Simultaneous reduction of arsenic(V) and uranium(VI) by mackinawite: role of uranyl arsenate precipitate formation.
Uranium (U) and arsenic (As) often occur together naturally and, as a result, can be co-contaminants at sites of uranium mining and processing, yet few studies have examined the simultaneous redox dynamics of U and As. This study examines the influence of arsenate (As(V)) on the reduction of uranyl (U(VI)) by the redox-active mineral mackinawite (FeS). As(V) was added to systems containing 47 or 470 μM U(VI) at concentrations ranging from 0 to 640 μM. In the absence of As(V), U was completely removed from solution and fully reduced to nano-uraninite (nano-UO2). While the addition of As(V) did not reduce U uptake, at As(V) concentrations above 320 μM, the reduction of U(VI) was limited due to the formation of a trögerite-like uranyl arsenate precipitate. The presence of U also significantly inhibited As(V) reduction. While less U(VI) reduction to nano-UO2 may take place in systems with high As(V) concentrations, formation of trögerite-like mineral phases may be an acceptable reclamation end point due to their high stability under oxic conditions.
Department of Chemistry, Colorado State University , 1872 Campus Delivery, Fort Collins, Colorado 80523, United States.
Lyndsay D
LD
Troyer
Yuanzhi
Y
Tang
Thomas
T
Borch
D001149:Arsenates / Q000737:chemistry*; D001151:Arsenic / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D014501:Uranium / Q000737:chemistry*
D001149:Arsenates; D005296:Ferrous Compounds; D014501:Uranium; D001151:Arsenic; C025657:arsenic acid; C022597:ferrous sulfide