Search

Based on environmental characteristics of reinforced concrete infrastructure in western China, cement mortar specimens were subjected to semi-immersed sulfate corrosion in low humidity and varying temperature. The influences of low humidity and varying temperature on semi-immersion sulfate attack cement-based materials were studied by combination of XRD, SEM, LF-NMR, and conductivity titration of sulfate ions. The results show that under low humidity and varying temperature, the mortar subjected to semi-immersion sulfate attack has a water film zone within 30 mm above the surface of sulfate solution, and the corrosion degree is relatively low. The evaporation zone above the solution surface of 30 ~ 60 mm has a higher degree of corrosion and obvious peeling phenomenon. Corrosion of evaporation zone of mortar semi-immersed in Na2SO4 solution is more seriously than that semi-immersed in MgSO4 solution due to their difference in saturation under different temperatures. The expansive salt crystallization within pores above 1 000 nm is prone to the occurrence in evaporation zone, which leads to the micro cracks inside mortar and an increase in the proportion of harmful pores, resulting in physical expansion damage being the main cause of this zone. Chemical corrosion in the immersion zone of mortar is dominant due to the formation of swelling corrosion products such as gypsum and ettringite. As corrosion products accumulated in the pores with pore sizes of 50 ~ 1 000 nm, the surface of mortar cracks and the proportion of macroscopic pores with pore sizes above 1 000 nm increases. The addition of ground granulated blast furnace slag in cement increases the sulfate corrosion resistance of the immersion zone of mortar via its secondary hydration effect, and the addition of limestone powder decreases the sulfate corrosion resistance of mortar due to its dilution effect. [ABSTRACT FROM AUTHOR]

The diffusion of chloride ions in reinforced concrete under the seawater environment will affect the physical or mechanical properties and durability. Sulfate ions also influence the diffusion of chloride ions by generating expansion products through physical and chemical reactions. Further research on the effects of chloride binding and sulfate ion attack on chloride ion diffusion will deepen the understanding of concrete failure mechanism. In this paper, a quaternary blend based on calcium sulfoaluminate (CSA) cement was prepared and laboratory immersion tests were conducted in artificial seawater with varying salt concentrations. Initially, chloride ion concentration measurements and XRD tests were conducted at different corrosion ages and salt concentrations. Subsequently, the chloride binding properties of CSA-based materials was quantified through the analysis of chloride ion concentration and the phases of hydration products. Meanwhile, the corrosive effect of sulfate ions on chloride ion diffusion was determined corresponds to the content of expansive hydration products. Furthermore, numerical simulations were employed to evaluate the impact of sulfate ion corrosion, chloride binding, and their combined effects on chloride ion diffusion, and the results were compared with free chloride ion concentration (Cf). The results indicate that the total chloride ion concentration (Ct) exhibits a linear relationship with increasing salt concentrations of seawater in CSA-based materials. Meanwhile, the bound chloride ion concentration (Cb) follows a logarithmic growth pattern. The chloride binding rate experiences a linear decline with the increase of chloride ion concentration in the artificial seawater. Additionally, the relationship between Cf and Cb or Ct can be described using different isothermal adsorption models for the CSA-based materials. Among these models, the Langmuir model is suitable for characterizing the relationship between Cf and Cb, while the Freundlich model is suitable for describing the relationship between Cf and Ct. Furthermore, it is noteworthy that sulfate ion attack and chloride binding exert nearly equivalent effects on the diffusion of chloride ions in CSA-based materials at short corrosion age and low chloride ion concentration. However, the corrosive impact of sulfate ions gradually evolves into the dominant factor in the progression of corrosion over time and the increase in seawater salt concentration.

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Fiber Inspection is the property of China Fiber Inspection and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to find a general corrosive treatment scheme suitable for underground structures in Foshan area, based on the geotechnical investigation of the Phase I project of Foshan Metro Line 4, this study adopted the method of literature research and comparative analysis of specifications to conduct in-depth analysis of the corrosion resistance requirements in different specifications. Furthermore, the existing problems in the GB/T 50476-2019 Durability Design Standard for Concrete Structures were discussed, and combined with the actual situation of the existing Foshan Metro Line 3 and Guangzhou Metro Line 7 West Extension to Shunde section, a set of groundwater corrosion prevention and control design standards suitable for subway structures in Foshan area were carried out. The application results in the early construction site of Foshan Metro Line 4 show that when executed according to the above design standards, the relevant performance indicators meet the regulatory requirements. [ABSTRACT FROM AUTHOR]

Corrosion of steel strand embedded in deficient grout has been associated with elevated concentrations of sulfate ions stemming from grout segregation and the adverse influences of excess mix water and grout prehydration. There have been discussions about appropriate ways to assess sulfate ion levels in the grout pore water. Various test methodologies can include varying material conditioning procedures, including heating, drying, and chemical reactions that can influence the level of sulfate ion aggregation in the test leachate from the initial bleed water from the bulk material. In this study, the sulfate content was measured by leaching and alternative methods such as XRF and bleed water testing. Six leaching methods were employed to assess the effect of leaching heating, heating time, leaching volume, grout sample mass, and drying temperature. Leaching of larger grout sample mass can yield higher leachate sulfate concentrations, but the concentrations were not commensurate with the larger grout mass. Leaching of a larger grout sample mass with a mass-to-water ratio of 1:10 was not shown to be efficient in the dissolution of sulfate ions. Larger mass-to-water ratio (1:40) yielded higher sulfate concentrations in the leachate and normalized grout mass. Pre-drying of grout samples to 100 °C for 24 h was shown to incur losses in sulfate content. Recommendations of test methods to assess the sulfate ion content from segregated and hardened grout were made.

