NaOH Aq Research Articles

Na-Promoted Bimetallic Hydroxide Nanoparticles for Aerobic C-H Activation: Catalyst Design Principles and Insights into Reaction Mechanism.

A precious metal-free bimetallic FexMn1-x(OH)y hydroxide catalyst was developed that is capable of catalyzing aerobic C-H oxidation reactions at low temperatures, without the need for an initiator, relying sustainably on molecular oxygen. Through a systematic synthetic effort, we scanned a wide nanoparticle synthesis parameter space to lay out a detailed set of catalyst design principles unraveling how the Fe/Mn cation ratio, NaOH(aq) concentration used in the synthesis, catalyst washing procedures, extent of residual Na+ promoters on the catalyst surface, reaction temperature, and catalyst loading influence catalytic C-H activation performance as a function of the electronic, surface chemical, and crystal structure of FexMn1-x(OH)y bimetallic hydroxide nanostructures. Our comprehensive XRD, XPS, BET, ICP-MS, 1H NMR, and XANES structural/product characterization results as well as mechanistic kinetic isotope effect (KIE) studies provided the following valuable insights into the molecular level origins of the catalytic performance of the bimetallic FexMn1-x(OH)y hydroxide nanostructures: (i) catalytic reactivity is due to the coexistence and synergistic operation of Fe3+ and Mn3+ cationic sites (with minor contributions from Fe2+ and Mn2+ sites) on the catalyst surface, where in the absence of one of these synergistic sites (i.e., in the presence of monometallic hydroxides), catalytic activity almost entirely vanishes, (ii) residual Na+ species on the catalyst surface act as efficient electronic promoters by increasing the electron density on the Fe3+ and Mn3+ cationic sites, which in turn, presumably enhance the electrophilic adsorption of organic reactants and strengthen the interaction between molecular oxygen and the catalyst surface, (iii) in the fluorene oxidation reaction the step dictating the reaction rate likely involved the breaking of a C-H bond (kH/kD = 2.4), (iv) reactivity patterns of a variety of alkylarene substrates indicate that the C-H bond cleavage follows a stepwise PT-ET (proton transfer-electron transfer) pathway.

Preparation and Application of Decanoic Acid/Arginine Hydrogels to a Transdermal Formulation.

We prepared a supramolecular hydrogel composed of decanoic acid and arginine (C10/Arg gel) and evaluated its application to a transdermal formulation. C10/Arg gel adjusted to pH 7 with 1 M NaOH aq or 1 M HCl aq provided a translucent hydrogel with a lamellar liquid crystal structure in the concentration region of decanoic acid ≥12% and arginine ≤9%. Rheological measurements showed that C10/Arg gel is a viscoelastic material with both solid and liquid properties, with elasticity being dominant over viscosity in the low shear stress region. The skin permeability of hydrocortisone (HC) and indomethacin (IM) from C10/Arg gels was investigated in vitro using hairless mouse skin and compared to control formulation drug suspensions (IM or HC) in water. The cumulative permeation amount of HC and IM from the C10/Arg gel at 10 h after application was approximately 16 and 11 times higher than that of the control, respectively. On the other hand, the flux of IM decreased with increasing arginine concentration, likely due to the acid-base interaction between Arg and IM in C10/Arg gel. Adequate drug skin permeation enhancement by C10/Arg gel requires optimizing the gel composition for each specific drug.

Effects of Curing Temperature on Expansion of Concrete Due to ASR.

