Solid-liquid equilibria of Mg(OH)2(cr) and Mg2(OH)3Cl·4H2O(cr) in the system Mg-Na-H-OH-Cl-H2O at 25°C

Altmaier, M.; Metz, Volker; Neck, V.; Müller, Ralf; Fanghänel, Th.

doi:10.1016/s0016-7037(03)00165-0

Cited by 152 publications

(102 citation statements)

References 20 publications

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“…The presence of Cl-is well established to both enhance Mg dissolution and disrupt the protectiveness of aqueous-formed MgO/Mg(OH) 2 films. These effects have been linked to enhanced dissolution and increased aqueous solubility by formation of MgCl 2 and/or Mg hydroxychloride complexes, 9,12,13,15,21,51 as well as possible cracking and rupture of the inner film regions [e.g. 17,22].…”

Section: Discussionmentioning

confidence: 99%

Film Breakdown and Nano-Porous Mg(OH)₂Formation from Corrosion of Magnesium Alloys in Salt Solutions

Brady

Rother

Anovitz

et al. 2015

J. Electrochem. Soc.

138

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Small angle neutron scattering (SANS) and scanning transmission electron microscopy (STEM) were used to study film formation by magnesium alloys AZ31B (Mg-3Al-1Zn base) and ZE10A (Elektron 717, E717: Mg-1Zn + Nd, Zr) in H 2 O and D 2 O with and without 1 or 5 wt% NaCl. No SANS scattering changes were observed after 24 h D 2 O or H 2 O exposures compared with as-received (unreacted) alloy, consistent with relatively dense MgO-base film formation. However, exposure to 5 wt% NaCl resulted in accelerated corrosion, with resultant SANS scattering changes detected. The SANS data indicated both particle and rough surface (internal and external) scattering, but with no preferential size features. The films formed in 5 wt% NaCl consisted of a thin, inner MgO-base layer, and a nano-porous and filamentous Mg(OH) 2 outer region tens of microns thick. Chlorine was detected extending to the inner MgO-base film region, with segregation of select alloying elements also observed in the inner MgO, but not the outer Mg(OH) 2 . Modeling of the SANS data suggested that the outer Mg(OH) 2 films had very high surface areas, consistent with loss of film protectiveness. Implications for the NaCl corrosion mechanism, and the potential utility of SANS for Mg corrosion, are discussed. Magnesium and its alloys are of great interest for a wide range of structural and functional applications, including lightweight automotive and aircraft structural materials, biomedical implants, fuel cells and hydrogen storage, batteries, etc.1-7 However, the high reactivity and rapid corrosion of Mg in many aqueous and humid environments is a key issue. [8][9][10][11] Of particular challenge and interest is the acceleration of Mg corrosion in the presence of salt species. Mechanisms of accelerated attack in salt solutions include enhanced local micro-galvanic coupling at alloy second phases and/or impurities (e.g. Fe, Ni, Cu etc.) and disruption of the MgO and/or Mg(OH) 2 base surface films by Cl-. 3,9,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Film formation by Mg alloys under aqueous conditions can be quite complex, involving MgO, Mg(OH) 2 , and MgCO 3 base phases, as well as complexes of those phases when alloy additions (e.g. Al) or environmental species (e.g. Cl-) become incorporated into parts or all of the film structure. [15][16][17]21,[27][28][29][30][31][32][33][34] In some cases, porous and even filiform-like corrosion films have been reported on bare or surface-modified Mg alloys. 11,14,16,18,24,[35][36][37][38] Small angle neutron scattering (SANS) has emerged as a powerful technique to assess structural and morphological features in the ∼1 to up to ∼200-300 nm feature size range (specific range accessed depends on the instrument capabilities and settings, as well as the nature of neutron scattering from the test samples). 39,40 Information can be obtained regarding size, morphology, and number density of scatterers (e.g. 2 nd phase precipitates, phase separation, grain structure, voids, pores, etc.), as well as surface area a...

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Section: Discussionmentioning

confidence: 99%

Film Breakdown and Nano-Porous Mg(OH)₂Formation from Corrosion of Magnesium Alloys in Salt Solutions

Brady

Rother

Anovitz

et al. 2015

J. Electrochem. Soc.

138

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“…The K sp value for ACP was set at 26.83, the mean value of the K sp for ACP from all the studies described by Mañas et al [28]. The Ksp for brucite was set at 17.01 according to the study of Altmaier et al [29].Several minerals were removed from the database as they cannot precipitate through the conditions of the runs: the monetite (CaHPO 4 ), the magnesite (MgCO 3 ), the aragonite (CaCO 3 ), the dolomite (CaMg(CO 3 ) 2 , the huntite (Mg 3 Ca(CO 3 ) 4 ), the ␤-tricalciumphosphate (Ca 3 (PO 4 ) 2 ) as they can only form at high temperature [30,31] [7,12,32,33]. The SI values were calculated using the initial concentrations.…”

Section: Determination Of the Final Solid Phases By Phreeqc®mentioning

confidence: 99%

Optimization of struvite precipitation in synthetic biologically treated swine wastewater—Determination of the optimal process parameters

