Precipitation Pattern Formation in the Copper(II) Oxalate System with Gravity Flow and Axial Symmetry

Baker, Anne; Tóth, Ágota; Horváth, Dezs ̋ o; Walkush, J; Ali, Asif; Morgan, William Ray; Kukovecz, Ákos; Pantaleone, J.; Masełko, Jerzy

doi:10.1021/jp9007703

Cited by 29 publications

(49 citation statements)

References 45 publications

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“…4 While initially the growth of chemical gardens was thought to rely essentially on the chemistry of silica, later studies revealed that also a number of other anions (e.g. aluminate, 5 oxalate, 6 carbonate, 7 phosphate, 8 hydroxide 9 or oxometalate 10 ) can produce similar architectures with a broad range of multivalent metal cations. 1,2,[11][12][13][14] The mechanism for the formation of the typically resulting tubular precipitates was found to be a complex interplay of osmosis, buoyancy and chemical reaction.…”

Section: Introductionmentioning

confidence: 99%

Diffusion and precipitation processes in iron-based silica gardens

Glaab

Rieder

García‐Ruiz

et al. 2016

Phys. Chem. Chem. Phys.

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Silica gardens are tubular structures that form along the interface of multivalent metal salts and alkaline solutions of sodium silicate, driven by a complex interplay of osmotic and buoyant forces together with chemical reaction. They display peculiar plant-like morphologies and thus can be considered as one of the few examples for the spontaneous biomimetic self-ordering of purely inorganic materials. Recently, we could show that silica gardens moreover are highly dynamic systems that remain far from equilibrium for considerable periods of time long after macroscopic growth is completed. Due to initial compartmentalisation, drastic concentration gradients were found to exist across the tube walls, which give rise to noticeable electrochemical potential differences and decay only slowly in a series of coupled diffusion and precipitation processes. In the present work, we extend these studies and investigate the effect of the nature of the used metal cations on the dynamic behaviour of the system. To that end, we have grown single macroscopic silica garden tubes by controlled addition of sodium silicate sol to pellets of iron(ii) and iron(iii) chloride. In the following, the concentrations of ionic species were measured as a function of time on both sides of the formed membranes, while electrochemical potentials and pH were monitored online by immersing the corresponding sensors into the two separated solution reservoirs. At the end of the experiments, the solid tube material was furthermore characterised with respect to composition and microstructure by a combination of ex situ techniques. The collected data are compared to the previously reported case of cobalt-based silica gardens and used to shed light on ion diffusion through the inorganic membranes as well as progressive mineralisation at both surfaces of the tube walls. Our results reveal important differences in the dynamics of the three studied systems, which can be explained based on the acidity of the metal cations and the porosity of the membranes, leading to substantially dissimilar time-dependent solution chemistry as well as distinct final mineral structures. The insight gained in this work may help to better understand the diffusion properties and precipitation patterns in tubular iron (hydr)oxide/silicate structures observed in geological environments and during steel corrosion.

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Section: Introductionmentioning

confidence: 99%

Diffusion and precipitation processes in iron-based silica gardens

Glaab

Rieder

García‐Ruiz

et al. 2016

Phys. Chem. Chem. Phys.

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“…Similarly, striped patterns have recently been evidenced experimentally in reactive systems when a pellet of copper sulfate is immersed in a sodium oxalate solution. 15 A precipitate in the form of a striped pattern is observed to grow radially. Such stripes also appear when the copper sulfate solution is pumped radially from below into a sodium oxalate solution covered to avoid evaporation.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of a buoyancy-driven instability of a miscible horizontal displacement in a Hele-Shaw cell

et al. 2014

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When a given fluid displaces another less viscous miscible one in a horizontal HeleShaw cell, the displacement is stable from the viscous point of view. Nevertheless, thin stripes perpendicular to the moving interface can be observed in the mixing zone between the fluids both in rectilinear and radial displacements. This instability is due to buoyancy effects within the gap of the cell which develop because of an unstable density stratification associated with the underlying concentration profile. To characterize this buoyancy-driven instability and the related striped pattern, we perform a parametric experimental study of viscously stable miscible displacements in a horizontal Hele-Shaw cell with radial injection. We analyze the influence of the flow rate, the thickness of the gap, and the relative physical fluid properties on the development and characteristics of the instability. C ⃝ 2014 AIP Publishing LLC.

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“…Since the gravity current carries the more concentrated solution, the precipitate formation depletes the dilute outer electrolyte above. The build-up of carbonate ion by diffusional flux is a substantially slower process, therefore diffusion is insignificant in the precipitate formation [30,13]. In general, these experiments not only demonstrate that transport processes create conditions for selective production of a crystalline form but also may provide insight into natural processes where various gradients play an important role.…”

Section: Discussionmentioning

confidence: 70%

“…These self-organized precipitates have been the subject of several recent studies [6][7][8][9][10], since their controlled synthesis may yield different ordered materials due to the presence of gradients [11,12]. When the precipitate evolves into separate crystalline structures instead of a membrane, the difference in the density of the two electrolytes lead to hydrodynamic instability that results in fluid flow allowing the local mixing of the components [13][14][15]. In this work we construct the latter system and show how morphology can be controlled in the example of calcium carbonate.…”

Section: Introductionmentioning

confidence: 99%