Pb2+ Uptake by Magnesite: The Competition between Thermodynamic Driving Force and Reaction Kinetics

When they are in put in contact with carbonate minerals dangerous environmental pollutants such as Pb2+ and Cd2+ are taken up by the solid phase assemblage and can be removed from aqueous solutions.*

As carbonates can be found almost everywhere and are easily exploitable this makes them interesting materials for environmental remediation.*

However, magnesite ( MGS ) is well-known for the slow dissolution and growth kinetics at room temperature conditions in the so-called dolomite problem.*

In their article “Pb2+ Uptake by Magnesite: The Competition between Thermodynamic Driving Force and Reaction Kinetics” Fulvio Di Lorenzo, Tobias Arnold and Sergey V. Churakov use in situ atomic force microscopy (AFM) to investigate the growth of {10.4} magnesite surfaces in the absence and in the presence of Pb2+ as well as the effect of solution ageing.*

In their study the authors attempt to answer the question if and under which circumstances magnesium carbonate could be used in removing Pb from wastewater.*

The experimental results presented in above mentioned article have the object to discuss and evaluate the theoretical possibilities and the practical limitations that must be taken into account for the development of environmental remediation technologies based on magnesite.*

The experiments conducted in this study by  Fulvio Di Lorenzo et al. demonstrate that, although the thermodynamic conditions are encouraging, the transformation reaction between magnesite and cerrusite makes it improbably that it will play a crucial role in the development of remediation processes for PbII pollution.*

The authors of the study conclude that, although the thermodynamic conditions are encouraging, an environmental remediation process based on MGS as the substrate for a solvent-mediated transformation reaction is unlikely to play a crucial part in industrial applications due to the slow kinetics of MGS dissolution. However, the sluggish kinetics of MGS precipitation is favourable for Pb entrapment by the precipitation of carbonate from Mg2+ and Pb2+-bearing solutions, leading to a strong PbII enrichment in the solid phase even in far-from-equilibirum conditions.*

The in situ flow-through Atomic Force Microscopy was performed using Arrow-UHFAuD AFM probes in tapping mode.

Figure 8 from “Pb2+ Uptake by Magnesite: The Competition between Thermodynamic Driving Force and Reaction Kinetics” by Fulvio Di Lorenzo et al:
 In situ observation of {10.4} surfaces of MGS in contact with acidic solution, pH 4 (HNO3). The images were acquired in tapping mode. The first row corresponds to height channels, while the second row reports the respective amplitude channels. (A) The dissolution at 25 °C is sluggish and it is not possible to detect any dissolution feature. (B) In the same conditions but at higher temperature (60 °C), dissolution features are observed on the {10.4} surfaces of MGS, despite the retrograde solubility. Yellow and blue lines of constant size are used to highlight the evolution of etch pits and step edges, respectively. This evidence demonstrates that the existence of kinetic barriers controls the dissolution of MGS at room temperature conditions. NanoWorld Arrow-UHFAuD AFM probes were used.
Figure 8 from “Pb2+ Uptake by Magnesite: The Competition between Thermodynamic Driving Force and Reaction Kinetics” by Fulvio Di Lorenzo et al:
 In situ observation of {10.4} surfaces of MGS in contact with acidic solution, pH 4 (HNO3). The images were acquired in tapping mode. The first row corresponds to height channels, while the second row reports the respective amplitude channels. (A) The dissolution at 25 °C is sluggish and it is not possible to detect any dissolution feature. (B) In the same conditions but at higher temperature (60 °C), dissolution features are observed on the {10.4} surfaces of MGS, despite the retrograde solubility. Yellow and blue lines of constant size are used to highlight the evolution of etch pits and step edges, respectively. This evidence demonstrates that the existence of kinetic barriers controls the dissolution of MGS at room temperature conditions.

