Pub Date : 2023-06-20DOI: 10.1186/s12932-023-00081-5
Anshuman Satpathy, Amy E. Hixon
Americium is a highly radioactive actinide element found in used nuclear fuel. Its adsorption on aluminum (hydr)oxide minerals is important to study for at least two reasons: (i) aluminum (hydr)oxide minerals are ubiquitous in the subsurface environment and (ii) bentonite clays, which are proposed engineered barriers for the geologic disposal of used nuclear fuel, have the same ≡AlOH sites as aluminum (hydr)oxide minerals. Surface complexation modeling is widely used to interpret the adsorption behavior of heavy metals on mineral surfaces. While americium sorption is understudied, multiple adsorption studies for europium, a chemical analog, are available. In this study we compiled data describing Eu(III) adsorption on three aluminum (hydr)oxide minerals—corundum (α-Al2O3), γ-alumina (γ-Al2O3) and gibbsite (γ-Al(OH)3)—and developed surface complexation models for Eu(III) adsorption on these minerals by employing diffuse double layer (DDL) and charge distribution multisite complexation (CD-MUSIC) electrostatic frameworks. We also developed surface complexation models for Am(III) adsorption on corundum (α-Al2O3) and γ-alumina (γ-Al2O3) by employing a limited number of Am(III) adsorption data sourced from literature. For corundum and γ-alumina, two different adsorbed Eu(III) species, one each for strong and weak sites, were found to be important regardless of which electrostatic framework was used. The formation constant of the weak site species was almost 10,000 times weaker than the formation constant for the corresponding strong site species. For gibbsite, two different adsorbed Eu(III) species formed on the single available site type and were important for the DDL model, whereas the best-fit CD-MUSIC model for Eu(III)-gibbsite system required only one Eu(III) surface species. The Am(III)-corundum model based on the CD-MUSIC framework had the same set of surface species as the Eu(III)-corundum model. However, the log K values of the surface reactions were different. The best-fit Am(III)-corundum model based on the DDL framework had only one site type. Both the CD-MUSIC and the DDL model developed for Am(III)-γ-alumina system only comprised of one site type and the formation constant of the corresponding surface species was ~ 500 times stronger and ~ 700 times weaker than the corresponding Eu(III) species on the weak and the strong sites, respectively. The CD-MUSIC model for corundum and both the DDL and the CD-MUSIC models for γ-alumina predicted the Am(III) adsorption data very well, whereas the DDL model for corundum overpredicted the Am(III) adsorption data. The root mean square of errors of the DDL and CD-MUSIC models developed in this study were smaller than those of two previously-published models describing Am(III)-γ-alumina system, indicating the better predictive capacity of our models. Overall, our results suggest that using Eu(III)
{"title":"Eu(III) and Am(III) adsorption on aluminum (hydr)oxide minerals: surface complexation modeling","authors":"Anshuman Satpathy, Amy E. Hixon","doi":"10.1186/s12932-023-00081-5","DOIUrl":"10.1186/s12932-023-00081-5","url":null,"abstract":"<div><p>Americium is a highly radioactive actinide element found in used nuclear fuel. Its adsorption on aluminum (hydr)oxide minerals is important to study for at least two reasons: (i) aluminum (hydr)oxide minerals are ubiquitous in the subsurface environment and (ii) bentonite clays, which are proposed engineered barriers for the geologic disposal of used nuclear fuel, have the same ≡AlOH sites as aluminum (hydr)oxide minerals. Surface complexation modeling is widely used to interpret the adsorption behavior of heavy metals on mineral surfaces. While americium sorption is understudied, multiple adsorption studies for europium, a chemical analog, are available. In this study we compiled data describing Eu(III) adsorption on three aluminum (hydr)oxide minerals—corundum (α-Al<sub>2</sub>O<sub>3</sub>), γ-alumina (γ-Al<sub>2</sub>O<sub>3</sub>) and gibbsite (γ-Al(OH)<sub>3</sub>)—and developed surface complexation models for Eu(III) adsorption on these minerals by employing diffuse double layer (DDL) and charge distribution multisite complexation (CD-MUSIC) electrostatic frameworks. We also developed surface complexation models for Am(III) adsorption on corundum (α-Al<sub>2</sub>O<sub>3</sub>) and γ-alumina (γ-Al<sub>2</sub>O<sub>3</sub>) by employing a limited number of Am(III) adsorption data sourced from literature. For corundum and γ-alumina, two different adsorbed Eu(III) species, one each for strong and weak sites, were found to be important regardless of which electrostatic framework was used. The formation constant of the weak site species was almost 10,000 times weaker than the formation constant for the corresponding strong site species. For gibbsite, two different adsorbed Eu(III) species formed on the single available site type and were important for the DDL model, whereas the best-fit CD-MUSIC model for Eu(III)-gibbsite system required only one Eu(III) surface species. The Am(III)-corundum model based on the CD-MUSIC framework had the same set of surface species as the Eu(III)-corundum model. However, the log K values of the surface reactions were different. The best-fit Am(III)-corundum model based on the DDL framework had only one site type. Both the CD-MUSIC and the DDL model developed for Am(III)-γ-alumina system only comprised of one site type and the formation constant of the corresponding surface species was ~ 500 times stronger and ~ 700 times weaker than the corresponding Eu(III) species on the weak and the strong sites, respectively. The CD-MUSIC model for corundum and both the DDL and the CD-MUSIC models for γ-alumina predicted the Am(III) adsorption data very well, whereas the DDL model for corundum overpredicted the Am(III) adsorption data. The root mean square of errors of the DDL and CD-MUSIC models developed in this study were smaller than those of two previously-published models describing Am(III)-γ-alumina system, indicating the better predictive capacity of our models. Overall, our results suggest that using Eu(III)","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://geochemicaltransactions.biomedcentral.com/counter/pdf/10.1186/s12932-023-00081-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4799034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-16DOI: 10.1186/s12932-023-00082-4