In the laboratory study of alkali-silica reaction (ASR), models attempt to predict the service life of concrete due to ASR by correlating the performance of concrete at high and low temperatures. However, the consequences of elevating temperature are not so encouraging. In this paper, the influence of temperature on the expansion of 2-graded concrete and 3-graded concrete caused by ASR was investigated by curing the concrete under different temperatures ranging from 40 °C to 80 °C. Increased temperature resulted in rapid expansion at the early stages, but the expansion rate of concrete prisms cured at the higher temperatures (70 °C and 80 °C) was slowed down at the later stages, and concrete prisms cured at 50 °C or 60 °C showed the highest expansions during the experimental period. The chemical analysis results of the pore solution expressed from the concrete show that the ASR expansion is significantly influenced by the [OH-]: the decrease in [OH-] leads to the retardation of the ASR expansion. The decrease in [OH-] is attributed to the consumption of OH- ions for the alkali-silica reaction and the decrease in activity of NaOH(aq) influenced by the temperature. For large cross-section specimens, the OH- within the concrete for alkali-silica reactions cannot be effectively compensated by the external alkali solution. In the accelerated test to evaluate ASR for large cross-section specimens, a curing temperature of less than 60 °C is suggested. This study provides critical insights into the temperature dependency of ASR expansion of concrete, offering a curing temperature range for developing predictive models of ASR expansion under varied environmental conditions.

Effects of promoter and dedoping process on electrorheological response of polyaniline-graft-chitosan copolymer

In this study, electrorheological (ER) properties of biodegradable and conducting polyaniline-graft-chitosan (PAni-g-CS) copolymer particles were investigated. For this purpose, PAni and PAni-g-CS particles were synthesized by using in situ oxidative radicalic polymerization method. At first, PAni and PAni-g-CS/silicone oil (SO) ER suspensions (15% V/V) were subjected to external electric field and they exhibited low ER activity. When the external electric field strengths ([Formula: see text] were increased, both the suspensions showed electrical breakdown. Therefore, virgin PAni and PAni-g-CS were first subjected to dedoping process by treating with 1.0 M NaOH(aq) and non-ionic surfactant Triton X-100 (T-X) surfactant to enhance the expected ER activity and prevent the electrical breakdown. But we observed that the addition of T-X as promoter had no significant effect on the ER activity. On the other hand, electric filed-induced viscosities of both the suspensions were observed to enhance after the dedoping (DD) process and electrical breakdown prohibited. After the DD process, DD PAni-g-CS/SO ER system exhibited the highest electric field-induced viscosity by reaching 400[Formula: see text]Pa[Formula: see text]⋅[Formula: see text]s at [Formula: see text][Formula: see text]kV/mm. The highest ER efficiency was also obtained for DD PAni-g-CS/SO system at 15% (V/V) as 79. Additionally, typical shear thinning non-Newtonian viscoelastic behavior was observed under externally applied E. The conduction model of DD PAni-g-CS/SO system was determined to well fit the conduction model by showing a slope of [Formula: see text] calculated from the E vb. yield stress graph. In conclusion, conducting and biodegradable-dedoped PAni-g-CS particles would be a good candidate for potential ER applications as dry-based ER materials having high colloidal stability of 76%.

Development of CuO/Cu4(OH)6SO4 Nanoparticle Mixtures to Optimize the H2S Adsorption.

In this paper, we report the H2S adsorption behavior of a sorbent composed of mixtures of tenorite (CuO) and brochantite [Cu4(OH)6SO4]. These materials are readily prepared through the addition of NaOH(aq) to CuSO4(aq). They can be loaded onto polymer foams to create effective filters that can remove malodorous H2S gas, as evidenced by breakthrough tests. X-ray diffraction shows that the ratio of the two compounds in the mixture can be finely tuned by varying the amount of NaOH(aq) that is added to the reaction mixture. X-ray photoelectron spectroscopy shows that brochantite, like tenorite, has the ability to chemically adsorb H2S. Correlation of the H2S breakthrough data with scanning transmission electron microscopy measurements shows that the most effective sorbents contain nanoscale needle-like particles. These are likely to be formed largely by the tenorite phase. The samples with the greatest H2S adsorption efficacy contained less than 20% tenorite in the mixture, where these particles had the greatest abundance. The application of this sorbent onto porous substrates to create effective filters, along with the synthetic ease of its production, could allow this methodology to find use in a number of areas where H2S poses a problem. This could include areas where protective clothing is required to adsorb the gas from environments where there is a high level of H2S, for example, in wastewater treatment plants, oil and gas wells, or in the medical sector, where it could be deployed as filter media.

