NaOH Alkaline Solution Research Articles

Fatigue analysis of ambient-cured geopolymer concrete for high-traffic pavements.

The building sector is growing at a rapid rate, leading to an increased demand for construction materials. Concrete made with Ordinary Portland Cement (OPC) has long been the preferred choice due to its excellent bonding properties and versatility as demanded by construction process. However, the manufacturing of Ordinary Portland Cement (OPC) leads to negative impacts on the environment, with the cement sector responsible for around 5-8% of global CO2 emissions. In addition, the manufacture of OPC necessitates significant amounts of natural raw materials and energy. Contrastingly, using geopolymers promises to save substantial amounts of energy and reduce CO2 emissions. This potential has sparked growing interest in the application of geopolymers within transportation infrastructure. For pavements, the workability requirement is less, and hence, geopolymer concrete (GPC) is a viable option, but fatigue-resistance of GPC is not seen reported in literatures. This article evaluates the properties of geopolymer concrete with low-calcium fly ash partially replaced with ground granular blast furnace slag (GGBS) with 8M NaOH alkaline solution and cured under ambient atmospheric conditions to evaluate its usage in pavements and develop an environmentally sustainable and durable GPC capable of withstanding heavy traffic. The study involves adjusting the pavement quality concrete (PQC) mix design; evaluating the mechanical characteristics, abrasion resistance, and shrinkage strain of the GPC; and analyzing its microstructure. Additionally, the study compares the fatigue life of GPC to that of PQC using various Weibull distribution approaches. The results showed that GPC4 (70% Fly ash and 30% GGBS) mix achieved best results at 28days, with a compressive strength of 45.68MPa, split tensile strength of 3.76MPa, and flexural strength of 4.62MPa. Also, shrinkage strains were nearly 31% lesser than PQC at 90days. In addition, developing GPC needs 27% lesser embodied energy than PQC. Fatigue analysis prove that ambient cured fly ash-GGBS based geopolymer concrete with 8M NaOH exhibits less stress development than PQC at medium loads, even though it is brittle. Thus, the study proves that it is suitable as a material for pavements to resist medium-loaded traffic-resisting pavements.

Compressed stabilised earth block synergistically valorising municipal solid waste incinerator bottom ash and sisal fiber: Strength, durability and life cycle analysis

Compressed stabilized earth blocks (CSEB) represent an eco-friendly substitute for traditional building materials, predominantly utilizing earth. Municipal Solid Waste Incineration Bottom Ash (MSWIBA) is a by-product of municipal waste treatment that can be creatively repurposed in construction projects. This research explores integrating MSWIBA as a substitute for Earth in CSEB production to conserve natural resources and repurpose waste, potentially reducing its landfill disposal. The sisal fibers (SF), often regarded as by-products of agricultural processes, offer an intriguing research material. The SF was treated with a 5 % NaOH alkaline solution to improve the CSEB bonding, increasing the flexural strength. The study aims to determine the optimal mix of stabilizers, in addition to a 10 % cement content, using various percentages of MSWIBA (10–40 % by weight of dry sand) and SF content (0.25–1 % by weight of dry soil). These blocks undergo comprehensive tests to determine their strength and durability. Wet and dry compression, flexural tests and indirect tensile tests were used to assess strength qualities, while wetting-drying cycles and acid exposure were used to determine durability. MSWIBA replaces 20 % sand in CSEB satisfying the strength. However, exceeding this amount increases void content and lowers strength, emphasizing the importance of balanced proportions for best performance. The 20 % MSWIBA and 0.75 % SF combination enhanced the compressive strength by 6.45 MPa, flexural strength by 0.92 MPa and water absorption by less than 18 %. The durability test displayed increases in compressive strength of 14.7 % and flexural strength of 93.48 % and optimized water absorption rate. Furthermore, microstructural analysis has been performed on CSEBs and the results highlight the importance of balanced cement and SF proportions for structural integrity. Life Cycle Analysis (LCA) investigation shows that construction costs using CSEB are 12.24 % higher than those with FCBs. Additionally, the study suggests that CSEB with MSWIBA and SF will be an environmentally sustainable construction material, considering factors such as energy usage, Global Warming Potential, and other environmental considerations

