Oversolubility in the microvicinity of solid–solution interfaces

Abstract

Water-solid interactions at the macroscopic level (beyond tens of nanometers) are often viewed as the coexistence of two bulk phases with a sharp interface in many areas spanning from biology to (geo)chemistry and various technological fields (membranes, microfluidics, coatings, etc.). Here we present experimental evidence indicating that such a view may be a significant oversimplification. High-resolution infrared and Raman experiments were performed in a 60 × 20 μm(2) quartz cavity, synthetically created and initially filled with demineralized water. The IR mapping (3 × 3 μm(2) beam size) performed using the SOLEIL synchrotron radiation source displays two important features: (i) the presence of a dangling free-OH component, a signature of hydrophobic inner walls; (ii) a shift of the OH-stretching band which essentially makes the 3200 cm(-1) sub-band predominate over the usual main component at around 3400 cm(-1). Raman maps confirmed these signatures (though less marked than IR's) and afforded a refined spatial distribution of this interfacial signal. This spatial resolution, statistically treated, results in a puzzling image of a 1-3 μm thick marked-liquid layer along the entire liquid-solid interface. The common view is then challenged by this strong evidence that a μm-thick layer analogous to an interphase forms at the solid-liquid interface. The thermodynamic counterpart of the vibrational shifts amounts to around +1 kJ mol(-1) at the interface with a rapidly decreasing signature towards the cavity centre, meaning that vicinal water may form a reactive layer, of micrometer thickness, expected to have an elevated melting point, a depressed boiling temperature, and enhanced solvent properties.

Structural evolution of water and hydroxyl groups during thermal, mechanical and chemical treatment of high purity natural quartz

“…In a recent vibrational spectroscopic imaging study, a mm thick interfacial layer between SiO 2 and H 2 O in a cavity was observed, showing the development of a "diffuse" interface even at room temperature. 70 It is possible that the transport paths discussed here along grain boundaries and including smaller inclusions occurs according to a mechanism involving similar "swollen" interfacial layers. With the results in this work, it is not possible to conrm or disprove that, however, the shape of the interfaces in Fig.…”

RTM for Waste Repositories

“…In these situations, Kozeny-Carman and Archie's law fail to reproduce experimental observations and thermodynamic properties such as solubility are also modified if pores reach micrometric size (e.g. Emmanuel and Berkowitz 2007, Mürmann et al 2013, Bergonzi et al 2016, Rajyaguru et al 2019. Although the precipitation of minerals, in general and in particular in this type of pores, should theoretically be described in RTM as a sequence of steps including nucleation, scavenging (or ripening), and growth, this approach has only been used by Savage et al (2010) in the context of waste repositories.…”

Diffraction-limited mid-infrared microspectroscopy to reveal a micron-thick interfacial water layer signature

“…More recently, in Earth science and porous media, our group has started using high-resolution infrared transmission microspectroscopy to explore the water behavior at the solid-liquid interface. 35 Probing interfaces is usually done through nonlinear techniques such as second-harmonic generation (SHG) or sum frequency generation spectroscopy (SFG), [36][37][38][39][40][41][42][43][44][45] but we decided to apply FTIR transmission microscopy according to classical linear spectroscopy. To increase the chance of getting specific spectral signatures near the interface, we opted to use a small beam, with a size close to or at the diffraction limit.…”

“…They allow achieving diffraction-limited spatial resolution (aperture size 3 × 3 µm) over the 3.33-2.63 μm range related to the OH stretching band of water (following the Abbe equation, the diffraction limit is 2.53 µm in the case of 2.7 µm wavelength). 35,[56][57][58] Meanwhile, owing to the recent development of infrared laser technology, quantum cascade lasers (QCLs) and supercontinuum generation of lasers (SCLs) have been employed as an alternative high-brilliance infrared radiation source. 51,56,[59][60][61][62][63][64] QCLs have enough power and brilliance to exploit an aperture size smaller than the wavelength of radiation and therefore perform high spatial resolution measurements.…”

“…[67][68][69][70] This paper aims to compare the efficiency of the mid-infrared microspectroscopy setups to deal with the interfacial water layer signatures in the light of previous SRS-based measurements revealing that liquid water can adopt specific infrared signatures along the water-quartz interfaces within a micronthick layer. 35 The test sample is an intra-mineral cavity, buried inside a quartz crystal with sharp solid walls, and containing a liquid-air mixture in a totally closed environment. The quartz fragment was double-side polished down to a 19 ± 1 µm thickness, and the cavity is located 4 µm beneath the top surface.…”