Jeffrey Paulo H Perez, A Li Han Chan, J Frederick W Mosselmans, Liane G Benning
{"title":"共存的磷酸盐控制铁(II)催化水合铁转化过程中砷酸盐的形态和分配。","authors":"Jeffrey Paulo H Perez, A Li Han Chan, J Frederick W Mosselmans, Liane G Benning","doi":"10.1021/acsearthspacechem.5c00061","DOIUrl":null,"url":null,"abstract":"<p><p>Arsenic immobilization in soils and sediments is primarily controlled by its sorption onto or incorporation into reactive soil minerals, such as iron (oxyhydr)-oxides. However, coexisting ions (e.g., dissolved bicarbonate, phosphate, silica, and organic matter) can negatively impact the interaction of the toxic arsenate species with iron (oxy)-hydroxides. Of special note is inorganic phosphate, which is a strong competitor for sorption sites due to its analogous chemical and structural nature to inorganic arsenate. Much of our understanding of this competing nature between phosphate and arsenate focuses on the impact on mineral sorption capacities and kinetics. However, we know very little about how coexisting phosphate will alter the stability and transformation pathways of arsenate-bearing Fe (oxyhydr)-oxides. In particular, the long-term fate and behavior regarding arsenate immobilization are unknown under anoxic conditions. Here, we document, through mineral transformation reactions, the immobilization of both phosphate (P) and arsenate [As-(V)] in secondary mineral products and characterize their changing compositions during the transformations. We did this while controlling the initial P/As-(V) ratios. Our results document that, in the absence or at low P/As-(V) ratios, the initial ferrihydrite rapidly transforms to green rust sulfate (GR<sub>SO<sub>4</sub></sub> ), which further transforms into magnetite after 180 days. Meanwhile, high P/As-(V) ratios resulted in a mixture of GR<sub>SO<sub>4</sub></sub> and vivianite, with magnetite as a minor fraction. Invariably, the speciation and partitioning of As-(V) were also affected by the P/As-(V) ratio. A higher P/As-(V) ratio also led to a faster partial reduction of mineral-bound As-(V) to As-(III). The most important finding is that the initial ferrihydrite-bound As-(V) became structurally incorporated into magnetite [low P/As-(V) ratio] or vivianite [high P/As-(V) ratio] and was thus immobilized and not labile. Overall, our results highlight the influence of coexisting phosphate in controlling the toxicity and mobility in anoxic, Fe<sup>2+</sup>-rich subsurface settings, such as contaminated aquifers.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"9 6","pages":"1642-1653"},"PeriodicalIF":2.9000,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12183708/pdf/","citationCount":"0","resultStr":"{\"title\":\"Coexisting Phosphate Controls Arsenate Speciation and Partitioning during Fe(II)-Catalyzed Ferrihydrite Transformation.\",\"authors\":\"Jeffrey Paulo H Perez, A Li Han Chan, J Frederick W Mosselmans, Liane G Benning\",\"doi\":\"10.1021/acsearthspacechem.5c00061\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><p>Arsenic immobilization in soils and sediments is primarily controlled by its sorption onto or incorporation into reactive soil minerals, such as iron (oxyhydr)-oxides. However, coexisting ions (e.g., dissolved bicarbonate, phosphate, silica, and organic matter) can negatively impact the interaction of the toxic arsenate species with iron (oxy)-hydroxides. Of special note is inorganic phosphate, which is a strong competitor for sorption sites due to its analogous chemical and structural nature to inorganic arsenate. Much of our understanding of this competing nature between phosphate and arsenate focuses on the impact on mineral sorption capacities and kinetics. However, we know very little about how coexisting phosphate will alter the stability and transformation pathways of arsenate-bearing Fe (oxyhydr)-oxides. In particular, the long-term fate and behavior regarding arsenate immobilization are unknown under anoxic conditions. Here, we document, through mineral transformation reactions, the immobilization of both phosphate (P) and arsenate [As-(V)] in secondary mineral products and characterize their changing compositions during the transformations. We did this while controlling the initial P/As-(V) ratios. Our results document that, in the absence or at low P/As-(V) ratios, the initial ferrihydrite rapidly transforms to green rust sulfate (GR<sub>SO<sub>4</sub></sub> ), which further transforms into magnetite after 180 days. Meanwhile, high P/As-(V) ratios resulted in a mixture of GR<sub>SO<sub>4</sub></sub> and vivianite, with magnetite as a minor fraction. Invariably, the speciation and partitioning of As-(V) were also affected by the P/As-(V) ratio. A higher P/As-(V) ratio also led to a faster partial reduction of mineral-bound As-(V) to As-(III). The most important finding is that the initial ferrihydrite-bound As-(V) became structurally incorporated into magnetite [low P/As-(V) ratio] or vivianite [high P/As-(V) ratio] and was thus immobilized and not labile. Overall, our results highlight the influence of coexisting phosphate in controlling the toxicity and mobility in anoxic, Fe<sup>2+</sup>-rich subsurface settings, such as contaminated aquifers.