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Fumed-Si-Pr-Ald-Barb as a Fluorescent Chemosensor for the Hgsup.2+ Detection and Crsub.2Osub.7sup.2− Ions: A Combined Experimental and Computational Perspective
The surface of fumed silica nanoparticles was modified by pyridine carbaldehyde and barbituric acid to provide fumed-Si-Pr-Ald-Barb. The structure was identified and investigated through diverse techniques, such as FT-IR, EDX, Mapping, BET, XRD, SEM, and TGA. This nanocomposite was used to detect different cations and anions in a mixture of H[sub.2]O:EtOH. The results showed that fumed-Si-Pr-Ald-Barb can selectively detect Hg[sup.2+] and Cr[sub.2]O[sub.7] [sup.2−] ions. The detection limits were calculated at about 5.4 × 10[sup.−3] M for Hg[sup.2+] and 3.3 × 10[sup.−3] M for Cr[sub.2]O[sub.7] [sup.2−] ions. A computational method (DFT) was applied to determine the active sites on the Pr-Ald-Barb for electrophilic and nucleophilic attacks. The HOMO-LUMO molecular orbital was calculated by B3LYP/6-311G(d,p)/LANL2DZ theoretical methods. The energy gap for the Pr-Ald-Barb and Pr-Ald-Barb+ion complexes was predicted by the E[sub.HOMO] and E[sub.LUMO] values. The DFT calculation confirms the suggested experimental mechanism for interacting the Pr-Ald-Barb with ions.
Journal Article
Impact of Low COsub.2 Footprint-Dissolution Treatment of Silica and Potassium-Rich Biomass Ashes on the Compressive Strength of Alkali-Activated Mortars
Using almond shell biomass ash (ABA) as a potassium alkaline source and rice husk ash (RHA) as a soluble silica source to produce blast furnace slag (BFS)-based alkali-activated mortars offers a sustainable alternative to commercial activators. However, some thermal treatment is often needed to enhance ash dissolution, potentially increasing the CO[sub.2] footprint. In this study, we evaluated how a low-CO[sub.2]-footprint thermal treatment for dissolving ABA, as well as RHA combined with ABA, affects the strength performance of binary (ABA/BFS) and ternary (RHA/ABA/BFS) alkali-activated mortars. This thermal treatment involved mixing the biomasses with hot water (85 °C) in a thermally insulated bottle (TIB). The binary alkali-activated mortar, cured for 7 days in a thermal bath at 65 °C, achieved 58.0 MPa in compressive strength, applying 1-h dissolution of ABA in a TIB. Additionally, the previous dissolution of RHA in conjunction with ABA for ternary alkali-activated mortar, cured also for 7 days in a thermal bath at 65 °C, resulted in mortars with a higher compressive strength, achieving 64.7 MPa. With the prior biomass dissolution method, the binary and ternary alkali-activated mortars cured at room temperature (20 °C) showed compressive strengths of 54.7 and 67.0 MPa after 28 curing days, respectively. Moreover, after 135 curing days, these mortars reached a compressive strength of 61.4 and 71.9 MPa, respectively. The BFS-alkali-activated binders with ABA and ABA plus RHA cut CO[sub.2] emissions by 86.8% and 85.7% compared to the OPC-based binder, respectively.
Journal Article
Effect of Curing Temperature on the Properties of a MgO-SiOsub.2-Hsub.2O System Prepared Using Dead-Burned MgO
The hydration of M-S-H prepared using silica fume (SF) and dead-burned MgO cured at 20 °C, 50 °C, and 80 °C was investigated, and the properties and performance of this M-S-H were measured. The formation of M-S-H was characterized using XRD, FTIR, TGA, and [sup.29]Si MAS-NMR. Results show that the compressive strength of paste prepared using MgO calcined at 1450 °C for 2 h reached 25 MPa after 28 d. The shrinkage of mortar made with low reactivity MgO was lower than that made with high reactivity MgO. The pH value of MgO/SF paste mixed with dead-burned MgO did not exceed 10.4 at room temperature. The shrinkage of M-S-H prepared using dead-burned MgO was less than that prepared using more active MgO, and its strength did not decrease over time. No (or only a small amount of) Mg(OH)[sub.2] was formed, which is why the strength of M-S-H prepared with dead-burned MgO continually increased, without decreasing. The promotion of curing temperature favor process of MgO hydration and is beneficial for degree of silica polymerization. The sample cured in 50 °C water showed the highest relative degree of reaction.