*Fulvio Di Lorenzo, Tobias Arnold, and Sergey V. Churakov
Pb2+ Uptake by Magnesite: The Competition between Thermodynamic Driving Force and Reaction Kinetics
Minerals 2021, 11(4), 415
DOI: https://doi.org/10.3390/min11040415

Please follow this external link to read the full article: https://www.mdpi.com/2075-163X/11/4/415

Open Access : The article “Pb2+ Uptake by Magnesite: The Competition between Thermodynamic Driving Force and Reaction Kinetics” by Fulvio Di Lorenzo, Tobias Arnold, and Sergey V. Churakov is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.

Self-assembly of small molecules at hydrophobic interfaces using group effect

Although common in nature, the self-assembly of small molecules at sold–liquid interfaces is difficult to control in artificial systems. The high mobility of dissolved small molecules limits their residence at the interface, typically restricting the self-assembly to systems under confinement or with mobile tethers between the molecules and the surface. Small hydrogen-bonding molecules can overcome these issues by exploiting group-effect stabilization to achieve non-tethered self-assembly at hydrophobic interfaces. Significantly, the weak molecular interactions with the solid makes it possible to influence the interfacial hydrogen bond network, potentially creating a wide variety of supramolecular structures.*

In the paper “Self-assembly of small molecules at hydrophobic interfaces using group effect” William Foster, Keisuke Miyazawa, Takeshi Fukuma, Halim Kusumaatmaja and Kislon Voϊtchovsky investigate the nanoscale details of water and alcohols mixtures self-assembling at the interface with graphite through group-effect. They explore the interplay between inter-molecular and surface interactions by adding small amounts of foreign molecules able to interfere with the hydrogen bond network and systematically varying the length of the alcohol hydrocarbon chain. The resulting supramolecular structures forming at room temperature are then examined using atomic force microscopy with insights from computer simulations.*

The authors show that the group-based self-assembly approach investigated in the paper is general and can be reproduced on other substrates such as molybdenum disulphide and graphene oxide, potentially making it relevant for a wide variety of systems.*

NanoWorld Arrow UHF-AuD ultra high frequency cantilevers for High Speed AFM were used for the amplitude modulation atomic force microscopy described in this paper.


Figure 4 from “Self-assembly of small molecules at hydrophobic interfaces using group effect“ by William Foster et al.:
Impact of the backbone length of primary alcohols on interfacial self-assembly on HOPG. The basic monolayer motif is visible as expected in a 50 : 50 methanol : water mixture (a), here imaged by amplitude-modulation AFM (topography image). In a 50 : 50 ethanol : water mixture (b), two organised layers are visible both in topography and in the phase where it is more pronounced, outlined by a white dashed line (blue and red arrows). In phase, the self-assembled layers appear darker than the directly exposed graphite, where no structures are present (black arrow). The lower layer shows few resolvable features and is bordered by wide rows that have a separation of 5.89 ± 0.28 nm. In 50 : 50 1-propanol : water mixture (c), novel structures with long, straight edges emerge (red arrow) and grow on top of the exposed graphite (black arrow). The structures have a row periodicity of 5.86 ± 0.25 nm. The inset shows details of the longitudinal row structures near an edge. Further variance is seen in a 50 : 50 2-propanol : water mixture (d) where two types of domains form (red and blue arrows), both demonstrating a clear phase contrast with the graphite surface (black arrow). The domains have longitudinal rows with periodicities of 6.10 ± 0.35 nm (blue arrow) and 4.91 ± 0.45 nm (red arrow). Unlike for (c), higher resolution of the row (inset) evidence curved edges. The scale bars are 50 nm in (a) and (b), 100 nm in (c) and (d) main image and 20 nm in the insets. The purple colour scale bar represents a height variation of 1 nm in (a), (b) and (d), 3 nm in (c) and 0.5 nm in the insets. The blue scale bar represents a phase variation of 1.5° in (b), 2° in (c) and its inset and 15° in (d) and its inset.

*William Foster, Keisuke Miyazawa, Takeshi Fukuma, Halim Kusumaatmaja and Kislon Voϊtchovsky
Self-assembly of small molecules at hydrophobic interfaces using group effect
Nanoscale, 2020,12, 5452
DOI: 10.1039/c9nr09505e

Please follow this external link to read the full article: https://pubs.rsc.org/en/content/articlepdf/2020/nr/c9nr09505e

Open Access: The paper « Self-assembly of small molecules at hydrophobic interfaces using group effect»  by William Foster, Keisuke Miyazawa, Takeshi Fukuma, Halim Kusumaatmaja and Kislon Voϊtchovsky is licensed under a Creative Commons Attribution 3.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/3.0/.

