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Maria Stromme - One of the best experts on this subject based on the ideXlab platform.
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Amine-Modified Mesoporous Magnesium Carbonate as an Effective Adsorbent for Azo Dyes
2019Co-Authors: Maria Vall, Maria Stromme, Ocean CheungAbstract:Mesoporous Magnesium Carbonate (MMC) was evaluated as a potential candidate material for removal of dyes from textile industry wastewater. The adsorption property of MMC was analyzed for three different azo dyes: reactive black 5 (RB5), amaranth (AM), and acid red 183 (AR183). Further, the effect of porosity, amine modification, ionic strength, and pH was evaluated. MMC modified with 3-(aminopropyl)triethoxysilane (aMMC) showed consistently high uptake levels for all of the azo dyes tested; the uptake of RB5, AM, and AR183 was ∼360, ∼143 and ∼170 mg/g, respectively. The results demonstrated the importance of porosity and surface chemistry in the effective adsorption of the azo dye in aqueous systems. The uptake of RB5 and AM on aMMC was not significantly affected by pH (when varied between 4 and 10), although reduced uptake of RB5 and AM was observed at pH values 12. The addition of NaCl salt at concentrations up to 1000 mM had minimal effect on the high uptake of RB5 on aMMC. The uptake of AM by aMMC was reduced by approximately 20% in the presence of NaCl even at low concentrations. The uptake of AR183 by aMMC varied noticeably by changes in pH and no specific trend was observed. The presence of NaCl also adversely affected the uptake of AR183 on aMMC. The adsorption of the azo dye on aMMC was most likely driven by electrostatic interactions. We show here that aMMC is a potential candidate adsorbent for the effective removal of azo dyes from textile wastewaters
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amine functionalised mesoporous Magnesium Carbonate dielectric spectroscopy studies of interactions with water and stability
2018Co-Authors: Isabelle Pochard, Maria Vall, Sara Frykstrand, Joakim Eriksso, Camille Farineau, Ocea Cheung, Ke Welch, Maria StrommeAbstract:A mesoporous Magnesium Carbonate (MMC) material that was first described in 2013 is currently being investigated for several industrial and life-science-based applications. In this paper, the effec ...
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enhanced release of poorly water soluble drugs from synergy between mesoporous Magnesium Carbonate and polymers
2017Co-Authors: Jiaojiao Yang, Teresa Zardan Gomez De La Torre, Christel A S Ergstrom, Maria Stromme, Peng Zhang, Caroline Alvebra, Ke WelchAbstract:The need to combat poor water solubility has increased interest in supersaturating drug delivery systems. In this study, amorphous mesoporous Magnesium Carbonate (MMC) was used as a drug carrier to achieve supersaturation of tolfenamic acid and rimonabant, two drug compounds with low aqueous solubility. The potential synergy between MMC and hydroxypropyl methylcellulose (HPMC), a polymer commonly included as a precipitation inhibitor in drug delivery systems, was explored with the aim of extending the time that high supersaturation levels were maintained. Release was studied under physiological conditions using USP-2 dissolution baths. A new small-scale method was developed to enable measurement of the initial drug release occurring when the MMC is immersed in the water phase. It was shown that MMC and HPMC together resulted in significant supersaturation and that the polymer enabled both the achievement of a higher API concentration and extension of the supersaturation period. The new small-scale release method showed that the release was linearly increasing with the dose and that similar release rates were observed for the two model compounds. It was hence concluded that the MMC release was diffusion limited for the compounds explored.
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nanostructure and pore size control of template free synthesised mesoporous Magnesium Carbonate
2016Co-Authors: Ocea Cheung, Sara Frykstrand, Peng Zhang, Haoqua Zheng, Taimi Yang, Marco Sommariva, Xiaodong Zou, Maria StrommeAbstract:The structure of mesoporous Magnesium Carbonate (MMC) first presented in 2013 is investigated using a bottom-up approach. MMC is found to be built from the aggregation of nanoparticles of amorphous MgCO3 and MgO with a coating of amorphous MgCO3. The nanoparticles have dimensions of approximately 2–5 nm as observed using transmission electron microscopy and the aggregation of the particles creates the pore structure of MMC. We further show that the average pore diameter of MMC can be controlled by varying the temperature during the powder formation process and demonstrate that altering the pore size opens the possibility to tune the amorphous phase stabilisation properties that MMC exerts on poorly soluble drug compounds. Specifically, we show the loading and release of the antifungal drug itraconazole using MMC as a drug carrier.