The effect of alkali treatment on the mechanical properties of date seed particulates waste polypropylene filled composites

Date seeds collected as waste were reduced to 63 µm particles and treated with NaOH (aq) at 1, 3, 5, 7 and 10 %. The extent of chemical modification was assessed using FTIR analysis. The waste polypropylene (wPP)/date seed particles (DSP) composites filled with untreated and treated particles at 20 % filler loadings were fabricated using compounding and compression moulding techniques by means of two rolls mill. Tensile, flexural, impact tests and hardness (HV) were conducted and evaluated. Subsequently, a morphological study of the fractured surface of the composites was achieved using SEM. The application of alkali treatment enhanced various properties of the composites at the optimal concentration of 10 % w/v. Specifically, the tensile strength, flexural strength, elongation at break, impact strength, and hardness were improved, resulting in values of 28.86 MPa, 140 MPa, 172.5 %, 0.92 J/m², and 23.8 Hv, respectively. While tensile and flexural moduli showed a decrease with increasing alkali concentration. The SEM of the fractured surface of the treated composite revealed a better dispersion of filler particles within the matrix with no cluster seen compared to the untreated.

ABATEMENT OF HARMFUL CARBON MONOXIDE OVER THE NICKLE DOPED CO3 O4 CATALYST

This work aimed at evaluating the effect of nickle (Ni) dopant on the catalytic performance of Co3 O4 catalyst for abatement of harmful carbon monoxide (CO), a resistance toward sintering and durability of catalytic activity were also pursued. Choose the Co(NO3 )2 ×6H2 O(aq) as precursor and NaOH as precipitant to prepare cobalt oxide (Co3 O4 ) with precipitation method, then calcined at 300 and 500 °C, separately (named as C3 and C5). The Ni dopant (0.1 ~ 5 wt%) was added by deposited precipitation through Ni(NO3)2 ×6H2 O(aq) with drop wisely added NaOH(aq) into suspended Co3 O4 solution, then put the NaOCl for oxidation to obtain series 0.1%Ni-Co3 O4 , 0.2%Ni-Co3 O4 , 1%Ni-Co3 O4 and 5%Ni-Co3 O4 catalysts. All catalysts were characterized through BET, XRD, TEM/SEM, Raman, ICP and TPR instruments, and evaluated the catalytic performance of CO oxidation with a self-devised fluidized micro-reactor. It was observed that the calcination temperature and loading of dopant remarkably influenced the physicochemical characteristics and catalytic performance of the catalysts. Preferential catalyst was obtained for calcination at 300 °C and loading of Ni dopant below 1%. The doping of Ni on the surface of Co3 O4 enhanced the performance due to the inducing of synergistic effect between Co3 O4 and NiO, while the excessive NiO incorporated to the surface constrained the activity due to the abundant NiO on the surface, overlaying the active sites caused the decreasing of surface area and reducible capacity. Among these series Ni-Co3 O4 catalysts, the 0.2%Ni-Co3 O4 (C3) catalyst behaved an eminent activity with T50 of 98 °C and durability without apparent deactivation for 50 hr reaction at 125 °C. The excellent performance is primarily attributed to the synergistic effect and formation of NiCo2 O4 composite oxide.

Cellulose gelation in NaOH(aq) by CO2 absorption: Effects of holding time and concentration on biomaterial development

We address the limited solubility and early onset of gelation of aqueous sodium hydroxide to position it as a preferred green solvent for cellulose. For this purpose, we expand the concentration window (up to 12 wt%) by using a CO2-depleted air and adjusting the time the dope remains in the given atmosphere, before further processing (holding time) and regeneration conditions. Cellulose solutions are extruded following characteristic (rheology and extrusion) parameters to yield aligned filaments reaching tenacities up to 2.3 cN·dtex−1, similar to that of viscose. Further material demonstrations are achieved by direct ink writing of auxetic biomedical meshes (Poisson's ratio of −0.2, tensile strength of 115 kPa) and transparent films, which achieved a tensile strength and toughness of 47 MPa and 590 kJ·m−3, respectively. The results suggest an excellent outlook for cellulose transformation into bioproducts. Key to this development is the control of the gelation ensuing solution flow and polymer alignment, which depend on CO2 absorption, cellulose concentration, and holding time.