</p>\",\"PeriodicalId\":15,\"journal\":{\"name\":\"ACS Earth and Space Chemistry\",\"volume\":\"9 6\",\"pages\":\"1642-1653\"},\"PeriodicalIF\":2.9000,\"publicationDate\":\"2025-06-10\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12183708/pdf/\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"ACS Earth and Space Chemistry\",\"FirstCategoryId\":\"92\",\"ListUrlMain\":\"https://doi.org/10.1021/acsearthspacechem.5c00061\",\"RegionNum\":3,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"2025/6/19 0:00:00\",\"PubModel\":\"eCollection\",\"JCR\":\"Q2\",\"JCRName\":\"CHEMISTRY, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"ACS Earth and Space Chemistry","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1021/acsearthspacechem.5c00061","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/6/19 0:00:00","PubModel":"eCollection","JCR":"Q2","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
Coexisting Phosphate Controls Arsenate Speciation and Partitioning during Fe(II)-Catalyzed Ferrihydrite Transformation.
Arsenic immobilization in soils and sediments is primarily controlled by its sorption onto or incorporation into reactive soil minerals, such as iron (oxyhydr)-oxides. However, coexisting ions (e.g., dissolved bicarbonate, phosphate, silica, and organic matter) can negatively impact the interaction of the toxic arsenate species with iron (oxy)-hydroxides. Of special note is inorganic phosphate, which is a strong competitor for sorption sites due to its analogous chemical and structural nature to inorganic arsenate. Much of our understanding of this competing nature between phosphate and arsenate focuses on the impact on mineral sorption capacities and kinetics. However, we know very little about how coexisting phosphate will alter the stability and transformation pathways of arsenate-bearing Fe (oxyhydr)-oxides. In particular, the long-term fate and behavior regarding arsenate immobilization are unknown under anoxic conditions. Here, we document, through mineral transformation reactions, the immobilization of both phosphate (P) and arsenate [As-(V)] in secondary mineral products and characterize their changing compositions during the transformations. We did this while controlling the initial P/As-(V) ratios. Our results document that, in the absence or at low P/As-(V) ratios, the initial ferrihydrite rapidly transforms to green rust sulfate (GRSO4 ), which further transforms into magnetite after 180 days. Meanwhile, high P/As-(V) ratios resulted in a mixture of GRSO4 and vivianite, with magnetite as a minor fraction. Invariably, the speciation and partitioning of As-(V) were also affected by the P/As-(V) ratio. A higher P/As-(V) ratio also led to a faster partial reduction of mineral-bound As-(V) to As-(III). The most important finding is that the initial ferrihydrite-bound As-(V) became structurally incorporated into magnetite [low P/As-(V) ratio] or vivianite [high P/As-(V) ratio] and was thus immobilized and not labile. Overall, our results highlight the influence of coexisting phosphate in controlling the toxicity and mobility in anoxic, Fe2+-rich subsurface settings, such as contaminated aquifers.
期刊介绍:
The scope of ACS Earth and Space Chemistry includes the application of analytical, experimental and theoretical chemistry to investigate research questions relevant to the Earth and Space. The journal encompasses the highly interdisciplinary nature of research in this area, while emphasizing chemistry and chemical research tools as the unifying theme. The journal publishes broadly in the domains of high- and low-temperature geochemistry, atmospheric chemistry, marine chemistry, planetary chemistry, astrochemistry, and analytical geochemistry. ACS Earth and Space Chemistry publishes Articles, Letters, Reviews, and Features to provide flexible formats to readily communicate all aspects of research in these fields.