External sulfate attack is a remarkable and complex phenomenon of degradation of cement matrixes. This paper proposes a method to calculate sulfate diffusion coefficients based on ion migration testing, in order to establish parameters for concrete service life prediction models based on a fast test. The influence of the type (sodium and magnesium) and concentration (5% and 10% SO42−) of the sulfate solution for a concrete matrix was evaluated in the tests. Sulfate concentrations were monitored by measuring the electrical conductivity of the anode compartment. The results were validated by comparing them with those obtained in natural diffusion tests. Similar sulfate profiles were obtained for concrete samples after 1 month of migration and after 3 and 6 months of diffusion, mainly for magnesium sulfate. The greatest correlations between the calculated diffusion coefficients were achieved at higher concentrations of SO42− in the cathode compartment. The results indicated that the proposed migration method enables the calculation of the sulfate diffusion coefficients in concrete. [ABSTRACT FROM AUTHOR]

In this paper, quaternary hydrotalcite [layered double hydroxide (LDH)] (CoFeMgAl-LDH) was first fabricated based on the coprecipitation method, and then, CoFeMgAl-LDH/carbon nanotubes (CNTs) composite was synthesized by CNTs and CoFeMgAl-LDH through the solid phase mixing method. Subsequently, the physical-chemical properties of CoFeMgAl-LDH/CNT composite were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, energy dispersive spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) analysis. Meanwhile, the performance of CoFeMgAl-LDH/CNT composite for SO42− adsorption was evaluated under different conditions, including different initial concentration, contact time, adsorbent dosage, solution pH, temperature, and coexisting ions. Afterward, the SO42− adsorption capacity of CoFeMgAl-LDH/CNT in cement paste was further studied. The results showed that the CoFeMgAl-LDH/CNT composite exhibited a three-dimensional structure with high specific surface area. The maximum SO42− adsorption amount of the CoFeMgAl-LDH/CNT composite was 116.27 mg/g , which was significantly higher compared with other absorbents of the same type. Pseudosecond-order kinetic model could reasonably describe the adsorption kinetics, and Freundlich isotherm could fit the adsorption data accurately. The results also suggest that the synthesized CoFeMgAl-LDH/CNT composite can serve as a potential material for the sulfate binding in cementitious materials. [ABSTRACT FROM AUTHOR]

The diffusion of Sulfate ions in concrete is a complex process and affects the performance of concrete. Experiments on the time-dependent distribution of sulfate ions in concrete under the coupling of pressure load, dry-wet circulation, and sulfate attack, and the diffusion coefficient of sulfate ions with various parameters was tested. The applicability of the cellular automata (CA) theory to simulate the diffusion of sulfate ions was discussed. In this paper, a multiparameter cellular automata (MPCA) model was developed to simulate the impacts of load, immersion ways, and sulfate solution concentration for the diffusion of sulfate ions in concrete. The MPCA model was compared with experimental data, considering compressive stress, sulfate solution concentration, and other parameters. The numerical simulations verify the calculation results based on the MPCA model are in good agreement with the test data. Finally, the applicability of the established MPCA model was also discussed.

One of the major operators' concerns in the injected water into oil reservoirs is the water source itself because sulfate scale formation occurs during waterflooding due to the incompatibility of injected and produced waters. In this work, multiwalled carbon nanotubes (MWCNTs) were prepared by chemical vapor deposition of condensate-gas at 1000 °C and oxidized with an acid mixture at 115 °C for 2 h and then applied as adsorbent for sulfate-removal. Variables Effects such as temperature, adsorbent dose, time and stirring speed, and their interactions during the adsorption were determined and optimized by response surface methodology (RSM) via central composite factorial design (CCF). The experimental data were examined by variance analysis (ANOVA) and fitted to a second-order polynomial equation. The optimum conditions were initial concentration = 800 mg/L, adsorbent dose = 0.14447 g, pH = 7, and temperature = 74.21 °C, 530 rpm during 240 min, and maximum sulfate-removal of 96% was achieved. Isotherm models were investigated to describe the sulfate-adsorption data and a higher suitable to the Langmuir isotherm was found. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The thermodynamic parameters indicated that adsorption was spontaneous and endothermic. Overall, MWCNTs are promising adsorbents for water treatment and have great potential application in oilfields to reduce scale ion content from the source. [ABSTRACT FROM AUTHOR]

This study aims to clarify how a solution's pH can influence the corrosion and formation of surface films on the AZ31 Mg alloy in aqueous solutions containing sulfate ions. The corrosion and surface film formation behaviors were examined using in situ observation, open-circuit potential (OCP) transient, weight change measurement and electrochemical impedance spectroscopy (EIS). The morphologies of the surface films were analyzed via metal/insulator/metal (MIM) coloring and FESEM. The findings show that at pH 2, severe corrosion occurred together with rapid hydrogen evolution and formation of a highly porous surface film with numerous cracks. However, at pH 3, the corrosion rate dropped significantly and remarkably low corrosion rates were observed at pH 4 and 10. At pH 11 and 12, weight gains were noticed, suggesting the growth of surface films on the AZ31 Mg alloy. Flake-like films formed at pH 12, while needle-like structures were present between pH 3 and 11. Impedance measurements revealed increased impedance at higher pH of sulfate-ion-containing solutions. Higher impedance was related to the formation of denser surface films on the AZ31 Mg alloy. In addition, the films displayed metal/insulator/metal (MIM) colors via Au coating above pH 4, indicating uniform film thickness despite the presence of needle-like or flake-like structures. [ABSTRACT FROM AUTHOR]

Organomodified bentonites were obtained by modification of bentonite clay from local mine Bogovina, with four different alkylammonium ions in the amounts that correspond to cation exchange capacity. Carbonized bentonites, obtained by pyrolyzing the organomodified bentonites in the flow of nitrogen, were characterized using XRD, low-temperature N2 physisorption and Raman spectroscopy. Structural and textural properties of carbonized bentonites depended on the arrangement of alkylammonium cations in the paternal organomodified bentonite, while the Raman spectroscopy confirmed the presence of amorphous carbon. The obtained carbonized bentonites were used for modification of the carbon paste electrode. The modified electrodes were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The electrosorption of chloride and sulfate anions on carbonized bentonites was studied by chronocoulometry. The results were interpreted in the terms of surface groups and textural properties of the carbonized bentonites.

