Sulfate Research Articles

Heterogeneous Activation of Persulfate by Petal-Shaped Co3O4@BiOI to Degrade Bisphenol AF

In catalytic tests, the results have shown that almost all the BPAF was removed within 30 min when the dosage of Co3O4@BiOI and sodium persulfate (PS) was 0.15 g and 0.1 mM, respectively. Acid conditions inhibited BPAF degradation, but the inclusion of a precise concentration of bicarbonate ions (HCO3−) promoted degradation. The presence of chloride (Cl−), sulfate ions (SO42−), and a high concentration of HCO3− inhibited the degradation process, whereas the addition of nitrate ions (NO3−) had a minor effect on the catalytic process. The presence of free radicals (sulfate (SO4•−), hydroxyl (•OH), and superoxide (O2•−)) and the non-free radical singlet oxygen (1O2) in the Co3O4@BiOI/PS system was determined by electron paramagnetic resonance (EPR) and quenching tests. We propose that the Co(II)/Co(III) and Bi(III)/Bi(V) redox pairs simultaneously activate PS where the Co3O4 and BiOI components work synergistically to promote the rapid oxidative degradation of BPAF in water.

Mechanical and micro-mechanical investigations of nano-SiO2 and polypropylene fiber reinforced cement soil in marine environments

The degradation of cement-stabilized soil foundations in coastal environments is primarily caused by the corrosive effects of chloride and sulfate ions. While Nano-SiO2 enhances the mechanical properties of cemented soil, it may also increase brittleness, affecting safety and cost-effectiveness. Polypropylene fibers improve ductility by inhibiting crack propagation but contribute minimally to strength enhancement. To optimize performance, this study employed 3.6% Nano-SiO2 and 0.8% polypropylene fibers. Unconfined compressive strength (UCS) tests indicate that with increasing curing time, erosion from Cl− and SO 4 2 − significantly increases the brittleness of Nano-modified cemented soil, with compressive strength initially rising and then declining. The incorporation of polypropylene fibers further enhances both compressive strength and deformation modulus. At 60 days of curing, the composite cemented soil exhibits strength improvements greater than the sum of the individual gains in various environments, with compressive strength increases of 248.9, 159.9, and 102.9% in freshwater, chloride, and sulfate conditions, respectively. Scanning electron microscopy and X-ray diffraction analyses indicate that excessive expansion products from Cl− and SO 4 2 − reduce Nano-SiO2’s effectiveness. The C-S-H gel fills the indentations on the fiber surface and tightly envelops it, while Nano-SiO2 further enhances the mechanical interlocking between the fibers and the matrix, thereby improving durability in marine.

Cyanide mediated conformational changes resulted in the displacement of sulfate ion from the active site of bovine pancreatic ribonuclease A

Ribonuclease A is a major hydrolyzing enzyme involved in the hydrolysis of RNA. The crystals of bovine pancreatic RNase A (bpRNase A) were grown at pH 5.5. The effect of sodium cyanide on bpRNase A was assessed by adding it directly to the crystal containing well. Treating the crystals of bpRNase A with sodium cyanide resulted in the displacement of the sulfate ion from the active site of bpRNase A, while the additional sulfate ion, bound to Ala-4, remained unaffected. The addition of sodium cyanide to bpRNase A crystals did not show change in the secondary structure elements of the enzyme. This study was conducted to check the effect of cyanide on bpRNase A crystals and to displace sulfate ion from its active site.

Experimental measurements and thermodynamic modeling of dissociation pressure of CO2 hydrate in sulfate solutions

