Reply to “Comment on ‘Interfacial pH of an Isolated Silica−Water Interface'”

Fisk, Jonathan D.; A, O'Reilly; Shaw, Andrew M.

doi:10.1021/jp056221e

Cited by 3 publications

(2 citation statements)

References 14 publications

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“…The chemistry of water at the mineral/water interface is complex, largely due to deviations in the behavior of water molecules at the interface from their counterparts in the bulk liquid. − In particular, the solution pH and electrolyte composition are among the most important parameters that affect the behavior of water at the silica/water interface. Many studies have examined the effect of pH and electrolyte composition on dissolution rates of silica and quartz, − with possible mechanisms of dissolution related to cation hydration and changes in water orientation at the silica/aqueous interface. , Consequently, elucidating the structural properties of water at the silica/aqueous interface is crucial in understanding the interfacial phenomena that play significant roles in chemical separations as well as geochemical, petrochemical, environmental, and biological processes. − …”

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confidence: 99%

pH-Dependent Inversion of Hofmeister Trends in the Water Structure of the Electrical Double Layer

DeWalt-Kerian

Kim

Azam

et al. 2017

J. Phys. Chem. Lett.

143

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Specific ion effects (SIEs) are known to influence the acid/base behavior of silica and the interfacial structure of water, yet evidence of the effect of pH on SIEs is lacking. Here broadband vibrational sum frequency generation (SFG) spectroscopy was used to study SIEs on the water structure at the electrical double layer (EDL) of silica as a function of pH and monovalent cation identity from pH 2-12 at 0.5 M salt concentration. SFG results indicate a direct Hofmeister series of cation adsorption at pH 8 (Li < Na < K < Cs), with an inversion in this series occurring at pH > 10. In addition, an inversion in SFG intensity trends also occurred at pH < 6, which was attributed to contributions from asymmetric cation hydration and EDL overcharging. The highly pH-dependent SIEs for silica/water have implications for EDL models that often assume pH-independent parameters.

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confidence: 99%

pH-Dependent Inversion of Hofmeister Trends in the Water Structure of the Electrical Double Layer

DeWalt-Kerian

Kim

Azam

et al. 2017

J. Phys. Chem. Lett.

143

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“…In one approach, pH-sensitive dyes have been used in conjunction with EW-CRDS to probe the change in resonant frequency of the dye upon interacting with the surface [10,11]. However, many have questioned whether the dye's acid dissociation equilibrium constant K a is different at the interface, knowing which is critical to accurately quantify the surface acidity using this approach [14,15].…”

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confidence: 99%

The influence of concentration on specific ion effects at the silica/water interface

Azam

Darlington²,

Gibbs³

2014

J. Phys.: Condens. Matter

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Second harmonic generation spectroscopy is a useful tool for monitoring changes in interfacial potential at buried insulator/liquid interfaces. Here we apply this technique to the silica/aqueous interface and monitor the changes in interfacial potential while varying the pH in the presence of different alkali halides at 0.1M concentration. Within the pH range explored, the bimodal distribution of acidic sites on planar silica is clearly observed, corresponding to two types of acidic SiOH groups. Comparing these data with previous work at 0.5M sheds light on whether the presence of the ions stabilizes the charged or neutral state of the surface sites. For the alkali chlorides, with the exception of NaCl, we observe that the presence of the alkali chlorides stabilize the less acidic site in the protonated (SiOH) rather than deprotonated (SiO(-)) form. This unusual influence of the cation is attributed to the combination of interactions at the interface between water, surface sites and the electrolyte. Overall, we observe that the influence of the alkali ion on the ratio of the two types of sites and their effective acid dissociation constants is minor at 0.1M, unlike that observed at 0.5M. In contrast, the influence of the anion on the cooperative dissociation of surface sites and their relative distribution is little affected upon decreasing the concentration, which indicates that these specific anion effects are prevalent in nature.

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Studying Specific Ion Effects at the Silica/Aqueous Interface

Kim¹

2017

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Reply to “Comment on ‘Interfacial pH of an Isolated Silica−Water Interface'”

Cited by 3 publications

References 14 publications

pH-Dependent Inversion of Hofmeister Trends in the Water Structure of the Electrical Double Layer

pH-Dependent Inversion of Hofmeister Trends in the Water Structure of the Electrical Double Layer

The influence of concentration on specific ion effects at the silica/water interface

Studying Specific Ion Effects at the Silica/Aqueous Interface

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