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Aqueous arsenic(V) remediation and redox transformation of arsenic(III) to arsenic(V) using Fe3O4/Douglas fir biochar.

Authors :
Rodrigo, Prashan M.
Navarathna, Chanaka M.
Bullard, Bailey N.
Hoffman, Brooke R.
Venson, Beverly L.
Honigfort, Holden
Timmons, Garrett L.
Montes, Maria L.
Thirumalai, Rooban V.K.G.
Stokes, Sean L.
Pittman, Charles U.
Mlsna, Todd E.
Source :
Journal of Cleaner Production. May2024, Vol. 455, pN.PAG-N.PAG. 1p.
Publication Year :
2024

Abstract

Magnetite nanoparticles were deposited on Douglas fir biochar (Fe 3 O 4 /DFBC) using aqueous, NaOH-induced chemical co-precipitation from Fe2+/Fe3+ salt solutions. Fe 3 O 4 /DFBC was used to remediate As(V)-contaminated water. Kinetics and isotherms were studied. pH 5 was selected as the optimized pH due to low iron leaching and closeness to groundwater pH. Adsorption equilibrium was reached after 3 h, 2 h, and 1 h for 0.5, 5, and 50 mg/L initial As(V) concentrations, respectively. Adsorption was endothermic, and the Langmuir capacity was 6.33 mg/g at 25 °C. Ionic strength, impacts of Fe 3 O 4 /DFBC particle size, and competitive ion/molecule effects during As(V) adsorption were studied. Continuous-flow fixed-bed column breakthrough studies performed at 0.5, 5, and 50 mg/L of As(V) at pH 5 exhibited maximum capacities of 3.47, 3.99, and 3.72 mg/g, respectively. Aqueous potassium phosphate was used successfully for column regeneration. Fe 3 O 4 /DFBC was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Mössbauer spectroscopy before and after As(III) and As(V) adsorption. Mössbauer found the "Fe 3 O 4 " was composed of several phases. A key target was the study of simultaneous toxic As(III) adsorption and its transformation to As(V) from pH 1–13. The highest removal of As(III) and oxidized As(V) was obtained at pH 3. The relationship between iron leaching and pH was investigated and the pH-dependent surface adsorption was monitored using X-ray photoelectron spectroscopy (XPS) from pH 1 to 13. One goal of this study was to enhance the understanding of the adsorption characteristics needed for initial scaling of a treatment facility that can efficiently remediate arsenic-contaminated wastewater. Experiments were conducted using batch and fixed bed continuous flow columns to optimize adsorption process parameters under various circumstances and solution matrices. Another goal was to further establish the surface structures of the chemisorbed arsenates versus pH. [Display omitted] • As(III) can be oxidized to As(V) in anoxic conditions when adsorbed. • Solution effects, dose optimizations, column separations, and Fe2+/3+ leaching versus pH were studied during As(V) removal. • AsO 4 3− adsorption capacity was 6.33 mg/g at 25 °C. • Redox transformation of As(III) to As(V) on Fe 3 O 4 /DFBC was studied from pH 1 to 13. • Mössbauer spectroscopy and pH-dependent XPS aided detailed mechanistic understanding. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
09596526
Volume :
455
Database :
Academic Search Index
Journal :
Journal of Cleaner Production
Publication Type :
Academic Journal
Accession number :
177063961
Full Text :
https://doi.org/10.1016/j.jclepro.2024.142254