Sodium Sulfate Solution Research Articles

Chromium oxide nanoparticles in‐situ immobilized onto nitrogen‐doped carbon plates with boosted catalytic activity toward nitrogen reduction reaction

AbstractA chromium oxide‐based nanocomposite (Cr2O3@NC) is designed and prepared via a simple pyrolysis route with Cr‐based metal organic framework (MOF) as a template. The research results indicate that Cr2O3 nanoparticles have an average size of ~70 nm and are in situ formed and imbedded onto the Cr‐based MOF‐derived 2D N‐doped carbon microplates. When employed as an inexpensive electrocatalyst for nitrogen reduction reaction (NRR) to synthesize ammonia, Cr2O3@NC demonstrates an improved and stable catalytic activity in comparison with bare Cr2O3. A large ammonia production rate of 29.42 μg mg−1cat h−1 under a lower potential of −0.4 V versus reversible hydrogen electrode (RHE) can be acquired with a Faradic efficiency of 9.89% in sodium sulphate solution. Additionally, a satisfactory selectivity can also be achieved without hydrazine byproduct. The greatly promoted catalytic activity of Cr2O3@NC is regarded to be concerned with its desirable structures such as 2D planar topological structure with expanded active surface area, abundant catalytic sites, and effective combination with conductive carbon.

Sulfate attack on portland-dolomite cement exposed to sodium sulfate solution at 5 ℃ and 20 ℃

The purpose of the study is to investigate the sulfate resistance of portland-dolomite cement (PDC) with varying dolomite contents, when exposed to sodium sulfate solution at 5 ℃ and 20 ℃. Visual appearance, expansion, mass change, and compressive strength of PDC mortars were tested, and XRD, FTIR, and SEM analyses were conducted to examine deterioration products and microstructure. Results indicate that at 20 ℃, the incorporation of 10 % dolomite in PDC had a negligible impact on sulfate resistance, whereas higher dolomite replacements of 20 % and 30 % notably diminished it. In contrast, exposure at 5 °C led to more severe deterioration in all PDC samples, regardless of dolomite content, and the higher dolomite content, the poorer resistance to sulfate attack. The increased formation of ettringite and gypsum resulted in reduced sulfate resistance of PDC at 20 ℃. However, at 5 ℃, the presence of dolomite significantly promoted the formation of thaumasite at later stages, which caused initial ettringite and subsequent late-stage thaumasite sulfate attack, ultimately leading to the failure of PDC. The findings suggest that PDC should be carefully considered when used in sulfate-rich environments, particularly at low temperatures.

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.

S858 Evaluation of an Oral Sodium Sulfate Solution for Patients With Prior Difficult or Incomplete Cleansing - A Prospective Case Series

S858 Evaluation of an Oral Sodium Sulfate Solution for Patients With Prior Difficult or Incomplete Cleansing - A Prospective Case Series

Salt weathering resilience in masonry: An accelerated laboratory study involving wind-induced variations

Salt weathering resistance is a critical parameter governing the durability of coastal masonry units and mortars. Accelerated weathering cycles are employed at the laboratory to investigate the responses of substrates and mortars upon exposure to salt, moisture, temperature fluctuations and humidity. In this paper, the individual and synergistic performances of bricks and mortar formulations when exposed to accelerated salt weathering cycles are investigated, incorporating the influence of wind on their resilience. The study examines the behaviour of brick-mortar sandwich specimens and separate specimens of bricks and mortar mixtures comprising cement, dry hydrated lime, fly ash, and limestone. These specimens are exposed to repeated weathering cycles in a 5 % sodium sulphate solution. Along with the mass variations during each weathering cycle, physicomechanical, microstructural, mineralogical and morphological characterization of the specimens are used to compare their salt weathering resistance. The results highlight that the responses of individual masonry components might not collectively translate to the overall performance of the combined system due to hygric resistance, which is minimal when the components have comparable pore size distribution. Higher microporosity (pores of diameter between 0.1 μm and 10 μm) and mechanical strength enough to resist the crystallization stresses together provide better resistance to salt weathering to the individual mortars. However, pore structure compatibility and pore fraction similarity between the components govern the behaviour of the combined system and, therefore, reflect the better performance of sandwich specimens with brick and lime mortars. The study demonstrated that wind accelerates material degradation during salt weathering through progressive erosion, accelerated evaporation and subsequent formation of isolated thenardite.

