Sulfate Content Research Articles

Valorization of biomass bottom ash in alkali-activated GGBFS-fly ash: Impact of biomass bottom ash characteristic, silicate modulus and aluminum-anodizing waste

Growing production of green energy from biomass has led to a surge in biomass bottom ash (BBA) generation, often relegated to landfills due to high leachable heavy metal content. This study proposed solidifying BBA in alkali-activated granulated ground blast furnace slag (GGBFS) and class F fly ash (CFA) blended binders. Investigations into the influence of BBA content, fineness, silicate modulus of activators, and aluminum-anodizing waste (AAW) on solidification performance were conducted, focusing on reaction mechanisms, phase assemblages, mechanical properties and leaching behavior. Results indicate relatively low reactivity of BBA and high leachable chloride (Cl-), sulphate (SO42-), chromium (Cr), molybdenum (Mo), lead (Pb) and zinc (Zn) contents from BBA. Increased BBA substitution leads to strength deterioration, while ground biomass bottom ash (GBBA) improves the mechanical performance slightly. This improvement is attributed to the increased reactive aluminosilicate content and an enhanced packing system resulting from finer particles. However, GBBA induces an increased heavy metals leaching. Higher silicate modulus activators enhance mechanical properties and reduce the leaching of Mo and Cl-, while lower silicate modulus activator accelerates the reaction process, promoting the formation of hydrotalcite-like phases and reducing the leaching of Cr and SO42-. Incorporating 0.5 wt% aluminum-anodizing waste improves immobilization efficiency of toxic ions, but further increases in dosage lead to higher leaching due to weakened mechanical performance. Overall, hybrid binders with 10 wt% G/BBA exhibit desirable mechanical properties, along with sufficient immobilization of leachable heavy metals, enabling their use as potential construction materials.

Prediction of the Properties of Vibro-Centrifuged Variatropic Concrete in Aggressive Environments Using Machine Learning Methods

In recent years, one of the most promising areas in modern concrete science and the technology of reinforced concrete structures is the technology of vibro-centrifugation of concrete, which makes it possible to obtain reinforced concrete elements with a variatropic structure. However, this area is poorly studied and there is a serious deficiency in both scientific and practical terms, expressed in the absence of a systematic knowledge of the life cycle management processes of vibro-centrifuged variatropic concrete. Artificial intelligence methods are seen as one of the most promising methods for improving the process of managing the life cycle of such concrete in reinforced concrete structures. The purpose of the study is to develop and compare machine learning algorithms based on ridge regression, decision tree and extreme gradient boosting (XGBoost) for predicting the compressive strength of vibro-centrifuged variatropic concrete using a database of experimental values obtained under laboratory conditions. As a result of laboratory tests, a dataset of 664 samples was generated, describing the influence of aggressive environmental factors (freezing–thawing, chloride content, sulfate content and number of wetting–drying cycles) on the final strength characteristics of concrete. The use of analytical techniques to extract additional knowledge from data contributed to improving the resulting predictive properties of machine learning models. As a result, the average absolute percentage error (MAPE) for the best XGBoost algorithm was 2.72%, mean absolute error (MAE) = 1.134627, mean squared error (MSE) = 4.801390, root-mean-square error (RMSE) = 2.191208 and R2 = 0.93, which allows to conclude that it is possible to use “smart” algorithms to improve the life cycle management process of vibro-centrifuged variatropic concrete, by reducing the time required for the compressive strength assessment of new structures.

Characterization and modulation of the pro-inflammatory effects of immune cells in the canine intervertebral disk.

