NaOH Solution Research Articles

Reinforced Concrete Columns with Treated Recycled Concrete Aggregate: An Experimental and Theoretical Study

Six Reinforced Concrete (RC) columns composed of Treated Recycled Concrete Aggregate (TRCA) and Natural Aggregate (NA) were subjected to experimental and theoretical analyses to ascertain their axial compressive behavior. The method of soaking recyclable aggregate in a NAOH solution was then employed to treat it. The TRCA was subjected to replacement ratios of 20%, 40%, 60%, 80%, and 100% relative to the total weight of NA. The dimensions of the column were 700 mm, 150 mm, and 150 mm, respectively. The column was reinforced with steel of varying diameters. The transverse reinforcement was 6 mm in diameter, whereas the longitudinal reinforcement was 8 mm in diameter. To examine the axial compressive behavior of the columns, the final load values obtained from the static tests were revealed. The measured axial capacity of the columns was then compared with the theoretical values derived from the ACI codes. The incorporation of TRCA contents was observed to enhance the columns' axial capacity, as evidenced by the experimental results. However, the computed theoretical values were found to be more conservative than the experimental observations. This suggests that there is no risk involved in using TRCA and NA-TRCA columns in construction.

Synthesis and performance of cross-linked poly(aryl ether nitrile) anion exchange membranes with dense cations and flexible side-chain structures for water electrolysis

Anion exchange membranes (AEMs) are the core components in anion exchange membrane water electrolysis (AEMWE), which play crucial role and affect the performance of AEMWE. In this work, a series of cross-linked poly(aryl ether nitrile) anion exchange membranes (CPAEN-dDQA-x) with dense cations and flexible side-chain structures are synthesized. By introducing multiple modification elements into the polymer structure simultaneously, the ion conductivity, dimensional stability, and alkali resistance stability of the prepared AEMs are effectively improved and balanced. The representative CPAEN-dDQA-0.25 showed water absorption of only 27.6 %, swelling rate of 11.2 %, and conductivity of 115.37 mS/cm at 80°C. The IEC and conductivity retention value of CPAEN-dDQA-0.25 after in 2 M NaOH solution at 80°C for 480 h were up to 86.2 % and 82 %, respectively. Meanwhile, the current density of the water electrolysis cell based on CPAEN-dDQA-0.25 is up to 477.0 mA/cm2 in 1 M KOH and 2.2 V, and its voltage don’t has significant change after 480 h of operation at a constant current density of 500 mA/cm2.

Multifunctional superhydrophobic sugarcane bagasse capable of efficiently separating oil-water mixtures and degrading MB

Biodegradable and low-cost superhydrophobic absorption materials are still urgently required for the removal of organic compounds from sewage. In this study, sugarcane bagasse (SCB), an abundant and readily available byproduct from sugarcane industries, was used as substrate to fabricate the superhydrophobic adsorbent through a facile dip-coating technique. Firstly, β-FeOOH particles were in-situ grown on the SCB surface, which was further decorated with SiO2 particles. Next, the modified SCB were coated with benzoxazine based on cardanol and dodecylamine (CD) followed by a thermal curing to obtain a superhydrophobic SCB (PC-D/β-FeOOH@SiO2/SCB) with a water contact angle (WCA) of 154°. PC-D/β-FeOOH@SiO2/SCB not only exhibited excellent oil absorption capacities in the range of 11.8 to 22.6 g/g for various organic solvents and oils, but also could successfully separate immiscible oil-water mixtures and emulsions with a separation efficiency of over 99.1 %. After 30 cycles of use, the absorption capacity of the modified SCB only displayed a slight decrease and its separation efficiencies for immiscible oil-water mixture, water-in-oil and oil-in-water emulsions are all more than 99.2 %, meanwhile, all these repeatedly used SCB still maintained a superhydrophobicity, demonstrating an outstanding reusability. Moreover, the WCA of PC-D/β-FeOOH@SiO2/SCB was still higher than 150o after 48 h of immersion in HCl, NaOH and NaCl solutions, exhibiting a satisfactory chemical stability. Besides, the prepared SCB also possessed a high photocatalytic degradation activity to methylene blue. Therefore, this work not only provides a sustainable and cheap superhydrophobic absorbent for wastewater treatment, but also presents a route for the better utilization of SCB.