Polymers play an important role in hybrid enhanced oil recovery (EOR), which involves both a polymer and low-salinity water. Because the polymer commonly used for low-salinity polymer flooding (LSPF) is strongly sensitive to brine pH, its efficiency can deteriorate in carbonate reservoirs containing highly acidic formation water. In this study, polymer efficiency in an acidic carbonate reservoir was investigated experimentally for different salinity levels and SO42- concentrations. Results indicated that lowering salinity improved polymer stability, resulting in less polymer adsorption, greater wettability alteration, and ultimately, higher oil recovery. However, low salinity may not be desirable for LSPF if the injected fluid does not contain a sufficient number of sulfate (SO42-) ions. Analysis of polymer efficiency showed that more oil can be produced with the same polymer concentration by adjusting the SO42- content. Therefore, when river water, which is relatively easily available in onshore fields, is designed to be injected into an acidic carbonate reservoir, the LSPF method proposed in this study can be a reliable and environmentally friendly method with addition of a sufficient number of SO4 2-ions to river water. [ABSTRACT FROM AUTHOR]

During the last decades, graphene oxide (GO)-based materials have been extensively studied as low-cost efficient solid electrolytes for fuel-cell application. However, the observed limited proton conductivity of GO in the out-of-plane directions and associated lower fuel-cell performance largely limit their practical application. Herein, we have demonstrated a sulfate ion-intercalated three-dimensional graphene oxide (3DSGO) showing an exceptionally high out-of-plane proton conductivity of 0.74 S cm–1 at room temperature and 90% RH, and an in-plane proton conductivity of 3.19 S cm–1. Additionally, measurement of cell performance using the prepared membrane as the electrolyte of the proton exchange membrane fuel cell (PEMFC) showed an optimum power density of 112.65 mW cm–2 at 100% RH and 30 °C, which is more than double that achieved for 3DGO (50 mW cm–2). This efficient proton conduction ability and PEMFC performance of the 3DSGO is linked with the 3D interconnected ionic highways and substantial interlayer void space, which provide the higher water retention capacity in the 3D spongy architecture and a facile proton conduction pathway. [ABSTRACT FROM AUTHOR]

SO42−-containing compounds are widely present in wastewater generated from various industries and mining industries, such as slag leachate, pulp and paper wastewater, modified starch wastewater, etc. When the concentration of SO42− is too high, it will not only be corrosive to metal equipment but also accumulate in the environmental media. Based on this, a novel cationic hydrogel HNM was synthesized in this study by introducing morpholine groups into the conventional hydrogel HEMA–NVP system for the adsorption of SO42− in aqueous solutions. Characterizations by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated that morpholine groups had been introduced into the as-synthesizedhydrogels. The scanning electron microscope (SEM) characterization results show that the introduction of morpholine groups changed the surface of the hydrogel from micron-scale wrinkles to nanoscale gaps, increasing the contact area with the solution. The results of static water contact angle (WCA), equilibrium water content (EWC), and SO42− adsorption capacity show that the introduction of morpholine groups not only further improved the equilibrium water content and hydrophilicity of the hydrogel but also greatly improved the SO42− adsorption capacity of the hydrogel, with the maximum SO42− adsorption amount of 21.59 mg/g, which was much higher than that of the hydrogel without morpholine groups of 5.15 mg/g. Further studies found that the adsorption of SO42− on the hydrogel HNM was pH-dependent, and acidic conditions were favorable for the adsorption. Therefore, the introduction of morpholine groups greatly enhanced the ability of conventional HEMA–NVP hydrogels to remove SO42− from aqueous solutions. [ABSTRACT FROM AUTHOR]

Cement-sodium silicate (C-S) grout is extensively employed as a grouting material in shield tunnel synchronous grouting projects. However, in water-rich areas, its hardened grout bodies are vulnerable to erosion damage caused by various ions. In order to elucidate the degradation mechanism of C-S hardened grout bodies' strength under salt ion erosion. This study analyzed the influence of SO 4 2- ions, Cl- ions, and SO 4 2- and Cl- mixed ions at different concentrations on the compressive strength of C-S hardened grout bodies through laboratory experiments. Moreover, microscopic techniques (XRD, SEM-EDS) were employed to illustrate the phase characteristics and microstructure of ion-eroded C-S hardened grout bodies, and the distribution of surface calcium elements. Molecular dynamics (MD) simulation investigated the adsorption, diffusion degree, and energy change of erosive ions in C-S-H gel. The results show that the higher the concentration of erosion ions, the faster the erosion rate. A nonlinear spatiotemporal strength degradation prediction model was developed, assessing the deterioration degree of hardened grout bodies due to ions: SO 4 2- > SO 4 2-and Cl- mixture > Cl- > water. Additionally, microscopic observations reveal a tight correlation between the degradation level of C-S hardened grout bodies and the loss of Ca2+ ions inside. The more significant the loss of Ca2+ ions from hydration products, the more evident the strength degradation of C-S hardened grout bodies. MD simulations demonstrate that SO 4 2- ions and Cl- ions occupy adsorption sites like SiOCa+ and SiOH, altering interatomic Coulomb forces and intermolecular van der Waals forces, changing system energy, thereby influencing the structure of C-S-H gel, leading to strength degradation in C-S hardened grout bodies. • Developing a predictive model for strength degradation of C-S grout hardened bodies. • Salt ion type and concentration effect the degree of deterioration of C-S stones. • Evaluated the erosion mechanism using molecular dynamics simulation methods. • Adsorption sites, electrostatic potential, and diffusion coefficients are discussed. • Derived energy dynamic balance from the total kinetic energy and temperature changes. [ABSTRACT FROM AUTHOR]

