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Field and Laboratory Evidence for Manganese Redox Cycling Controlling Iron and Arsenic Retention in Household Sand Filters
https://orcid.org/0000-0002-7521-9627
https://orcid.org/0000-0002-3558-9500
Application of household sand filters (SFs) is widespread in low-income regions, such as West Bengal, Bangladesh, and Vietnam, for the removal of groundwater contaminants including Fe, Mn, and As. SF operation typically transitions from (oxic) unsaturated conditions to saturated conditions, creating oxygen-limited zones within sand layers. To ensure the safe and effective use of SFs, understanding filter performance and spatiotemporal changes of solid-associated Fe, As, and Mn in different saturation conditions is crucial but remains unknown. Therefore, column experiments were conducted to follow Fe, As, and Mn removal and their distribution and speciation on sand grain surfaces under unsaturated and saturated conditions. On average, 99 ± 0.2, 93 ± 0.7, and 91 ± 8% of Fe(II)aq, As(III)aq, and Mn(II)aq were removed under unsaturated conditions. Under saturated conditions, Fe and As removal remained constant, whereas up to 5 mg/L Mn(II)aq was leached from columns. μXANES analysis showed that solid-associated Fe(III), As(V), and Mn(III)/(IV) dominated in unsaturated sand. However, under saturated conditions, up to 46 and 15% of Fe(III) and As(V) were reduced, and the presence of Mn(II) was confirmed in the anoxic zones. The results suggest that Mn(IV) oxides formed during unsaturated conditions, serving as hosts and oxidants for Fe and As in SFs under reducing conditions.
Formation of Mn(IV) oxides under the oxic flow acted as the host and oxidant for Fe(II) and As(III)/(V) under saturated conditions.
Field and Laboratory Evidence for Manganese Redox Cycling Controlling Iron and Arsenic Retention in Household Sand Filters
https://orcid.org/0000-0002-7521-9627
https://orcid.org/0000-0002-3558-9500
Application of household sand filters (SFs) is widespread in low-income regions, such as West Bengal, Bangladesh, and Vietnam, for the removal of groundwater contaminants including Fe, Mn, and As. SF operation typically transitions from (oxic) unsaturated conditions to saturated conditions, creating oxygen-limited zones within sand layers. To ensure the safe and effective use of SFs, understanding filter performance and spatiotemporal changes of solid-associated Fe, As, and Mn in different saturation conditions is crucial but remains unknown. Therefore, column experiments were conducted to follow Fe, As, and Mn removal and their distribution and speciation on sand grain surfaces under unsaturated and saturated conditions. On average, 99 ± 0.2, 93 ± 0.7, and 91 ± 8% of Fe(II)aq, As(III)aq, and Mn(II)aq were removed under unsaturated conditions. Under saturated conditions, Fe and As removal remained constant, whereas up to 5 mg/L Mn(II)aq was leached from columns. μXANES analysis showed that solid-associated Fe(III), As(V), and Mn(III)/(IV) dominated in unsaturated sand. However, under saturated conditions, up to 46 and 15% of Fe(III) and As(V) were reduced, and the presence of Mn(II) was confirmed in the anoxic zones. The results suggest that Mn(IV) oxides formed during unsaturated conditions, serving as hosts and oxidants for Fe and As in SFs under reducing conditions.
Formation of Mn(IV) oxides under the oxic flow acted as the host and oxidant for Fe(II) and As(III)/(V) under saturated conditions.
Field and Laboratory Evidence for Manganese Redox Cycling Controlling Iron and Arsenic Retention in Household Sand Filters
https://orcid.org/0000-0002-7521-9627
https://orcid.org/0000-0002-3558-9500
Application of household sand filters (SFs) is widespread in low-income regions, such as West Bengal, Bangladesh, and Vietnam, for the removal of groundwater contaminants including Fe, Mn, and As. SF operation typically transitions from (oxic) unsaturated conditions to saturated conditions, creating oxygen-limited zones within sand layers. To ensure the safe and effective use of SFs, understanding filter performance and spatiotemporal changes of solid-associated Fe, As, and Mn in different saturation conditions is crucial but remains unknown. Therefore, column experiments were conducted to follow Fe, As, and Mn removal and their distribution and speciation on sand grain surfaces under unsaturated and saturated conditions. On average, 99 ± 0.2, 93 ± 0.7, and 91 ± 8% of Fe(II)aq, As(III)aq, and Mn(II)aq were removed under unsaturated conditions. Under saturated conditions, Fe and As removal remained constant, whereas up to 5 mg/L Mn(II)aq was leached from columns. μXANES analysis showed that solid-associated Fe(III), As(V), and Mn(III)/(IV) dominated in unsaturated sand. However, under saturated conditions, up to 46 and 15% of Fe(III) and As(V) were reduced, and the presence of Mn(II) was confirmed in the anoxic zones. The results suggest that Mn(IV) oxides formed during unsaturated conditions, serving as hosts and oxidants for Fe and As in SFs under reducing conditions.
Formation of Mn(IV) oxides under the oxic flow acted as the host and oxidant for Fe(II) and As(III)/(V) under saturated conditions.
Field and Laboratory Evidence for Manganese Redox Cycling Controlling Iron and Arsenic Retention in Household Sand Filters
Le, Anh Van (author) / Muehe, E. Marie (author) / Bone, Sharon (author) / Drabesch, Sören (author) / Fischer, Stefan (author) / Kappler, Andreas (author)
ACS ES&T Water ; 4 ; 33-43
2024-01-12
Article (Journal)
Electronic Resource
English
biogeochemical processes , As , Mn , sand filters , Fe
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