Solubility Of Gypsum Research Articles

Spatially refined salinity hazard analysis in gypsum‐affected irrigated soils

AbstractThe global extent of salt‐affected agricultural land, 20% of which is deemed gypsiferous, results in billions of dollars of annual economic loss, a serious problem deserving of attention. However, the analysis of gypsiferous saline soils, such as in the irrigated Lower Arkansas River Valley (LARV) of Colorado, can result in an inflated estimation of soil salinity when using the traditional soil saturated paste extract electrical conductivity (ECe), leading to inaccurate crop yield loss predictions and misguided decisions for remediation. Sparingly soluble gypsum (CaSO4 2H2O) in these soils dissolves more readily during laboratory preparation of saturated paste extracts because of excess soil water dilution coupled with sample disturbance. We present a pragmatic linear‐regression approach to correct for this phenomenon, calibrated using two adapted methods for correcting ECe on an individual sample basis. The novel approach used electrical conductivity of pore water samples from saline fields to evaluate the accuracy of the correction methods. The approach was applied on soil samples from two surface‐irrigated, saline fields in the LARV, which were mapped using electromagnetic induction data and analysis of covariance linear regression, calibrated for ECe and ECe corrected for excess gypsum dissoultion (ECeg). Average ECeg values are as much as 26% lower than uncorrected ECe in gypsum‐biased portions of the fields. Estimation of corn salinity hazard in these gypsum‐affected areas using ECeg in lieu of ECe in a traditional yield response function generated mean relative yield values that are higher by up to 13 percentage points. We discuss lessons learned and suggest enhancements to the techniques.

COMPARSION OF SEVERAL METHODS FOR DETERMINATION OF GYPSUM CONTENT IN SOILS

Due to the solubility of gypsum, gypseous soils are known to be very problematic for civil enlineers. Tr.r assign the volume of the problem and the manner of dealing with it, it is essential to estirnate the arnount of'gypsum in the soil as acourate as possible .The aim of this study is to highlight the methodologies available in the literature that a reusetl to detect the presence of gypsum in soil and to determine its content . The study involves a comparison arnong four of the most popular methods used to determine the soil gypsum . The lbur rnethods rvere used to recover tire soil gypsum in gypsofied soil sarnples containing known amount r:f gypsum . The analyses fbr the test results showed that the method proposed by Berigari and Al-Any (1994 ) was the most accurate one .

Modeling gypsum (calcium sulfate dihydrate) solubility in aqueous electrolyte solutions using extreme learning machine

Due to various operational conditions, experimental determination of gypsum solubility in water-based systems comprising multiple ionic compounds is often impractical or costly. In this regard, computer-based intelligent approaches can provide highly effective and economical alternatives. In this study, after providing a database with 2288 experimental data-points gathered from 31 various literatures, four advanced artificial intelligence techniques were developed: Adaptive Boosting-Support Vector Regression (AdaBoost-SVR), Extreme Learning Machine (ELM), Gradient Boosting-Support Vector Regression (GB-SVR), and Multivariate Adaptive Regression Splines (MARS). The aim of these techniques was to predict the gypsum solubility in aqueous electrolyte solutions as a function of the solutions' temperature and 22 distinct salts' Molal concentrations. After performing various statistical and graphical analyses, it was observed that the ELM model has a more accurate prediction capability for gypsum solubility in aqueous electrolyte solutions compared to the other three models. For this model, the highest Coefficient of Determination (R2 = 0.9926) and the lowest Root Mean Square Error (RMSE = 0.00373) were obtained. Furthermore, after conducting a sensitivity analysis to calculate the relevancy factors of the ELM model's input and output variables, the variation trend of gypsum solubility was evaluated. According to the multiple evaluations, the ELM model predictions reasonably agreed with the experimental data on gypsum solubility in the chosen solutions and temperature ranges. The ELM model can be implemented in numerical modeling frameworks for improving the treatment and reclamation operations of saline water sources, optimizing the oil and gas recovery and production processes, and controlling the complicated geotechnical issues.