Massive quantities of marine sedimentary rock are excavated from urban coastal areas. The excavated rock often releases arsenic with concurrent oxidation of framboidal pyrite, but the arsenic release is naturally suppressed with subsequent atmospheric exposure. The present study evaluated the re-release of arsenic from excavated rock in which arsenic release has been naturally suppressed by the atmospheric exposure in the presence of sulfate ions under various redox conditions using the biological reduction method. The atmospheric exposure and subsequent batch leaching test revealed that the amount of arsenic release that was naturally suppressed corresponded to 1.2% of the total arsenic content. The sequential extraction analysis also showed that the arsenic in the exposed rock was altered to insoluble phases. We observed a re-release of 6.0–18.2% of the total arsenic content under reductive conditions (< + 70 mV of Eh), exceeding the amount of arsenic that was naturally suppressed, even in the presence of sulfate ions. The correlation in the amount of arsenic and iron re-released demonstrates that arsenic re-release under reductive conditions is mainly regulated by the iron dissolution up to 10 mg kg−1 even in the presence of sulfate ion. Further reduction and dissolution of iron did not cause further increase in the arsenic re-release. Therefore, excavated marine sedimentary rock should be reused under redox conditions in which iron is not reduced. Otherwise, treatments such as chemical immobilization should be performed. [ABSTRACT FROM AUTHOR]

The Raman spectra of H2O/D2O−Na2SO4 solutions are measured at temperatures (T) up to 573 K. The hydrating structure of SO42− is investigated based on the solute‐correlated (SC) OD/OH stretch bands obtained by the multivariate curve resolution method. Remaining a nearly constant wavenumber of the main peak with increasing temperature, the SC OD/OH bands are narrowed first due to the reduced relative intensity of the shoulder at 2395/~3245 cm−1 when T < ~473 K/~513 K but then because the OD/OH bands get sunken around 2610/3580 cm−1 above ~473/~513 K (letting the ~2660/~3635 cm−1 mode be more prominent and even a separate peak). These spectral features incline to support a temperature‐dependent water structure in the SO42− hydration shell balanced by the SO42−···H2O(D2O) and O–H(D)···O hydrogen bonds (those with D are stronger) as well as the electrostatics. Most hydrating water molecules are engaged in hydrogen bonding configurations of single donor (SD) and single hydrogen‐bond water (SHW). As temperature rises, the average number of hydrogen bonds per hydrating water molecule decreases below ~373 K because of the SD → SHW transition and increases afterward owning to the rapid increase of the ion pairs, and SO42− changes its role from structure breaker to structure maker above ~453 K. The temperature‐dependent solubility behavior of Na2SO4 in H2O can be rationalized by the ion pairing effect and temperature‐dependent structure details in SO42− hydration shell. [ABSTRACT FROM AUTHOR]

Immobilization of erosion ions in seawater by Fe-Al bimetallic hydroxide was systematically analyzed. Firstly, Fe-Al bimetallic hydroxide was synthesized in the simulated solution of marine concrete crack area, and immobilization of chloride ion and sulfate ion was studied. The treatment effects of chloride ion and sulfate ion were obviously different, indicating that it had selectivity for ion immobilization. Secondly, immobilization of hydroxyl ion by bimetallic hydroxide was also demonstrated according to the high alkali environment in marine concrete crack area. The pH value of simulated solution decreased significantly, and the more solid products, the greater the decrease. Finally, microstructure and composition of Fe-Al bimetallic hydroxide was studied by SEM and EDS. The crystal presented spherical and spherical accumulation, which provided a natural place for immobilization of erosion ions. In addition to Fe, Al C, O, Na and Mg, chlorine and sulfur were found in Fe-Al bimetallic hydroxides. The simulated solution treated by Fe-Al bimetallic hydroxides was studied by FTIR. Erosion ions entered the interlayer structure of Fe-Al bimetallic hydroxide through ion exchange, while lactate ions were replaced into simulated solution. The results provided a new idea for improving the repair effect of concrete crack based on microbial mineralization. [ABSTRACT FROM AUTHOR]

This study aims to clarify how a solution’s pH can influence the corrosion and formation of surface films on the AZ31 Mg alloy in aqueous solutions containing sulfate ions. The corrosion and surface film formation behaviors were examined using in situ observation, open-circuit potential (OCP) transient, weight change measurement and electrochemical impedance spectroscopy (EIS). The morphologies of the surface films were analyzed via metal/insulator/metal (MIM) coloring and FESEM. The findings show that at pH 2, severe corrosion occurred together with rapid hydrogen evolution and formation of a highly porous surface film with numerous cracks. However, at pH 3, the corrosion rate dropped significantly and remarkably low corrosion rates were observed at pH 4 and 10. At pH 11 and 12, weight gains were noticed, suggesting the growth of surface films on the AZ31 Mg alloy. Flake-like films formed at pH 12, while needle-like structures were present between pH 3 and 11. Impedance measurements revealed increased impedance at higher pH of sulfate-ion-containing solutions. Higher impedance was related to the formation of denser surface films on the AZ31 Mg alloy. In addition, the films displayed metal/insulator/metal (MIM) colors via Au coating above pH 4, indicating uniform film thickness despite the presence of needle-like or flake-like structures.