Synergistic effect of alcohol polyoxyethylene ether sodium sulphate and copper foam on methane hydrate formation

AbstractNatural gas is the cleanest fossil energy source and its consumption is increasing rapidly, so an efficient natural gas way of storing and transporting is urgently needed. Solidified natural gas (SNG) technology is gaining traction because of its higher safety, lower cost, and flexible storage and transportation modes. To improve the methane uptake rate in SNG technology, this work investigated the growth of methane hydrate in fatty alcohol polyoxyethylene ether sodium sulphate (AES) solution with the addition of three different pores per inch (PPI) of copper foam (CF). The results showed that the addition of AES caused the hydrate to grow upwards along the wall, and the methane uptake in the 300 ppm AES solution was increased by 623% compared to pure water. CF not only provided more nucleation sites for hydrate but also transferred the heat generated during hydration. Moreover, there was a synergistic effect between AES and CF and the solution could continuously transport upward along the continuous metal skeleton to increase the gas–liquid contact area. Thus, the formation rate and induction time of methane hydrate improve. Hydrate had the highest methane uptake in the 20 PPI CF system and the lower the pressure, the greater the ability of CF to promote hydrate formation. The methane uptake improved by 27.6% and the induction time was reduced by 59.7% compared to the pure AES system at 6 MPa. This work is aimed at advancing SNG technology (especially at low pressure) and informs the theoretical foundation.

Study on performance deterioration and life prediction of reed straw-recycled brick aggregate concrete after freeze-thaw cycle

The current rate of carbon dioxide emissions poses a significant threat to global climate, making it increasingly important and urgent to lead the carbon-intensive construction industry to achieve carbon neutrality. Currently, the most practical method involves reusing waste materials. In this study, waste red bricks were used to replace 75 % of natural aggregates in concrete, and three different forms of reed stalks (including reed straw ash, reed straw strips, and reed straw powder) were added to prepare the recycled reed straw brick aggregate concrete (RSAC). Freeze-thaw tests were carried out for 25, 50, 75, and 100 cycles in water and sodium sulfate solution to establish a freeze-thaw deterioration model and perform life prediction. The results showed that the degree of freeze-thaw deterioration of the specimens in sulfuric acid solution was small, and the degree of deterioration of reed powder concrete (RSAC-F) and reed ash concrete (RSAC-H) was more serious than reed strip concrete (RSAC-T) and additive-free concrete (RSAC-0). After 100 water freeze-thaw cycles, the strength losses of the specimens were 21.55 %, 21.7 %, 18.71 %, and 20.54 %, and the relative dynamic elastic modulus losses were 6.11 %, 7.25 %, 4.39 %, and 5.79 %, and the mass losses were 1.79 %, 2.04 %, 1.4 %, and 1.5 %. The fitting results showed that the predicted values of the parabolic model and two-parameter Weibull distribution damage model were closer to the experimental values, and the fitting rates are both greater than 90 %. The life prediction results show that the freeze-thaw resistance of the four types of reed-brick aggregate recycled concrete can reach more than 80 years in southern China, meeting the durability requirements, and the RSAC-T and RSAC-0 group concrete could also be used in projects with lower frost resistance requirements in the north region of China.