Carbon capture and storage (CCS) has been a popular strategy to mitigate climate change and has attracted significant attention from both industry and academia. CO2 can be stored in the form of CO2 hydrate in deeper locations in an ocean, which makes it a potential option for CO2 sequestration. Dissolved salts in the ocean brine can significantly affect the dissociation pressure of CO2 hydrate. Sulfate salts are one of the most common salt species in the oceanic brine. Although various experimental studies have been conducted to investigate the phase behavior of CO2 hydrate in brine, few studies focus on the effect of sulfate salts on the dissociation pressure of CO2 hydrate. In this study, we build an in-house experimental setup to investigate the effect of monovalent and divalent sulfate salts on the dissociation pressure of CO2 hydrate. The dissociation pressure of CO2 hydrate in Na2SO4, K2SO4, MgSO4, and CuSO4 aqueous solutions is measured using the isochoric pressure search method at different concentrations over the temperature range of 274.36–––282.15 K and the pressure range of 1.50–––4.03 MPa. A hybrid methodology incorporating the Soave-Redlich-Kwong Equation of State (SRK EOS), the van der Waals-Platteeuw (vdW-P) model, and the Pitzer model is applied to predict the dissociation pressure of CO2 in sulfate solutions. In addition, the dissociation enthalpies of CO2 hydrate in these sulfate solutions are calculated using the Clausius-Clapeyron equation based on the measured dissociation points. The experimental results show that the dissociation pressure of CO2 hydrate in Na2SO4, K2SO4, and MgSO4 solutions is higher than that in pure water, and the dissociation pressure of CO2 hydrate in sulfate solutions increases with an increasing salt concentration. Conversely, CuSO4 barely affects the dissociation pressure of CO2 hydrate, which is mainly attributed to the lower molar concentration of the ions compared with the other salt solutions and the ion specificity of Cu2+. The prediction results are in alignment with the experimental data measured in this study, which proves the feasibility of the thermodynamic model in predicting the dissociation pressure of CO2 hydrate in sulfate solutions. Additionally, the calculated dissociation enthalpies of CO2 hydrate show a dependence on both temperature and salt concentration. It is also revealed that Cu2+ exhibits ion specificity in affecting the dissociation enthalpy of CO2 hydrate, likely due to its distinct ability to impact the cage occupancy of CO2 hydrate compared with the other ions. These findings enhance our understanding of the impact of sulfate salts on the dissociation behavior of CO2 hydrate and offer valuable insights for CO2 sequestration.

Feasibility of vanadium ion adsorption/desorption using nickel–aluminum complex hydroxides with different molar ratios

Herein, metal complex hydroxides containing nickel (Ni) and aluminum (Al) at different molar ratios (Ni:Al = 1:1 (NA11), 1:2 (NA12), 2:1 (NA21), 3:1 (NA31), and 4:1 (NA41)) were prepared. Scanning electron microscopy images, X-ray diffraction patterns, specific surface area, number of hydroxyl groups, and pHpzc were evaluated. Further, the adsorption capacity of vanadium ions was assessed, with NA21 showing a high potential to adsorb vanadium ions from the aqueous phase (177.5 mg/g). In addition, the effects of various factors, including pH, contact time, initial concentration, and temperature, on the adsorption of vanadium ions were demonstrated in this study using NA21. The optimal pH value for adsorbing vanadium ions was 5.0. Adsorption isotherms and kinetic data were fitted to a pseudo-second-order model (correlation coefficient: 0.958) and a Freundlich model (correlation coefficient: 0.930–0.982), respectively. This study elucidated that a part of the adsorption mechanism of vanadium was related to ion exchange and characteristics of NA21 surface. Moreover, NA21 showed capability to selectively adsorb vanadium ions from binary solution system containing chloride, nitrate, or sulfate ions. Vanadium ions adsorbed onto NA21 were more easily desorbed by a sodium hydroxide solution than a sodium sulfate solution. NA21 demonstrated consistent performance over at least three adsorption and desorption cycles under experimental conditions of this study. These findings provided valuable insights into the recovery of vanadium ions from aqueous media via adsorption/desorption treatment using NA21.

