TY - JOUR

T1 - Dissolved phosphate decreases the stability of amorphous ferric arsenate and nano-crystalline yukonite

AU - Stubbe, Petra

AU - Mikutta, Christian

AU - Matulková, Irena

AU - Drahota, Petr

N1 - Funding Information: This research was supported by the Grant Agency of the Charles University (GAUK no. 790120) and the Czech Science Foundation (GA\u010CR no. 22-27939 S). The authors wish to thank our colleagues for the laboratory and instrumental support: Marie Fayadov\u00E1 (sample digestion), Claus H. R\u00FCscher and Adam Culka (Raman spectroscopy), as well as Lenka J\u00EDlkov\u00E1 and V\u011Bra Von\u00E1skov\u00E1 (ICP-OES analyses). The authors would also like to thank the German Federal Environmental Foundation that awarded a fellowship to the main author.

PY - 2024/6/5

Y1 - 2024/6/5

N2 - Extensive research has been conducted on the competitive adsorption of arsenate (AsO43-) and phosphate (PO43-) to mineral surfaces, but the stability of ferric arsenate mineral(oid)s under elevated phosphate levels remains poorly understood. Therefore, we investigated the impact of dissolved phosphate (0, 0.5, 50 mM) on the stability of amorphous ferric arsenate (AFA; FeAsO4·nH2O) and nano-crystalline yukonite [Ca2Fe3(AsO4)3(OH)4·4H2O], both synthetic and contained in natural As-contaminated soil (∼16 g/kg As) and mine-waste material (∼39 g/kg As) for up to one year. Substantial amounts of As (∼45% of total As) were released into solution from AFA and yukonite at high phosphate concentrations due to incongruent dissolution of the solids and substitution of arsenate by phosphate in both mineral(oids). After one year, both solids sequestered ∼8 wt% P with approximately 20–30% accounting for adsorbed and precipitated species. This P increase was also observed in the soil and mine-waste samples, where AFA and yukonite comprised up to 4.3 and 4.9 wt% P, respectively. The high reactivity of ferric arsenates with aqueous phosphate may lead to a substantial overestimation of adsorbed As determined by sequential As extractions of materials containing these phases and requires increased caution when applying phosphate to stabilize polymetallic mine wastes. Furthermore, long-term phosphate additions via fertilization of As-contaminated soil or renaturalized mine tailings containing amorphous or nano-crystalline ferric arsenates should be reduced to limit the export of As(V) into surface streams and groundwater.

AB - Extensive research has been conducted on the competitive adsorption of arsenate (AsO43-) and phosphate (PO43-) to mineral surfaces, but the stability of ferric arsenate mineral(oid)s under elevated phosphate levels remains poorly understood. Therefore, we investigated the impact of dissolved phosphate (0, 0.5, 50 mM) on the stability of amorphous ferric arsenate (AFA; FeAsO4·nH2O) and nano-crystalline yukonite [Ca2Fe3(AsO4)3(OH)4·4H2O], both synthetic and contained in natural As-contaminated soil (∼16 g/kg As) and mine-waste material (∼39 g/kg As) for up to one year. Substantial amounts of As (∼45% of total As) were released into solution from AFA and yukonite at high phosphate concentrations due to incongruent dissolution of the solids and substitution of arsenate by phosphate in both mineral(oids). After one year, both solids sequestered ∼8 wt% P with approximately 20–30% accounting for adsorbed and precipitated species. This P increase was also observed in the soil and mine-waste samples, where AFA and yukonite comprised up to 4.3 and 4.9 wt% P, respectively. The high reactivity of ferric arsenates with aqueous phosphate may lead to a substantial overestimation of adsorbed As determined by sequential As extractions of materials containing these phases and requires increased caution when applying phosphate to stabilize polymetallic mine wastes. Furthermore, long-term phosphate additions via fertilization of As-contaminated soil or renaturalized mine tailings containing amorphous or nano-crystalline ferric arsenates should be reduced to limit the export of As(V) into surface streams and groundwater.

KW - Adsorption

KW - Amorphous ferric arsenate

KW - Mobility

KW - Phosphate

KW - Precipitation

KW - Substitution

KW - Yukonite

UR - http://www.scopus.com/inward/record.url?scp=85191479941&partnerID=8YFLogxK

U2 - 10.1016/j.jhazmat.2024.134374

DO - 10.1016/j.jhazmat.2024.134374

M3 - Article

C2 - 38688215

AN - SCOPUS:85191479941

VL - 471

JO - Journal of hazardous materials

JF - Journal of hazardous materials

SN - 0304-3894

M1 - 134374

ER -