Biphasic BiFeO3 ceramics based on rhombohedral and tetragonal polymorphs

ABSTRACT From a new perspective, polymorphism is now often considered as a functional property that extends the applications of many materials. BiFeO3 is still an interesting material from both fundamental and applied points of view. A unique characteristic of BiFeO3 film, the polymorphism was stabilised only using the epitaxial strain caused by the substrate of the film. Here we report the hydrothermal synthesis of biphasic BiFeO3 ceramics using low NaOH concentration and temperature. The ability of BiFeO3 ceramics to morph into tetragonal and rhombohedral allotropic phases was demonstrated, confirming the theoretical prediction that the polymorphism can be stabilised even in powder form. Based on our experimental study NaOH(aq) is proposed as responsible for the strain on the structure of the rhombohedral phase. In addition, the in-depth characterisation of this biphasic ceramic opens up new opportunities for the technological applications of BiFeO3 material.

Acid Resistance of Alkali-Activated Natural Pozzolan and Limestone Powder Mortar

The development of sustainable, environmentally friendly alkali-activated binder has emerged as an alternative to ordinary Portland cement. The engineering and durability properties of alkali-activated binder using various precursor combinations have been investigated; however, no study has focused on the impact of high-volume natural pozzolan (NP) on the acid resistance of alkali-activated NP and limestone powder. Therefore, the current study assesses the impact of high-volume natural pozzolan (volcanic ash) on the durability properties of alkali-activated natural pozzolan (NP) and limestone powder (LSP) mortar by immersion in 6% H2SO4 for 365 days. The samples were prepared with different binder ratios using alkaline activators (10 M NaOH(aq) and Na2SO4) combined in a 1:1 ratio and cured at 75 °C. NP was combined with the LSP at three different combinations: NP:LSP = 40:60 (AAN40L60), 50:50 (AAN50L50), and 60:40 (AAN60L40), representing low-volume, balanced, and high-volume binder combinations. Water absorption, weight change, and compressive strength were examined. The microstructural changes were also investigated using FTIR, XRD, and SEM/EDS characterization tools. Visual examination showed insignificant deterioration in the sample with excess natural pozzolan (AAN60L40) after 1 year of acid exposure, and the maximum residual strengths were 20.8 MPa and 6.68 MPa in AAN60L40 and AAN40L60 with mass gain (1.37%) and loss (10.64%), respectively. The high sulfuric acid resistance of AAN60L40 mortar was attributed to the high Ca/Si = 10 within the C-A-S-H and N-A-S-H formed. The low residual strength recorded in AAN40L60 was a result of gypsum formation from an acid attack of calcium-dominated limestone powder. The controlling factor for the resistance of the binder to acid corrosion was the NP/LSP ratio, whose factor below 0.6 caused significant debilitating effects.

Impact of Sulfate Adsorption on Particle Morphology during Precipitation of Ni-Rich Precursors for Li-Ion Cathode Active Materials