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The procedure is proposed for X-ray fluorescence determination of sulfate ion in aqueous solutions with preliminary concentrating by the dried-drop technique using a portable energy dispersive spectrometer NITON FXL 959 GOLDD+. The procedure was tested for a wide range of sulfate ion concentrations (10–4200 mg/L) in the course of analyses of groundwater samples from the Over-Jurassic aquifer complex of Moscow region, as well as of the waters draining the sulfide porphyry–copper mineralization of the Nakhodka ore field in Western Chukotka. The procedure was verified by the data of water analyses using ion chromatography and titration techniques. [ABSTRACT FROM AUTHOR]

The contamination of groundwater by uranium, nitrate, ammonium, and sulfate near uranium sludge storage sites due to the degradation of engineering safety barriers is an urgent problem during their long-term operation. The purification of such multicomponent contaminants is a complex task and one of the promising methods for this purpose is in situ bioremediation using the metabolic potential of aborigenic microflora. The work focused on the geochemical, geological, and microbiological parameters of groundwater with multi-component contamination near the uranium sludge storage sites of four chemical plants. In conditions of extreme nitrate contamination (up to 15 g/L), denitrifying bacteria were found to be the dominant group of microorganisms. In conditions of nitrate–ammonium contamination, bacteria responsible for the Anammox process were found. In laboratory, optimal conditions were selected to stimulate microflora to promote nitrate removal. For this purpose, sources of carbon (acetate, whey) were added to the water samples in concentrations necessary for the complete removal of nitrate by microbial denitrification. The experiment was carried out at ambient temperature in hermetically sealed vials. Uranyl nitrate was added to the samples at a concentration of 5 mg/L for uranium. It was found that nitrate removal contributes to the cycle of anaerobic processes of authigenic sedimentation because of sulfate and iron reduction processes, which provide the formation of a mineral geochemical barrier for uranium immobilization. As a result of the experiment, after 3–6 months, depending on the concentration of nitrate in the groundwater sample, the uranium content in the liquid phase decreased by 92–98%.

Saline soil is widely distributed in the marine sediments along the coast of the world and the arid-semi-arid areas of the Middle East and Iraq, and calcium sulfate erosion has become one of the important factors affecting the durability of concrete in this area. In order to clarify the mechanism of sulfate ion damage to concrete, this paper mainly takes saline soil with high sulfate content in coastal area as well as arid-semi-arid area as the research object, and uses indoor geotechnical test, field test and numerical simulation to study the influence of different dry-wet cycle times on the unconfined compressive strength of concrete test blocks, and puts forward the relationship between the erosion arrival depth and time of sulfate ion in concrete, so as to predict the long-term erosion depth by using the erosion depth of sulfate ion in concrete in short time. The results show that the shorter the erosion time when the erosion reaches a certain depth, and the larger the erosion reaches when the erosion time is the same, the faster the erosion reaches the depth with the increase of erosion time. Compared with rectangular section concrete, circular section concrete penetrates faster. The results of this study can provide a reference for the durability design of concrete in saline soil sites containing sulfate. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The usage of microorganisms to clean the environment from xenobiotics, in particular chlorine-containing ones, is a promising method of detoxifying the contaminated environment. Sulfate-reducing bacteria Desulfovibrio desulfuricans Ya-11, isolated from Yavoriv Lake, and Desulfotomaculum AR1, isolated from the Lviv sewage treatment system, are able to grow under conditions of environmental contamination by aromatic compounds and chlorine-containing substances. Due to their high redox potential, chlorate and perchlorate ions can be ideal electron acceptors for the metabolism of microorganisms. To test the growth of the tested microorganisms under the influence of perchlorate ions, bacteria were cultured in modified Postgate C medium with ClO4–. Biomass was determined turbidimetrically, the content of sulfate ions and hydrogen sulfide – photoelectrocolorimetrically, the content of perchlorate ions – permanganatometrically. The study of the ability of sulfate-reducing bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 to grow in a medium with perchlorate ions as electron acceptors showed the inhibitory effect of ClO4– on sulfate ion reduction by bacteria. Bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 are able to grow in environments with aromatic hydrocarbons, in particular toluene. The possibility of the growth of sulfate-reducing bacteria in the presence of toluene as an electron donor and perchlorate ions as an electron acceptor was investigated. The efficiency of perchlorate ion utilization by sulfate-reducing bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 was about 90 %. The effect of molybdenum on the reduction of perchlorate ions by Desulfotomaculum AR1 is shown in the paper. Immobilization of bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 was carried out in 3% agar and on wood chips. The ability of bacteria, immobilized on these media, to purify the aqueous medium from perchlorate ions was investigated. Reduction of perchlorate ions is more efficiently performed by cells of Desulfotomaculum AR1 and D. desulfuricans Ya-11 bacteria immobilized in agar than on wood chips. Sulfate-reducing bacteria Desulfotomaculum AR1 and D. desulfuricans Ya-11 are able to use perchlorate ions as electron acceptors, purifying the polluted aquatic environment from these pollutants.