Thomas Ray Jones, Jordan Poitras, Emma Gagen, David John Paterson, Gordon Southam
Microbiological weathering of coarse residue deposit (CRD) kimberlite produced by the Venetia Diamond Mine, Limpopo, South Africa enhanced mineral carbonation relative to untreated material. Cultures of photosynthetically enriched biofilm produced maximal carbonation conditions when mixed with kimberlite and incubated under near surface conditions. Interestingly, mineral carbonation also occurred in the dark, under water-saturated conditions. The examination of mineralized biofilms in ca. 150 µm-thick-sections using light microscopy, X-ray fluorescence microscopy (XFM) and backscatter electron—scanning electron microscopy-energy dispersive x-ray spectrometry demonstrated that microbiological weathering aided in producing secondary calcium/magnesium carbonates on silicate grain boundaries. Calcium/magnesium sulphate(s) precipitated under vadose conditions demonstrating that evaporites formed upon drying. In this system, mineral carbonation was only observed in regions possessing bacteria, preserved within carbonate as cemented microcolonies. 16S rDNA molecular diversity of bacteria in kimberlite and in natural biofilms growing on kimberlite were dominated by Proteobacteria that are active in nitrogen, phosphorus and sulphur cycling. Cyanobacteria based enrichment cultures provided with nitrogen & phosphorus (nutrients) to enhance growth, possessed increased diversity of bacteria, with Proteobacteria re-establishing themselves as the dominant bacterial lineage when incubated under dark, vadose conditions consistent with natural kimberlite. Overall, 16S rDNA analyses revealed that weathered kimberlite hosts a diverse microbiome consistent with soils, metal cycling and hydrocarbon degradation. Enhanced weathering and carbonate-cemented microcolonies demonstrate that microorganisms are key to mineral carbonation of kimberlite.
{"title":"Accelerated mineral bio-carbonation of coarse residue kimberlite material by inoculation with photosynthetic microbial mats","authors":"Thomas Ray Jones, Jordan Poitras, Emma Gagen, David John Paterson, Gordon Southam","doi":"10.1186/s12932-023-00082-4","DOIUrl":"10.1186/s12932-023-00082-4","url":null,"abstract":"<div><p>Microbiological weathering of coarse residue deposit (CRD) kimberlite produced by the Venetia Diamond Mine, Limpopo, South Africa enhanced mineral carbonation relative to untreated material. Cultures of photosynthetically enriched biofilm produced maximal carbonation conditions when mixed with kimberlite and incubated under near surface conditions. Interestingly, mineral carbonation also occurred in the dark, under water-saturated conditions. The examination of mineralized biofilms in ca. 150 µm-thick-sections using light microscopy, X-ray fluorescence microscopy (XFM) and backscatter electron—scanning electron microscopy-energy dispersive x-ray spectrometry demonstrated that microbiological weathering aided in producing secondary calcium/magnesium carbonates on silicate grain boundaries. Calcium/magnesium sulphate(s) precipitated under vadose conditions demonstrating that evaporites formed upon drying. In this system, mineral carbonation was only observed in regions possessing bacteria, preserved within carbonate as cemented microcolonies. 16S rDNA molecular diversity of bacteria in kimberlite and in natural biofilms growing on kimberlite were dominated by Proteobacteria that are active in nitrogen, phosphorus and sulphur cycling. Cyanobacteria based enrichment cultures provided with nitrogen & phosphorus (nutrients) to enhance growth, possessed increased diversity of bacteria, with Proteobacteria re-establishing themselves as the dominant bacterial lineage when incubated under dark, vadose conditions consistent with natural kimberlite. Overall, 16S rDNA analyses revealed that weathered kimberlite hosts a diverse microbiome consistent with soils, metal cycling and hydrocarbon degradation. Enhanced weathering and carbonate-cemented microcolonies demonstrate that microorganisms are key to mineral carbonation of kimberlite.</p></div>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://geochemicaltransactions.biomedcentral.com/counter/pdf/10.1186/s12932-023-00082-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4650137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-29DOI: 10.1186/s12932-022-00080-y
Orion Farr, Evert J. Elzinga, Nathan Yee
In this study, we investigated Ni2+, Zn2+, and Co2+ mineralogical incorporation and its effect on green rust transformation to magnetite. Mineral transformation experiments were conducted by heating green rust suspensions at 85 °C in the presence of Ni2+, Zn2+, or Co2+ under strict anoxic conditions. Transmission electron microscopy and powder X-ray diffraction showed the conversion of hexagonal green rust platelets to fine grained cubic magnetite crystals. The addition of Ni2+, Zn2+, and Co2+ resulted in faster rates of mineral transformation. The conversion of green rust to magnetite was concurrent to significant increases in metal uptake, demonstrating a strong affinity for metal sorption/co-precipitation by magnetite. Dissolution ratio curves showed that Ni2+, Zn2+, and Co2+ cations were incorporated into the mineral structure during magnetite crystal growth. The results indicate that the transformation of green rust to magnetite is accelerated by metal impurities, and that magnetite is a highly effective scavenger of trace metals during mineral transformation. The implications for using diagenetic magnetite from green rust precursors as paleo-proxies of Precambrian ocean chemistry are discussed.