Effects of Na-salt solutions on the biomass pyrolysis and CO2-assisted gasification behavior

This study aims to explore the effects of different Na-salt solutions on the behavior of biomass pyrolysis and gasification. The same molar number of Na was introduced via the impregnation method. The distinction was that pine wood impregnated with neutral NaCl and Na2SO4 solutions was the Na in physical adsorption form, whereas the alkaline Na2CO3, CH3COONa, and NaOH solutions resulted in both carboxylate form and physical adsorption form. Thermogravimetric analysis results showed that impregnating alkaline Na solution was more potent than the neutral Na solution in reducing the thermal stability of pine wood structures. Results of pyrolysis and CO2-assisted gasification indicated that samples impregnated with the alkaline Na solutions obtained lower CO and higher CO2 evolution than that from the neutral Na solution during pyrolysis. The Na in carboxylate form was more difficult to volatilize, and formed more Na-containing active catalytic structures, resulting in biochar that provided higher reactivity in gasification. However, different Na solutions on the biochar's gasification reactivity showed the order of NaCl-loaded sample < CH3COONa-loaded sample ∼ NaOH-loaded sample < Na2SO4-loaded sample < Na2CO3-loaded sample. This can be attributed to the combined effects of Na-containing active catalytic structures, along with the active surface salt complex formed by molten Na species and biochar. As for the overall energy efficiency of pine wood impregnated with different Na solutions, gasification of Na2CO3-loaded sample provided the highest maximum overall energy efficiency (49.2 %). The results presented here provide useful insights for practical application of using syngas for electricity generation.

Facile fabrication of next-generation sustainable brick and mortar through geopolymerization of construction debris

Waste from construction and demolition (also known as CDW) is one of the most harmful environmental issues. This study's primary goal is to produce new mortar and brick materials from recycled concrete powder (RCP) and recycled brick powder (RBP), two of the most popular CDW. Geopolymeric mortar and brick samples were produced by passing RCP and RBP through sieve No. 50 (with sand filler if necessary) and combining them with an alkaline solution made of water glass (WG) and NaOH. In this study, the mixture was then cured for three days at 80 °C in an oven. The effects of filler, RBP amount, WG amount, and the concentration of NaOH alkaline solution on the samples’ strength were examined. Additionally, XRF and SEM/XRD tests were performed to verify the materials' composition and microstructure. The mechanical strength of the samples showed an increase with the increase of RCP values, so the brick sample with filler showed the highest compressive strength, measuring 59.53 MPa. The study's samples exhibited strong mechanical properties. Additionally, all of the bricks' water absorption fell within the standard range. In summary, according to different standards, both waste concrete and waste brick can be used to produce geopolymer materials especially bricks for construction and paving purposes.

Aging of Adhesives of External Reinforcement Systems of Building Structures. Part 2. Structural Studies

The structural changes of cross-linked epoxy polymer adhesive for external reinforcement systems of building structures after exposure to artificial climatic factors have been studied by the method of IR Fourier spectroscopy. The aim of the study was to determine the significance of influencing factors (UV radiation, temperature, water and alkaline environment) for the development of a method for accelerated assessment of the durability of selected systems. The objectives of the study were to identify the mechanism of aging and obtain differential spectra of aged and initial samples. The processes of destruction of samples of cross-linked epoxy polymer of amine curing under the influence of artificial climatic factors of aging have been studied by IR spectroscopy. It has been established that the most significant factors influencing structural changes in the polymer are UV radiation and an alkaline solution of NaOH and KOH.