Effect of super absorbent polymers on the self-healing capability of macrocracked ultra-high performance concrete under highly aggressive environments

In this study, the performance of superabsorbent polymers (SAPs) as self-healing agents in macrocracked ultra-high performance concrete (UHPC) was extensively evaluated, with a focus on compressive strength behavior in different aggressive environments. Three UHPC mixtures were designed: a control mixture, a UHPC with 0.3 % sodium polyacrylate (poly(AA)), and a UHPC with 0.3 % polyacrylate-co-acrylamide (poly(AA-co-AM)). Samples with macrocrack widths of 0.3 mm, 0.5 mm, and 1 mm, as well as uncracked samples, were prepared. The samples underwent immersion in deionized water, chloride saltwater, and compound saltwater. The performance of self-healing was evaluated by measuring crack closure rates, recovered compressive strength, and stereomicroscopic inspections. Further, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) was performed to monitor mineral formation and the healing process. The results indicate that both poly(AA) and poly(AA-co-AM) SAPs significantly enhanced the self-healing capabilities of UHPC, with poly(AA) demonstrating superior performance. Self-healing was more pronounced in samples with cracks width of 0.3 mm, whereas samples with cracks widths of 0.5 mm and 1.0 mm exhibited incomplete and negligible healing, respectively. The healed samples recovered a substantial portion of their compressive strength, regardless of the crack width. However, the presence of chloride and/or sulfate ions was found to impede the self-healing process. As observed from the SEM/EDX results, in addition to CaCO3 and C-S-H gel, undesirable healing products like Friedel’s salt and ettringite were also formed in chloride and compound saltwater environments which significantly affected self-healing durability.

Current Status of Processes and Hazardous Chemicals of Lithium-Ion Battery Industries in the Republic of Korea

BackgroundWith global trends of carbon neutrality and eco-friendliness, the demand for lithium-ion batteries (LIBs) has been rapidly increasing. However, occupational health research within this sector is significantly lacking. Thus, this study aimed to understand the industrial value chain, processes, and current status of hazardous chemicals associated with LIBs. MethodsThrough a literature review and a survey of business sites, the LIB industry was categorized into 10 industrial groups. We visited 32 workplaces in the Republic of Korea, and conducted on-site surveys. ResultsPrimary mineral raw materials used in LIBs include lithium (Li), nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al) often in compound forms, alongside graphite, posing significant challenges in management due to their micrometer-sized particles. Furthermore, metals used in salt form (such as LiOH or sulfate salts) can irritate the skin or respiratory system, particularly Ni and Co known to be toxic substances designated as human carcinogens by IARC. Acids, bases, and various solvents are also used to improve batteries’ electrical properties. Dichloromethane classified as carcinogenic 2A by the IARC is widely used in the separator industry. Carbonate-based solvents are widely used in electrolytes with potential for exposure in battery cell manufacturers and recycling industries. However, they are not classified as regulated substances, leading to inadequate management practices. ConclusionThis study identified processes of each industry and chemical substances utilized in LIB industry in the Republic of Korea. Based on this study, it is necessary to implement appropriate management measures tailored to industrial processes and types of harmful factors.

Controllable synthesis of monodisperse hierarchical porous carbon nanorods and their derived superstructures for supercapacitors

Monodisperse hierarchical porous carbon nanorods (HPCNs-1) are synthesized through hydrothermal carbonization and KHCO3 activation using D-xylose, sodium dodecyl sulfate (SDS) and poly (4-styrene sulfonic acid-maleic acid) sodium salt (PSSMA). PSSMA regulates morphology and the accumulation of SDS micelles through inhibition and electrostatic repulsion. SDS serves as a microreactor for hydrothermal processes and a pore-forming agent. KHCO3 generates micropore and ensures a high specific surface area. Additionally, raspberry-like and spindle-like hierarchical porous nanocarbons are obtained with sodium laurate and sodium oleate. Hierarchical porous nanocarbons exhibit controllable morphology, high pore utilization, demonstrating useful electrochemical performance. In a 6 mol·L-1 KOH electrolyte, HPCNs-1 achieves a specific capacitance of 302F·g−1 at a current density of 0.2 A·g−1 with a retention rate of 98 % after 10,000 charge–discharge cycles at 10 A·g−1. In pure 1-butyl-3-methylimidazolium tetrafluoroborate electrolyte, an assembled symmetric supercapacitor with HPCNs-1 demonstrates an energy density of 39.06 W·h·kg−1 at 0.1 A·g−1.