Intervertebral disk (IVD) degeneration affects both humans and canines and is a major cause of low back pain (LBP). Mast cell (MC) and macrophage (MØ) infiltration has been identified in the pathogenesis of IVD degeneration (IVDD) in the human and rodent model but remains understudied in the canine. MC degranulation in the IVD leads to a pro-inflammatory cascade and activates protease activated receptor 2 (PAR2) on IVD cells. The objectives of the present study are to: (1) highlight the pathophysiological changes observed in the degenerate canine IVD, (2) further characterize the inflammatory effect of MCs co-cultured with canine nucleus pulposus (NP) cells, (3) evaluate the effect of construct stiffness on NP and MCs, and (4) identify potential therapeutics to mitigate pathologic changes in the IVD microenvironment. Canine IVD tissue was isolated from healthy autopsy research dogs (beagle) and pet dogs undergoing laminectomy for IVD herniation. Morphology, protein content, and inflammatory markers were assessed. NP cells isolated from healthy autopsy (Mongrel hounds) tissue were co-cultured with canine MCs within agarose constructs and treated with cromolyn sodium (CS) and PAR2 antagonist (PAR2A). Gene expression, sulfated glycosaminoglycan content, and stiffness of constructs were assessed. CD 31+ blood vessels, mast cell tryptase, and macrophage CD 163+ were increased in the degenerate surgical canine tissue compared to healthy autopsy. Pro-inflammatory genes were upregulated when canine NP cells were co-cultured with MCs and the stiffer microenvironment enhanced these effects. Treatment with CS and PAR2 inhibitors mediated key pro-inflammatory markers in canine NP cells. There is increased MC, MØs, and vascular ingrowth in the degenerate canine IVD tissue, similar to observations in the clinical population with IVDD and LBP. MCs co-cultured with canine NP cells drive inflammation, and CS and PAR2A are potential therapeutics that may mitigate the pathophysiology of IVDD in vitro.

Exogenous additive ferric sulfate regulates sulfur-oxidizing bacteria in cow manure composting to promote carbon fixation.

Enhancing carbon fixation in the composting process was of great significance in the era of massive generation of organic solid waste. In this study, the experimental results showed that the contents of dissolved organic matter (DOM) in the experimental group (CT) were 37.58% higher than those in the control group (CK). The CO2 emission peaked on day 5, and the value of CK was 1.34 times that of CT. Significant differences were observed between the contents of sulfur fractions in CT and CK. This phenomenon may be due to the suppression of sulfur-reducing gene expression in CT. On day 51 of composting, the abundance of sulfur-oxidizing bacteria (SOB) Rhodobacter (5.33%), Rhodovulum (14.76%), and Thioclava (23.83%) in CT was higher than that in CK. In summary, the composting fermentation regulated by Fe2(SO4)3 increased the sulfate content, enhanced the expression of sulfur-oxidizing genes and SOB, and ultimately promoted carbon sequestration during composting.

Raman spectral quantification of Li2SO4, Na2SO4, K2SO4 and Cs2SO4 at 25 to 250 °C and its potential implications for the determination of sulfate contents in natural fluid inclusions

The quantitative study of the sulfate content in natural fluid inclusions (FIs) will help our understanding of the processes of metal transport and related mineralization. The sulfate-rich FIs typically contain several types of sulfates with diverse cations such as Na+, K+, and so on. In order to get the sulfates contents in natural FIs, in situ Raman spectral quantitative calibration method is used to calibrate the Li2SO4, Na2SO4, K2SO4 and Cs2SO4 solutions at temperatures ranging from 25 °C to 250 °C in our study. The results show that the A(SO42−)/A(H2O) ratio increases linearly with increasing mSO42− in sulfate solutions containing single cation of Li, Na, K or Cs at the set temperatures, where A is Raman peak area and m is molality (mol/kg H2O), and a negative linear relationship exists between k (quantitative calibration coefficient) and temperature for sulfate solutions with specific cations up to 250 °C. Meanwhile, the slopes and the intercepts of the k-T correlation curves are obviously different among sulfate solutions with different cations, and the coefficients k of these sulfate solutions at certain temperature decrease with the increase of atomic number of the cation, in accordance with the following order: Li+ > Na+ > K+ > Cs+. As Na+ and K+ are the main cations in the natural sulfate-bearing FIs, the quantification of the multi-cation (Na ± K ± Li) sulfate solutions was evaluated by using the Raman quantitative calibration curves of Li2SO4, Na2SO4, K2SO4 and Cs2SO4 separately, the errors exist due to the use of calibration curves with different cations; the average concentration errors derived from the use of Na2SO4 or K2SO4 Raman quantitative calibration curves are within about 5 %, while those from the use of Li2SO4 or Cs2SO4 Raman quantitative calibration curves are within about 15 %. Therefore, the acceptable errors suggest that the calibration curves of individual sulfates can be applied to the determination of sulfate content of natural sulfate-bearing FIs.