Fabrication and Mechanical Evaluation of Eco-Friendly Geopolymeric Mortars Derived from Ignimbrite and Demolition Waste from the Construction Industry in Peru

Ignimbrite rock is a volcanic material located in the Arequipa region (Peru), and for centuries, it has been used as a construction material, giving a characteristic light pastel, white to pink color to the city of Arequipa, with white being the most common. In the present study, the potential use of three types of Arequipa raw materials (ignimbrite rock powder, calcined clay powder, and demolition mortar powder) as the main source of new binders or the manufacture of environmentally friendly mortars, without the addition of ordinary Portland cement (OPC) is discussed. In this work, an in-depth characterization of the materials used was carried out. The proposed fabrication route for geopolymeric materials was considered for the manufacture of binders and mortars using an alkaline solution of NaOH with values between 12 and 18 molar, as a trigger for the geopolymerization process. Geopolymeric mortars were obtained by adding a controlled amount of fine sand to the previously prepared mixture of binder raw material and an alkaline solution. Conventional OPC and geopolymeric mortars manufactured under the same conditions were mechanically evaluated by uniaxial compression tests at a constant compression rate of 0.05 mm/min and under normal conditions of temperature and atmosphere, where the most optimal values were obtained for 15 molar alkaline solutions of ignimbrite without the addition of aggregates, with values of compressive strength of 42 MPa and a modulus elastic of 30 GPa. The results revealed a significant increase in the maximum strength and modulus of elasticity values when the volumetric fractions of OPC are completely replaced with geopolymeric binders in the study conditions of this work, demonstrating the enormous potential of the ignimbrite rock and construction waste studied, as raw material of alternative mortar binders without the addition of OPC. With this work, the ignimbrite rock, of great value in the region and also found in other areas of the Earth’s geography, was characterized and valued, in addition to the calcined clay and demolition mortar of the region.

The Study of the Glass Fiber Surface Treatment Effect on the Base Strength Characteristics of the Composite Material

This article examines the impact of surface treatment of glass fibers on the strength of a composite material with an unsaturated polyester polymer matrix reinforced with glass fibers. The strength tests conducted include tensile, bending, and impact strength tests, as well as weight loss measurements. The research was conducted in two stages: in the first stage, the time was kept constant while the fibers were treated with varying concentrations of an alkaline NaOH solution; in the second stage, the concentration was fixed and the variable parameter was the treatment time. The results of the study indicate that surface treatment of glass fibers significantly improves their adhesion to the matrix materials, resulting in improved strength test results for the composite samples. The impact resistance, bending resistance, and tensile strength values all increased compared to the reference samples. However, certain changes in the individual parameters of fiber processing led to a slight decrease in tensile strength when it fell below the reference values. Additionally, it was observed that as the concentration of the solution and treatment time increased, the weight of the fibers decreased.

Development of Spectrophotometric Method for The Determination of Mesalazine as Pure Form and in Tablets

This method involves development of a highly sensitive spectrophotometric procedure to estimate mesalazine as pure substance and in the tablets. This particular procedure was focused on the diazotization of mesalazine with an excess quantity of sodium nitrite (NaNO2) in an acid medium using HCl solution to produce a corresponding diazonium compound which reacts with 8-hydroxyquinoline reagent in an alkaline solution of NaOH to yield read-orange azo dye which is soluble in water and showed maximum absorption peak at the wavelength of 500 nm against the blank solution. The calibration graph was linear and compatible to Beer's law over the concentration range from 0.25 to 12.5 μg/ml with an exceptional determination coefficient (R2= 0.9994) and apparent molar absorptivity 2.88 × 104 L.mol-1cm-1. The limits of detection (LOD) and quantitation (LOQ) were premeditated and found to be 0.2023 and 0.6524 μg/ml, correspondingly. A relative error percent (accuracy) and the relative standard deviation (RSD%) was also calculated and found to be in the range -3.84% - 2.70%, and 0.17% - 1.94%, correspondingly. No interferences were observed from other ingredients that may be exist in the tablets. The stoichiometry of the resulting azo dye has been examined and the experimental results revealed that the mole ratio of mesalazine to 8-hydroxyquinoline is 1:1. The advised procedure was successfully applied for the determination of mesalazine in its pharmaceutical form (tablets).

