TY - GEN
T1 - Effect of ferrous iron on arsenate sorption to amorphous ferric hydroxide
AU - Mukiibi, Muhammed
AU - Ela, Wendell P.
AU - Sáez, A. Eduardo
PY - 2008/10
Y1 - 2008/10
N2 - Amorphous ferric hydroxide (AFH) sorbents are commonly used for removal of arsenate from water. When disposed in microbially active, reducing environments, such as landfills, Fe(II) will be generated by reductive dissolution of the AFH surface and arsenate will be desorbed. However, the observed ratio of arsenate (and, in fact, total arsenic) to total iron in the leachate is not consistent with the original ratio of arsenate to iron on the AFH. Work to determine if ferrous iron re-adsorption to the AFH can partially explain this inconsistency is described. As pH increases above 7, Fe(II) increasingly sorbs onto the AFH surface. This sorption is largely independent of ionic strength and somewhat irreversible at high pH. In contrast, arsenate partitioning to AFH decreases with increasing pH. However, over the pH range from 5 to 9, the presence of Fe(II) sorbed to the AFH surface increases the capacity for arsenate sorption. In addition, when no Fe(II) is present, arsenate binding is largely to surface sites inaccessible to Fe(II) binding. The results are also consistent with Fe(II) sorption to AFH sites, otherwise unfavorable to arsenate binding and transformation of those sites into arsenate-amenable binding sites.
AB - Amorphous ferric hydroxide (AFH) sorbents are commonly used for removal of arsenate from water. When disposed in microbially active, reducing environments, such as landfills, Fe(II) will be generated by reductive dissolution of the AFH surface and arsenate will be desorbed. However, the observed ratio of arsenate (and, in fact, total arsenic) to total iron in the leachate is not consistent with the original ratio of arsenate to iron on the AFH. Work to determine if ferrous iron re-adsorption to the AFH can partially explain this inconsistency is described. As pH increases above 7, Fe(II) increasingly sorbs onto the AFH surface. This sorption is largely independent of ionic strength and somewhat irreversible at high pH. In contrast, arsenate partitioning to AFH decreases with increasing pH. However, over the pH range from 5 to 9, the presence of Fe(II) sorbed to the AFH surface increases the capacity for arsenate sorption. In addition, when no Fe(II) is present, arsenate binding is largely to surface sites inaccessible to Fe(II) binding. The results are also consistent with Fe(II) sorption to AFH sites, otherwise unfavorable to arsenate binding and transformation of those sites into arsenate-amenable binding sites.
KW - ABSR
KW - Amorphous ferric hydroxide
KW - Arsenate
KW - Arsenic residuals disposal
KW - As(V)
KW - Fe(II)
KW - Ferrous iron
KW - Sorption
KW - Water treatment residuals
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U2 - 10.1196/annals.1454.024
DO - 10.1196/annals.1454.024
M3 - Conference contribution
C2 - 18991933
AN - SCOPUS:54949091146
SN - 9781573317405
T3 - Annals of the New York Academy of Sciences
SP - 335
EP - 345
BT - Environmental Challenges in the Pacific Basin
PB - Blackwell Publishing Inc.
ER -