Ion transport mechanism and diffusion model establishment in recycled aggregate concrete subjected to magnesium, sulfate, and chloride attack

Recycled aggregate concrete (RAC), which is used in Northwest China, is inevitably subjected to various aggressive environments. However, the aggressive ions of chloride, sulfate, and magnesium and the original ions of calcium and hydroxide in RAC under the combined action of magnesium-sulfate-chloride attack and dry–wet (D&W) cycles have received little attention in previous studies. Therefore, in this study, the content of aggressive and original ions in exposed RAC was quantified, and the influence of the replacement ratio of supplementary cementitious materials (SCMs) on diffusion was investigated. Results showed that the contents of chloride, sulfate, and magnesium in exposed RAC increased with an increase in the replacement ratio of silica fume (SF) and metakaolin (MK). In contrast, the contents decreased with the increase in the replacement ratio of granulated blast furnace slag (GBFS). At the same exposure time and depth, the content of RAC with ternary cementitious materials from the highest to the lowest was in the order of cement–fly ash –SF, cement–fly ash–MK, and cement–fly ash–GBFS. Visual appearance, relative compressive strength, and the diffusion coefficient exhibited a similar change law. An exponential relationship was observed between the diffusion and time delay coefficients and the replacement ratio of SCMs, and the content of aggressive ions on the exposed surface decreased linearly with increasing exposure time. Diffusion models of aggressive ions were established to consider the multiple effects. Aggressive ion–original ion interaction influenced the mineral phases’ composition in the corrosive zone and led to a difference in the diffusion process and depth.

A comprehensive study of melt foaming in E‐glass batch‐to‐melt conversion process: Effects of sulfate content and chemistry of raw materials

AbstractControl of sulfate‐induced melt fining without excessive foaming is one of the critical steps in maintaining the stability of E‐glass fiber manufacturing processes. Besides, the efficiency of combustion or energy utilization is directly affected by the extent of the melt‐foaming. A fundamental understanding of key factors affecting melt foaming under the simulated oxy‐fuel combustion environment will enable commercial E‐glass fiber production to optimize both batch chemistry and operation conditions to achieve adequate furnace control. In this study, six types of E‐glass batches with the same target glass composition were prepared by using four different CaO sources; calcined limes with different SO3 contents, limestone, limestone with sodium sulfate, and a mixture of limestone and calcined lime. All batch samples were examined by HTMOS‐EGA system (high temperature melting observation system with evolved gas analysis). HTMOS enables monitoring batch‐to‐melt conversation steps by using a high‐resolution camera and EGA detects the evolved reaction gaseous, such as CO, CO2, and SO2 via an Fourier transform infrared (FTIR) gas analyzer. Gases of water vapor, N2, and O2 were introduced accordingly into the fused quartz crucible to simulate similar oxy‐fuel atmosphere of the furnace operation. This study aimed to investigate the effects of different SO3 contents in batches and different raw material chemistries on the foam formation in E‐glass melts under the oxy‐fuel atmosphere. Different raw materials were characterized by mineralogical analysis, chemical analysis, particle size distribution, chemical oxygen demanding (COD) level, and Brunauer–Emmett–Teller (BET) analysis. Although some of the batches contained the same SO3 content, different foam formations resulted from the effect of the batch chemistry. Our detailed HTMOS‐EGA investigations show that not only SO3 content in the batch affects foam formation in E‐glass melts, but also raw material chemistry and particle size have strong effects on the melt foaming in E‐glass batch melting, especially for those of ingredients having hydroxide phases and/or finer particles with higher specific areas.