Experimental study on the impact of sulfate attack on the performance of shaft lining concrete under sustained compressive load

To investigate the impact of sulfate corrosion on the performance of shaft lining concrete under sustained compressive loads, this study immersed samples in a 10 % sodium sulfate solution after subjecting to sustained compressive loads of 0.2fcand 0.4fc. The variation in compressive strength, ultrasonic velocity, and dynamic elasticity modulus with corrosion age were examined. The corrosion mechanisms were analyzed using field emission scanning electron microscope and energy dispersive spectrometer. The impact tendency of concrete was also evaluated. The results indicated that under sustained compressive loads of 0.2fcand 0.4fc, the compressive strength, ultrasonic velocity, and dynamic elasticity modulus are all increased with age, in the order of 0.2fc> 0.4fc>no-load. When exposed to a 10 % sodium sulfate solution under sustained compressive loads, these properties initially increased and then decreased, peaking at 90 days of corrosion age, and the order was 0.2fc> no-load > 0.4fc when the corrosion age was longer than 240 days.The shaft lining concrete exhibited weak impact tendency, with the brittleness index increasing as the corrosion age progressed. The outcome of this work might provide a reference for the further research on the design of shaft lining concrete materials.

The Anodic Behavior of Manganese Silicide-Germanides in Aqueous Sodium Sulfate Solutions: The Effect of the Germanium Content

The Anodic Behavior of Manganese Silicide-Germanides in Aqueous Sodium Sulfate Solutions: The Effect of the Germanium Content

Durability of Non-Heat-Cured Geopolymer Mortars Containing Metakaolin and Ground Granulated Blast Furnace Slag

This study presents the durability, strength and microstructure of non-heat-cured geopolymer mortars (GMs) containing metakaolin (MK), ground granulated blast furnace slag (GGBFS), potassium hydroxide (KOH), sodium metasilicate (Na2SiO3), CEN sand and network water. Optimum MK, GGBFS and activator solution ratios were investigated, and the compressive strength of non-heat-cured 28-day GMs reached 55 MPa. Analysis of GMs using scanning electron microscopy (SEM), energy-dispersive X-ray spectrophotometry (EDX) and X-ray powder diffraction (XRD) revealed alumino-silicate formation, potassium from KOH solution and calcium from GGBFS. It showed that the grains containing high silica in the form of quartz crystals were found in the gel formation. The strength and durability of MK- and GGBFS-based GMs exposed to freeze–thawing, a high temperature, wear loss, magnesium sulfate (MgSO4), sodium sulfate (Na2SO4) and HCl solutions were found to be sufficient.

Nitrogen-doped carbon confined Cr2S3 hybrid as an efficient low-cost catalyst for electrochemical ammonia synthesis under ambient condition

A chromium sulfide-based nanohybrid (NC/Cr2S3) has been fabricated by a facile strategy of pyrolysis and vulcanization of metal complex. In this nanocomposite, the in situ formed Cr2S3 nanoparticles with a mean size about ∼ 100 nm are confined by the nitrogen-doped carbon plates-derived from the metal complex. The composite is endowed with some structural advantages involving extended surface areas, increased catalytically active centers and enhanced conductivity. As an earth-abundant low-cost electrocatalyst for nitrogen reduction reaction (NRR), compared with bare Cr2S3, NC/Cr2S3 hybrid delivers a boosted and stable catalytic activity for NRR at a low potential under mild conditions. NC/Cr2S3 is able to exhibit a high ammonia yield rate of 30.33 μg mg-1cat h−1 at −0.4 V vs RHE in sodium sulfate solution with a Faradic efficiency up to 7.66 %. Moreover, no hydrazine byproduct can be detected, showcasing a satisfactory selectivity.

Experiments on Chloride Binding and Its Release by Sulfates in Cementitious Materials.

The aim of this study was to experimentally investigate the process of chloride binding and its sulfate-induced release in cementitious materials. The cementitious materials were replaced with hardened cement paste particles (HCPs) with water-to-cement ratios (w/c) of 0.35 and 0.45. A long-term immersion experiment of HCPs in 0.1 M sodium chloride solution was performed to investigate its chloride-binding capacity, and then it was immersed in sodium sulfate solutions with concentrations of 0.1 and 0.5 M to explore the release of chloride binding induced by sulfates. Silver nitrate titration and quantitative X-ray diffraction (QXRD) were used to measure the concentration of free chlorides in the solutions and the content of bound chlorides in HCPs, respectively. The results show that there is a higher chloride-binding capacity in HCPs with a w/c ratio of 0.45 compared to 0.35, and the content of chemically bound chlorides is associated with the formation and decomposition of Friedel's and Kuzel's salts in HCPs. The presence of sulfates can easily result in the release of bound chlorides in Friedel's salt, but it cannot cause a complete release of bound chlorides in Kuzel's salt. Physically bound chlorides are more easily released by sulfates than chemically bound chlorides, and a high w/c ratio or sulfate concentration can increase the release rate of bound chlorides in HCPs.