Screening of Soil Ameliorants to Enhance the Productivity of Green Gram (Vigna radiata L.) under Sodic Soil in Cauvery Delta Zone of Tamil Nadu

Background: In India, about 6.75 million ha, which is around 2.3% of the country’s geographical area is salt affected of which 3.79 million ha is sodic soil. Total sodic soil area in Tamil Nadu is around 0.36 million ha, accounting for 9.5% of total sodic soil area in India. Reclamation of salt-affected soil using drainage is expensive and leaching with good quality water is uneconomical in shallow water table areas. Addition of organic amendments performs a dual role in these situations by enhancing gypsum solubility and improving soil physico-chemical characteristics. Methods: In this context a field experiment was conducted at Anbil Dharmalingam Agricultural College and Research Institute, Tiruchirappalli during summer season of 2021 and 2022 to study the reclamation potential of ameliorants under sodic soil. The experiments were laid out in split plot design with three replications. The treatments comprised of different soil amendments in main plot and foliar nutrition in sub plot. Result: The results showed that, gypsum @ 50% GR+CSR GROMOR @ 25 kg ha-1 registered significantly higher growth parameters viz., plant height (53.5 and 58.4 cm), no. of branches plant-1 (7.27 and 6.75), DMP (2791 and 2801 kg ha-1), physiological characters viz.,CGR (4.12 and 4.46 g m-2 day-1), SPAD value (27.70 and 29.96), RWC (64.10 and 56.15%) and soluble protein (74.60 and 69.72 mg g-1) at harvest. It also increased grain yield of 834 and 875 kg ha-1 with higher exchangeable Ca and Mg with lower Na content during 2021 and 2022 year of experiments.

Study on Early Hydration Mechanism of Double-Liquid Grouting Material Modified by Composite Early Strength Agent.

To achieve an adjustable setting time and significantly improved early strength of a new type of sulphoaluminate cement-based double-liquid grouting material (SACDL), the effects of calcium formate, sodium sulfate, lithium carbonate, and a composite early strength agent on the setting hardening and early hydration behavior of SACDL paste were studied by means of setting time, fluidity, compressive strength, and viscosity tests. The results showed that the adsorption and osmosis of calcium formate, the complex decomposition of sodium sulfate, the precipitation polarization of lithium carbonate and the synergistic action of the composite early strength agent could accelerate the early hydration rate of SACDL, shorten the coagulation time, and improve the early strength of SACDL. The composite effect of 0.8% calcium formate and 0.5% sodium sulfate is the most significant in promoting coagulation and early strength; the initial setting time and final setting time of the slurry were shortened to 5 min and 10 min, respectively; and the 3 h compressive strength was capable of reaching 16.7 MPa, 31% higher than that of the blank group. In addition, X-ray diffraction and SEM morphology observation were used to study the composition of the hydration products and the evolution of the microstructure, which revealed the early hydration mechanism of SACDL under the synergistic effect of the composite early strength agent: (1) The solubility of tricalcium aluminate (C3A) and dihydrate gypsum (CaSO4·2H2O) increased under the low content composite early strength agent condition, which increased the ettringite (AFt) formation rate. HCOO- was able to penetrate the hydration layers of tricalcium silicate (C3S) and dicalcium silicate (C2S), accelerating the dissolution of C3S and C2S and promoting the early hydration of SACDL. (2) Under the condition of a high dosage of the composite early strength agent, the further increase in Ca2+ concentration promoted the crystallization nodules and precipitation of CH and accelerated the formation of calcium silicate hydrate (C-S-H) gel. C-S-H was filled between a large number of rod-like AFt crystals, thus making the structure more dense.

Solubility of anhydrite and gypsum at temperatures below 100°C and the gypsum-anhydrite transition temperature in aqueous solutions: a re-assessment

Anhydrite and gypsum are omnipresent in sedimentary rocks of all types. They occur as massive layers or are distributed within other geological formations as in clays. Understanding the conditions of formation and the stability of the hydrated and anhydrous form of calcium sulfate is crucial in an elucidation of the genesis of the geological formations envisaged as potential host rock for radioactive waste disposal. Estimations of the temperature, where gypsum is dehydrated to anhydrite in water vary between 30°C and 60°C. The extremely slow crystallization kinetics of anhydrite at T < 90°C prevents a direct determination of this transition temperature. In the present work the different approaches to fix this temperature are discussed. It is shown that careful assessment of solubility data and calorimetric measurements yields a transition temperature of 42°C ± 1°C. For results essentially deviating from this value methodic deficiencies are revealed and discussed. Thus, a long-standing discussion about the thermodynamic aspect of the gypsum-anhydrite conversion can be closed, not the kinetic part.

Long-term groundwater geochemical evolution induced by coal mining activities-a case study of floor confined limestone aquifer in Yaoqiao Coal Mine, Jiangsu, China.