A Comparison of Different Protocols for the Extraction of Microbial DNA Inhabiting Synthetic Mars Simulant Soil.

Compared with typical Earth soil, Martian soil and Mars simulant soils have distinct properties, including pH > 8.0 and high contents of silicates, iron-rich minerals, sulfates, and metal oxides. This unique soil matrix poses a major challenge for extracting microbial DNA. In particular, mineral adsorption and the generation of destructive hydroxyl radicals through cationic redox cycling may interfere with DNA extraction. This study evaluated different protocols for extracting microbial DNA from Mars Global Simulant (MGS-1), a Mars simulant soil. Two commercial kits were tested: the FastDNA SPIN Kit for soil ("MP kit") and the DNeasy PowerSoil Pro Kit ("PowerSoil kit"). MGS-1 was incubated with living soil for five weeks, and DNA was extracted from aliquots using the kits. After extraction, the DNA was quantified with a NanoDrop spectrophotometer and used as the template for 16S rRNA gene amplicon sequencing and qPCR. The MP kit was the most efficient, yielding approximately four times more DNA than the PowerSoil kit. DNA extracted using the MP kit with 0.5 g soil resulted in 28,642-37,805 16S rRNA gene sequence reads and 30,380-42,070 16S rRNA gene copies, whereas the 16S rRNA gene could not be amplified from DNA extracted using the PowerSoil kit. We suggest that the FastDNA SPIN Kit is the best option for studying microbial communities in Mars simulant soils.

Surface properties of schwertmannite with different sulfate contents and its effect on Cr(VI) adsorption

Sulfate is a critical component of schwertmannite. However, the sulfate content of schwertmannite decreases with the increase in AMD-polluted river pH value, and its impact on the surface properties and Cr(VI) adsorption of schwertmannite remains unclear. To address this issue, different methods, including batch adsorption, N2 physisorption, scanning electron microscopy (SEM), potentiometric titration, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) in combination with two-dimensional correlation spectroscopy (2D-COS) analysis, and surface complexation modeling (SCM) were employed. Our results showed that sulfate existed as both non-protonated bidentate-binuclear complexes and non-protonated outer-sphere complexes in schwertmannite. The surface morphology and particle size of schwertmannite were unaffected by the sulfate content. However, a decrease in sulfate content resulted in a drop in the negative charge on the surface of schwertmannite, which is conducive to particle aggregation. An increase in pH, on the other hand, raised the negative charge and encouraged the dispersion of the particles. And then, reducing the sulfate content of schwertmannite led to a decrease in acid-base buffer and Cr(VI) adsorption capacity of schwertmannite. The adsorption process of Cr(VI) by schwertmannite can be divided into two stages. In the first stage, Cr(VI) was adsorbed primarily through anion exchange reactions with the sulfate; however, the contribution of surface complexation gradually increased as the initial sulfate content decreased because of a reduced likelihood of anion exchange and an increase in the specific surface area of schwertmannite. Additionally, the behavior of sulfate and Cr(VI) in this stage could be predicted based on the initial sulfate content of schwertmannite. In the second stage, surface complexation with hydroxyl sites became the predominant mechanism of adsorption, which still exhibited great potential at higher Cr(VI) concentrations. Finally, the aforementioned hypothesis was used to establish a CD-MUSIC model, and the fitting results demonstrated that the density and Cr(VI) adsorption capacity of the sulfate site dropped as the sulfate content decreased, while the hydroxyl site was less impacted. The findings have provided insights into further understanding the properties of schwertmannite and its adsorption of Cr(VI).