Investigation of Weathering Resistance and Damage Manifestations of Mortar Formulations for Heritage Structures in Saline Environment

ABSTRACT Salt, moisture, wind, relative humidity, and temperature fluctuations accelerate the deterioration of heritage masonry mortars. The salt entering the structure crystallizes on water evaporation, resulting in efflorescence and cryptoflorescence. As the conservation of built heritage primarily focuses on protecting the structure’s functionality, durability, and compatibility with the materials, salt weathering resistance must be emphasized when choosing a repair material for conservation. This study investigates the resistance of five different mortar compositions to salt exposure. Mortar cubes of size 50 mm were cast using five different binder compositions — dry hydrated lime, lime aged for one month, lime aged for one year, lime mortar with 20% Ordinary Portland Cement by weight and lime mortar with 50% Ordinary Portland Cement by weight. Alternate wetting and drying cycles were simulated by immersing the cubes in a 10% anhydrous sodium sulphate solution followed by drying. Physicomechanical characterization of the mortar was conducted before weathering. X-ray diffraction and Scanning Electron Microscopy provided the mineralogical and morphological alterations of the mortar specimens with weathering, respectively. Along with the microstructural assessment, observations on the mass change during the weathering cycles indicated that the partial replacement of lime with cement improved the weathering resistance of the mortar by changing the pore structure of the matrix. However, salt weathering resistance was unaffected by the changes in the ageing duration of lime. The study provides options for alternative lime-based systems with enhanced salt weathering resistance and investigates the role of the compositional differences and their impact on the pore structure and strength of the matrix, which in turn governs the salt weathering resistance.

Adequate Colon Preparation in Screening Colonoscopy

Colorectal cancer (CRC) is one of the most common forms of cancer worldwide, being the fourth most prevalent cancer and the third most common in terms of mortality. A decrease in the incidence and mortality of CRC has been observed among adults over 50 years of age, screening colonoscopy being a contributory factor for this improvement. Adequate preparation of the colon is essential for obtaining accurate results and minimizing the risks associated with the colonoscopy procedure. Both ESGE (European Society of Gastrointestinal Endoscopy) and UEG (United European Gastroenterology) recommend adequate preparation in at least 90% of cases, calculated both at the endoscopy center level and for each individual endoscopist. The purpose of our article is to review the literature on different bowel preparation products for colonoscopy and demonstrate the non inferiority of low-volume preparations over the standard PEG 4L. Preparations containing PEG are the most common in preparation for colonoscopy. A recent meta-analysis suggests that high-volume, mutiple-dose regimens are superior in terms of efficacy to low-volume, multiple- dose regimens, including low-volume PEG with various adjuvants and sodium phosphate, although with lower tolerability. Due to low levels of compliance, tolerability and acceptability, standard 4L single-dose regimens of PEG have been gradually and successfully replaced by newer regimens that include low-volume solutions. An eample of low-volume split-dose preparation is the solution of low-volume PEG4000, sodium sulphate, citric acid, sodium citrate, sodium chloride, potassium chloride and simethicone. In several studies this 2 L low volume preparations ehibit similar effectiveness with safety profiles that are comparable to classic 4 L PEG, with lower incidence of adverse effects and good tolerability. In conclusion, adequate preparation increases the quality of colonoscopy procedures as proper patient preparation is essential to obtain an optimal visualization of the intestinal mucosa. Low-volume bowel preparation is effective, safe and well tolerated by the patients, with higher acceptability compared to the standard volume PEG.

