Alkali Extraction of Arsenic from Groundwater Treatment Sludge: An Essential Initial Step for Arsenic Recovery
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Alkali Extraction of Arsenic from Groundwater Treatment Sludge : An Essential Initial Step for Arsenic Recovery. / Wang, Kaifeng; Holm, Peter E.; van Genuchten, Case M.
In: Environmental Science and Technology, Vol. 58, No. 25, 2024, p. 11175-11184.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Alkali Extraction of Arsenic from Groundwater Treatment Sludge
T2 - An Essential Initial Step for Arsenic Recovery
AU - Wang, Kaifeng
AU - Holm, Peter E.
AU - van Genuchten, Case M.
N1 - Funding Information: This work was supported by a Start-up Grant from GeoCenter Denmark and by a Project1 Grant (Thematic Research for the Green Transition) from the Independent Research Fund Denmark (project no. 1127-00207B). Kajsa Sigfridsson Clauss and Susan Nehzati at MAX IV are thanked for support during XAS data collection. We acknowledge MAX IV Laboratory for time on the Balder beamline under Proposal 20221096. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research council under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and Formas under contract 2019-02496. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III, and we would like to thank Edmund Welter for assistance in using the P.65 beamline.
PY - 2024
Y1 - 2024
N2 - Arsenic (As)-bearing Fe(III) precipitate groundwater treatment sludge has traditionally been viewed by the water sector as a disposal issue rather than a resource opportunity, partly due to assumptions of the low value of As. However, As has now been classified as a Critical Raw Material (CRM) in many regions, providing new incentives to recover As and other useful components of the sludge, such as phosphate (P) and the reactive hydrous ferric oxide (HFO) sorbent. Here, we investigate alkali extraction to separate As from a variety of field and synthetic As-bearing HFO sludges, which is a critical first step to enable sludge upcycling. We found that As extraction was most effective using NaOH, with the As extraction efficiency increasing up to >99% with increasing NaOH concentrations (0.01, 0.1, and 1 M). Extraction with Na2CO3 and Ca(OH)2 was ineffective (<5%). Extraction time (hour, day, week) played a secondary role in As release but tended to be important at lower NaOH concentrations. Little difference in As extraction efficiency was observed for several key variables, including sludge aging time (50 days) and cosorbed oxyanions (e.g., Si, P). However, the presence of ∼10 mass% calcite decreased As release from field and synthetic sludges considerably (<70% As extracted). Concomitant with As release, alkali extraction promoted crystallization of poorly ordered HFO and decreased particle specific surface area, with structural modifications increasing with NaOH concentration and extraction time. Taken together, these results provide essential information to inform and optimize the design of resource recovery methods for As-bearing treatment sludge.
AB - Arsenic (As)-bearing Fe(III) precipitate groundwater treatment sludge has traditionally been viewed by the water sector as a disposal issue rather than a resource opportunity, partly due to assumptions of the low value of As. However, As has now been classified as a Critical Raw Material (CRM) in many regions, providing new incentives to recover As and other useful components of the sludge, such as phosphate (P) and the reactive hydrous ferric oxide (HFO) sorbent. Here, we investigate alkali extraction to separate As from a variety of field and synthetic As-bearing HFO sludges, which is a critical first step to enable sludge upcycling. We found that As extraction was most effective using NaOH, with the As extraction efficiency increasing up to >99% with increasing NaOH concentrations (0.01, 0.1, and 1 M). Extraction with Na2CO3 and Ca(OH)2 was ineffective (<5%). Extraction time (hour, day, week) played a secondary role in As release but tended to be important at lower NaOH concentrations. Little difference in As extraction efficiency was observed for several key variables, including sludge aging time (50 days) and cosorbed oxyanions (e.g., Si, P). However, the presence of ∼10 mass% calcite decreased As release from field and synthetic sludges considerably (<70% As extracted). Concomitant with As release, alkali extraction promoted crystallization of poorly ordered HFO and decreased particle specific surface area, with structural modifications increasing with NaOH concentration and extraction time. Taken together, these results provide essential information to inform and optimize the design of resource recovery methods for As-bearing treatment sludge.
KW - Arsenic recovery
KW - Critical raw materials
KW - Synchrotron X-ray characterization
KW - Waste management
KW - Waste upcycling
KW - Water treatment residuals
KW - Arsenic recovery
KW - Critical raw materials
KW - Synchrotron X-ray characterization
KW - Waste management
KW - Waste upcycling
KW - Water treatment residuals
U2 - 10.1021/acs.est.4c00939
DO - 10.1021/acs.est.4c00939
M3 - Journal article
C2 - 38857431
AN - SCOPUS:85196141473
VL - 58
SP - 11175
EP - 11184
JO - Environmental Science & Technology
JF - Environmental Science & Technology
SN - 0013-936X
IS - 25
ER -
ID: 395870960