PVC plasticized membranes modified with Fe3O4 nanoparticles for potentiometric sensing of sulfate

Potentiometric sensing is one of the most wide spread platforms for analysis of aqueous solutions. The development of potentiometric sensors for hydrophilic anions such as sulfate, phosphate and bicarbonate is a challenging problem, since their high hydration energy results in a low affinity for non-polar polymer membranes – a standard material for potentiometric sensor production.In this study we propose a new type of polymeric sensor membranes for ion-selective sensors with pronounced selectivity to hydrophilic anions. The membranes are based on inorganic Fe3O4 nanoparticles (NP) embedded into plasticized poly(vinyl chloride). Six different formulations of membranes with various combinations of Fe3O4 nanoparticles and other membrane-active components were synthesized and characterized with a wide range of physico-chemical methods. Contact angle measurements, FTIR spectra, SEM and AFM imaging, magnetization hysteresis curves, ZFC/FC studies were performed. The obtained results proved the formation of nanocomposites and demonstrated a structure with “cavities” in membranes with embedded nanoparticles. Potentiometric sensitivity and selectivity of the developed sensors in aqueous solutions of SO42−, HPO42−, HCO3−, H2PO4−, NO3− and Cl−anions were studied. The developed sensors showed high sensitivity to sulfate ion (-22 mV/dec in the concentration range from 10−5 to 10−3 M) and low sensitivity to the typical interfering anions – chloride and nitrate (-14 mV/dec). The optimized sensor membrane composition demonstrated sulfate selectivity higher than that of commercially available ion-selective sensor formulations. The novel sensors were tested for quantification of SO42− in real samples of natural mineral water and the obtained content of sulfate was in a good agreement with the reference data (relative error < 3 %)

Influences of alumina type and sulfate content on hydration and physicochemical changes in Portland–limestone cement

This study explored the influence of alumina type and gypsum content on the hydration, mechanical properties, and chemical changes of Portland–limestone cement (PLC) using isothermal calorimetry, inductively coupled plasma-optical emission spectroscopy (ICP-OES), ionic chromatography (IC), compressive strength testing, X-ray diffraction (XRD), 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR) spectroscopy, and mercury intrusion porosimetry (MIP) testing. The addition of alumina shortened the induction period, accelerated the acceleration period, and increased the mechanical strength of the PLC pastes with 3 and 7 wt% gypsum. The acceleration effect and strength enhancement were not distinct in the PLC pastes with less gypsum (0.1 wt%). The addition of γ-alumina led to the greatest accelerating effect and strength improvement in the PLC pastes with 3 and 7 wt% gypsum, and the compressive strength achieved was comparable to those of pure Ordinary Portland cement (OPC) pastes without limestone. The addition of γ-alumina induced the rapid dissolution of gypsum and consumption of sulfate ions. The chemical change affected by the addition of alumina varied greatly depending on the gypsum content, and trends in AFt and AFm formation in the PLC pastes with different gypsum contents were confirmed. Finally, pore size refinement was observed through the addition of alumina to PLC pastes with 3 and 7 wt% gypsum.

Sulphate-temperature-time interactions and their influence on rheological characteristics of cemented paste backfill

Cement paste backfill (CPB) can provide social and economic benefits such as treating mine waste, preventing surface settlement, providing a safe working platform in underground mines and improving ore recovery. Rheological properties (including yield stress and viscosity) are key factors influencing the ability of CPB to be successfully transported into specified mine stopes. However, no study has been carried out to comprehensively examine the rheological properties of CPB under the combined effects of sulfate, temperature and time. This study was therefore carried out to evaluate the yield stress and viscosity of CPB samples with different sulfate contents (0 ppm, 5000 ppm, 15,000 ppm and 25,000 ppm), exposed to different temperatures (2 °C, 20 °C and 35 °C) and subjected to different curing or transport times (0, 20 min., 1 h and 2 h). Additional measurements, such as TG/DTG, pH, zeta potential and EC monitoring, were also carried out. It was found that CPB viscosity increased significantly with the simultaneous increase in sulfate, time and temperature, and that yield stress also increased, but at a relatively limited rate. There was competition between the yield stress-reducing factor (e.g. sulfate) and the increasing factors (temperature, time). Higher temperatures had a compensatory or counterbalancing effect on the reduction in CPB yield stress caused by the addition of sulfate. It was also found that the significant increase in viscosity was due to the combined effect of a greater number of ettringite crystals generated by the addition of sulfate and a greater number of hydration products produced by higher temperature and/or longer time. The results of this research will be useful for the efficient design of a long-distance transport system for CPB in mines located in permafrost and/or warm regions, in deep mines as well as for CPB containing sulfate.