Selective dissolution and kinetics of leaching zinc from lime treated electric arc furnace dust by alkaline media

The EAF steelmaking process generates 10–20 kg of dust per ton of steel, containing 15–30% zinc, making it a valuable secondary zinc resource. In this work, selective dissolution and kinetics of leaching zinc from lime (CaO) treated EAF dust using NaOH, KOH, and LiOH alkaline solutions were investigated. By reacting with CaO, insoluble ZnFe2O4 in EAF dust is converted to soluble ZnO and stable Ca2Fe2O5. Optimal zinc leaching conditions were achieved after 2 h at 70 °C and a S/L ratio of 1/300 (mg/ml). Among the alkaline solutions used, the zinc leaching rate was highest using 2 M NaOH solution at 99% zinc recovery. On the other hand, thermodynamic solubility calculations indicate that KOH is a better candidate for practical extraction as it can dissolve 6–8 times more zinc than NaOH. The prevailing rate-controlling mechanisms when using NaOH, KOH, and LiOH solutions were found to be the same. From 25 °C to 50 °C, chemical reaction was primarily rate-limiting. In contrast, from 50 °C to 70 °C, the controlling step later shifted to a product layer diffusion control – implying that higher temperatures and finer particle size are vital to achieving high zinc leaching rates. Finally, a solid by-product containing Ca2Fe2O5 and CaO only, which can be recycled in the iron and steelmaking process, was obtained via calcination at 500 °C.

Cu2O films without impurities fabricated via the mist spin spray technique using a mixed alkaline solution for flexible glucose sensors

The mist spin spray (MSS) technique was used to fabricate crystalline Cu2O thin films on seed-free glass substrates and a flexible indium tin oxide (ITO)/polyethylene terephthalate (PET) substrate. In this technique, a solution containing Cu+ ions and a mixed alkaline solution of NH3 and NaOH were separately atomized by ultrasonication to generate mists. These mists were sprayed with a nitrogen carrier gas onto the substrates heated to 90°C on a rotating table under atmospheric pressure. This led to nanoscale-thick, dense, and high-purity Cu2O films with good adhesion to the substrates. The NaOH concentrations of the initial solution affected the film morphology, and the specimen films prepared with a NaOH concentration higher than 0.2 mol/L exhibited rough surfaces, whereas those prepared with a NaOH concentration of 0.1 mol/L and lower had dense and flat surfaces. The crystallized Cu2O film with nano-sized structure was fabricated directly on the ITO/PET substrate at 90°C to produce a flexible glucose sensor and exhibited good validity with a sensitivity of 561.6 µA cm−2 per concentration of mmol L−1.

Synthesis of titanate-based lepidocrocite nanostructures by reacting TiC, TiB2, and TiN with NaOH or KOH at 95 °C under ambient pressure

With great optical, catalytic and electrical characteristics, titania (TiO2) and TiO2-based titanates present many potential applications in chemical and photocatalysis, solar cells, electrochemical water splitting, chemical/gas sensing, among others. Herein, we show that lepidocrocite-based titanates of low-dimensional nanotubes, NTs, nanowires, NWs, and nanoribbons, NRs, can be synthesized near ambient conditions through a bottom-up approach starting with titanium carbide, TiC, nitride, TiN, or boride, TiB2. Successful reactions were conducted at 95 °C in alkaline solutions of sodium hydroxide, NaOH, or potassium hydroxide, KOH, thereby producing NTs/NRs, and NWs, respectively. Such nanostructures self-assemble into fibrous structures that, in turn, form free flowing, mesoporous particles. The production of these materials from common binary Ti precursors under such relatively mild reaction conditions highlights a breakthrough in the efficient and scalable production of low-dimensional titanate materials. We synthesized and characterized these materials under various conditions and believe they present significant potential where similar titanate species have succeeded.