Groundwater chemical composition can be changed due to long-term coal mining activities, but it was unclear how it was induced in Taiyuan Formation limestone (TFL) regarding the lack of relevant quantitative studies. The aim of this research is to improve understanding of the chemical composition changes in groundwater of L4 limestone in the coal mining area based on the available hydrochemical and hydrodynamical reports and studies during the period 1978-2020. The systematical analysis of the groundwater composition and field allows to make the hydrogeological characterization with the relatively independent blocks by the factor groups "Planar division & Vertical zonation" and "High water pressure, Poor recharge & Little water inflow," which determines different hydrochemical types and high TDS concentration. The long-term groundwater drainage has caused the eastern and southern limestone aquifer to demonstrate a wide range of depression cones and depletion of groundwater resources, the majority areas were dewatered, and the karstification process changed significantly. An analysis of chemical compositions changes due to extensive permanent drainage of L4 limestone water revealed the decrease in the TDS concentration. The solubility of calcite, dolomite, and gypsum changed, which resulted in the decreasing tendency of Ca2+ + Mg2+ ions. Evaporation and concentration were found to be the main factors determining the L4 limestone water composition, whereas ion exchange was the primary factor for rock-water interaction. These findings are helpful for mine enterprises to take necessary measures for preventing and controlling the groundwater quality degradation from the extensive coalmine drainage.

Facile preparation of α-calcium sulfate hemihydrate whisker from by-product gypsum in chloride-free salt solution system

Lactic acid gypsum (LAG), the by-product from lactic acid preparation, has caused land occupation and environmental pollution. Herein, hemihydrate gypsum (HHG) whisker, an inorganic material with excellent performance, prepared using LAG as the raw material via atmospheric pressure salt solution method was investigated. Nitrate enhanced the salt effect of the solution, which increased the solubility of dihydrate gypsum (DDG), and further accelerated the conversion into HHG. NaNO3 was proved to accelerate the formation of α- HHG whisker, while Mg(NO3)2 promoted its aspect ratio. The whiskers with an average length of 75.9 µm and aspect ratio of 17.8 were achieved under optimum conditions of NaNO3/Mg(NO3)2–0.5:1, mass fraction of LAG–15%, reagent concentration–40%, and the reaction temperature–100 °C. Mg2+ was found to bind with SO42- on the side of the whisker, promoting the growth of the whisker along the c-axis orientation and forming the morphology of high aspect ratios. Hence, it was feasible to achieve the recycling of salt medium by adding medicament containing Mg2+. By employing direct recycling, the salt medium was limited to be effective in two cycles. However, with the addition of the medicament, the salt medium can now be effectively recycled up to four times or more. Such technique realized the high-value utilization of industrial by-product gypsum, guided the HHG whisker preparation via the green and convenient method and reduced the environmental hazards.

Hydration caves and cavities from the recent weathering zone of anhydrites at Dingwall (Nova Scotia, Canada)

Hydration of anhydrite to gypsum (gypsification of anhydrite) in the weathering zone sometimes causes a volume increase. This can lead to local detachments of the surface layer of the weathering anhydrite rocks and creation of the hydration cavities and rare hydration caves (or swelling caves; German: Quellungshöhlen) inside domes formed by the uplifted layer. Currently growing hydration cavities at the anhydrite bottom of the abandoned quarry at Dingwall, Canada, were studied with the use of photogrammetric, statistic, and petrographic methods. Seventy seven cavities were documented including 48 caves (cavities with the height ≥0.30 m large enough to accommodate an adult man). Forty three caves had proper entrances (inlets large enough for an adult to get inside). The cavities contain one flat domed or, less often, tepee-like chamber generally similar in shape to the host hydration landform. The majority of cavities showed the length <4.6 m, the width <3.0 m, and the height <0.85 m. Only 3 caves had the length >8.00 m and the height ≥0.80 m. The largest and the highest cave showed the sizes 10.7 × 6.6 × 1.1 m measured in 2008 which changed into 8.87 × 2.97 × 1.35 m in 2019. The other caves and cavities exhibit also morphological changes with time due to vertical and horizontal movements of rocks slabs and collapse of the roofs depending mainly on the location of expansive gypsification and its intensity. Precipitation (rain- and meltwater) accumulating at the foot of the initial uplift intensifies the hydration in this zone causing a centripetal pressure towards the landform and contributing to its further rising and enlargement of the cavity height. The basic condition required for hydration cave formation is temperature between 0 and 30 °C in which the solubility of gypsum is much lower than that of anhydrite. The meteoric water solution infiltrating in the vadose zone is dissolving the anhydrite and gradually reaches Ca sulphate concentration higher than the level of gypsum and lower than the level of anhydrite solubility. Then, the dissolving anhydrite yields a solution supersaturated with gypsum, capable of its precipitation, and the dissolution of anhydrite is simultaneous with in situ replacive/displacive gypsum crystallization. The crystallization pressure of gypsum is a direct cause of the rock deformations and creation of hydration caves.