SO42−-containing compounds are widely present in wastewater generated from various industries and mining industries, such as slag leachate, pulp and paper wastewater, modified starch wastewater, etc. When the concentration of SO42− is too high, it will not only be corrosive to metal equipment but also accumulate in the environmental media. Based on this, a novel cationic hydrogel HNM was synthesized in this study by introducing morpholine groups into the conventional hydrogel HEMA–NVP system for the adsorption of SO42− in aqueous solutions. Characterizations by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated that morpholine groups had been introduced into the as-synthesizedhydrogels. The scanning electron microscope (SEM) characterization results show that the introduction of morpholine groups changed the surface of the hydrogel from micron-scale wrinkles to nanoscale gaps, increasing the contact area with the solution. The results of static water contact angle (WCA), equilibrium water content (EWC), and SO42− adsorption capacity show that the introduction of morpholine groups not only further improved the equilibrium water content and hydrophilicity of the hydrogel but also greatly improved the SO42− adsorption capacity of the hydrogel, with the maximum SO42− adsorption amount of 21.59 mg/g, which was much higher than that of the hydrogel without morpholine groups of 5.15 mg/g. Further studies found that the adsorption of SO42− on the hydrogel HNM was pH-dependent, and acidic conditions were favorable for the adsorption. Therefore, the introduction of morpholine groups greatly enhanced the ability of conventional HEMA–NVP hydrogels to remove SO42− from aqueous solutions.

In this paper, the adsorption potential of activated carbon prepared by Ziziphus spina-christi lotus leaf for the removal of sulfate from aqueous solution was investigated. To this end, the effect of different parameters such as pH, contact time, temperature, adsorbent concentration, and initial sulfate ion concentration was investigated. The results indicated that the highest adsorption efficiency (84.5%) was obtained at pH 6, adsorbent concentration of 5 g/L, sulfate ion concentration of 20 ppm, 65 min and temperature of 45 °C. Also, the adsorption equilibrium study showed that the adsorption process follows the Langmuir isotherm model with the maximum adsorption capacity of 9.3 mg/g. In addition, the thermodynamic study showed that the adsorption process on the activated carbon surface was spontaneous. Moreover, the adsorption process was exothermic accompanied by a decrease in irregularity. Furthermore, the adsorption kinetic study indicated that the adsorption process follows the pseudo-second-order kinetic model.

Water pollution derived from organic pollutants is one of the global environmental problems. The Fenton reaction using Fe2+ as a homogeneous catalyst has been known as one of clean methods for oxidative degradation of organic pollutants. Here, a layered double hydroxide (Fe2+Al3+‐LDH) containing Fe2+ and Al3+ in the structure was used to develop a "heterogeneous" Fenton catalyst capable of mineralizing organic pollutants. We found that sulfate ion (SO42−) immobilized on the Fe2+Al3+‐LDH significantly facilitated oxidative degradation (mineralization) of phenol as a model compound of water pollutants to carbon dioxide (CO2) in a heterogeneous Fenton process. The phenol conversion and mineralization efficiency to CO2 reached >99% and ca. 50%, respectively, even with a reaction time of only 60 min. [ABSTRACT FROM AUTHOR]

Rivers serve as one of the main sources of water supply. Human activities, salts in the soil and rocks and urban runoffs, as well as air contaminants, lead to contamination of river water. In this research, Gamasiab river, which is the upstream of Karkheh river, was selected as a case study. Sixteen stations were selected along this river to determine the sulfate content of water samples. Samples were taken from these stations according to the guidelines (ISO 5667-5, 1991). The samples were then transferred to laboratory and were filtered using nanoparticles of natural clinoptilolite. The X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) andFourier-Transform Infrared Spectroscopy (FTIR) images were taken to determine the properties of the adsorbents. The images indicated that the selected methods for preparation of the nanoparticles were correctly implemented. After examining the filtered samples, the adsorption efficiency was 95% for clinoptilolite. Whatman filter paper 42 was used for desorption of the natural nano-clinoptilolite. Adsorption isotherm of the natural clinoptilolite was Freundlich with a determination coefficient of R2=0.918. By using Design Expert software and assumption of two pH factors and adsorbent to contaminant ratios (D/C), optimum adsorption points were found and theoretical adsorption values were calculated as well. Results showed that the optimum adsorption points for clinoptilolite were pH = 9.51 (mg)adsorbent/(mg/l)initial and D/C=18.91(mg)adsorbent/(mg/l) initial. Comparison of the adsorbent function indicated that clinoptilolite had good performance in removal of sulfate ion from river water samples.

Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, effect of calcium and gypsum on scheelite and fluorite was investigated using sodium oleate as collector. Micro-flotation and contact angle results showed that the adsorption of calcium could inhibit the hydrophobicity of scheelite and fluorite. Moreover, sulfate could enhance the inhibition. FT-IR results showed that calcium could be priori precipitated into calcium oleate and adsorb on mineral surface. The adsorption of calcium could increase the scheelite potential to IEP, while it showed limited effect on fluorite potential. However, the interaction of calcium on scheelite and fluorite in gypsum solution was more complex than that in calcium solution. [ABSTRACT FROM AUTHOR]

In Cypridina (Vargula) hilgendorfii, Cypridina luciferin is converted from Cypridina luciferyl sulfate by a sulfotransferase with adenosine 3′, 5′-diphosphate (PAP), and is used for the luminescence reaction of Cypridina luciferase. We found that the luminescence activity of crude extracts of C. hilgendorfii was significantly stimulated by the addition of acetic acid. This stimulation may be explained by an efficient supply of PAP from 3′-phosphoadenosine 5′-phosphosulfate (PAPS) catalyzed by a sulfotransferase. Thus, acetic acid acts as a sulfate acceptor from PAPS, followed by forming acetyl sulfate and PAP. The structure of acetyl sulfate was identified using mass spectrometry and it spontaneously decomposed to acetic acid and free sulfate ion in aqueous solutions. This enzymatic conversion from Cypridina luciferyl sulfate to Cypridina luciferin could be coupled with acetic acid and PAPS by a sulfotransferase. Image 1 • Cypridina luciferyl sulfate is converted to Cypridina luciferin by a sulfotransferase. • Acetic acid stimulates luminescence activity in crude extracts of Cypridina specimens. • Acetic acid is sulfated with PAPS to produce acetyl sulfate in crude extracts. • Production of acetyl sulfate and PAP stimulates Cypridina luciferin formation. • Unstable acetyl sulfate is decomposed to acetic acid and SO 4 2− in aqueous solutions. [ABSTRACT FROM AUTHOR]