Effect of electrode composition over performance of dissimilar stainless-steel welds

In this study, the effect of composition of the electrodes ER347 and ER310 is investigated on the microstructure, mechanical and corrosion properties of dissimilar weld between AISI 430 and AISI 304L; made using gas metal arc welding. The mechanical properties were investigated by uniaxial tensile tests whereas corrosion properties were analyzed via polarization tests in H2SO4 (acidic) and NaOH (alkaline) solutions with varying concentrations − 0.1 M, 0.3 M and 0.5 M. It has been found that electrode composition does not change the hardness of the weldments; however it has affected the hardness of heat affected zones (HAZ). Hardness of HAZ near AISI 304L was higher, when the weldment was made using ER 347 due to presence of finer grains in HAZ. In contrast to this, hardness of HAZ near AISI 430 was higher, when the weldment was made using ER 310 due to carbide formation at grain boundaries. Unlike hardness, strength of welded specimens was approximately 54% and 14% lower than AISI 304L and AISI 430 respectively due to the presence of HAZ zones. Width of HAZ zones has also decided the extent of decrease in elongation values, showing the lowest elongation for the welded specimen made using ER347. The higher carbon content can lead to wider HAZ zone, thus not only results in degradation of mechanical properties but also decreases the passivation ability of the welds. At very low pH level (0.44), passive layer can get ruptured and Ni wt. % plays a detrimental role over corrosion resistance of the welds.

Experimental Investigation on Strengthening of Geo-Polymer Concrete Slab with Bubble Technology

The bubble deck technology developed in Europe makes use of high-viscosity concave polyethene spheres to replace the ineffective concrete in the centre of the slab, therefore dwindling the dead weight and adding the effects of the bottom. This system is used in the concrete floor system. Concrete is good in contraction and hence is more useful in the contraction region than in the pressure region. The reduction in concrete can be done by replacing the pressure zone concrete. An experiment has been carried out to find out the effectiveness of plastic bubbles by replacing concrete in the pressure zone of Ordinary Portland Cement Concrete (OPCC) and Geo-Polymer Concrete (GPC) slab. Constituents named are cement, sand, and coarse aggregate for OPCC and for GPC cement is fully replaced with 70% fly ash, 15% GGBS and 15% glass powder. NaOH(12M) alkaline solution is added instead of water for GPC. In this design, M45 concrete blend is used to prepare both OPCC and GPC slabs. The trial blend is tested for compressive strength in 7 days and 28 days. A flexure test is done for 7 days and 28 days of curing of the beams. The procedure is repeated for beam samples with bubble mesh and bubble mesh along with shear underpinning. Relative analysis of the OPCC and GPC slabs is done to observe the chance reduction in tone-weight and cost-effectiveness. Analysis of the geste of the GPC beam in comparison with that of the OPCC beam is also carried out.

Effect of Portland Cement on Mechanical and Durability Properties of Geopolymer Concrete at Ambient Temperature

Environmental concerns have prompted researchers to focus on the development of alternative building materials like geopolymer concrete. However, their implementation requires curing beyond 60°C, which limits their application on building sites. This study aims to design a geopolymer concrete at room temperature (30 ± 5°C) in a laboratory in Burkina Faso using a metakaolin-based geopolymer binder activated by an alkaline solution of NaOH and natural aggregates. Portland cement type CEM I 42.5 was used by mass substitution (0 to 25%) of metakaolin to promote curing at ambient temperature. The samples were cured for 7 to 28 days and characterized for physical, mechanical, and durability properties. The results showed that the incorporation of 0 to 20% cement significantly improved the compressive strength from 9.9 to 30.5 MPa and the tensile strength from 1.2 to 2.2 MPa. However, Portland cement has various effects on the durability of geopolymer concrete. It reduces the porosity accessible by water from 15 to 13% and decreases the resistance to acid attack by increasing the mass loss from 2 to 7%. This confirms that common concrete types C20/25 or C25/30 can be casted using geopolymer concrete on the sites in Burkina Faso once their durability is confirmed. Doi: 10.28991/CEJ-2023-09-07-04 Full Text: PDF

Synthesis, characterization, and gas sensing application of crumpled CdO sheets prepared in alkaline media