Electrical resistivity tomography of a gypsiferous subsurface soil: Geotechnical detection of a geoenvironmental phenomenon

The near-surface soils are generally exposed to environmental changes and can be influenced by water, humidity, temperature, and other factors related to erosion or physical changes. It has been reported that serious distress occurred in the ground surface and below ground for many areas subjected to seasonal weather changes. The gypsum rich material is often linked to the cavity formation, uplift, and cracking of road surfaces due to the high solubility of gypsum in water and acidic media. Electrical resistivity techniques along with the advanced method of identifications (Scanning electron microscope; SEM and X-ray diffraction: XRD) were utilized to detect cavities and gypsum rich subsurface soils. A site where many cavities were formed as a result of dissolving gypsum and anhydrite was considered for this study. Syscal R1 electrical resistivity equipment (IRIS instrument) was used for several cross-sections established within the site. Several electrical resistivity tomography lines were constructed and studied. The SEM (scanning electron microscope) was used to examine and compare forms and fabrics of gypsum and minerals containing sulfates. The chemical analysis (EDAX) using an electron beam was conducted to establish elements present within tested samples. Quantitative chemical tests for some parameters including sulfate ions were carried out. A prediction model based on statistical correlations between sulfate ion content and the electrical resistivity is presented. Electrical resistivity is found to be inversely proportionalto the sulfate content for concentrations of 0 to 5%.

Studies of the kinetics of the reaction of dissolution of gypsum-anhydrite rocks in water of the initial stages

Experimental studies of the kinetics of dissolution of gypsum-anhydrite rocks in water (25 °C; P = 0,1 MPa) made it possible to formulate a process model in the form of a system of equations for the kinetics of dissolution of gypsum and anhydrite (of the first and second order, respectively). The calculated values turned out to be more comparable with the experimental data, taking into account the common-ion effect on the solubility of gypsum and anhydrite, and changes in their values of the specific reaction surface.

Mechanisms shaping the gypsum stromatolite-like structures in the Salar de Llamara (Atacama Desert, Chile)

The explanation of the origin of microbialites and specifically stromatolitic structures is a problem of high relevance for decoding past sedimentary environments and deciphering the biogenicity of the oldest plausible remnants of life. We have investigated the morphogenesis of gypsum stromatolite-like structures currently growing in shallow ponds (puquíos) in the Salar de Llamara (Atacama Desert, Northern Chile). The crystal size, aspect ratio, and orientation distributions of gypsum crystals within the structures have been quantified and show indications for episodic nucleation and competitive growth of millimetric to centimetric selenite crystals into a radial, branched, and loosely cemented aggregate. The morphogenetical process is explained by the existence of a stable vertical salinity gradient in the ponds. Due to the non-linear dependency of gypsum solubility as a function of sodium chloride concentration, the salinity gradient produces undersaturated solutions, which dissolve gypsum crystals. This dissolution happens at a certain depth, narrowing the lower part of the structures, and producing their stromatolite-like morphology. We have tested this novel mechanism experimentally, simulating the effective dissolution of gypsum crystals in stratified ponds, thus providing a purely abiotic mechanism for these stromatolite-like structures.

A simple correlation for predicting gypsum deposition from brine solutions

Calcium sulfate scale occurrence is one of the major problems encountered on heat exchanger surfaces, membrane surfaces of reverse osmosis (RO) plants, and oilfield facilities. Scale prevention and treatment are extensively applied for confronting this problem. A successful scaling prevention and treatment need to be able to identify whether sulfate scale is likely to occur under certain operating conditions. This paper is aimed at assessing the solubility product of calcium sulfate (gypsum) in brine solutions, through which the gypsum scaling tendency can be easily obtained. The simple solubility product prediction correlation, described by a simple equation, is established from experimental sodium sulfate solubilities available in the literature. The predicted gypsum solubilities show excellent agreement with the experimental data for the temperature range of 25 to 80 °C and pressures up to 1,000 bar with NaCl concentration up to 5 M. The method is simple, compact, and reliable and can be applied to any environment where gypsum is expected to precipitate.