Hydrochemical Assessment of Tigris River for Irrigation Purposes within Baghdad Province, Iraq

The aims of this study are (1) to determine whether Tigris River water is suitable for irrigation using specific irrigation indices. (2) Analysis of thirteen hydrochemical parameters, including pH, EC, TDS, , , , , , , , , TA and as total hardness. Also, seven irrigation water quality indices were used: Magnesium Hazard (MH), Kelly's Index (KI), Sodium Adsorption Ratio (SAR), Sodium Percentage (Na%), Soluble Sodium Percentage (SSP), Potential Salinity (PS), and Sodium Hazard (SH), supported by the most specific irrigation diagrams (Piper, USSL and Wilcox). Samples were taken monthly from twelve different sites along the river for two consecutive years (2021-2022). The results revealed that the water is suitable for irrigation chemically according to SAR, Na%, SSP, KI, and MH, except for PS due to high levels of sulfate and chloride ions. Furthermore, the USSL diagram indicated Irrigation water quality, that 100% of water samples taken from the Tigris fell into the appropriate class within 2021. While in 2022, 83.33% of samples were within the appropriate class (C3-S1). According to the Wilcox diagram, 91.66% and 83.33% among the water samples within a good class (low sodium and moderate salinity) for two consecutive years

Discovery and characterization of cyclotides, plant-based peptides from <i>Viola dalatensis</i> Gadnep

Cyclotides demonstrate remarkable stability due to their unique characteristic - the cyclic cystine knot motif. Cyclotides exhibit a wide range of biological activities. This study aims to explore the presence of cyclotides in Viola dalatensis Gadnep, a plant indigenous to Vietnam, through the utilization of LC-MS and LC-MS/MS techniques. We conducted a comprehensive analysis of three extraction methods: 50% acetonitrile with 1% formic acid, 70% ethanol, and 50% methanol. The initial method is extremely efficient for cyclotide extraction when utilizing LC-MS analysis. An ammonium sulfate salt concentration of 30% is used to enhance the cyclotide content and optimize the RP-HPLC purification procedure. The precipitates demonstrate a notable advantage in terms of antibacterial properties compared to the extracts, particularly when the antibacterial concentration is decreased by a factor of four in comparison to the extracts. The combination of cyclotides demonstrated potent antimicrobial activity against Bacillus subtilis and Pseudomonas aeruginosa. The impact was most noticeable when the concentration of the cyclotide mixture was ten times lower than the precipitates. The inhibition zones for these bacteria measured 17.17 ± 2.24 mm and 20.23 ± 0.84 mm, respectively. The identification of the primary structure of nine cyclotides through LC-MS/MS analysis was successfully achieved.

Tensile Performance and Aging Increase Factor Constitutive Model of High-Strength Engineered Cementitious Composites under Sulfate Salt Attack

This study investigates the uniaxial tensile behavior of high-strength engineered cementitious composites (HS-ECCs) in sulfate erosion environments. Five different sulfate erosion ages were established (0 days, 30 days, 60 days, 90 days, and 120 days), and the development of the macro-mechanical properties of HS-ECCs was revealed from a microscopic perspective using scanning electron microscopy (SEM). The results indicate that, under the influence of sulfate erosion, the strength of HS-ECCs exhibits a trend of initial increase followed by a decrease, while ductility shows a continuous decline. This phenomenon is primarily attributed to changes in the microstructure and reaction products. Based on the test results, an aging growth factor was introduced to fit the stress–strain curve, demonstrating that the model can effectively predict the tensile performance of HS-ECCs with greater accuracy compared to traditional models. This study not only provides data references for the engineering application of HS-ECCs in sulfate environments but also offers a novel approach for constructing predictive models in other environmental contexts.

