLH2, CuLH, CuL, and CuLOH (L = AsO4 3− ). For the Zn 2+ –arsenate system, a speciation model with only two species with both 1 : 1 and 1 : 2 metal to ligand ratios was obtained, namely ML and ML2 . Spectrophotometric titrations were also employed in the study of the Cu 2+ –AsO4 3− system, and the results of the analysis of experimental data fully confirmed potentiometric ones. The potentiometric titrations were performed under different conditions of temperature (288.15 ≤ T /K ≤ 310.15, at I = 0.15 mol L −1 ) and ionic strength (0.15 ≤ I /mol L −1 ≤ 1 in NaCl). The dependence of formation constants of the complex species on ionic strength and temperature was also evaluated, as well as the enthalpy and entropy change values were obtained. Laser desorption mass spectrometry (LD MS) and tandem mass spectrometry (MS/MS) were exploited to confirm Cu 2+ –AsO4 3− and Zn 2+ –AsO4 3− complex formation and to determine both their composition and structural characteristics. Simulation of speciation profiles under natural water conditions was performed. The sequestering ability of arsenate towards Cu 2+ and Zn 2+ was quantified under different conditions of pH, temperature and ionic strength, typical of several natural waters. Examples of arsenate distribution under seawater and freshwater conditions were reported.