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Uptake and release of arsenic and antimony in alunite-jarosite and beudantite group minerals

Karen A. Hudson-Edwards
Uptake and release of arsenic and antimony in alunite-jarosite and beudantite group minerals
American Mineralogist (May 2019) 104 (5): 633-640

Abstract

Arsenic and antimony are highly toxic to humans, animals, and plants. Incorporation in alunite, jarosite, and beudantite group minerals can immobilize these elements and restrict their bioavailability in acidic, oxidizing environments. This paper reviews research on the magnitude and mechanisms of incorporation of As and Sb in, and release from, alunite, jarosite, and beudantite group minerals in mostly abiotic systems. Arsenate-for-sulfate substitution is observed for all three mineral groups, with the magnitude of incorporation being beudantite (3-8.5 wt% As) > alunite (3.6 wt% As) > natroalunite (2.8 wt%) > jarosite (1.6 wt% As) > natroalunite (1.5 wt% As) > hydroniumalunite (0.034 wt% As). Arsenate substitution is limited by the charge differences between sulfate (-2) and arsenate (-3), deficiencies in B-cations in octahedral sites and for hydroniumalunite, difficulty in substituting protonated H (sub 2) O-for-OH- groups. Substitution of arsenate causes increases in the c-axis for alunite and natroalunite, and in the c- and a-axes for jarosite. The degree of uptake depends on, but limited by, the AsO (sub 4) /TO (sub 4) ratio. Aerobic and abiotic As release from alunite and natroalunite is limited, especially between pH 5 and 8. Release of As is also very limited in As-bearing jarosite, natrojarosite, and ammoniumjarosite at pH 8 due to the formation of secondary maghemite, goethite, hematite, and Fe arsenates that resorb the liberated As. Abiotic reductive dissolution of As-bearing jarosite at pH 4, 5.5, and 7 is likewise restricted by the formation of secondary green rust sulfate, goethite, and lepidocrocite that take up the As. Similar processes have been observed for the aerobic dissolution of Pb-As-jarosite (beudantite analog), with secondary Fe oxyhydroxides resorbing the released As at pH 8. Higher amounts of As are released, however, during microbial-driven jarosite dissolution. Natural jarosite has been found to contain up to 5.9 wt% Sb (super 5+) substituting for Fe (super 3+) in the B-site of the mineral structure. Sb(V) is not released from jarosite at pH 4 during abiotic reductive dissolution, but at pH 5.5 and 7, up to 75% of the mobilized Sb can be structurally incorporated into secondary green rust sulfate, lepidocrocite, or goethite. Further research is needed on the co-incorporation of As, Sb, and other ions in, and the uptake and release of Sb from, alunite, jarosite, and beudantite group minerals, the influence of microbes on these processes and the long-term (>1 yr) stability of these minerals.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 104
Serial Issue: 5
Title: Uptake and release of arsenic and antimony in alunite-jarosite and beudantite group minerals
Affiliation: University of Exeter, Environment & Sustainability Institute, Penryn, Cornwall, United Kingdom
Pages: 633-640
Published: 201905
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 59
Accession Number: 2019-048639
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201925
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