Current standard industrial manufacturing of lithium layered transition metal oxides (LiMO2) as cathode active material (CAM) can be divided into two major process steps: The first step involves coprecipitation of mixed transition metal hydroxide (M(OH)2) particles (M consisting mainly of Ni, Co, and Mn) by mixing a transition metal sulfate solution (MSO4(aq.)) and a sodium hydroxide solution (NaOH(aq.)) in a stirred tank reactor. The resulting hierarchally structured secondary particles are composed of many primary particles which are used as precursors for CAMs (referred to as pCAM). Subsequently, the obtained pCAM is mixed with a lithium source such as Li2CO3 or LiOH and calcined at elevated temperatures to yield LiMO2.1 Recently, reports in the literature have shown clear correlations of CAM morphology with their electrochemical performance in a battery cell.2 Furthermore, it has been demonstrated that the electrochemical performance of a CAM is affected by the morphology of the associated pCAM.3, 4 However, a detailed understanding of the impact of the process parameters on the course of precipitation reaction and on the physical properties of the pCAM precipitate is still lacking.In order to gain a mechanistic understanding of the M(OH)2 pCAM particle formation, ten distinctive Ni0.8Co0.1Mn0.1(OH)2 particle lots were prepared by the coprecipitation method in a stirred tank reactor. The precipitation pH-value was systematically varied between pH = 8.6-12.7, while all other process parameters were kept constant. The S-content of the resulting pCAM powders, representing the residual sulfate (SO4 2-) content, was investigated by S-combustion and is depicted as a function of precipitation pH-value in Figure 1a. In the pH-value range between 8.57 and 10.27 (red), a slight increase in residual SO4 2- from 10.29 mol% to 12.60 mol% is observed until it decreases again to 11.10 mol%. Between pH = 10.27 and pH = 10.74, a sharp transition takes place and residual SO4 2- is reduced by a factor of 4 from 11.10 mol% to 2.60 mol%, which even decreases further with increasing pH-value, namely from 2.60 mol% at pH = 10.74 to 0.35 mol% at pH = 12.69 (green). Interestingly, the turning point in S-content between pH = 10.27 and pH = 10.74 (dashed blue line in Figure 1a) coincides with the point-of-zero-charge (pzc) of Ni(OH)2, which is reported to be at pH = 10.50-10.60.5 This result is rationalized by a pH-dependent SO4 2- adsorption equilibrium that is governing the SO4 2- uptake during the precipitation reaction, as depicted schematically in Figure 1b. For a precipitation below the pzc, positive charged surface hydroxyl-groups of Ni0.8Co0.1Mn0.1(OH)2 attract SO4 2-, resulting in high SO4 2- uptake during M(OH)2 formation and vice versa.In light of these results, it is further demonstrated by x-ray diffraction analysis that SO4 2- adsorption not only governs the crystallinity of the Ni0.8Co0.1Mn0.1(OH)2 material, but also suppresses the vertical crystal growth in the 001-direction during particle formation. This in turn seems to affect the vertical primary particle size as well as the secondary particle porosity, both observable by SEM imaging. The morphological trend is quantitatively verified by extracting the primary particle size distribution from SEM images and by measurements of the secondary particle porosity via nitrogen physisorption. As proof-of-concept for the proposed adsorption mechanism, precipitation reactions at pH = 12.0 with different metal feed sources (MX(aq.), with X = SO4 2-, (NO3 -)2, (CH3COO-)2) were conducted. The resulting clearly distinct physical properties of the Ni0.8Co0.1Mn0.1(OH)2 particles obtained from the different anion systems with different anion adsorption affinities can be well understood based on the Fajans-Paneth-Hahn law for crystallization.6 Finally, desorption experiments indicate options to reduce the residual SO4 2- amount after the Ni0.8Co0.1Mn0.1(OH)2 particle formation has been completed.Based on the results of this study, guidelines for pCAM design are formulated and discussed with respect to composition and subsequent manufacturing steps in industrial CAM production.

Calcium Silicate Hydrate Cation-Exchanger from Paper Recycling Ash and Waste Container Glass