Impact of hydrophobic and hydrophilic surface properties on Pseudomonas aeruginosa adhesion in materials used in mineral water wells

Microbiologically contaminated water is a significant source of infections in humans and animals, with Pseudomonas aeruginosa (PSA) being particularly concerning due to its ability to thrive in water environments and its resistance to many disinfectants. Therefore, this study investigates the adhesion potential of PSA strains on various materials used in mineral water extraction wells, focusing on hydrophobic and hydrophilic properties. Mineral water samples were collected from three wells (P-01, P-07, and P-08) within the Guarani Aquifer System and Fractured Aquifer System (SAF) in Brazil. The physicochemical properties of the water, including concentrations of Sr (strontium), Fe (iron), Si (silicon), SO4 2− (sulfate ions), Cl− (chloride ions), and ORP (oxidation-reduction potential), were analyzed. Results indicated higher PSA adhesion on hydrophobic materials, particularly high-density polyethylene (HDPE) and geomechanically plasticized polyvinyl chloride (PVC). Multiple correlation analyses revealed positive correlations between PSA adhesion on hydrophilic materials and Sr, Fe, Si, SO4 2−, and Cl− concentrations. Conversely, ORP negatively correlated with bacterial adhesion on PVC surfaces, suggesting higher ORP values reduced PSA attachment. These findings highlight the importance of water composition and material properties in influencing bacterial adhesion and potential biofilm formation in mineral water extraction systems.

Production, Characterization, Kinetics, and Thermodynamics Analysis of Amyloglucosidase from Fungal Consortium.

The current study aimed to produce an amyloglucosidase enzyme from the fungal consortium. The best amylolytic fungal consortia were identified as Alternaria alternata and Aspergillus niger through the 18S rDNA technique. Fermentation kinetics and various nutritional and cultural parameters were analyzed. Maximum production was obtained in M4 media, pH 5.5, 30°C, and 4mL inoculum at 150rpm after 72h of incubation. Along with that, sodium nitrate at 2.5%, maltose, beef extract 1%, zinc sulfate (0.1%), and Tween 80 (0.1%) supported the maximum amyloglucosidase production. Amyloglucosidase was partially purified up to 1.6 purification fold with a specific activity of 1.84 Umg-1 in a stepwise manner by ammonium sulfate purification, dialysis, and ion exchange chromatography. The AMG enzyme also revealed maximum activity at 50°C with 5.0 pH. Upon the kinetic analysis, the specific yield coefficient Yp/x and volumetric rates Qp and Qx were also found to be significant in the above optimized conditions. The Km value 0.33mgmL-1 and Vmax 26.31 U mL-1 were obtained at 1% soluble starch substrate. Thermodynamic parameters for soluble starch hydrolysis were as follows: ΔH = 48.78kJmol-1, (Ea) = - 46.0kJmol-1, and ΔS = - 43.10Jmol-1K-1. This finding indicates the indigenously isolated fungal consortium can be the best candidate for industrial applications.

Electrically enhanced adsorption performance of functionalized aluminum-nitride nanotubes for removal of sulfate ions in water

Here, density functional theory(DFT) calculations were carried out to investigate the effect of applied electric field on the adsorption of sulfate ions in water by doped functional aluminum nitride nanotubes. The stable structure of the adsorption system, the adsorption energy of SO42− on the adsorbent, and the electronic and thermodynamic properties of the adsorption system under applied electric field were calculated and analyzed. The results show that the adsorption energy of boron doped aluminum nitride nanotubes (AlNNT-B) on SO42− can be greatly improved under the action of electric field (EF). The electric field promotes the electron transfer of SO42− to AlNNT-B, and gradually increases the Mayer bond levels of B-N25 and B-N27, indicating that the binding of B atoms to N atoms is enhanced. In addition, the thermodynamic analysis shows that the adsorption of SO42− on the surface of AlNNT-B is a spontaneous heat release process, and the trend of spontaneous heat release can be enhanced by EF. Our research results not only propose a novel method for removing sulfate ions from water, but also have significant implications for other applications of nanomaterials (such as delivery system of anticancer drugs).

Enhanced phosphate anion flux through single-ion, reverse-selective mixed-matrix cation exchange membrane

Phosphate recovery from wastewater is vital for both environmental sustainability and resource conservation, offering the dual benefit of reducing phosphate pollution while providing a valuable source of this essential nutrient. We previously reported an approach for synthesizing hydrous manganese oxide (HMO) nanoparticles within a polymeric cation-exchange membrane (CEM) to achieve a phosphate-selective mixed-matrix membrane (PhSMMM); however, the phosphate flux was lower than desired. Herein, we demonstrate a next-generation PhSMMM membrane with enhanced phosphate flux and selectivity. Experimental results confirm the successful incorporation of up to 28 wt% HMO nanoparticles into the polymeric CEM. The new PhSMMM exhibits a phosphate flux of 1.57 mmol∙m–2.hr–1 (an 8.5X enhancement), with selectivity over chloride, nitrate, and sulfate ions of 9, 11, and 104, respectively. This significant enhancement in phosphate flux marks a promising advancement in a sustainable solution for phosphate removal and recovery from wastewater.