Optical manipulation of sphingolipid biosynthesis using photoswitchable ceramides

Ceramides are central intermediates of sphingolipid metabolism that also function as potent messengers in stress signaling and apoptosis. Progress in understanding how ceramides execute their biological roles is hampered by a lack of methods to manipulate their cellular levels and metabolic fate with appropriate spatiotemporal precision.*

In the article “Optical manipulation of sphingolipid biosynthesis using photoswitchable ceramides” Matthijs Kol, Ben Williams, Henry Toombs-Ruane, Henri G Franquelim, Sergei Korneev, Christian Schroeer, Petra Schwille, Dirk Trauner, Joost CM Holthuis and James A Frank report on clickable, azobenzene-containing ceramides, caCers, as photoswitchable metabolic substrates to exert optical control over sphingolipid production in cells.*

They combine atomic force microscopy on model bilayers with metabolic tracing studies in cells, and demonstrate that light-induced alterations in the lateral packing of caCers lead to marked differences in their metabolic conversion by sphingomyelin synthase and glucosylceramide synthase. These changes in metabolic rates are instant and reversible over several cycles of photoswitching. The findings described in the article disclose new opportunities to probe the causal roles of ceramides and their metabolic derivatives in a wide array of sphingolipid-dependent cellular processes with the spatiotemporal precision of light.*

The High-speed AFM in AC mode described in the article was done with NanoWorld Ultra-Short Cantilevers USC-F0.3-k0.3 with a typical stiffness of 0.3 N/m. The AFM cantilever oscillation was tuned to a frequency of 100–150 kHz and the amplitude kept below 10 nm. The scan rate was set to 25–150 Hz. Images were acquired at 256 × 256 pixel resolution. All measurements were performed at room temperature. The force applied on the sample was minimized by continuously adjusting the set point and gain during imaging. Height, error, deflection and phase-shift signals were recorded and images were line-fitted as required.*

Figure 2 b from “ Optical manipulation of sphingolipid biosynthesis using photoswitchable ceramides “ by Matthijs Kol et al. :
Photo-isomerization of caCers affects membrane fluidity and lipid domain structure in supported lipid bilayers.
(b) Atomic force microscopy of supported lipid bilayers ( SLBs )prepared as in (a). Isomerization of caCer-3 (top) and caCer-4 (bottom) to cis with UV-A light (365 nm) resulted in a fluidification inside the Lo domains, as indicated by the appearance of small fluid Ld lakes and an increased Ld/Lo area ratio. This effect was reversed on isomerization back to trans with blue light (470 nm), marked by a drop in the Ld/Lo area ratio. Scale bars, 2 μm. (c) Time-course plotting the normalized Lo area over multiple 365/470 nm irradiation cycles for caCer-3 (top) and caCer-4 (bottom).
Please refer to https://doi.org/10.7554/eLife.43230.007 for the full figure.

*Matthijs Kol, Ben Williams, Henry Toombs-Ruane, Henri G Franquelim, Sergei Korneev, Christian Schroeer, Petra Schwille, Dirk Trauner, Joost CM Holthuis, James A Frank
Optical manipulation of sphingolipid biosynthesis using photoswitchable ceramides
eLife 2019;8:e43230
DOI: 10.7554/eLife.43230
https://doi.org/10.7554/eLife.43230.001
https://doi.org/10.7554/eLife.43230.007

Please follow this external link to read the full article: https://elifesciences.org/articles/43230

Open Access The article “Optical manipulation of sphingolipid biosynthesis using photoswitchable ceramides “ by Matthijs Kol, Ben Williams, Henry Toombs-Ruane, Henri G Franquelim, Sergei Korneev, Christian Schroeer, Petra Schwille, Dirk Trauner, Joost CM Holthuis and  James A Frank is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.