Laboratory simulation of gypsum rock dissolution at different pressures, water-flow velocities and pH ranges

Sulfate rocks, particularly gypsum rock as its most common near-surface form in the Earth's crust, are among the evaporitic rocks that due to their solubility can cause serious problems if they are present in the foundations and abutments of reservoir dams. To investigate the solubility of gypsum, gypsum blocks were taken from Gachsaran Formation outcrops located at a reservoir dam construction site in Iran. To perform the rock-dissolution experiments under pressure and water-flow conditions, a pneumatic–hydraulic pressure vessel with internal water circulation was designed and manufactured. Dissolution simulation experiments were performed at a constant temperature (25°C) and for a range of pressures, water-flow velocities and water acidities, the solution-rate constants for the experimental conditions considered. The results confirmed, first, that there are strong direct increasing relationships between pressure and the water-flow velocity with the solution-rate constant, while these relationships with increasing pH are reversed. Secondly, the values obtained from the rock-dissolution experiments under atmospheric conditions cannot be trusted as design parameters for dam foundation or abutments because the solution-rate constant values at the affected depth below reservoir dams can be several times higher than the surface value.

Comment on “Kawahara, H., Yoshida, H., Yamamoto, K., Katsuta, N., Nishimoto, S., Umemura, A., Kuma, R., 2022. Hydrothermal formation of Fe-oxide bands in zebra rocks from northern Western Australia. Chemical Geology 590 (2022), 120699”

This comment questions an hypothesis for formation of the ornamental stone “zebra rock” from Ediacaran red shales of northwestern Australia as hydrothermal alteration zones. The hypothesis is falsified by absence of Eu anomalies in REE arrays, lack of associated carbonate, low degree of chemical weathering, associated soluble gypsum, strata concordance in narrow bands, low thermal stability of magnetization, modest diagenetic alteration, and patterns unlike liesegang banding. Rather than Cambrian hydrothermal veins, zebra rocks were gleyed paleosols with redox banding, from acid sulfate weathering at low temperature during the Ediacaran.

Performance of green binder developed from flue gas desulfurization gypsum incorporating Portland cement and large-volume fly ash

• Developing green binder using FGDG incorporating OPC and large-volume FA. • FGDG-based binder has high strength and good water resistance. • Evolution law and mechanism of pH value during curing of blended binder were analyzed. • Many C S H gels and ettringite were observed on the surface of gypsum crystals by micro tests. Flue gas desulfurization gypsum (FGDG) and fly ash (FA) are by-products from coal-fired power plants that urgently need to be recycled in a sustainable way. This study aims to develop a green binder using FGDG incorporating cement and large-volume FA that can substitute some cement in structural and geotechnical engineering applications. The engineering properties including initial setting time, compressive strength, pH value, water absorption and water resistance of the blended binder with different amounts of FGDG were investigated. The results indicate that the addition of FGDG can decrease the initial setting time and water absorption of the blended paste, and is more helpful for the improvement of the early strength. The maximum compressive strength of the blended paste can be obtained when the dosages of FA and cement are the same. When the amount of cement is more than 20%, the softening coefficient of the blended paste was always greater than 0.6 regardless of the amount of FGDG. In addition, the change of pH value with curing time could be divided into four typical stages, which can be explained by the hydration process of the blended binder. Micro-analysis showed that many C S H gels and ettringite were interwoven on the surface of gypsum crystals, which greatly restrained the solubility of gypsum in water and improved the water resistance of the binder.

Ion-nucleating competition cooperated with antiscalant for effectively mitigating gypsum scaling in membrane distillation

Membrane distillation (MD) that can sustainably recover freshwater until salt crystallization is a potential candidate for hypersaline wastewater treatment. However, a huge challenge for MD is membrane scaling, which sharply decreases membrane flux and salts rejection efficiency. This study reported an ion-nucleating competition cooperated with commercial antiscalants to mitigate membrane scaling. Results showed that the superhydrophobic PVDF (SH-PVDF) membrane could effectively delay the gypsum nucleation on the slippery membrane surface owing to the increased membrane surface roughness, but scaling inevitably occurs on the membrane surface in the supersaturated condition. Introducing the foreign ions such as one-component Na+ or Mg2+ and two-component Na+/Mg2+ mixture can improve the gypsum solubility and delay gypsum nucleation for mitigating membrane scaling. Besides, the synergistic combination of commercial antiscalant and ion-nucleating competition is extraordinarily effective in retarding membrane scaling and preventing membrane pore wetting, achieving a high-water recovery of ~85 % and robust salt rejection of ~100 %. The mechanisms of ion-nucleating competition cooperated with antiscalants were also discussed with the help of characterizations. This work provided a novel ion-nucleating competition in collaboration with antiscalants for hypersaline wastewater management, which is important for MD to be applied in near-zero liquid discharge (ZLD).