Electrochemical behavior and microstructure of diffusion welding of zirconium alloy and super duplex stainless steel

In this study, the effect of welding temperature on interface microstructure, mechanical properties, and electrochemical behavior of diffusion welded joints (DWJs) of zirconium alloy (ZrA, Zr702 grade) and super duplex stainless steel (2205 duplex stainless steel grade) were investigated. Alloys were welded in a vacuum atmosphere at four different temperatures (800, 850, 900, and 925 °C) for 75min under 4MPa compressive pressure. The optical, scanning electron microscopy, electron probe micro-analyzer, and X-ray diffraction techniques were used to characterize the interfacial microstructure of the DWJs. Layers of intermetallics were formed along the welded interface at 850 °C and above welding temperatures. At 850 °C, a single reaction layer (phase mixture of ZrFe2+ZrCr2) was observed; however, bilayers (ZrFe2+ZrCr2 and Fe2Zr+FeZr3 phase mixtures), and triple layers (ZrFe2+ZrCr2, Fe2Zr+FeZr3, and β-Zr+FeZr3 phase mixtures) were observed at the welded interface of the joints processed at 900 and 925 °C, respectively. Width of the reaction layer (phase mixtures) increases with an increase in the welding temperature. The DWJs processed at 900 °C reach the maximum joint strength of ~312MPa along with ~6.4% ductility. For corrosion analysis, studies of the base alloys and DWJs in 0.1mol/L HCl and 0.1mol/L NaOH solutions separately using electrochemical techniques, such as open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization were undertaken.

Experimental analysis on mechanical properties of sea sand geopolymer recycled aggregate concrete

Traditional silicate concrete has the problem of high CO2 emissions, in the context of the large-scale use of portland concrete, aggregate resources are increasingly scarce, which poses a non-negligible threat to the natural environment. Therefore, to cope with the influence of traditional silicate concrete on the natural environment, a new type of sea sand geopolymer recycle aggregate concrete (SGRAC) was prepared by replacing river sand with sea sand and using recycled aggregate instead of natural aggregate. In this study, a total of 120 test blocks were designed. Firstly, the mechanical properties of geoplymer recycle aggregate concrete (GRAC) and SGRAC under different slag substitution rates were analyzed from the perspective of compressive strength and microstructure. In addition, the mechanical properties of SGRAC under different slag substitution rates and NaOH solution concentrations were further studied. Finally, the strength conversion formula of SGRAC is established.The results show that the compressive strength of SGRAC is 7.24 % higher than that of GRAC, and the activation degree of the two is consistent under different dosage. The influence of slag substitution rate and NaOH solution concentration on the mechanical properties of SGRAC is different. The correlation coefficient of slag substitution rate is lower, and its comprehensive mechanical properties are the best at 10 mol/L-60 %. This study lays a theoretical foundation and experimental basis for the subsequent research and application of SGRAC, and the technology helps to reduce CO2 emissions during construction engineering and promotes the sustainable development of the natural environment on which human beings depend.

Prescription versus over-the-counter venotonics: HPLC-DAD and static digestive model simulation comparison.