Ferrock cement and oxalic acid for enhanced concrete strength and durability against sulphate attack

Concrete is widely known for being plentiful, durable, and strong, but it can be damaged by different chemicals and environments, that can shorten its lifespan. Consequently, there is a growing interest among researchers to find more durable, stronger, and environmentally friendly cement alternatives. This study focuses on evaluating the workability, strength, durability properties, and morphological aspects of ferrock cement-based concrete, which involves substituting varying percentages of ferrock cement (0%, 5%, 10%, 15%, and 20%) for conventional cement. Ferrock, comprising Iron Powder, Fly Ash, Lime Powder, and glass powder offers pozzolanic potential as a sustainable cement substitute. Additionally, oxalic acid is introduced into the mixes to explore its role in catalyzing reactions between CO2 and water, thereby enhancing the concrete’s strength and durability. Compressive and flexural strength are analyzed after replacing the cement with ferrock, with and without oxalic acid, while durability is assessed through water absorption and resistance to sodium sulphate solution after 28 days of curing. Nine sets of mixes, all with a consistent water-cement ratio of 0.49, are investigated. Results indicate that concrete containing ferrock-based cement, particularly with oxalic acid, exhibits superior strength and enhanced resistance to sulphate attack. The addition of 5% and 10% ferrock with the integration of oxalic acid has 32.28% and 38.7% of compressive strength respectively, the same proportion has 0.2% and 0.1% of mass loss regarding resistance to sulphate attack. Notably, a 10% ferrock replacement with oxalic acid demonstrates the highest performance of concrete as determined by the multi-decision methods.

Improvement in crystallization and digestion resistance of debranched amylopectin dextrins using sodium sulfate

In this study, sodium sulfate, a typical kosmotrope salt (100–500 mM), was used to resistant dextrin crystals prepared via enzymatic debranching, and its effects on the crystallization behavior and in vitro digestibility of the dextrin crystals were investigated. Waxy maize starch was enzymatically debranched (50 °C for 24 h) and simultaneously crystallized (50 °C for 2 d) in aqueous solutions containing sodium sulfate (0–500 mM). The yield of dextrin crystals was increased using a sodium sulfate solution (84% at 500 mM sodium sulfate). The dextrin crystals comprise an A-type arrangement of double helices with higher thermal stability than native starch. Based on the DSC, XRD, and in vitro digestibility test, the high thermal stability and crystallinity of the dextrin crystals provide high resistance to digestive enzymes. The addition of sodium sulfate during crystallization increased the crystallinity and thus increased the digestion resistance. According to the in vitro digestibility test, dextrin crystals prepared with 500 mM sodium sulfate contained a resistant fraction of 80.36% in the uncooked state. After cooking (boiling), over half of the dextrin crystals remain resistant to digestive enzymes. This study showed that sodium sulfate, a typical kosmotrope salt, could accelerate the crystallization process of the debranched waxy maize starch chain, increasing yield, thermal stability, crystallinity, and digestion resistance in a short reaction period.

Evolution of LWAC–OC interfacial properties during sulfate dry–wet cycles: Bonding strength and micro–properties

The interface properties between lightweight aggregate concrete (LWAC) and ordinary concrete (OC) have drawn significant research interest. However, its evolution during sulfate dry–wet cycles has yet to be elucidated. Therefore, the LWAC–OC composite specimens were subjected to 15 cycles of dry and wet cycles test, using 5 wt% sodium sulfate solution. The dry–wet cycling method consisted of complete immersion for 7 days, followed by natural drying for 8 days. Moreover, tests for splitting tensile, direct shear, scanning electron microscopy and microhardness were conducted on the LWAC–OC interfaces at varying numbers of dry and wet cycles. The results showed that the failure mode of specimens changed from mixed cohesive failure to interfacial bonding failure during sulfate dry–wet cycles. Direct shear and splitting tensile strength slightly increased and then markedly decreased as the number of dry–wet cycles increased. The ratio of direct shear strength to splitting tensile strength showed a distinct negative linear relationship with the number of sulfate dry–wet cycles. Moreover, when the number of dry–wet cycles increased, the porosity of interfacial transition zone first decreased and then increased. The mean value of the interfacial micro–hardness first increased and then decreased. Interfacial micro–properties correlated well with bonding strength throughout the process.