Impact of sulfate salts on water structure: insights from molecular dynamics

Ions significantly alter the water's structure, impacting properties such as the temperature of maximum density and the freezing point. We study structural changes in water upon adding sulfate anions, specifically Na 2 SO 4 , K 2 SO 4 , Li 2 SO 4 , and Mg SO 4 , using computer simulations. We employ the TIP4P/2005 water and the Madrid-2019 force field. By simulating solutions at various concentrations (0.64, 1.30, 1.90, and 3 mol kg − 1 ) and two temperatures ( 300 and 240 K), we explore how these electrolytes disrupt water's structure and how they modify the interplay between Low Density Water and High Density Water. Increased salt concentration perturbed water's radial distribution functions (RDFs), particularly up to 240 K. Na 2 SO 4 significantly disrupted water structure, reducing RDF peak heights and indicating decreased tetrahedrality, while Mg SO 4 increased structural order. K 2 SO 4 displayed anomalous behaviour, minimally affecting water at 1.90 mol kg − 1 and ambient temperature but causing more ordered structures at 240 K. Orientational order parameter q t analysis supported these findings. Hydrogen bond network analysis showed notable perturbations at lower temperatures. Diffusion coefficients generally decreased with concentration, with K 2 SO 4 exhibiting increase at 240 K. These results highlight the complex interactions between sulfate ions and water, enhancing our understanding of electrolyte solutions.

Silicon surface texturing via TBAB-SDS composite additives enhanced copper-assisted chemical etching

Uneven etching and low fabrication efficiency impede the large-scale applications of copper-assisted chemical etching (Cu-ACE) for texturing light-trapping structures on the surface of silicon wafers. To address this, a composite additive composed of tetrabutylammonium bromide (TBAB) and sodium dodecyl sulfate (SDS) was introduced into the Cu-ACE system. The results indicated that TBAB accelerated the etching rate and improved the texturing uniformity, while SDS enlarged the size of the formed structures and enhanced their ultraviolet light absorption efficiency. The prepared inverted pyramid structure reduced the reflectivity of the silicon wafer surface to 3.8 %, thus exhibiting efficient light-trapping capabilities. The etching evolution under various TBAB concentrations and different HF/H2O2 ratios was studied by characterizing the surface contact angle and copper deposition morphology. The results indicated that electrostatic attraction between TBAB and dangling bonds on the silicon wafer surface enhanced material transfer at the reaction interface and changed the electron distribution around dangling bonds, thus facilitating the catalytic metal attack on these bonds. The copper ion reactivity was decreased due to complexation between the dissociated alkyl sulfate ions of SDS and copper ions, which favored the deposition of larger copper nanoparticles during etching, thereby increasing the size of structures. This research offers valuable insights to enable the large-scale applications of Cu-ACE.

Sulfate resistance of mortars under semi-immersion condition: Impact of environmental humidity and fly ash content

Fly ash can effectively improve the sulfate resistance of immersed concrete by refining the pore size. However, increase of capillary pores may not be a good thing for salt crystals. In this paper, the effects of fly ash contents and environmental humidity on the sulfate resistance of semi-immersed mortars was investigated by appearance, mechnical strength, and microstructure. Capillary adsorption capacity, ingressed sulfate concentration and erosion productes were further investigated to analyze damage mechanism of mortar under semi-immersion condition. Lower environmental humidity and higher fly ash content were not conducive to the sulfate resistance of semi-submerged mortar, when the humidity was lower than 55 %, the fly ash content should be further reduced. The migration of sulfate ions in capillary pores and the physical salt crystallization in the region of humidity change are the main reasons for the damage.