Venotonics are a class of therapeutically active molecules that have vaso-protective effects. They are used to alleviate venous diseases and disorders, particularly venous insufficiency. We compared the composition of prescription versus over-the-counter (OTC) venotonics using high-performance liquid chromatography with UV detection (HPLC-DAD) and simulating their digestion using a static digestive model. From each drug, five tablets were weighed. A homogenate was prepared, and 25 mg of crushed homogenized tablets were weighed into 25 ml volumetric flasks. Dissolved in MeOH and added two drops of saturated NaOH solution. The samples were filtered into vials (Teflon, 0.45 μm) and used for analysis. An Ultimate 3000 HPLC system (Thermo Fisher Scientific, Waltham, MA, USA) consisting of a quaternization pump, autosampler, column thermostat and DAD (UV/VIS detector) was used. The composition of the mobile phase proceeded in a linear gradient from 30% methanol and 70% phosphoric acid (0.15%) in water at time t=0 min. to 80% methanol and 20% phosphoric acid (0.15%) at time t=15 min., at a constant mobile phase flow rate of 1.2 mL/min. Detection was performed using a DAD detector in the 190-450 nm wavelength range. The content of monitored flavonoids was calculated from peaks at a wavelength of 277 nm, in which both flavonoids have their absorption maxima. The static digestive model was used to simulate the digestive phase from the oral cavity to the corresponding intestinal phase. The content of diosmin and hesperidin (mg per table) for a prescription drug: Detralex: 480 mg, 26 mg. The content of diosmin and hesperidin (mg per tablet) for OTC drugs: Venostop: 502 mg, 48 mg, Diosminol: 520 mg, 50 mg, Devenal: 496 mg, 49 mg, Diohes: 493 mg, 46 mg. Digestion did not affect the solubility of all tested drugs. The active substances could not be determined in the non-alkalized sample. After alkalization, part of the insoluble matter was visibly dissolved and converted to a yellow flavonoid complex. Neither diosmin nor hesperidin could be identified afterwards. Our experimental results show that the contents of both listed active substances, diosmin and hesperidin, met the declared amounts in all tested medicaments. Digestion simulation showed identical behaviour in prescription and OTC venotonics. The active substances could not be determined in the non-alkalized sample. Digestion did not affect the solubility of the tested drugs.

Effect of 60Co Irradiation on Boehmite Dissolution in Caustic Solutions.

Here, we examine how radiation impacts the dissolution behavior of boehmite by subjecting dry nanoparticles of different sizes to 60Co γ radiation and subsequently analyzing their dissolution behavior in caustic solutions as a function of temperature. The measured kinetics show that irradiation with an amount 228.24 Mrad significantly slows the dissolution rate, particularly for smaller sizes at lower temperatures. Specifically, the temperature-dependent dissolution rates of irradiated 20 nm boehmite versus pristine material in 3 M NaOH solutions were several times lower (e.g., rate constant of 0.026 vs 0.075 h-1 at 60 °C), with an apparent activation energy 40 kJ mol-1 higher. Although various imaging techniques and X-ray diffraction measurements consistently revealed no obvious differences between pristine and irradiated samples, after irradiation significant binding energy shifts were detected in the X-ray photoelectron Spectroscopy peaks of Al 2p and O 1s, and a change in their relative intensities indicated a lower O/Al ratio. This suggests that γ-irradiation may stabilize boehmite particle surfaces by driving their chemistry and structure toward more stable aluminum oxide forms. This finding may help explain slower dissolution rates of boehmite in nuclear waste and may be useful for the development of more robust predictive models and effective strategies for waste processing.

Charge Inversion by Monovalent Hydroxide Ions.

The interaction between the hydroxide ion (OH-) and the headgroup of a model cationic lipid (DPTAP, 1,2-dipalmitoyl-3-trimethylammonium-propane chloride) was investigated for different concentrations of NaOH solutions by using sum-frequency vibrational spectroscopy. The OH signal (3000-3700 cm-1) of the interfacial water under the Langmuir monolayer of DPTAP decreased with increasing NaOH concentration, due to screening of the surface charge by OH- counterions. Surprisingly, after reaching a minimum at 5 mM NaOH, the OH signal steadily increased. The phase-sensitive spectra revealed a sign change in the OH stretch band, indicating the overcompensation of the surface charge by OH-. By contrast, for a DODAB (didodecyldimethylammonium bromide) monolayer (a cationic surfactant without ester groups), the OH stretch signal decreased monotonically with NaOH addition. This charge inversion behavior is driven by the specific interaction between the ester moiety of DPTAP and the OH- that overcomes the Coulomb repulsion between the adsorbed ions.

Field-Based cDNA-Biosensor for Accurate Detection of Canine Distemper Virus in Tissue Samples.