The paper presents the formation of the chemical composition of water in the sulfate mineral lakes of western Transbaikalia. It is shown that sodium sulfate water in the regional lakes forms in two zones of continental salinization, the Barguzin and Gusinoe Ozero-Orongoi depressions. The average mineralization of the lakes reaches 30.8 g/L, pH = 7.90-8.84, the fractional content of sulfate ion is 55.2-81.8% eq, and the fractional content of sodium ion is 59.1-82.1% eq. The paper presents the major-ion and trace-element composition of lake waters and the chemical and mineral composition of bottom sediments. It is shown that groundwater enriched in sodium sulfate plays a major role in the lake formation. [ABSTRACT FROM AUTHOR]

Hot spring discharge was linked to the 2011 Mw 6.6 Iwaki earthquake. Periodic surveys revealed that the discharge continued for more than 7 years, which is a rare and valuable long-term record of hot spring discharge triggered by an earthquake in a non-volcanic area. In terms of coseismic changes, based on a comparison of the spatial distribution of changes in the coseismic water head and calculated crustal volumetric strain using a fault model, hot spring water discharge was found to be caused by a change in the coseismic crustal volumetric strain. As for the postseismic changes, observations over 7 years revealed a gradual rise in the temperature and chloride ion concentration of the hot spring water. Such long-term hot spring discharge may be explained by the following two causes: the rise of thermal water from the deep part and the permeability changes along the hot spring channels. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Three different kinds of sepiolite (Type A, Type B and Sepiolite fiber) were processed by calcination and analyzed by thermogravimetric analysis (TG), X-ray diffraction diffractometer (XRD), scanning electron microscopy (SEM), BET (specific surface area from N2 adsorption isotherms), mercury intrusion porosimetry (MIP), and infrared spectroscopic analysis (IR), respectively. The results show that the adsorption performance of sepiolite can be changed by calcination and environment temperatures, especially for calcination. The adsorption capacity of sepiolite fiber is bigger than that of Type A and B, and adsorption capacity of each sepiolite to sulfate is smaller than that of the chloride ions. Especially, the maximum value for adsorption of the sepiolite fibers, calcined at 600 ℃ and water bath at 60 ℃, to chlorine ion and sulfate are 5.95 and 5.71 mg/g, respectively (mg/g: the ions quantity adsorbed by a unit of sepiolite weight). The minimum adsorption of calcined sepiolite fiber to sulfate ions increased from 5.02 to 5.55 mg/g. While microstructure analysis of sepiolite by TG indicated that its structure was, for temperature not exceeding 700 ℃, was not changed significantly. Sepiolite has a porous structure, especially for sepiolite fiber, which can be observed by SEM. BET indicates that sepiolite fiber has a larger pore volume than others and this can be increased by calcination. IR shows that the adsorption of sepiolite to Cl- and SO4 2- belongs to physical absorption, instead of chemisorption. [ABSTRACT FROM AUTHOR]

Three landfills are located in the eastern part of the Chengdu City, and two traffic tunnels pass beneath the south portion of landfill-1. The landfills have a simple leachate collection system without any bottom liner and impermeable wall, which causes a severe corrosion of the traffic tunnels from 175 to 250 m in the test section. In order to explore how the traffic tunnels impact the transport path of contaminants infiltrating from landfills, a groundwater flow model and a solute transport model were established in the present study. It was found that, after 16 years of operation, the traffic tunnels will accelerate the vertical migration of sulfate ions in the area between the tunnels. Furthermore, 64 water samples along the traffic tunnels were collected to test the concentration of the contaminants. According to the distribution mechanism of the measured concentrations in the traffic tunnels, a preliminary treatment plan was proposed to control the further corrosion of the tunnels and the spread of the contaminants. [ABSTRACT FROM AUTHOR]

Hydroxyl radicals are commonly produced either by metal activation or by using external energy. However, the application of these methods is limited by low working pH and secondary contamination with metal ions. Alternatively, the reaction between hydrogen peroxide (H2O2) and hydroxylamine is an environmentally friendly process that generates active radicals, but the reaction rate is slow. To improve this, we report here a novel and efficient activator for the H2O2/hydroxylamine system that uses sulfate ions ( SO 4 2 - ). We tested the effects of different systems, concentrations of H2O2, hydroxylamine and SO 4 2 - , and pH on the degradation of Rhodamine B. The mechanism was also investigated by kinetic calculation, a radical scavenging experiment, and anions comparison. Results show that the addition of SO 4 2 - effectively improved Rhodamine B degradation and widened the working pH. The hydroxyl radical was found to be the primary radical responsible for dye degradation. Moreover, only SO 4 2 - shows an enhanced effect under the same ionic strength conditions. Overall, our findings reveal a new method for water purification at acidic and near-neutral pH, especially for sulfate-rich wastewater treatment. [ABSTRACT FROM AUTHOR]

