@article{fdi:010058984,
  title = {{S}tructure and reactivity of {A}s({III})- and {A}s({V})-rich schwertmannites and amorphous ferric arsenate sulfate from the {C}arnoules acid mine drainage, {F}rance : {C}omparison with biotic and abiotic model compounds and implications for {A}s remediation},
  author = {{M}aillot, {F}. and {M}orin, {G}. and {J}uillot, {F}arid and {B}runeel, {O}dile and {C}asiot, {C}. and {O}na-{N}guema, {G}. and {W}ang, {Y}. {H}. and {L}ebrun, {S}. and {A}ubry, {E}. and {V}laic, {G}. and {B}rown, {G}. {E}.},
  editor = {},
  language = {{ENG}},
  abstract = {{P}oorly ordered nanocrystalline hydroxysulfate minerals of microbial origin, such as schwertmannite, {F}e8{O}8({OH})(6){SO}4, are important arsenic scavengers in sulfate-rich acid mine drainage ({AMD}) environments. {H}owever, despite the fact that {A}s({III}) and {A}s({V}) have been shown to sorb on schwertmannite, little is known about the actual mechanism of arsenic scavenging processes after microbial {F}e({II}) oxidation in {AMD} environments. {T}he major focus of the present study is to determine the molecular-level structure of poorly ordered {A}s({III}) and {A}s({V}) bearing {F}e oxyhydroxysulfate minerals from the {C}arnoules {AMD}, {F}rance, which exhibits exceptional {A}s({III}) concentrations. {P}owder {X}-ray diffraction ({XRD}) and extended {X}-ray absorption fine structure ({EXAFS}) spectroscopy were used to compare field samples with a large set of synthetic analogs prepared via biotic or abiotic pathways, with {A}s/{F}e ratios typical of minerals and mineraloids ranging from nanocrystalline schwertmannite to amorphous hydroxysulfate compounds. {O}ur results yield further evidence for the poisoning effect of {A}s({V}) in limiting the nucleation of schwertmannite. {F}or initial dissolved {A}s({V})/{F}e({III}) molar ratios >= 0.2, amorphous {F}e({III})-{A}s({V}) hydroxysulfate forms, with a local structure consistent with that of amorphous ferric arsenate. {EXAFS} data for this amorphous material are consistent with corner-sharing {F}e{O}6 octahedra to which {A}s{O}4 tetrahedra attach via double-corner {C}-2 linkages. {F}or {A}s({V})/{F}e({III}) molar ratios lower than 0.2, {A}s({V}) binds to schwertmannite via {C}-2 surface complexes. {I}n contrast with the {A}s({V})-containing samples, {A}s({III}) has a lower affinity for schwertmannite following its nucleation, as this mineral phase persists up to an initial {A}s({III})/{F}e({III}) molar ratio of 0.6. {EXAFS} data indicate that during the precipitation process, {A}s({III}) forms dominantly {C}-2 surface complexes on schwertmannite surfaces, likely on the sides of double-chains of {F}e({III})({O}, {OH})(6) octahedra, with a smaller proportion of edge-sharing {E}-2 surface complexes at the apexes of these chains. {I}mportantly, dissolved {A}s({V}) concentrations in contact with {A}s({V})-schwertmannite or ferric arsenate were found to be similar to 10 times lower than dissolved {A}s({III}) concentrations in contact with {A}s({III})-schwertmannite for similar {A}s/{F}e ratios in the solid phase. {C}onsequently, remediation of {A}s-rich {AMD} environments is greatly improved by oxidation of {A}s({III}) to {A}s({V}).},
  keywords = {{FRANCE}},
  booktitle = {},
  journal = {{G}eochimica et {C}osmochimica {A}cta},
  volume = {104},
  numero = {},
  pages = {310--329},
  ISSN = {0016-7037},
  year = {2013},
  DOI = {10.1016/j.gca.2012.11.016},
  URL = {https://www.documentation.ird.fr/hor/fdi:010058984},
}