Eco-friendly fiberboards with low formaldehyde content and enhanced mechanical properties produced with activated soybean protein isolate modified urea-formaldehyde resin

Urea-formaldehyde (UF) resin is one of the most widely used resin adhesive for wood-based panels. The main concern of UF resin bonded wood-based panels is formaldehyde emission and poor water resistance. In this study, activated soybean protein isolate (SPI) was used to modify UF resin for the production of eco-friendly fiberboard panels. The effects of different activated SPI on the properties of UF resins and the resin bonded medium-density fiberboard (MDF) panels were investigated. The free formaldehyde content of the urea-activated SPI modified UF resin was only 0.13 %. Approximately 27.8 % lower than that of the unmodified UF resin. The resin bonded MDF panel with a density of 760 kg/m3 shows a modulus of rupture (MOR) and modulus of elasticity (MOE) of 45.73 MPa and 4005 MPa, which is increased by 25 % and 15 % compared to the unmodified UF resin group. The internal bonding strength (IB) reaches 0.71 MPa, which is about 15 % higher than that of the unmodified UF resin group. The tested 24-hour thickness swelling (24 h TS) of the modified UF resin group is only 8.1 %. The tested formaldehyde content of the sodium dodecyl sulfate (SDS)-activated SPI modified UF resin bonded MDF panel is only 4.8 mg/100 g, which is 20 % lower than that of the control UF resin group. The activated SPI modified UF resin shows great improvement in bonding strength and lower formaldehyde content for MDF panels as compared to the pure UF resin. The chemical groups, crystalline properties, and thermal stability of the pure and the modified UF resins were characterized via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric (TG) analysis. It is confirmed that the activated SPI modified UF resin has similar chemical structure, higher ratio of crystalline regions, and slightly lower thermal stability with compared to the pure UF resin. This study proposes a practical and applicable solution for the utilization of eco-friendly UF resin in wood-based panel production.

Исследование стойкости бетонов анизотропной и вариатропной структур к попеременному увлажнению и высушиванию

Objective: study of the influence of a number of operational factors on the final resistance of varitropic concrete to alternating cycles of wetting and drying. This work identifies the problem of concrete resistance to cyclic wetting and drying, and also formulates a scientific deficiency consisting in the inadequacy of the existing knowledge base regarding the relationship between the type of concrete structure and its resistance to cyclic influences, including alternating wetting and drying. Methods: test samples were made using three different technologies: vibration, centrifugation, and vibration centrifugation. The following main characteristics were studied: compressive strength, tensile strength in bending, water resistance. Experimental studies have shown that concretes with a varitropic structure (centrifugation and vibration centrifugation) have higher resistance to alternating wetting and drying than concretes with an anisotropic structure (vibration). After 500 cycles of wetting-drying and a high degree of aggressiveness of the saturated aqueous environment in terms of the content of sulfate, chloride and nitrate salts, the loss of compressive and tensile strength in bending for vibrated concrete was 28.7 and 32.7 respectively, for centrifuged concrete — 26.2 and 27.8%, respectively, and for vibrocentrifuged ones — 19.6 and 21.4 %, respectively. Results: Vibrocentrifuged varitropic concretes showed the greatest resistance to the effects of alternating wetting in an aqueous environment with varying degrees of aggressiveness and drying compared to centrifuged varitropic and vibrated anisotropic concretes.

