Surfactant Adsorption to Gypsum Surfaces and the Effects on Solubility in Aqueous Solutions

Yiyen, Galip; Duck, Kodie V; Walker, Robert A.

doi:10.1021/acs.langmuir.1c02890

Cited by 3 publications

(2 citation statements)

References 50 publications

(72 reference statements)

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“…The assembly used for measurements presented in this study has been described previously. − Briefly, the output (3.2 W, 1 kHz, 85 fs) from an amplified Ti:sapphire laser (Coherent Libra HE) is split by an 80/20 beam splitter. 80% of the intensity is used to pump Coherent OPerA Solo to produce an IR beam tuned at 3 different parts in the −OH stretching frequency region.…”

Section: Experimental Methodsmentioning

confidence: 99%

Nonlinear Optical Studies of Water at Gypsum–Air and Gypsum–Aqueous Interfaces

Yiyen,

Sobolewski,

Walker

2024

J. Phys. Chem. C

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Vibrational sum frequency generation (VSFG), Fourier transform infrared (FTIR) absorbance, and Raman scattering were used to investigate the water structure at the gypsum (CaSO 4 •2H 2 O)−air and gypsum−water interfaces under ambient thermal and atmospheric conditions. Results show that water structurally embedded in the gypsum matrix consists of two different populations. One population has decoupled −OH bonds with one bond oriented in-plane, while the second water population has a more traditional, normal mode structure with the molecular C 2 symmetry axis aligned along the surface normal. Based on previously reported molecular dynamics simulations, we propose that surface water molecules having the decoupled −OH bonds (population 1) result from strong hydrogen bond donation to gypsum's sulfate oxygens, whereas water molecules in the second population sample a more symmetric environment that shifts water's vibrational frequencies to ∼3400 cm −1 . Gypsum samples in contact with bulk water show significantly diminished VSFG signals with no observable new features. This result is attributed to loss of VSFG response due to the signal transmission into the bulk water and to an absence of surface-induced structure in the adjacent aqueous phase, consistent with a mineral surface near its point of zero charge. Removal of the bulk aqueous phase results in VSFG spectra that are very similar to those measured prior to water immersion, even when the aqueous phase consisted of D 2 O although relative intensities of individual bands change following exposure to D 2 O. These results imply that some fraction of gypsum's surface structural water remains associated with the substrate and does not readily exchange with an adjacent phase. Furthermore, these findings provide direct molecular-level insight into previous force microscopy studies that proposed the existence of tightly bound surface waters at the gypsum/aqueous interface.

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Section: Experimental Methodsmentioning

confidence: 99%

Nonlinear Optical Studies of Water at Gypsum–Air and Gypsum–Aqueous Interfaces

Yiyen,

Sobolewski,

Walker

2024

J. Phys. Chem. C

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“…Even though conductometric titration is more commonly used to analyze acids and bases as an alternative to pH titrations, its potential for sulfate analysis was investigated and proven successful by Garcia and Schultz in an undergraduate laboratory experiment, 23 as well as for laboratory-controlled gypsum dissolution experiments. 24 This technique, however, has not been previously adapted to examine chemically complex aqueous solutions having high ionic strengths, and, to our knowledge, data from conductometric titration experiments have not been benchmarked against more conventional analytical techniques traditionally used to assess groundwater quality.…”

Section: ■ Introductionmentioning

confidence: 99%

Accurately Determining Groundwater Sulfate Concentrations from Reclaimed Landscapes with Conductometric Titrations

et al. 2023

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Conductometric titrations were used to measure sulfate concentrations in ground and surface water samples taken from land reclaimed after open-air coal mining. Sulfate concentrations ranged from 460 mg/L in surface water upstream of the former coal mine’s location to almost 3500 mg/L in groundwater sampled at the spoil site. Data from the titration measurements were benchmarked against EPA-approved ion chromatography (IC) measurements and results agreed to within ±3.6% (averaged over 36 samples) with a range of +10.4 and −11.3%. To test the generality of conductometric titration as a method for measuring dissolved constituents in environmental aquatic systems, additional measurements testing for chloride were performed with surface water samples collected from four different sites in south central and southwest Montana. Chloride concentrations ranged from 2.2 to 12 ppm. Based on measurements with control samples prepared in the laboratory, the environmental sample measurements are believed to be accurate to within ±6.4%. These conductometric titration studies highlight the technique’s simplicity, accuracy, cost effectiveness, and potential to produce rapid results. Additional analyses suggest that even simpler, non-species-specific conductivity data can provide an on-site, rapid assessment of sulfate levels in ground and surface water when historical speciation data are available.

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