Regeneration of conventional and emerging PFAS-selective anion exchange resins used to treat PFAS-contaminated waters

Anion exchange resins (AERs) have emerged as a promising separation technology to remediate PFAS-contaminated waters due to their improved selectivities and capacities in comparison to legacy activated carbon adsorbents. Presently, site managers choose between AER systems employing resins defined as being ‘regenerable’ with relatively low PFAS selectivity, and PFAS-selective resins that are marketed as ‘single-use’ media intended for disposal upon PFAS breakthrough. However, the potential for these highly-selective adsorbents to be regenerated and/or reused remains poorly characterized. This study presents a comprehensive evaluation of the efficacy of various regenerant solution constituents, mixtures, and operational considerations on the regenerability of both ‘regenerable’ and ‘PFAS-selective’ AERs that were loaded during a pilot treatment study of PFAS-contaminated groundwater. Batch screening of regenerant solution constituents found that both classes of resins may be effectively regenerated using combinations of salt brine and organic cosolvent, with high cosolvent fractions being necessary for PFAS-selective AERs. While neither brine-only nor solvent-only regenerant solutions led to effective PFAS desorption, the efficacy of regeneration with brine/cosolvent mixtures varied with salt type and cosolvent composition. Chloride salts outperformed sulfate and bicarbonate salts, cosolvent efficacy depended on the volume fraction and type used, and highly non-polar solutions led to optimal PFAS desorption. Continuous-flow regeneration experiments showed near-complete PFAS desorption from regenerable AERs using 10 bed volumes (BVs) of 70 % methanolic brine solutions, whereas PFAS-selective resins required more bed volumes (30) of brines with higher methanol content (90 %) or a more hydrophobic cosolvent (n-propanol); increasing regenerant empty-bed contact time had minimal effect on PFAS desorption. > 90 % methanol recovery from the resulting waste regenerant mixtures was accomplished with negligible PFAS contamination using distillation, leaving a minimal volume of a PFAS-concentrated still bottoms waste that may be further treated for PFAS destruction. Life cycle analyses revealed that groundwater treatment using PFAS-selective AERs operated in a regenerable mode have lower environmental impacts and costs than systems using conventional regenerable AERs, and lower treatment costs than systems operated using PFAS-selective resins in a single-use mode. Although counterintuitive, these findings stem from the fact that higher cosolvent requirements for regeneration of PFAS-selective resins lead to greater internal recycling of regenerant solutions and much lower volumes of residual waste still bottoms that require off-site incineration or disposal.

Drying-Wetting Correlation Analysis of Chloride Transport Behavior and Mechanism in Calcium Sulphoaluminate Cement Concrete.

In response to rising CO2 emissions in the cement industry and the growing demand for durable offshore engineering materials, calcium sulphoaluminate (CSA) cement concrete, known for its lower carbon footprint and enhanced corrosion resistance compared to Ordinary Portland Cement (OPC), is increasingly important. However, the chloride transport behavior of CSA concrete in both laboratory and marine environments remains underexplored and controversial. Accordingly, the chloride ion transport behaviors and mechanisms of CSA concrete in laboratory-accelerated drying-wetting cyclic environments using NaCl solution and seawater, as well as in marine tidal environments, were characterized using the rapid chloride test (RCT), X-ray diffraction (XRD), mercury infiltration porosimetry (MIP), and thermogravimetric analysis (TGA). The results reveal that CSA concrete accumulates more chloride ions in NaCl solution than in seawater, with concentrations 2-3.5 times higher at the same water-cement ratio. Microscopic analysis indicates that calcium and sulfate ions present in seawater facilitate the regeneration of ettringite, thereby increasing the density of the surface pore structure. The hydration and repair mechanisms of CSA concrete under laboratory conditions closely resemble those in marine tidal conditions when exposed to seawater. Additionally, this study found that lower chloride ion concentrations and pH levels inhibit the formation of Friedel's salt. Therefore, laboratory experiments with seawater can effectively simulate CSA concrete's chloride transport properties in marine tidal environments, whereas NaCl solution does not accurately reflect actual marine conditions.