CdO crumpled sheets have been synthesized by microwave-assisted irradiation in alkaline solutions of NH4OH and NaOH, respectively, and in presence of a surfactant. The morphology of CdO samples have been investigated using Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). X-ray diffraction analysis (XRD) has been used to determine the cadmium oxy/hydroxide crystalline phases of CdO formed during synthesis and successive annealing at 300 °C. Crystallite sizes of CdO nanostructures obtained from NH4OH and NaOH reagent-assisted synthesis are 44 nm and 57 nm, respectively. The specific surface area (SSA), lattice parameter, X-ray density, dislocation density, macrostrain, and texture coefficient (TC), have also been determined. The optical characteristics of CdO samples were investigated using UV reflectance (DRS) and K-M plot. NO2 gas detecting capabilities of CdO nanostructures have been investigated at low working temperature of 150 °C. When compared to its NaOH counterpart, the CdO sample prepared by NH4OH reagent-assisted synthesis demonstrated a superior sensitivity to NO2, being demonstrated even at the low concentration of 0.14 ppm, with excellent selectivity.

Effect of enzymatic hydrolysis and nitrogen on Saccharomyces cerevisiae β-glucan production from Manihot utilissima and Maranta arunadinacea waste

This experiment utilised cassava (Manihot utillissima) and arrowroot (Maranta arunadinacea) wastes as the medium of propagation of Saccharomyces cerevisiae to produce β-glucan. The amyloglucosidase hydrolysed the waste, followed by fermentation in the nitrogenous medium by S. cerevisiae. The β-glucan pellet was extracted using 2% NaOH alkaline solution at 90°C for 5 hours, followed by a series of centrifugation processes. The highest glucose concentration from hydrolysis resulted from adding 57.5 mg amyloglucosidase enzyme for arrowroot waste with 95.93% conversion and 50 mg enzyme for cassava waste with 64.70% conversion. The highest amount was obtained for producing S. cerevisiae by adding 4.75 g peptone to all samples. The optimum number of cells was obtained at 1.61 x 108 colonies at t = 48 hours for arrowroot waste and 8.55 x 107 colonies at t = 48 hours for cassava waste. For β-glucan production, the highest number was obtained by using 3.99 g of peptone for cassava waste with a yield of 1.20% and by using 4.75 g of peptone for arrowroot waste with a yield of 1.23%. For β-glucan pellet, the highest number was 1.77 g L-1 (0.18 % b/v) from cassava waste medium and 1.91 g L-1 (0.19% b/v) from arrowroot waste. Mutant cells in the Yeast Extract–Peptone–Glycerol (YPG) medium produced 6.56 g L-1 (0.66% b/v) β-glucan pellet, while wild-type cells in the similar medium produced 1.84 g L-1 (0.18% b/v).

Effect of Solution pH on the Synthesis of Two-Dimensional Molybdenum–Tungsten Sulfide Nanostructures

Compared with binary transition-metal dichalcogenides (TMDCs), ternary alloys or heterojunctions have more abundant properties. The spin-coating method has been widely used in the synthesis of TMDCs. However, there is still a lack of research on the effect of acidity and alkalinity of precursor solutions on the epitaxial growth of TMDCs. It is found that the MoxW1–xS2 ternary alloy is formed when an acidic solution of (NH4)2MoO4 and (NH4)2WO4 is used for spin-coating, while the MoS2/WS2 lateral heterojunction with a sharp boundary is formed when an alkaline solution of Na2MoO4, Na2WO4, and NaOH is used. According to the calculation, under alkaline conditions, sulfur atoms preferentially bind to MoO42– due to lower energy and finally form a lateral heterojunction. However, under acidic and neutral conditions, MoO42– and WO42– in the precursor solution will undergo a complex reaction, respectively. Because there is no significant difference in the binding energy of the reaction between the sulfur atom and two complexes, a ternary alloy will be formed. The controllable synthesis of different types of TMDCs can be achieved by regulating acidity and alkalinity.

Effect of surface treatment on the technological properties of coconut fiber-reinforced plant polyurethane composites.