Synthetic 11 Å tobermorite (Ca5Si6O16(OH)2.4H2O) and its Al-substituted analogue are layer-lattice ion-exchangers with potential applications in nuclear and hazardous wastewater treatment. The present study reports the facile one-pot hydrothermal synthesis of an Al-tobermorite-rich cation-exchanger from a combination of paper recycling ash, post-consumer container glass, and lime, with compositional ratios of [Ca]/[Si + Al] = 0.81 and [Al]/[Si + Al] = 0.18. The reaction products were characterized by powder X-ray diffraction analysis, 29Si magic angle spinning nuclear magnetic resonance spectroscopy, and scanning electron microscopy. Hydrothermal processing in 4 M NaOH(aq) at 100 °C for 7 days yielded an Al-tobermorite-rich product that also contained katoite (Ca3Al2SiO12H8), portlandite (Ca(OH)2), calcite (CaCO3), and amorphous silicate gel. The hydrothermal product was found to have a Cs+ cation exchange capacity of 59 ± 4 meq 100 g−1 and selective Cs+ distribution coefficients (Kd) of 574 ± 13 and 658 ± 34 cm3 g−1 from solutions with molar ratios [Cs+]:[Na+] and [Cs+]:[Ca2+] of 1:100. In a batch sorption study at 20 °C, the uptakes of Pb2+, Cd2+, and Cs+ were determined to be 1.78 ± 0.04, 0.65 ± 0.06, and 0.36 ± 0.03 mmol g−1, respectively. The kinetics of Pb2+, Cd2+, and Cs+ removal were described by the pseudo-second-order rate model, which gave respective rate constants (k2) of 0.010, 0.027, and 1.635 g mmol−1 min−1, and corresponding correlation coefficients (R2) of 0.997, 0.996, and 0.999. The metal ion sorption properties of the tobermorite-rich product compared favorably with those of other waste-derived tobermorites reported in the literature. Potential strategies to improve the yield, crystallinity, and sorption characteristics of the product are discussed.

Imidazolium structural isomer pyrazolium: A better alkali-stable anion conductor for anion exchange membranes

Anion exchange membranes (AEMs) are a core component for energy conversion technologies such as fuel cells and water electrolyzers. Unfortunately, the functional cations in AEM often suffer from inferior durability in caustic media, especially at elevated temperatures or highly concentrated alkaline solutions. Therefore, the exploitation of novel cations that can endure highly alkaline environments while with synthetic feasibility and good ion conducting property is desired. Herein, a simple and easily available pyrazolium cation was evaluated and was alkaline stable in 5 M NaOH (aq) at 80 °C for at least 240 h, which is substantially stable than its structural isomer, imidazolium. The alkaline stability of pyrazolium was rationalized through analyses of the degradation energy barriers calculated by density functional theory. The excellent alkaline stability of pyrazolium cation encouraged the fabrication of AEMs functionalizing with pyrazolium head group anchored to poly(arylene alkylene) architecture. In contrast to imidazolium-based counterpart, pyrazolium cation enable the AEM with higher base stability, retaining ～80% of its initial conductivity after a 1000-h treatment in 1 M NaOH (aq) at 80 °C. Moreover, the AEM based on pyrazolium showed a high hydroxide ion conductivity up to 120 mS cm−1 at 80 °C and a high peak power density of 502 mW cm−2 after assembled into a H2–O2 fuel cell device.

Cellulose interactions with CO2 in NaOH(aq): The (un)expected coagulation creates potential in cellulose technology

Upon the search for a suitable processing method for cellulose, the dissolution in NaOH(aq) presents a real green potential, including its ability to sorb environmental CO2(g) affecting dissolution. Here, CO2(g) was delivered in a controlled way to the cellulose/NaOH(aq) system during the in-situ analysis with FTIR, pH and temperature meters, resulting in efficient coagulation of cellulose. Surprisingly, the coagulation occurred with a minimal loss of alkalinity. This was considered an effect of a specific interaction between the dissolved polymer and gas, resulting in the introduction of carbonate species, highly influential in the coagulation process. The process repeated at 25 °C and 5 °C suggested a strong influence of temperature. The conversion routes of the CO2(g) coagulant were also related to the dissolved state of the polymer. The recovered cellulose appeared competitive with EtOH recovery in terms of structure. The presented finding put a perspective on the utilisation of both the coagulation process and final materials in cellulose technology.