Canine distemper, a viral disease with a global impact on various animals including dogs, foxes, wolves, lions, and leopards, requires early diagnosis for effective treatment and outbreak control. Common laboratory methods, such as enzyme-linked immunosorbent assay, polymerase chain reaction, and viral isolation, face challenges such as extended turnaround times, high costs, and the expertise required. This study has developed a field-based biosensor for detecting the canine distemper virus (CDV), utilising a screen-printed carbon electrode (SPCE) and a computer-assisted portable potentiostat. A 30-mer oligonucleotide capture probe, designed using Primer3 Plus software version 3.3.0, detected hybridisation with the CDV complementary strand through electrochemical analysis via differential pulsed voltammetry. The developed biosensor exhibited good linearity in quantifying the target analyte concentration (0.1 to 12.8µM), with a detection limit of 0.05µM, indicating high sensitivity. Specificity tests using complementary and non-complementary sequences confirmed the biosensor's accuracy. The electrode can be reused up to eight times with a residual capacity of 93.72 ± 5.45% after regeneration using a 50mM NaOH solution. The developed biosensor was also used to detect CDV in biological samples after RNA extraction and amplification. Results from the biosensor aligned with those from reverse transcriptase polymerase chain reaction (RT-PCR) findings, showing 100% agreement. These findings support the potential development of a field-deployable portable device for effectively diagnosing canine distemper in biological samples.

Engineered Mg-modified biochar-based sorbent for arsenic separation and pre-concentration

The utilization of biochar as a relatively efficient sorbent or stationary phase for the separation and preconcentration of a wide range of analytes represents an innovative approach in current sample pretreatment methods. Appropriate pre- and post-pyrolysis modification of the input precursor and pyrolysis product, respectively, allows targeted design of the physicochemical properties and sorption characteristics of the resulting sorbent. The present work deals with the preparation of pyrolysis materials based on unmodified cattail leaf biomass (BC) and its Mg-modified analogue (MgBC) by a slow pyrolysis process at 500 °C and a residence time of 1 h in a pyrolysis reactor. Physicochemical characterization of BC and MgBC carried out by pH, total C, N, surface size analysis (SSA), 13C NMR, SEM-EDX and XRD confirmed significant morphological and mineralogical differences between the prepared sorbents. By performing sorption experiments using a model anionic analyte (As) and application of Langmuir isotherm, we found that the predicted maximum sorption capacity of MgBC for As is 13.5-fold higher than that of BC. The sorption process of As by both sorbents is best described by the Sips adsorption isotherm (R2 ≥ 0.995) and a pseudo-nth order kinetic model (R2 ≥ 0.997). The optimum pH for As sorption by BC and MgBC sorbents is in the interval 5–6. The presence of competitive phosphate anions (equimolar concentration of 1:1) in the solution significantly reduces the sorption capacity of MgBC for As by 40% for BC by 70%. The presence of Cl- ions showed no significant effect on the sorption capacity of Bc and MgBC for As. Both sorbents were best recovered using 0.1 mol/L NaOH solution when the desorption efficiency for both sorbents was more than 95%. The MgBC sorbent showed 35% retention of As from the real sample in the model SPE column at a flow rate of 0.12 mL/s. Based on the obtained knowledge, it is evident that biochar-based sorbent prepared from Mg-modified precursor represents an effective sorbent for anionic forms of analytes and opens the possibility of its use also in preconcentration and separation techniques.

Corrosion Inhibition of PAAS/ZnO Complex Additive in Alkaline Al-Air Battery with SLM-Manufactured Anode

In order to improve the electrochemical activity and discharge performance of aluminum–air batteries and to reduce self-corrosion of the anode, an SLM-manufactured aluminum alloy was employed as the anode of the Al-air battery, and the influence of PAAS and ZnO inhibitors taken separately or together on the self-corrosion rate and discharge performance of the Al-air battery in a 4 M NaOH solution were investigated. The experimental result indicated that the effect of a composite corrosion inhibitor was stronger than that of a single corrosion inhibitor. The addition of the compound inhibitor not only promoted the activation of the anode but also formed a more stable composite protective film on the surface of the anode, which effectively slowed down the self-corrosion and improved the utilization rate of the anode. In NaOH/PAAS/ZnO electrolytes, the dissolution of the Al6061 alloy was mainly controlled by the diffusion of the electric charge in the corrosion products or the zinc salt deposition layer. Meanwhile, for the Al-air battery, the discharge voltage, specific capacity, and specific energy increased by 21.74%, 26.72%, and 54.20%, respectively. In addition, the inhibition mechanism of the composite corrosion inhibitor was also expounded. The excellent discharge performance was due to the addition of the composite corrosion inhibitor, which promoted the charge transfer of the anode reaction, improved the anode’s activity, and promoted the uniform corrosion of the anode. This study provides ideas for the application of aluminum–air batteries in the field of new energy.