Enhancing alkaline resistance of concrete using alccofine and metakaolin in mineral admixtures of sustainable development

Addressing the need for sustainable construction materials that minimize environmental impact and reduce CO2 emissions, particularly in OPC compositions. Assessing alccofine and metakaolin in OPC compositions to determine their impact on concrete strength, durability, and microstructure in alkaline environments for sustainable material development. Experimental investigation involved incorporating alccofine and metakaolin into OPC concrete mixes, creating binary and ternary blended systems. Modified concrete specimens were subjected to various alkaline attacks using diluted solutions of magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), and sodium chloride (NaCl) both individually (5%) and in combination (2.5%), resulting in significant improvements in concrete strength and durability. The modified concrete exhibits enhanced resistance to alkaline attacks, reduced weight and compression strength loss, and superior performance in Base Durability Factor (BDF) and Base Attack Factor (BAF) compared to conventional specimens. Scanning electron microscopy (SEM) study of the altered concrete’s microstructure shows that it has a densely packed microstructure, which increases its load-bearing capability. Mineral admixtures aid pore clogging, leading to denser, more alkali-resistant concrete due to finer particles. Notably, Alccofine and metakaolin offer effective solutions for sustainable construction materials, aiding in the decrease of CO2 releases during cement production and addressing critical gaps in sustainable material development.

Hydrothermal vs. Electrochemical reduction of graphene oxide: A physico-chemical and quartz crystal microbalance study

Reduced Graphene Oxide possesses numerous interesting properties, making it one of the most studied materials today. By this way, applications in various fields, including fundamental research, can be found. Nevertheless, the complexity of reduced Graphene Oxide lies in its fabrication process which defines their properties. In this paper, two fabrication methods -electrochemical and hydrothermal reduction of graphene oxide - were compared using physico-chemical and electrogravimetric analysis. Our findings reveal significant morphological differences between the two methods, accompanied by different electrochemical behaviors, when tested in aqueous electrolyte (i.e. 0.5 M Na2SO4). Specifically, electrochemically reduced graphene oxide exclusively involves sodium (whether hydrated or not) in its charge compensation mechanism, whereas hydrothermally reduced graphene oxide also involves proton in sodium sulfate solution.

Experimental study on dynamic and static mechanical properties of polyvinyl alcohol fiber cement soil under salt freezing cycle

A universal testing machine and a 50 mm split Hopkinson pressure bar (SHPB) were used to conduct salt erosion and freeze-thaw (F-T) cycle coupling tests on cement soil specimens with 0.5% polyvinyl alcohol (PVA) fiber and without fiber in order to study the effects of salt solution and F-T cycles on the dynamic and static mechanical properties of cement soil. In four distinct solution settings (clear water, 9 g/L sodium sulphate solution, 9 g/L sodium chloride solution, and 9 g/L sodium sulphate and sodium chloride mixed solution). After F-T cycles, the cement soil specimens underwent the unconfined compressive strength (UCS) test, SHPB test, and SEM test. The findings indicate that as the number of F-T cycles increases, the dynamic and static mechanical properties of cement soil specimens decrease, and the rate of decline is rapid followed by slow. After five F-T cycles, the combined solution's unconfined compressive strength dropped to 15.91% (without fiber) and 29.41% (with fiber), respectively. After five F-T cycles, the dynamic compressive strength in sodium sulphate solution fell by 95.17% (without fiber) and 93.86% (with fiber). Fibers help to some degree by preventing salt erosion and F-T cycles. With more F-T cycles, the absorbed energy declines exponentially, and the order of the solutions' effects on the absorbed energy is: mixed sodium chloride and sodium sulphate solution > sodium chloride solution > sodium sulphate solution > clear water.