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diffusion controlled drug release from the mesoporous Magnesium Carbonate upsalite
2016Co-Authors: Peng Zhang, Teresa Zardan Gomez De La Torre, Joha Forsgre, Christel A S Ergstrom, Maria StrommeAbstract:In vitro drug release from well-defined particle-size fractions of the mesoporous Magnesium Carbonate material Upsalite® was investigated in detail using ibuprofen, a biopharmaceutics classificatio ...
Nathaniel Findling - One of the best experts on this subject based on the ideXlab platform.
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Amorphous Calcium–Magnesium Carbonate (ACMC) Accelerates Dolomitization at Room Temperature under Abiotic Conditions
2020Co-Authors: German Montes-hernandez, François Renard, Anne-line Auzende, Nathaniel FindlingAbstract:The challenge to produce dolomite CaMg(CO3)2 at low temperature (20–35 °C) over laboratory time scales so far has remained unsuccessful, which has led to long-lasting scientific debates in the last two centuries. This mineral exerts a major control on the natural carbon dioxide sequestration into various sedimentary, basaltic, and mantellic rocks. The present study reports on specific abiotic conditions that allow the precipitation of disordered dolomite, high Mg calcite, and high Ca magnesite at room temperature over time scales of hours to days. Here we show that an amorphous calcium Magnesium Carbonate (ACMC) phase accelerates dolomitization at room temperature. ACMC is initially precipitated by mixing a Carbonate (HCO3–/CO32– = 1; pH ∼10.3 ≈ pKa2) alkaline solution with a Mg-Ca ionic solution (Mg molar fraction between 0 and 1). Then, time-resolved in situ Raman spectroscopy monitored the transformation of ACMC into Mg-rich Carbonate minerals. The initial Mg molar fraction controlled both the reaction mechanism (e.g., nature of transient crystalline phases) and the kinetics. Nanosized crystallites with short-range order, called disordered dolomite CaMg(CO3)2, precipitated following a complex reaction pathway. First, nesquehonite (MgCO3·3H2O: nucleation time 2.5 h) and then disordered dolomite (CaMg(CO3)2: nucleation time 3.2 h) followed by monohydrocalcite (CaCO3·H2O: nucleation time 3.4 h) formed from ACMC transformation. Nesquehonite and monohydrocalcite are transient phases that nourish the slow precipitation of disordered dolomite, which reached a spectral equilibrium after 7 days of reaction. The direct transformation of ACMC into disordered dolomite was also measured. Our experimental results demonstrate that disordered dolomite precipitates at room temperature when an ideal Mg/Ca ratio, high Carbonate alkalinity, and high ionic concentration are reached in abiotic systems. This result suggests the possibility of a physicochemical rather than biotic control on the formation of disordered dolomite at low temperature in several geosystems.
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amorphous calcium Magnesium Carbonate acmc accelerates dolomitization at room temperature under abiotic conditions
2020Co-Authors: German Monteshernandez, François Renard, Anne-line Auzende, Nathaniel FindlingAbstract:The challenge to produce dolomite CaMg(CO3)2 at low temperature (20–35 °C) over laboratory time scales so far has remained unsuccessful, which has led to long-lasting scientific debates in the last...
Abir Altabbaa - One of the best experts on this subject based on the ideXlab platform.
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reply to the discussion of the papers impact of hydrated Magnesium Carbonate additives on the carbonation of reactive mgo cements and enhancing the carbonation of mgo cement porous blocks through improved curing conditions by s a walling and j l provis
2016Co-Authors: Cise Unluer, Abir AltabbaaAbstract:This paper is a reply to the discussion by S.A. Walling and J.L. Provis on our papers “Impact of hydrated Magnesium Carbonate additives on the carbonation of reactive MgO cements” and “Enhancing the carbonation of MgO cement porous blocks through improved curing conditions”. Walling and Provis discuss the assignment of X-ray diffraction patterns, the use of acid digestion to quantify the degree of carbonation, the interpretation of thermal analysis data, and the stability of hydrated Magnesium Carbonates. In this reply, we confirm the conclusions made in the two papers based on the combined evidence of microstructural and mechanical performance results.
