Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments
Lead- and Pb-As-jarosites are minerals common to acidic, sulphate-rich environments, including weathering zones of sulphide ore deposits and acid rock or acid mine drainage (ARD/AMD) sites, and often form on or near galena. The structures of these jarosites are based on linear tetrahedral-octahedral...
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| Format: | Journal Article |
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Elsevier Science BV
2006
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| Online Access: | http://hdl.handle.net/20.500.11937/32129 |
| _version_ | 1848753575680802816 |
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| author | Wright, Kathleen Smith, A. Dubbin, W. Hudson-Edwards, K. |
| author_facet | Wright, Kathleen Smith, A. Dubbin, W. Hudson-Edwards, K. |
| author_sort | Wright, Kathleen |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | Lead- and Pb-As-jarosites are minerals common to acidic, sulphate-rich environments, including weathering zones of sulphide ore deposits and acid rock or acid mine drainage (ARD/AMD) sites, and often form on or near galena. The structures of these jarosites are based on linear tetrahedral-octahedral-tetrahedral (T-O-T) sheets, comprised of slightly distorted FeO6 octahedra and SO4 2- (-AsO4 3- in Pb-As-jarosites) tetrahedra. To better understand the dissolution mechanisms and products of the break down of Pb- and Pb-As-jarosite, preliminary batch dissolution experiments were conducted on synthetic Pb- and Pb-As-jarosite at pH 2 and 20 C, to mimic environments affected by ARD/AMD, and at pH 8 and 20 C, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH)2). All four dissolutions are incongruent. Dissolution of Pb-jarosite at pH 2 yields aqueous Pb, Fe and SO4 2-. The pH 8 Pb-jarosite dissolution yields aqueous Pb, SO4 2- and poorly crystalline Fe(OH)3, which does not appear to resorb Pb or SO4 2-, possibly due to the low solution pH (3.44-3.54) at the end of the experiment. The pH 2 and 8 dissolutions of Pb-As-jarosite result in the formation of secondary compounds (poorly crystalline PbSO4 for pH 2 dissolution; poorly crystalline PbSO4 and Fe(OH)3 for pH 8 dissolution), which may act as dissolution inhibitors after 250 to 300 h of dissolution. In the pH 2 dissolution, aqueous Fe, SO4 2- and AsO4 3- also form, and in the pH 8 dissolution, Fe(OH)3 precipitates then subsequently resorbs aqueous AsO4 3-. The dissolutions probably proceed by preferred dissolution of the A- and T-sites, which contain Pb, and SO4 2-and AsO4 3-, respectively, rather than Fe, which is sterically remote, within the T-O-T Pb- and Pb-As-jarosite structures.These data provide the foundation necessary for further, more detailed investigations into the dissolution of Pb- and Pb-As-jarosites. |
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| format | Journal Article |
| id | curtin-20.500.11937-32129 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T08:26:42Z |
| publishDate | 2006 |
| publisher | Elsevier Science BV |
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| spelling | curtin-20.500.11937-321292019-02-19T05:35:35Z Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments Wright, Kathleen Smith, A. Dubbin, W. Hudson-Edwards, K. Acid mine drainage Pb-jarosite Dissolution Fe hydroxide Pb As-jarosite Pb sulphate Lead- and Pb-As-jarosites are minerals common to acidic, sulphate-rich environments, including weathering zones of sulphide ore deposits and acid rock or acid mine drainage (ARD/AMD) sites, and often form on or near galena. The structures of these jarosites are based on linear tetrahedral-octahedral-tetrahedral (T-O-T) sheets, comprised of slightly distorted FeO6 octahedra and SO4 2- (-AsO4 3- in Pb-As-jarosites) tetrahedra. To better understand the dissolution mechanisms and products of the break down of Pb- and Pb-As-jarosite, preliminary batch dissolution experiments were conducted on synthetic Pb- and Pb-As-jarosite at pH 2 and 20 C, to mimic environments affected by ARD/AMD, and at pH 8 and 20 C, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH)2). All four dissolutions are incongruent. Dissolution of Pb-jarosite at pH 2 yields aqueous Pb, Fe and SO4 2-. The pH 8 Pb-jarosite dissolution yields aqueous Pb, SO4 2- and poorly crystalline Fe(OH)3, which does not appear to resorb Pb or SO4 2-, possibly due to the low solution pH (3.44-3.54) at the end of the experiment. The pH 2 and 8 dissolutions of Pb-As-jarosite result in the formation of secondary compounds (poorly crystalline PbSO4 for pH 2 dissolution; poorly crystalline PbSO4 and Fe(OH)3 for pH 8 dissolution), which may act as dissolution inhibitors after 250 to 300 h of dissolution. In the pH 2 dissolution, aqueous Fe, SO4 2- and AsO4 3- also form, and in the pH 8 dissolution, Fe(OH)3 precipitates then subsequently resorbs aqueous AsO4 3-. The dissolutions probably proceed by preferred dissolution of the A- and T-sites, which contain Pb, and SO4 2-and AsO4 3-, respectively, rather than Fe, which is sterically remote, within the T-O-T Pb- and Pb-As-jarosite structures.These data provide the foundation necessary for further, more detailed investigations into the dissolution of Pb- and Pb-As-jarosites. 2006 Journal Article http://hdl.handle.net/20.500.11937/32129 10.1016/j.chemgeo.2005.11.006 Elsevier Science BV fulltext |
| spellingShingle | Acid mine drainage Pb-jarosite Dissolution Fe hydroxide Pb As-jarosite Pb sulphate Wright, Kathleen Smith, A. Dubbin, W. Hudson-Edwards, K. Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments |
| title | Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments |
| title_full | Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments |
| title_fullStr | Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments |
| title_full_unstemmed | Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments |
| title_short | Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments |
| title_sort | dissolution of lead- and lead-arsenic-jarosites at ph 2 and 8 and 20 c: insights from batch experiments |
| topic | Acid mine drainage Pb-jarosite Dissolution Fe hydroxide Pb As-jarosite Pb sulphate |
| url | http://hdl.handle.net/20.500.11937/32129 |