Synergistic effect of alkali treatment and graphene filler on the mechanical characteristics of nettle fiber reinforced polymer composite

This study examines the synergistic effects of alkali treatment and the addition of graphene fillers to nettle fiber-reinforced polymer (NFRP) composites. NFRP composites were fabricated using NaOH-treated nettle fibers at concentrations of 3%, 5%, and 7%. Gr-NFRP composites were produced by varying the graphene content (1wt%, 2wt%, and 3wt%) in the epoxy resin that impregnated 5% NaOH-treated nettle fibers. The composites were prepared using a hand layup combined with a compression molding technique. A comprehensive analysis of the physical, mechanical, and wear properties of the treated NFRP composites was performed. FTIR analysis confirmed the effect of alkali surface treatment on the nettle fibers, whereas SEM was employed to examine the morphology of the fractured specimens. The experimental results revealed that a 5% NaOH solution was the optimal concentration for improving the characteristics of nettle fibers within the polymer composite. Moreover, the inclusion of 2wt% graphene noticeably enhanced the mechanical properties of the NFRP composites, resulting in increases of 21%, 17%, 65%, and 10% in the tensile strength, flexural strength, impact strength, and Shore D hardness, respectively. The wear resistance improved by 38%, and the water absorption decreased by 32%. SEM images revealed that a balanced contribution between fiber breakage and pullout was the primary failure mechanism in the Gr-NFRP composites. The NFRP composite containing 2wt% graphene demonstrated significant improvements in both mechanical and wear properties, along with reduced water absorption, making it a highly promising material for structural applications.

Biodegradable and reinforced membranes based on polycaprolactone and collagen for guided bone regeneration

Meshes or reinforcement for membranes for guided bone regeneration (GBR) are currently made of titanium with high specific mechanical strength, but it is not resorbable and second surgeries are needed. In this project, it was hypothesized that titanium can be replaced by polycaprolactone (PCL), a long-term biodegradable polymer, while applying a collagen coating to provide a cell barrier effect required in GBR. Different meshes with different patterns were designed and manufactured using 3D printing. Mechanical tests of the meshes were also performed to assess pattern influence on the mechanical properties and, later, a finite element model (FEM) was set to further understand the mechanical behavior of these meshes. In order to obtain the cell barrier effect, meshes were coated with collagen previously treated with NaOH solution using different molarities (1 and 5 M), assuring a uniform and adhesive collagen coating. The results showed that the patterns influenced the mechanical properties, and the model was validated with the experimental data. Contact angle and SEM analysis confirmed the extension of the alkaline treatment to enhance PCL meshes wettability, needed for the collagen coating. Meshes treated with 5 M NaOH for 24 hours at 37°C or room temperature achieved an adequate collagen adhesion that did not exhibit any toxic effect and was able to provide a fibroblast barrier up to 7 days. Finally, it was confirmed that thanks to the application of heat, the meshes can be shaped as required.

A Simple Preparation of Crosslinked, Highly Alkaline Diallyldimethylammonium Hydroxide Hydrogel Particles via Inverse Static Anion Exchange.