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impact of hydrated Magnesium Carbonate additives on the carbonation of reactive mgo cements
2013Co-Authors: Cise Unlue, Abir AltabbaaAbstract:Reactive magnesia (MgO) cements have emerged as a potentially more sustainable and technically superior alternative to Portland cement due to their lower production temperature and ability to sequester significant quantities of CO2. Porous blocks containing MgO were found to achieve higher strength values than PC blocks. A number of variables are investigated to achieve maximum carbonation and associated high strengths. This paper focuses on the impact of four different hydrated Magnesium Carbonates (HMCs) as cement replacements of either 20 or 50%. Accelerated carbonation (20 °C, 70–90% RH, 20% CO2) is compared with natural curing (20 °C, 60–70% RH, ambient CO2). SEM, TG/DTA, XRD, and HCl acid digestion are utilized to provide a thorough understanding of the performance of MgO-cement porous blocks. The presence of HMCs resulted in the formation of larger size carbonation products with a different morphology than those in the control mix, leading to significantly enhanced carbonation and strength.
François Renard - One of the best experts on this subject based on the ideXlab platform.
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Amorphous Calcium–Magnesium Carbonate (ACMC) Accelerates Dolomitization at Room Temperature under Abiotic Conditions
2020Co-Authors: German Montes-hernandez, François Renard, Anne-line Auzende, Nathaniel FindlingAbstract:The challenge to produce dolomite CaMg(CO3)2 at low temperature (20–35 °C) over laboratory time scales so far has remained unsuccessful, which has led to long-lasting scientific debates in the last two centuries. This mineral exerts a major control on the natural carbon dioxide sequestration into various sedimentary, basaltic, and mantellic rocks. The present study reports on specific abiotic conditions that allow the precipitation of disordered dolomite, high Mg calcite, and high Ca magnesite at room temperature over time scales of hours to days. Here we show that an amorphous calcium Magnesium Carbonate (ACMC) phase accelerates dolomitization at room temperature. ACMC is initially precipitated by mixing a Carbonate (HCO3–/CO32– = 1; pH ∼10.3 ≈ pKa2) alkaline solution with a Mg-Ca ionic solution (Mg molar fraction between 0 and 1). Then, time-resolved in situ Raman spectroscopy monitored the transformation of ACMC into Mg-rich Carbonate minerals. The initial Mg molar fraction controlled both the reaction mechanism (e.g., nature of transient crystalline phases) and the kinetics. Nanosized crystallites with short-range order, called disordered dolomite CaMg(CO3)2, precipitated following a complex reaction pathway. First, nesquehonite (MgCO3·3H2O: nucleation time 2.5 h) and then disordered dolomite (CaMg(CO3)2: nucleation time 3.2 h) followed by monohydrocalcite (CaCO3·H2O: nucleation time 3.4 h) formed from ACMC transformation. Nesquehonite and monohydrocalcite are transient phases that nourish the slow precipitation of disordered dolomite, which reached a spectral equilibrium after 7 days of reaction. The direct transformation of ACMC into disordered dolomite was also measured. Our experimental results demonstrate that disordered dolomite precipitates at room temperature when an ideal Mg/Ca ratio, high Carbonate alkalinity, and high ionic concentration are reached in abiotic systems. This result suggests the possibility of a physicochemical rather than biotic control on the formation of disordered dolomite at low temperature in several geosystems.
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amorphous calcium Magnesium Carbonate acmc accelerates dolomitization at room temperature under abiotic conditions
2020Co-Authors: German Monteshernandez, François Renard, Anne-line Auzende, Nathaniel FindlingAbstract:The challenge to produce dolomite CaMg(CO3)2 at low temperature (20–35 °C) over laboratory time scales so far has remained unsuccessful, which has led to long-lasting scientific debates in the last...
Vasileios Mavromatis - One of the best experts on this subject based on the ideXlab platform.
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solubility investigations in the amorphous calcium Magnesium Carbonate system
2019Co-Authors: Ettina Purgstalle, Vasileios Mavromatis, Katja E Goetschl, Marti DietzelAbstract:Amorphous precursors are known to occur in the early stages of Carbonate mineral formation in both biotic and abiotic environments. Although the Mg content of amorphous calcium Magnesium Carbonate (ACMC) is a crucial factor for its temporal stabilization, to date little is known about its control on ACMC solubility. Therefore, amorphous CaxMg1−xCO3·nH2O solids with 0 ≤ x ≤ 1 and 0.4 ≤ n ≤ 0.8 were synthesized and dispersed in MgCl2–NaHCO3 buffered solutions at 24.5 ± 0.5 °C. The chemical evolution of the solution and the precipitate clearly shows an instantaneous exchange of ions between ACMC and aqueous solution. The obtained ion activity product for ACMC (IAPACMC = “solubility product”) increases as a function of its Mg content ([Mg]ACMC = (1 − x) × 100 in mol%) according to the expression: log(IAPACMC) = 0.0174 (±0.0013) × [Mg]ACMC − 6.278 (±0.046) (R2 = 0.98), where the log(IAPACMC) shift from Ca (−6.28 ± 0.05) to Mg (−4.54 ± 0.16) ACMC endmember, can be explained by the increasing water content and changes in short-range order, as Ca is substituted by Mg in the ACMC structure. The results of this study shed light on the factors controlling ACMC solubility and its temporal stability in aqueous solutions.