Capdevielle

Sýkorová

Biscans

et al. 2013

Journal of Hazardous Materials

140

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-Line Daumer. Optimization of struvite precipitation in synthetic biologically treated swine wastewater -Determination of the optimal process parameters. Journal of Hazardous Materials, Elsevier, 2013Elsevier, , vol. 244-245, pp. 357-369. <10.1016Elsevier, /j.jhazmat.2012 h i g h l i g h t sStruvite precipitation is mainly influenced by the quantity of MgO added. Optimized parameters favoured struvite formation despite of high [Ca 2+ ] without adding other reagents. 90% of the total dissolved phosphorus is recovered as large crystals of struvite. Raman spectroscopy and solid dissolution show co-precipitation of ACP and presence of CaCO 3 in solid.Keywords: Struvite P-recovery MgO Calcium phosphate Swine wastewater Raman a b s t r a c t A sustainable way to recover phosphorus (P) in swine wastewater involves a preliminary step of P dissolution followed by the separation of particulate organic matter. The next two steps are firstly the precipitation of struvite crystals done by adding a crystallization reagent (magnesia) and secondly the filtration of the crystals. A design of experiments with five process parameters was set up to optimize the size of the struvite crystals in a synthetic swine wastewater. More than 90% of P was recovered as large crystals of struvite in optimal conditions which were: low Mg:Ca ratio (2.25:1), the leading parameter, high N:P ratio (3:1), moderate stirring rate (between 45 and 90 rpm) and low temperature (below 20• C).These results were obtained despite the presence of a large amount of calcium and using a cheap reactant (MgO). The composition of the precipitates was identified by Raman analysis and solid dissolution. Results showed that amorphous calcium phosphate (ACP) co-precipitated with struvite and that carbonates were incorporated with solid fractions.

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“…Altmaier et al 109 have shown that Mg(OH) 2 reacts to form the Mg 2 (OH) 3 Cl Á 4H 2 O (hydroxychloride) in magnesium chloride solutions with concentrations greater than 2 molal. The K sp for magnesium hydroxide is 1.25 Â 10 À11 at 25 1C.…”

Section: Resultsmentioning

confidence: 99%

A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol

Shaka

Robertson

Finlayson-Pitts

2007

Phys. Chem. Chem. Phys.

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A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol. Diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) is a powerful technique for analyzing solid powders and for following their reactions in real time. We demonstrate that it can also be applied to studying the uptake and reactions of gases in liquid films. Within the DRIFTS cell, a 10% (w/w) mixture of MgCl 2 Á 6H 2 O in NaCl was equilibrated with air at 50% RH, which is above the deliquescence point of the magnesium salt but below that of NaCl. This mixture of NaCl coated with an aqueous magnesium chloride solution was then reacted with gas phase OH to generate hydroxide ions via a previously identified interface reaction. This treatment, hereafter referred to as OH-processing, was sufficient to convert some of the magnesium chloride to Mg(OH) 2 and Mg 2 (OH) 3 Cl Á 4H 2 O, making the aqueous film basic and providing a reservoir of alkalinity. Subsequent addition of SO 2 to the basic processed mixture resulted in its uptake and conversion to sulfite which was measured by FTIR. The sulfite was simultaneously oxidized to sulfate by HOCl/OCl À that was formed in the initial OH-processing of the salt. Further uptake and oxidation of SO 2 in the aqueous film took place when the salt was subsequently exposed to O 3 . These studies demonstrate that DRIFTS can be used to study the chemistry in liquid films in real time, and are consistent with the hypothesis that the reaction of gaseous OH with chloride ions generates alkalinity that enhances the uptake and oxidation of SO 2 under these laboratory conditions.

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Solid-liquid equilibria of Mg(OH)2(cr) and Mg2(OH)3Cl·4H2O(cr) in the system Mg-Na-H-OH-Cl-H2O at 25°C

Cited by 152 publications

References 20 publications

Film Breakdown and Nano-Porous Mg(OH)₂Formation from Corrosion of Magnesium Alloys in Salt Solutions

Film Breakdown and Nano-Porous Mg(OH)₂Formation from Corrosion of Magnesium Alloys in Salt Solutions

Optimization of struvite precipitation in synthetic biologically treated swine wastewater—Determination of the optimal process parameters

A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol

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Solid-liquid equilibria of Mg(OH)2(cr) and Mg2(OH)3Cl·4H2O(cr) in the system Mg-Na-H-OH-Cl-H2O at 25°C

Cited by 152 publications

References 20 publications

Film Breakdown and Nano-Porous Mg(OH)2Formation from Corrosion of Magnesium Alloys in Salt Solutions

Film Breakdown and Nano-Porous Mg(OH)2Formation from Corrosion of Magnesium Alloys in Salt Solutions

Optimization of struvite precipitation in synthetic biologically treated swine wastewater—Determination of the optimal process parameters

A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol

Contact Info

Product

Resources

About

Film Breakdown and Nano-Porous Mg(OH)₂Formation from Corrosion of Magnesium Alloys in Salt Solutions

Film Breakdown and Nano-Porous Mg(OH)₂Formation from Corrosion of Magnesium Alloys in Salt Solutions