Reducing the threats of sulfate ion (SO42−) deposition to terrestrial ecosystems is a great challenge. The canopy interception effect on SO42− deposition has been well documented, but the interception efficiency of the gap edge remains unknown. Therefore, a subalpine dragon spruce (Picea asperata) plantation was evaluated in the upper reaches of the Yangtze River. The dynamics of the SO42− concentration in the throughfall were investigated from the gap edge to the closed canopy during the rainfall and snowfall periods from August 2015 to July 2016. The annual input of SO42− totaled 2.56 kg/ha through rainfall and 0.69 kg/ha through snowfall. The total annual net interception fluxes (NIFs) of SO42− at the gap edge and in the closed canopy were 1.48 kg/ha and 0.66 kg/ha, respectively, and the net interception ratios (NIRs) accounted for 45.40% and 20.25%, respectively. The NIF and the NIR of SO42− at the gap edge were higher than those in the closed canopy. Therefore, the results suggested that a significant amount of SO42− deposition was intercepted by the tree canopy in the subalpine plantation, with more SO42− deposition at the gap edge than in the closed canopy, which is beneficial for improving the water quality in the upper reaches of the Yangtze River via forest management. [ABSTRACT FROM AUTHOR]

As part of a series of studies on the interaction between ferric ions and silicic acid in the hydrosphere, the exchange reaction between SO 4 2- in the schwertmannite tunnel structure and silicic acid in solution was investigated. Increasing pH of the solution from 6 to 11.5 resulted in an increase of adsorbed silicic acid. It was found that rapid substitution of SO 4 2- took place with silicic acid which inhibited the transformation of schwertmannite to goethite. This observation implies more effective stabilization of schwertmannite by silicate compared to that of SO 4 2-, which acts as a template ion in the formation of schwertmannite under acidic conditions. The substitution reaction was determined to be as follows: Schwertmannite-{SO 4 2-} + Si(OH) 3 O- + OH- → Schwertmannite-{Si(OH) 2 O 2 2-} + SO 4 2-+ H 2 O, where schwertmannite-{ SO 4 2-} and schwertmannite-{Si(OH) 2 O 2 2-} indicate that the SO 4 2- and Si(OH) 2 O 2 2- species are present in the schwertmannite tunnel structure. The uptake mechanism of silicic acid by schwertmannite is significantly different from its uptake mechanisms by ferrihydrite and goethite. [Display omitted] • The adsorption behavior of silicic acid onto schwertmannite was examined. • The amount of adsorbed silicic acid onto schwertmannite increased with increasing pH. • Schwertmannite transforms to goethite in the absence of silicic acid. • Schwertmannite is stabilized by the ion exchange of sulfate ion by silicate ion. [ABSTRACT FROM AUTHOR]

Since a concrete structure exposed to a sulfate environment is subject to surface ion ingress that yields cracking due to concrete swelling, its service life evaluation with an engineering modeling is very important. In this paper, cementitious repair materials containing bacteria, Rhodobacter capsulatus, and porous spores for immobilization were developed, and the service life of RC (Reinforced Concrete) structures with a developed bacteria-coating was evaluated through deterministic and probabilistic methods. Design parameters such protective coating thickness, diffusion coefficient, surface roughness, and exterior sulfate ion concentration were considered, and the service life was evaluated with the changing mean and coefficient of variation (COV) of each factor. From service life evaluation, more conservative results were evaluated with the probabilistic method than the deterministic method, and as a result of the analysis, coating thickness and surface roughness were derived as key design parameters for ensuring service life. In an environment exposed to an exterior sulfate concentration of 200 ppm, using the deterministic method, the service life was 17.3 years without repair, 19.7 years with normal repair mortar, and 29.6 years with the application of bacteria-coating. Additionally, when the probabilistic method is applied in the same environment, the service life was changed to 9.2–16.0 years, 10.5–18.2 years, and 15.4–27.4 years, respectively, depending on the variation of design parameters. The developed bacteria-coating technique showed a 1.47–1.50 times higher service life than the application of normal repair mortar, and the effect was much improved when it had a low COV of around 0.1.

In this paper, the adsorption potential of activated carbon prepared by Ziziphus spina-christi lotus leaf for the removal of sulfate from aqueous solution was investigated. To this end, the effect of different parameters such as pH, contact time, temperature, adsorbent concentration, and initial sulfate ion concentration was investigated. The results indicated that the highest adsorption efficiency (84.5%) was obtained at pH 6, adsorbent concentration of 5 g/L, sulfate ion concentration of 20 ppm, 65 min and temperature of 45 °C. Also, the adsorption equilibrium study showed that the adsorption process follows the Langmuir isotherm model with the maximum adsorption capacity of 9.3 mg/g. In addition, the thermodynamic study showed that the adsorption process on the activated carbon surface was spontaneous. Moreover, the adsorption process was exothermic accompanied by a decrease in irregularity. Furthermore, the adsorption kinetic study indicated that the adsorption process follows the pseudo-second-order kinetic model. [ABSTRACT FROM AUTHOR]

This paper presents evidence on the possible impact of aerobic and anaerobic microbiological processes on uranium migration in upper aquifers polluted by sulfates and nitrates at the Novosibirsk chemical concentrate plant (PAO NCCP). Uranium can be immobilized in local areas with high contents of organic substances, and the most important microbiological process is a decrease in redox potential owing to aerobic respiration, which can be followed under anaerobic conditions by redox-dependent uranium reduction in areas with negative Eh values. Moreover, in the presence of sufficient amounts of sulfate ions, further anaerobic processes of microbial sulfate and iron reduction result in the formation of iron sulfide, which serves as an antioxidant buffer in the case of oxygen infiltration into the sediment and transforms to molecular sulfur or sulfate preventing uranium oxidation. [ABSTRACT FROM AUTHOR]