Mechanical characteristics of Biomaterial Particles Reinforced Epoxy Resin Composites for Automobile Accessories

Abstract In this study, rattan corncob composite materials were developed and their mechanical properties were determined. This was with a view to producing alternative composite materials for automobile applications. Dried corncobs and rattan cane were crushed, treated with caustic alkali NaOH (aq) and transferred into a water bath machine to reduce the hydrophilic nature of the fibres in the polymer. The shredded corncobs and rattans cane were sun-dried after the treatment to remove the moisture content and were further pulverized and sieved to obtain 400μm particle size. Compositions of the particles were varied for seven samples with the binder kept constant at 80wt% of the whole mixture and forming them into particle panels using a metal mould. The process was repeated in order to obtain three replicates to get the exact mean value. The produced panels were tested for density, water absorption, tensile strength and modulus, flexural strength and modulus, and optical microstructure. The results revealed that the densities ranged between 1.06g/cm3 to 1.30g/cm3, the water absorption properties ranged between 0.87% to 4.55%, tensile strength ranged between 42MPa to 90MPa, tensile modulus ranged between 2.2GPa to 5.9GPa, flexural strength ranged between 50MPa to 70MPa and flexural modulus ranged between 1.5GPa to 2.7GPa. It was concluded that the developed composite materials have good mechanical properties and could serve as alternative materials for making automobile accessories like bumpers and spoilers. It could also help in solving the problem of environmental pollution caused by open burning.

Dissolution and precipitation behaviors of zircon under the atmospheric environment

The reactive behavior of zircon in three different solutions: 0.1 M HCl (aq), ultrapure water, and 0.1 M NaOH (aq) was examined under normal temperature and pressure conditions. Dissolved Si and Zr concentrations show that considerable Zr precipitated on the surface in all immersion cases. Bulk changes in the zircon were insignificant. However, the obvious surface change of the zircon immersed in 0.1 M NaOH (aq) was confirmed. Porous layer comprising an amorphous SiOx phase and needle crystals of ZrSiO4 around pores were detected on the near-surface area of the zircon immersed in 0.1 M NaOH (aq). Consequently, the reaction was limited when zircon was immersed in ultrapure water. Zr precipitated on the surface after the dissolution of ZrSiO4 in 0.1 M HCl (aq). Dissolved Zr and Si in 0.1 M NaOH (aq) precipitated on the surface, then the dissolution of ZrSiO4 formed a porous layer, and most dissolved Zr precipitated as zircon crystals.

Waste Glass-Derived Tobermorite Carriers for Ag+ and Zn2+ Ions

In this study, the layer-lattice calcium silicate hydrate mineral, tobermorite, was synthesized from waste green or amber container glass and separately ion-exchanged with Ag+ or Zn2+ ions under batch conditions. Hydrothermal treatment of stoichiometrically adjusted mixtures of waste glass and calcium oxide in 4 M NaOH(aq) at 125 °C yielded tobermorite products of ~75% crystallinity with mean silicate chain lengths of 17 units after one week. Maximum uptake of Zn2+ ions, ~0.55 mmol g−1, occurred after 72 h, and maximum uptake of Ag+ ions, ~0.59 mmol g−1, was established within 6 h. No significant differences in structure or ion-exchange behavior were observed between the tobermorites derived from either green or amber glass. Composite membranes of the biopolymer, chitosan, incorporating the original or ion-exchanged tobermorite phases were prepared by solvent casting, and their antimicrobial activities against S. aureus and E. coli were evaluated using the Kirby–Bauer assay. S. aureus and E. coli formed biofilms on pure chitosan and chitosan surfaces blended with the original tobermorites, whereas the composites containing Zn2+-substituted tobermorites defended against bacterial colonization. Distinct, clear zones were observed around the composites containing Ag+-substituted tobermorites which arose from the migration of the labile Ag+ ions from the lattices. This research has indicated that waste glass-derived tobermorites are functional carriers for antimicrobial ions with potential applications as fillers in polymeric composites to defend against the proliferation and transmission of pathogenic bacteria.

Cellulose dissolution and gelation in NaOH(aq) under controlled CO2 atmosphere: supramolecular structure and flow properties.