Highly alkaline hydrogels are gaining increasing attention in building materials research. Specifically, cationic alkaline hydrogels based on diallyldimethylammonium hydroxide (DADMAOH) as the monomer have been effectively used to seal water-bearing cracks or serve as coupling media for electrochemical chloride extraction. However, the residual halogen content and challenges in scaling up monomer production have hindered broader application. Attempts to use a commercially available cation-selective membrane for ion exchange achieved up to 90% chloride-to-hydroxide switch, but the approach proved ineffective due to significant monomer decomposition during the process. By contrast, neutral gels and gel particles can be readily prepared from diallyldimethylammonium chloride (DADMAC) in large quantities and with a wide range of compositions. It is demonstrated here that these neutral gel particles undergo inverse static anion exchange when suspended in NaOH solution, generating DADMAOH particles with residual halide contents of <0.3%, without the need for ion-selective or dialysis membranes. This corresponds to an up to 100-fold reduction in residual chloride content compared to particles produced directly from alkaline monomer solutions, thereby significantly enhancing the efficiency of hydroxide ion release. The swelling behaviour of the particles is primarily influenced by the initial monomer concentration, while conductivity remains largely unaffected, indicating that charge transport occurs mainly along the particle surface. Despite the pronounced increase in swelling with decreasing particle radii, the specific conductivity of 2.8 Ω-1 m-1 is still sufficient for their use as coupling media in concrete applications. In summary, the alkaline particles prepared via inverse static anion exchange meet all necessary requirements for building materials applications, offering a broader range of tuneable properties and greater ease of production compared to gels or particles derived from DADMAOH.

Electrochemical Analysis of Chloride Impacts on Passivation of Archaeological Iron in Desalination Solutions

ABSTRACT Based on the passivation of iron in alkaline solutions, aqueous alkaline treatment has been taken as an effective desalination technique to increase the stability of archaeological iron. However, chlorides may destroy the passivation of iron artifacts, causing damage to the treated artifacts during desalination. In this study, electrochemical and microstructure analyses were carried out in alkaline solutions with known chloride content, using archaeological iron and pre-corroded iron coupons with varying chloride levels within the rust layer. The study revealed that alkalinity ensures passivation even in the presence of chloride within the rust layer. However, the passivation weakens as the concentration of ‘free’ chloride ions in the alkaline solution increases due to their migration from the rust layer, leading to active corrosion. A chloride threshold value (CTV) of 355 ppm in 0.1 mol/L NaOH solution was established as a chloride level for the replacement of the alkaline solution. The determination of CTV based on electrochemical measurements is intended to guide the timely replacement of the desalination solutions, thereby preventing chloride-induced iron corrosion during desalination treatments.

Early Strength and Microscopic Mechanisms of Alkali-Metal Hydroxide-Activated Tungsten Tailings

The excellent mechanical properties of alkaline-activated tailings are essential for their increased use in building materials. While numerous studies have been conducted on activated tailings, the strength of alkaline-activated tungsten slag has not been extensively explored due to the low reactivity of silicon and aluminum in these tailings. This research delves into the early unconfined compressive strength of tungsten tailings activated by two alkali solutions (NaOH and KOH) at three different alkali concentrations (mass ratio of alkali to tungsten tailings), cured at 80 °C over periods of one day, three days, and seven days. The study finds significant improvements in the stability of tungsten tailings when forming (C, N)-A-S-H or (C, K)-A-S-H gels with both alkalis. Scanning Electron Microscope (SEM) results show that the morphology of the (C, N)-A-S-H gels transitions from membranous to flocculated and then to a three-dimensional network as the NaOH content and curing time increase. Conversely, the (C, K)-A-S-H gels primarily exhibit thin-film morphology with some three-dimensional network structures. The presence of flocculation and three-dimensional mesh in the gels fosters the formation of a robust skeletal structure, enhancing the strength of the samples. Furthermore, specimens treated with NaOH solution exhibit a higher gel content compared to those treated with KOH solution. These factors contribute to the superior efficacy of sodium hydroxide in enhancing the strength of tungsten tailings compared to potassium hydroxide. X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) results identify the formation of new phases such as pirssonite, buetschliite, potassium bicarbonate, and potassium carbonate. The first new phase results from the carbonization of excess NaOH solution, while the latter phases arise from the carbonization of excess KOH solution. These carbonization processes negatively impact the strength of the materials.

Mechanical characterization of natural fiber composites prepared with untreated and treated ficus religiosa root fibers

Surface modification techniques are used to modify the surface of the natural fibers in order to improve the surface characteristics; in turn other relevant significant properties of the fiber and its composites. In the present work, epoxy composites have been prepared with the untreated and treated F. religiosa root fiber samples at 5, 10, 15, 20, and 25 wt.% fiber loading. Mechanical properties such as tensile, flexural and impact strength of the prepared composite specimens have been tested as per the ASTM standards. From the results, it has been identified that the strength of the proposed composites increases with the increase in fiber loading, and the composites made up of 20 wt.% of the NaOH solution treated fiber sample exhibits better properties under mechanical characterization study. Alkalization filled the holes, cracks, and pores on the outer layer of fibers and significantly improved the surface roughness, which was reflected in the improvement of the proposed composites.