Influence of the availability of calcium on the hydration of tricalcium aluminate (C3A) in seawater‐mixed C3A–gypsum system

AbstractThis work examined the effects of seawater (SW) on the hydration of tricalcium aluminate (C3A) in C3A–gypsum and C3A–gypsum–Ca(OH)2 systems through the characterization of hydration heat release, the evolution of aqueous phase composition and hydration products with the hydration time. It was found that SW increased the dissolution driving force of C3A and solubility of gypsum, which accelerated the early hydration of C3A and the formation of ettringite (AFt), leading to a higher hydration degree of C3A at an early age compared with the deionized (DI) water–mixed pastes. After gypsum depletion to form AFt, and in the absence of Ca(OH)2, the formation of chloroaluminate hydrates was slower due to the insufficient Ca resulted in an accumulation of Al in solution. This would delay the subsequent transformation of AFt to monosulfate (SO4–AFm) and the formation of hydrogarnet (C3AH6), which would further reduce the hydration degree of the C3A at the later ages. However, in the presence of Ca(OH)2, the hydration degree of C3A–gypsum–Ca(OH)2 at later ages was increased, which was similar to that of the corresponding DI pastes. This can be inferred that the amount of Ca available in SW‐mixed cement concrete can affect the hydration degree of C3A in cement.

Modeling Solubility of Anhydrite and Gypsum in Aqueous Solutions: Implications for Swelling of Clay-Sulfate Rocks

The swelling of clay-sulfate rocks is a well-known phenomenon often causing threats to the success of various geotechnical projects, including tunneling, road and bridge construction, and geothermal drilling. The origin of clay-sulfate swelling is usually explained by physical swelling due to clay expansion combined with chemical swelling associated with the transformation of anhydrite (CaSO4) into gypsum (CaSO4∙2H2O). The latter occurs through anhydrite dissolution and subsequent gypsum precipitation. Numerical models that simulate rock swelling must consider hydraulic, mechanical, and chemical processes. The simulation of the chemical processes is performed by solving thermodynamic equations, which usually contribute a significant portion of the overall computation time. This paper employs feed-forward neural network (FFNN) and cascade-forward neural network (CFNN) models trained with a Bayesian regularization (BR) algorithm as an alternative approach to determine the solubility of anhydrite and gypsum in the aqueous phase. The network models are developed using calcium sulfate experimental data collected from the literature. Our results indicate that the FFNN-BR is the most accurate model for the regression task. The comparison analysis with the Pitzer ion interaction model as well as previously published data-driven models shows that the FFNN-BR model is highly accurate in determining the solubility of sulfate minerals in acid and salt-containing solutions. We conclude from our results that the FFNN-BR model can be used to determine the solubility of anhydrite and gypsum needed to address typical subsurface engineering problems such as swelling of clay-sulfate rocks.

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

Vibrational sum frequency generation (VSFG) spectroscopy, conductometric titration measurements, and EDX elemental mapping were used to examine surfactant adsorption to the gypsum (010) surface and assess the effects of surfactant adsorption on gypsum solubility in aqueous solutions. Sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium chloride (DTAC) were used as anionic and cationic surfactants, respectively. Gypsum/SDS interactions result in an ordered precipitate layer on the gypsum surface after water evaporation; gypsum/DTAC interaction did not show a similar effect, despite exposure of gypsum to equivalent amounts of surfactant. VSFG spectra showed that SDS molecules adsorb with their chains parallel to the gypsum surface; spectra from gypsum surfaces treated with DTAC, however, showed no measurable response, implying that these surfactants form disorganized aggregates with no polar ordering. Vibrational data were supported by independent EDX measurements that show a uniform distribution of SDS across the gypsum surface. In contrast, element-specific EDX images showed that DTAC clustered in tightly localized patches that left most of the gypsum surface exposed. The uniform adsorption of SDS on the gypsum surface suppresses long-term dissolution up to 40% when compared to samples exposed to DTAC. Gypsum samples in DTAC-containing solutions lose approximately the same amount of material to dissolution as samples immersed in pure water.