We investigate the interplay between cellulose crystallization and aggregation with interfibrillar interactions, shear forces, and the local changes in the medium's acidity. The latter is affected by the CO2 chemisorbed from the surrounding atmosphere, which, combined with shear forces, explain cellulose gelation. Herein, rheology, nuclear magnetic resonance (NMR), small and wide-angle X-ray scattering (SAXS/WAXS), and focused ion beam scanning electron microscopy (FIB-SEM) are combined to unveil the fundamental factors that limit cellulose gelation and maximize its dissolution in NaOH(aq). The obtained solutions are then proposed for developing green and environmentally friendly cellulose-based materials.

Pharmacognostic Potentials of Dried Powdered Seeds of Traditional Medicinal Plant Usteria guineensis used for the Treatment of Typhoid Fever in Sierra Leone

Pharmacognostic potentials and mineral analysis was carried out on the of dried powdered seeds of traditional medicinal plant Usteria guineensis used for the treatment of Typhoid fever in Sierra Leone. The results indicate the colour of the dried powdered seeds of the plant to be light yellow with fruit odour and had a bitter taste indicating that the powdered plant material contains alkaloids. The following reagents 1M NaOH (aq), 1M NaOH (alc.), Ammonia, 50% HCl, and 50% HNO3 exhibited fluorescent activities when added to portions of the dried powdered seeds of U. guineensis and viewed under UV Lamp. The plant organ investigated contained high contents of carbohydrates, alkaloids, flavonoids, proteins sterols/terpenes and tannins, saponins in the Ethanolic, methanol and aqueous extract during phytochemical screening. The detection of the above secondary plant metabolites supports the use of the plant in traditional medicine. Elemental analysis of the dried powdered seeds of U. guineensis using Niton XL3t GOLDD + Hand held X-ray Fluorescence (Thermo Fisher). The spectrum acquisition time was 480sec for the sample and the dead time was around 50% a total of fifteen elements (K, Ca, Mg, Al, Ti, V, Mn, Fe, Cu, Zn, Rb, Sr, Zr, Mo, and Sc) were determined in the dried powdered seeds of Usteria guineensis plant by using EDXRF. The results indicate that the plant organ investigated contained K (29458 ± 163 ppm), Ca (3702 ± 54.00 ppm), Mg (5528 ± 1223 ppm), Al (1389 ± 168 ppm) and Fe (167.11 ± 9.20 ppm). The other elements present in smaller quantities were Ti (64 ± 12.00 ppm), Sr (4.74 ± 0.40 ppm), Zn (56.65 ±2.46 ppm), Rb (47.34 ± 1.00 ppm), Zr (20.73 ± 0.67 ppm), and Mo (6.94 ± 0.74 ppm). The elements Sc, Mn, Cu and V were out of limit of detection of the equipment. The above elements detected are essential components of biological structures that mediate vital effect on and play a key role in a variety of the biochemical processes necessary for life.

Technological Aspects of Highly Selective Synthesis of Allyloxyalcohols—New, Greener, Productive Methods

Allyl ethers bearing free hydroxyl groups of CH2=CH-CH-O-A-OH type (hydroxyalkyl allyl ethers, allyloxyalcohols) are valuable chemicals in many environmentally friendly industrial applications. The development of technologically attractive methods for their production is necessary. The two pathways (L-L PTC and non-catalytic solvent-free conditions) were optimized for the highly selective and yield synthesis of 4-allyloxybutan-1-ol. Improvements in the PTC method (50% NaOH(aq), the equimolar ratio of NaOH to diol, cyclohexane as solvent) with a new highly selective and effective PT catalyst, i.e., Me(n-Oct)3N+Br− (0.3 mol%), resulted in 88% yield and 98% selectivity of 4-allyloxybutan-1-ol with minimal formation of allyl chloride hydrolysis by-products (<1%). In turn, application of non-catalytic solvent-free conditions and the change in the key substrate with an excess of diol and use of solid NaOH solely led to a mono-O-allylation product with an excellent yield of 99% in a relatively short reaction time (3.5 h), with trace amounts of by-products (<0.1%). This sustainable method is perfectly suitable for the synthesis on a larger scale (3 moles of the key substrate) and for the full O-allylation process.