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Using Mg Isotopes to Trace Cyanobacterially Mediated Magnesium Carbonate Precipitation in Alkaline Lakes
2013Co-Authors: Liudmila S. Shirokova, Irina Bundeleva, Christopher R. Pearce, Vasileios Mavromatis, Pascale Bénézeth, Oleg S. Pokrovsky, Emmanuelle Gérard, Eric H. OelkersAbstract:This study assesses the potential use of Mg isotopes to trace Mg Carbonate precipitation in natural waters. Salda Lake (SW Turkey) was chosen for this study because it is one of the few modern environments where hydrous Mg Carbonates are the dominant precipitating minerals. Stromatolites, consisting mainly of hydromagnesite, are abundant in this lake. The Mg isotope composition of incoming streams, groundwaters, lake waters, stromatolites, and hydromagnesite-rich sediments were measured. Because Salda Lake is located in a closed basin, mass balance requires that the Mg isotopic offset between Lake Salda water and precipitated hydromagnesite be comparable to the corresponding offset between Salda Lake and its water inputs. This is consistent with observations; a δ^26Mg offset of 0.8–1.4 ‰ is observed between Salda Lake water and it is the incoming streams and groundwaters, and precipitated hydromagnesite has a δ^26Mg 0.9–1.1 ‰ more negative than its corresponding fluid phase. This isotopic offset also matches closely that measured in the laboratory during both biotic and abiotic hydrous Mg Carbonate precipitation by cyanobacteria (Mavromatis, V., Pearce, C., Shirokova, L. S., Bundeleva, I. A., Pokrovsky, O. S., Benezeth, P. and Oelkers, E.H.: Magnesium isotope fractionation during inorganic and cyanobacteria-induced hydrous Magnesium Carbonate precipitation, Geochim. Cosmochim. Acta, 2012a . 76, 161–174). Batch reactor experiments performed in the presence of Salda Lake cyanobacteria and stromatolites resulted in the precipitation of dypingite (Mg_5(CO_3)_4(OH)_2·5(H_2O)) and hydromagnesite (Mg_5(CO_3)_4(OH)_2·4H_2O) with morphological features similar to those of natural samples. Concurrent abiotic control experiments did not exhibit Carbonate precipitation demonstrating the critical role of cyanobacteria in the precipitation process.
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Magnesium isotope fractionation during hydrous Magnesium Carbonate precipitation with and without cyanobacteria
2012Co-Authors: Vasileios Mavromatis, Irina Bundeleva, Christopher R. Pearce, Pascale Bénézeth, Liudmila S. Shirokova, Oleg S. Pokrovsky, Eric H. OelkersAbstract:The hydrous Magnesium Carbonates, nesquehonite (MgCO3·3H2O) and dypingite (Mg5(CO3)4(OH)2·5(H2O)), were precipitated at 25 °C in batch reactors from aqueous solutions containing 0.05 M NaHCO3 and 0.025 M MgCl2 and in the presence and absence of live photosynthesizing Gloeocapsa sp. cyanobacteria. Experiments were performed under a variety of conditions; the reactive fluid/bacteria/mineral suspensions were continuously stirred, and/or air bubbled in most experiments, and exposed to various durations of light exposure. Bulk precipitation rates are not affected by the presence of bacteria although the solution pH and the degree of fluid supersaturation with respect to Magnesium Carbonates increase due to photosynthesis. Lighter Mg isotopes are preferentially incorporated into the precipitated solids in all experiments. Mg isotope fractionation between the mineral and fluid in the abiotic experiments is identical, within uncertainty, to that measured in cyanobacteria-bearing experiments; measured δ26Mg ranges from −1.54‰ to −1.16‰ in all experiments. Mg isotope fractionation is also found to be independent of reactive solution pH and Mg, CO32−, and biomass concentrations. Taken together, these observations suggest that Gloeocapsa sp. cyanobacterium does not appreciably affect Magnesium isotope fractionation between aqueous fluid and hydrous Magnesium Carbonates.