Polymeric composites reinforced with plant fibers have numerous advantages, such as low cost, high raw material availability and good physical, mechanical and thermal properties. Thus, in recent years, they have been studied as thermal insulation substitutes for synthetic polymers in buildings. The aim of this study was to evaluate the technological properties of castor oil-based polyurethane composites reinforced with coconut fibers treated with hot water, alkaline solutions of NaOH and Ca(OH)2 and corona discharge and without surface treatment as materials for the thermal insulation of buildings. The composites were produced by the hand lay-up method followed by compression; 10% by weight coconut fibers were used to replace the synthetic polymer. Specimens were produced, and physical, mechanical, thermal and microstructural tests were performed. The results showed that the polymer had a thermal conductivity of 0.016 W/(mK), while the composites produced with fibers treated with NaOH had a thermal conductivity of 0.028 W/(mK); therefore, these polymers are considered insulating materials (k = 0.01 to 1.0 W/(mK)). Thus, the composites produced with coconut fibers can be considered as lighter, less expensive and environmentally friendly alternatives to synthetic polymers.

Highly alkali-stable polyolefin-based anion exchange membrane enabled by N-cyclic quaternary ammoniums for alkaline fuel cells

Polyolefin-based anion exchange membranes (AEMs) have shown great promise in AEM fuel cells thanks to the excellent membrane-forming ability and chemical inertness of all-carbon backbones. Here, we attached alkali-stable N-cyclic cations, dimethyl piperidinium (DMP), or 6-azonia-spiro [5.5] undecane (ASU), onto soluble polyolefin backbones to produce highly alkali-stable AEMs. The synthetic procedure included Ziegler-Natta polymerization, azidation, and Cu(I)-mediated azide-alkyne cycloaddition reaction. The as-prepared PBFB-DMP or PBFB-ASU copolymers were blended with poly (2,2′-(1,4-naphthalene)-5,5′-bibenzimidazole) (NPBI) polymer to achieve mechanical robust and flexible membranes. Polyolefin-based AEMs and their blend AEMs containing DMP or ASU cations showed superior alkali-resistance with over 91.9% of initial conductivities remaining and no obvious chemical degradation after 95 days (2280 h) of immersion in 1 M NaOH alkaline solution at 80 °C as proved by NMR spectroscopy. The blend AEM bearing DMP cations (B–PBFB-DMP) with an ion exchange capacity of 1.54 mmol g−1 displayed a higher hydroxide conductivity of 65.1 mS cm−1 at 80 °C than the analogue with ASU cations. In a single H2/O2 fuel cell, the integration of the B–PBFB-DMP membrane into membrane electrode assemblies resulted in a peak power density of 402 mW cm−2 under optimized anode humidification. Moreover, the short-term durability of the cell under reduced anode humidification was carried out at 200 mA cm−2 for 6 h, and post-cell analysis confirmed that no chemical degradation took place for the blend membrane.

Effect of super-absorbent polymer on swelling pressure of compacted bentonite infiltrated by alkaline solutions

The application of bentonite in geological disposal of radioactive waste is still under evaluation, especially concerning the decreased swelling pressure of pure bentonite exposed to alkaline groundwater. In this paper, in order to improve the chemical resistance of bentonite to alkaline solutions, super-absorbent polymer (SAP), a hydrophilic polymer with much higher swelling ability than that of bentonite, was dry-blended with Gaomiaozi (GMZ) bentonite and compacted into blocks of different dry densities. Swelling pressure of the bentonite-SAP composites infiltrated with deionized water, NaOH and KOH alkaline solutions were tested, accompanied with scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and X-ray diffractometer (XRD) tests conducted on the selected specimens. Results showed that, for the specimens hydrated by deionized water, the swelling pressure increased with increasing SAP content, dry density and concentration of NaOH solutions. With increasing concentration of KOH solutions, however, the swelling pressure decreased obviously and tended to undergo a slow long-term degradation. Results of SEM, MIP and XRD indicate that the SAP hydrogels swell extensively to clog the inter-aggregate pores and coat the aggregates (for high density specimens) or montmorillonite stacks (for low density specimens), while do not insert into the interlayer spaces. The swelling pressure was therefore mainly contributed by the crystalline swelling of montmorillonite and the osmotic swelling of SAP. The SAP chains could be associated with the montmorillonite crystallites, protecting them from chemical attack and thus improving the chemical resistance of bentonite to alkaline solutions.