Uso de indicadores naturais ácido-base do contexto amazônico no ensino de equilíbrio químico

This work was objective to investigate new natural acid-base indicators with potential application in experimental activities and in the context of the acid-base equilibrium. For this purpose, alcoholic and aqueous extracts from Buriti (Mauritia flexuosa), Camu-camu (Myrciaria dubia) fruits were tested and Dão (Ziziphus mauritiana) and leaves of the vegetable species sara-tudo (Justicia acuminatissima). The extracts were tested in HCl and NaOH solutions for the pH range 1 to 14, and as a context for teaching Chemistry, they were applied to products with acidic and basic characteristics present in our daily lives. The extracts of the camu-camu fruit and the leaves of sara-tudo showed the best acid-base indicators due to the greater distinction between colors at different pH values. Therefore, these extracts of acid-base indicators were used by students of the second series of regular high school, in experimental classes that addressed the content of acid-base equilibrium, and highlighted the importance of contextualizing the teaching of chemistry with their daily lives.

Direct Recycling of LixNi0.5Mn0.3Co0.2O2 from Production Scrap and End‐Of‐Life Batteries, Using Solid‐State Relithiation

AbstractDirect recycling of Li‐ion battery cathodes offers a sustainable and potentially cost‐effective alternative to conventional methods, often involving complex chemical processes and significant material losses. This study focuses on the relithiation of cathode materials from quality control reject (QCR) and end‐of‐life (EoL) Li‐ion cells to restore their physical structure, morphology, and electrochemical performance. Two NMC532/graphite pouch cells from the same manufacturer were studied. QCR cells, stored under ambient conditions, experienced corrosion and degradation before recycling, while EoL cells were cycled to the end of life. The cells were disassembled, and the cathode materials were delaminated using NaOH solution, then relithiated with LiOH at 700 °C for 15 hours in the air. Extensive characterization analyzed elemental composition, structural properties, thermal stability, and particle size distribution. Results indicated that relithiation successfully restored lithium content and improved the structural ordering and morphology of the cathode materials. The electrochemical performance of the relithiated cathodes exhibited good stability over 100 charge‐discharge cycles. The relithiated QCR samples achieved a capacity of 155.57 mAh g−1, while EoL samples reached 152.53 mAh g−1, comparable to pristine materials. This study highlights relithiation's potential to extend the lifecycle of Li‐ion cathodes, contributing to a more sustainable circular economy for battery materials.

Impacts of thermal activation on lunar regolith simulant-based precursor and resulting geopolymer: Composition, structure, solubility, and reactivity

Alkali activation presents a promising method for the in situ resource utilization (ISRU) of lunar regolith. Enhancing the geopolymerization reactivity of lunar regolith simulant is key in minimizing alkali activator usage and improving raw material utilization. This study investigates the impact of thermal activation on precursor materials and the resultant geopolymers. Initially, the mineralogical composition and chemical structural changes in thermally activated samples were analyzed using XRD-Rietveld, XPS, and Raman spectroscopy. Subsequently, ICP-OES was employed to measure the solubility of various thermally activated samples in NaOH solution. Finally, the physicochemical composition and microstructure of the geopolymers were evaluated using SEM-EDS, FTIR, DSC, and compressive strength tests. The results show that thermal activation enhances precursor reactivity by increasing the non-bridging oxygen (NBO) content, reducing polymerization, and altering the binding energies of Si, Al, and O. Following thermal activation, the solubility of Si and Al in the NaOH solution was significantly improved. A more comprehensive thermal activation process produces geopolymers with improved compressive strength, a higher reaction degree, and a denser microstructure, and encourages the formation of Si-rich gels. Hence, treating precursor materials via thermal activation offers vast potential for creating lunar regolith geopolymer-based building materials with excellent properties.