The change of coordination environments induced by vacancy defects in hematite leads to a contrasting difference between cation Pb(II) and oxyanion As(V) immobilization

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Hematite is an iron oxide commonly found in terrestrial environments and plays an essential role in controlling the migration of heavy metal(loid)s in groundwater and sediments. Although defects were shown to exist both in naturally occurring and laboratory-synthesized hematite, their influences on the immobilization of heavy metal(loid)s remain poorly understood. In this study, hematite samples with tunable vacancy defect concentrations were synthesized to evaluate their adsorption capacities for the cation Pb(II) and for the oxyanion As(V). The defects in hematite were characterized using XRD, TEM-EDS mapping, position annihilation lifetime spectroscopy, and XAS. The surface charge characteristics in defective hematite were investigated using zeta potential measurements. We found that Fe vacancies were the primary defect type in the hematite structure. Batch experiments confirmed that Fe vacancies in hematite promoted As(V) adsorption, while they decreased Pb(II) adsorption. The reason for the opposite effects of Fe vacancies on Pb(II) and As(V) immobilization was investigated using DFT calculations and EXAFS analysis. The results revealed that Fe vacancies altered As-Fe coordination from a monodentate to a bidentate complex and increased the length of the Pb-Fe bond on the hematite surface, thereby leading to an increase in As(V) bonding strength, while decreasing Pb(II) adsorption affinity. In addition, the zeta potential analysis demonstrated that the presence of Fe vacancies led to an increase in the isoelectric point (IEP) of hematite samples, which therefore decreased the attraction for the cation Pb(II) and increased the attraction for the oxyanion As(V). The combination of these two effects caused by defects contributed to the contrasting difference between cation Pb(II) and oxyanion As(V) immobilization by defective hematite. Our study therefore provides new insights into the migration and fate of toxic heavy metal(loid)s controlled by iron minerals.

Medienart:

E-Artikel

Erscheinungsjahr:

2024

Erschienen:

2024

Enthalten in:

Zur Gesamtaufnahme - volume:344

Enthalten in:

Environmental pollution (Barking, Essex : 1987) - 344(2024) vom: 01. Feb., Seite 123318

Sprache:

Englisch

Beteiligte Personen:

Xiang, Yongjin [VerfasserIn]
Liu, Juan [VerfasserIn]
Chen, Yiwen [VerfasserIn]
Zhang, Hongjun [VerfasserIn]
Ren, Lu [VerfasserIn]
Ye, Bangjiao [VerfasserIn]
Tan, Wenfeng [VerfasserIn]
Andreas, Kappler [VerfasserIn]
Hou, Jingtao [VerfasserIn]

Links:

Volltext

Themen:

1K09F3G675
2P299V784P
Arsenate
E1UOL152H7
Ferric Compounds
Ferric oxide
Iron
Iron oxide
Journal Article
Lead
Minerals
Mobility
Vacancy defect

Anmerkungen:

Date Completed 26.02.2024

Date Revised 26.02.2024

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1016/j.envpol.2024.123318

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM367090961