From risk study to field evidence: an unprecedented and isolated case of delayed ettringite formation in Brazil

This paper describes the first ever reported case in Brazil where delayed ettringite formation (DEF) has been confirmed as the sole cause of deterioration in field concrete. Still under construction and less than 2 years old, numerous cracks were observed in the foundation structures of a building located in Recife, a city known for its history of alkali–aggregate reaction (AAR) cases. In addition to a field survey of cracks, microstructural analyses, tests for residual expansion and compressive strength, a review of the structural design, determination of sulfate content in the groundwater and simplified thermal analysis were carried out. The results confirmed that DEF was the sole cause of the damage present in cast-in-place concrete structures, with no evidence of AAR or any other deterioration process. This work corroborates previously published studies on the high risk of the occurrence of DEF in the region, demonstrating the urgent need for a preventive technical standard in the country, considering the chemical composition of cements and prior thermal analyses to adopt possible preventive measures to limit the maximum internal temperature of concrete.

An integrated process incorporating pH-controlled biomineralization and sulfate bioreduction to facilitate recovery of schwertmannite and sulfated polysaccharides from acid mine drainage

Acid mine drainage (AMD) poses an environmental challenge to the global mining industry. However, it is also a potential source of iron and sulfate for recovery. In this work, we proposed an integrated process of pH-controlled biomineralization of iron and biological sulfate reduction to facilitate the concurrent purification of AMD and selective recovery of iron and sulfate as valuable products. Compared with the biomineralization controlling pH at 2.8, the modified biomineralization controlling pH at 3.2 improved the iron precipitation efficiency from 9.7 % to 95.3 %, leading to a 53–fold increase in pure-grade schwertmannite Fe8O8(OH)4.08(SO4)1.96 production in AMD. This improvement may be related to the relatively low Gibbs free energy value of the Fe3+ mineralization reaction at pH 3.2. The solution equilibrium calculation using Visual MINTEQ indicated that keeping the system pH at an appropriate level is crucial for the spontaneous and effective biomineralization of Fe to schwertmannite at room temperature. The specific pH required for Fe biomineralization is slightly affected by the content of metal cations (e.g., Al3+, Ca2+, Mg2+, Cu2+, and Mn2+) and oxoanion (AsO33−/AsO43−) in AMD but greatly affected by sulfate content (mM) (pH = 0.149 ln c(SO42−) + 2.551). For the effluent resulting from AMD biomineralization, sulfate reduction at pH 5.0 removed residual Zn2+ (99.9 %), Mn2+ (97 %), Cu2+ (100 %), and sulfate (87.1 %) while recovering sulfated polysaccharides with antiangiogenic bioactivity (as confirmed by the chorioallantoic membrane tests). The pilot-scale continuous flow operation experiments demonstrated that this integrated method has the potential to recover valuable iron/sulfate products from AMD.

Effect of high sulfate content on viscosity of recovery boiler molten smelt

A systematic study was conducted to examine the effect of high sulfate content on the freezing temperature of molten smelt and how this may contribute to the formation of viscous jellyroll smelt in recovery boilers. The results show that even for recovery boilers with a smelt reduction as low as 70%, the sulfate content in smelt has no or little effect on smelt freezing temperature, and hence, on molten smelt fluidity. The perceived adverse effect of high sulfate content on smelt fluidity and on jellyroll smelt formation comes from the high sulfate content in deposits that have fallen from the upper furnace. Fallen deposits may or may not form jellyroll smelt, depending on whether or not they can melt and be well-mixed with molten smelt by the time they reach the smelt spouts. It is not the high sulfate content in smelt resulting from the low smelt reduction efficiency that makes molten smelt viscous and forms jellyroll smelt, but rather, it is the incomplete melting of fallen deposits that results in one of the proposed mechanisms for jellyroll smelt formation.