Journal Article
Lithium Orthosilicate Solid Porous Membranes for COsub.2 Capture Obtained from Silica Microfibers
What are the main findings? Silica microfibers obtained by the Cofiblas technique were reacted with lithium to produce lithium orthosilicate membranes. The method involving immersion of silica microfibers in an aqueous lithium solution followed by calcination was demonstrated to be effective. What is the implication of the main finding? Their unique shape leads to the formation of 3D porous membranes, enabling their direct use as filters without the need for pelletizing. These membranes exhibited superior performance, as they adsorbed 31 wt.% of CO[sub.2] and demonstrated complete regeneration capacity. Lithium orthosilicate (Li[sub.4]SiO[sub.4]) has demonstrated a high CO[sub.2] adsorption rate and capacity and its suitability to be implemented in industry as CO[sub.2] capture technology at high temperatures. The optimum solid adsorbent should present a porous structure to maximize surface and enable a high sorption rate. In this work, we present an original approach based on the use of a novel architecture of precursors in the form of very thin free-standing solid silica fibers. An original technique called continuous fiberizing by laser melting (Cobiflas) was used to obtain membranes of pure silica fibers with diameters in the micrometer range, forming a porous membrane which offer a high surface and porous connectivity to be used as precursors without any supporting substrate. Then, we employed a method based on the impregnation of the silica fibers within a lithium-containing aqueous solution and subsequent calcination to obtain a porous solid adsorbent with the maximum proportion of lithium orthosilicate. This method is compared with the results obtained using a sol-gel powder method by analyzing their composition using X-Ray Diffraction (XRD), and their adsorption capacity and adsorption kinetics by Thermogravimetric analyses (TGA). As a result, an outstanding type of solid adsorbent is reported with a 31% adsorption capacity and a total regeneration capacity, which is over 0.8 efficiency with regard to the theoretical maximum adsorption of this material.
Journal Article
Microscopic Transport and Degradation Behavior of COsub.2 in C-S-H with Varying Ca/Si Ratios during Carbonation
Carbonation is a critical factor contributing to the degradation of reinforced concrete systems. Understanding the micro-mechanism of concrete carbonation is essential for mitigating corrosion losses. This study investigates the transport and reaction processes of water and CO[sub.2] in CSH pores with varying calcium–silica ratios using reactive force field molecular dynamics. Simulation results reveal that CO[sub.2] and its hydration products occupy adsorption sites on the CSH, hindering solution transport within the pores. As the Ca/Si ratio increases, the adsorption of Ca ions on the CSH matrix weakens, facilitating Ca’s reaction with CO[sub.2] and its displacement from the CSH surface. Consequently, a wider distribution of Ca on the surface occurs, and CO[sub.2] directly adsorbs onto the CSH matrix, widening the transport space and accelerating transport speed. Furthermore, the impact of bridging silica–oxygen on the CSH surface is analyzed, indicating that the absence of bridging silica–oxygen enhances adsorption sites for Ca ions, thus intensifying their adsorption on CSH.
Journal Article
Lethal Effects of a Commercial Diatomaceous Earth Dust Product on Amblyomma americanum
With increasing development of resistance to conventional synthetic acaricides in economically and medically important ixodid species, interest in finding alternative control tactics has intensified. Laboratory bioassays were conducted, using the lone star tick, Amblyomma americanum (L.), as a model species, to assess the efficacy of a diatomaceous earth-based product, Deadzone, in comparison with a silica gel-based product, CimeXa. CimeXa is already known to be highly lethal against A. americanum larvae and nymphs.The two dust treatments were 100% effective against larvae and nymphs within 24 h after contact occurred by immersion in dry dusts and after crawling across a surface treated with the dry dusts. Contact by crawling on a dried aqueous film of the dusts, even at a concentration of 10%, was not as effective as exposure to the dusts in dry powder form. As has been demonstrated with CimeXa, it is likely that Deadzone will be capable of providing prophylactic protection of cattle from economically important one-host ixodids, such as the southern cattle fever tick, Rhipicephalus microplus (Canestrini), which vectors the causal agents of babesiosis. Diatomaceous earth can be stored indefinitely, will remain efficacious for as long as sufficient quantities remain on the substrate, it is a natural (organic) substance, and it might be amenable for limited use in environmentally protected habitats.
Journal Article
Selective assembly of Au-Fe.sub.3O.sub.4 nanoparticle hetero-dimers
Hetero-dimeric magnetic nanoparticles of the type Au-Fe.sub.3O.sub.4 have been synthesised from separately prepared, differently shaped (spheres and cubes), monodisperse nanoparticles. This synthesis was achieved by the following steps: (a) Mono-functionalising each type of nanoparticles with aldehyde functional groups through a solid support approach, where nanoparticle decorated silica nanoparticles were fabricated as an intermediate step; (b) Derivatising the functional faces with complementary functionalities (e.g. amines and carboxylic acids); (c) Dimerising the two types of particles via amide bond formation. The resulting hetero-dimers were characterised by high-resolution TEM, Fourier transform IR spectroscopy and other appropriate methods.
Journal Article