Effects of Ultrafine Fly Ash against Sulphate Reaction in Concrete Structures.

In this study, Afşin Elbistan C-type fly ash (FA) was used, which protects against the sulphate reaction that damages concrete. The detrimental effects of post-reaction decrease with increasing fly ash fineness. The study used 10%, 30%, and 50% weight substitutes of cement. The fly ash was ground in a ball mill for 0, 10, 20, 30, 45, and 60 min, and Blaine fineness values of 1555, 1632, 2347, 2589, 2766, and 3433 cm2/g were obtained, respectively. The effect of the samples on the sulphate resistance was investigated by exposing the samples to 5% or 10% added sulphate solutions, and the compressive strength and ultrasonic pulse velocity of the concrete were tested. The compressive strength values obtained decreased with the increase in sulphate content, and the increase in the grinding time and the amount of substituted FA increased the compressive strength values. It was observed that weight loss increased with increasing sulphate content and decreased with the addition of FA with a high Blaine fineness. It was determined that as the Blaine fineness value increased, the sulphate content, FA substitution amount, and ultrasonic pulse speed decreased. This study was carried out to determine the effects of fly ash used at different fineness and replacement ratios on the performance and strength of concrete after exposure to external influences such as sulphate. The use of fly ash instead of cement will reduce the use of waste materials and natural resources and prevent environmental pollution. The cost of cement and concrete will be reduced.

Optimization of alginate extraction conditions from the brown seaweed Dictyota mertensii using a central composite design

This work extracts alginate from Dictyota mertensii, a brown macroalga found on the north coast of northeastern Brazil. A Central Composite Design (CCD) using Response Surface Methodology (RSM) was used to optimize the process of extracting the alginate present in the brown alga Dictyota mertensii, considering the factors of time, temperature, and concentration Na2CO3. Extraction yield (η), sulfate content, intrinsic viscosity ([η]), viscosimetric molar mass (Mv), color parameters (a*, b* e L*), M/G ratio and inhibitory concentration IC50 are model response variables. The Dictyota mertensii algae has its chemical composition expressed. Response surfaces are plotted from the variables studied, a quadratic model was predicted, the influence of factors is analyzed, and response variables are subjected to analysis of variance (ANOVA) and F-test at 95 % confidence. The predicted conditions are experimentally validated. The antioxidant potential was evaluated at seven concentrations (0.2–5.0 mg/mL) based on the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging. The maximum extraction yield was 29.28±0.02 %, and sulfate content ranged from 3.50±0,00 % to 12.33±0.29 %. The maximum values of [η] and Mv were 5.84±0.06 dL/g and 278.00±2.66 kDa, respectively. The alginate showed a dark brown color and M/G ratio < 1, indicating that the extracted alginate provides rigid and compact gels, which allows its application in films, encapsulations, and protecting probiotics. The maximum antioxidant capacity and the IC50 were 54.93±0.27 % and 0.51±0.07 mg/mL, respectively, indicating the material obtained as a moderate natural antioxidant.

Reduced chondroitin sulfate content prevents diabetic neuropathy through transforming growth factor-β signaling suppression

Diabetic neuropathy (DN) is a major complication of diabetes mellitus. Chondroitin sulfate (CS) is one of the most important extracellular matrix components and is known to interact with various diffusible factors; however, its role in DN pathology has not been examined. Therefore, we generated CSGalNAc-T1 knockout (T1KO) mice, in which CS levels were reduced. We demonstrated that diabetic T1KO mice were much more resistant to DN than diabetic wild-type (WT) mice. We also found that interactions between pericytes and vascular endothelial cells were more stable in T1KO mice. Among the RNA-seq results, we focused on the transforming growth factor β signaling pathway and found that the phosphorylation of Smad2/3 was less upregulated in T1KO mice than in WT mice under hyperglycemic conditions. Taken together, a reduction in CS level attenuates DN progression, indicating that CS is an important factor in DN pathogenesis.