Search

This research investigates the potential of mechanosynthesis to transform inert waste mixtures into sustainable construction materials. Three waste streams were employed: recycled glass, recycled concrete, and excavated soils. Two alternative material formulations, F1 (50% recycled concrete, 30% recycled glass, 20% excavated soil) and F2 (60% excavated soil, 20% recycled concrete, 20% recycled glass), were developed. Cement pastes were produced by partially substituting cement (CEM I) with 50% of either F1 or F2. Characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (ATR-FTIR), and mechanical testing, were performed. Cement pastes incorporating milled waste materials exhibited significantly enhanced compressive strength compared to their unmilled counterparts. At 28 curing days, compressive strengths reached 44, 47, 45, and 49.7 MPa, and at 90 curing days, they increased to 47.5, 50, 55, and 61 MPa for milling conditions of 200 rpm for 5 min, 200 rpm for 15 min, 400 rpm for 5 min, and 400 rpm for 15 min, respectively. In addition, F1 formulations showed higher compressive strengths than the reference CEM II and CEM III pastes. These results highlight the efficacy of mechanosynthesis in valorizing construction waste, mitigating CO2 emissions, and creating environmentally friendly construction materials. [ABSTRACT FROM AUTHOR]

This research investigates the potential of mechanosynthesis to transform inert waste mixtures into sustainable construction materials. Three waste streams were employed: recycled glass, recycled concrete, and excavated soils. Two alternative material formulations, F1 (50% recycled concrete, 30% recycled glass, 20% excavated soil) and F2 (60% excavated soil, 20% recycled concrete, 20% recycled glass), were developed. Cement pastes were produced by partially substituting cement (CEM I) with 50% of either F1 or F2. Characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (ATR-FTIR), and mechanical testing, were performed. Cement pastes incorporating milled waste materials exhibited significantly enhanced compressive strength compared to their unmilled counterparts. At 28 curing days, compressive strengths reached 44, 47, 45, and 49.7 MPa, and at 90 curing days, they increased to 47.5, 50, 55, and 61 MPa for milling conditions of 200 rpm for 5 min, 200 rpm for 15 min, 400 rpm for 5 min, and 400 rpm for 15 min, respectively. In addition, F1 formulations showed higher compressive strengths than the reference CEM II and CEM III pastes. These results highlight the efficacy of mechanosynthesis in valorizing construction waste, mitigating CO2 emissions, and creating environmentally friendly construction materials.

Melting furnace slag (MFS) is a potentially active by-product of the synergistic treatment of iron and steel dust sludge and Municipal Solid Waste (MSW) incineration fly ash in the flue gas magnetization fusion separator furnace of the “fire method + wet method”. This paper focuses on the MFS reactivated by mechanical grinding, and the reactivity of MFS is synergistically enhanced by alkaline, sulfate-based solid wastes. The particle size distribution, specific surface area, morphology, and physical phase composition of MFS with different grinding times resulted in the best performance of MFS when mechanically ground for 80 min and the specific surface area reached 450 m2/kg, and the reactivity indexes reached 100.94% and 103.7% for 7 and 28 d, respectively. The synergistic activation of steel slag and flue-gas desulfurization gypsum can play an effective role in stimulating the MFS, and the optimal proportion is m (MFS): m (SS): m (FGDG) = 42%: 42%: 16%. The reactivity enhancement mechanism of the ternary slag-based system on MFS: SS provides high alkalinity hydration reaction conditions for MFS and FGDG provides SO42−, which continuously promotes the hydrolysis of MFS under the synergistic reactivity stimulation to generate AFt and C–S–H gels.

Use of mechanical milling to increase micrometric powder reactivity is of interest due to several intrinsic advantages of this technique (e. g. versatility and safety). In this work, 30 μm propulsion‐grade aluminum has been activated with and without metal oxides. The powders so obtained were characterized in terms of particle size distribution, metal content, morphology, and ignition temperature. This last parameter represents a good indicator to rate the reaction properties of powders and the effects of activation parameters on the final product. All the ingredients containing metal oxides feature an enhanced reactivity as a consequence of both additives and modification of particle morphology. [ABSTRACT FROM AUTHOR]

CaO sorbent is one of the most promising sorbents for CO 2 capture. However, the reactivity of CaO sorbent decreased rapidly with carbonation-calcination cycles. Steam activation is a feasible approach to improve the sorbent reactivity. In this study, the effects of steam on CaCO 3 calcination (CaO regeneration), CaO carbonation and CaO hydration were both investigated. Compared with pure CO 2 calcination atmosphere, introducing steam into calcination atmosphere enhanced CaCO 3 decomposition rate, which was because that (1) the partial pressure of CO 2 decreased; (2) the absorption of H 2 O by active site CaO* weakened the binding ability between CO 2 and CaO*; (3) the amount of heat-transfer between steam and CaCO 3 was higher. Lower decomposition temperature in steam/CO 2 calcination atmosphere resulted in lower sorbent sintering and higher sorbent reactivity. Besides, the carbonation reactivity of CaO sorbent was over doubled when steam was introduced into carbonation atmosphere, which was due to the formation of OH – . In CaO hydration reaction, sorbent particle pore structure was also developed by hydration treatment. The hydrated Ca(OH) 2 sorbent reactivity as well as cyclic reactivity of CaO sorbent was therefore enhanced. [ABSTRACT FROM AUTHOR]

The enhanced reactivity of α-nucleophiles, which contain an electron lone pair adjacent to the reactive site, has been demonstrated in solution and in the gas phase and, recently, for the gas-phase S2 reactions of the microsolvated HOO(HO) ion with methyl chloride. In the present work, we continue to explore the significance of microsolvation on the α-effect as we compare the gas-phase reactivity of the microsolvated α-nucleophile HOO(HO) with that of microsolvated normal alkoxy nucleophiles, RO(HO), in reactions with methyl formate, where three competing reactions are possible. The results reveal enhanced reactivity of HOO(HO) towards methyl formate, and clearly demonstrate the presence of an overall α-effect for the reactions of the microsolvated α-nucleophile. The association of the nucleophiles with a single water molecule significantly lowers the degree of proton abstraction and increases the S2 and B2 reactivity compared with the unsolvated analogs. HOO(HO) reacts with methyl formate exclusively via the B2 channel. While microsolvation lowers the overall reaction efficiency, it enhances the B2 reaction efficiency for all anions compared with the unsolvated analogs. This may be explained by participation of the solvent water molecule in the B2 reaction in a way that continuously stabilizes the negative charge throughout the reaction. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Highlights: [•] Reactivity of copper in CaO/CuO sorbents is near its theoretical maximum value. [•] Thermal pre-treatment of copper can help maintaining the reactivity of calcium. [•] Steam in carbonation/calcination can greatly reduce the rate of decay of calcium. [•] Methods to enhance reactivity of CaO/CuO were firstly comprehensively investigated. [Copyright &y& Elsevier]

Abstract: We investigate the conditions for reactivity enhancement of a catalytic cracking process in porous crystalline solids using the concept of molecular traffic control (MTC). Using dynamic Monte Carlo simulations we obtain a quantitative description of the MTC effect for a bimodal network of intersecting size-selective channels over a wide range of grain parameters, diffusivities and reaction constants, and external operating conditions. The results are compared with those obtained on a similar network but with only one type of channels, called the reference system. We find significant reactivity enhancement in the MTC system with respect to the reference system. This effect is observed to increase with the grain size, and also with longer segments between lattice intersections. We find that in certain regions of the microscopic reaction rate the reactivity enhancement is up to 68%. [Copyright &y& Elsevier]

Abstract: Extremely efficient and high-speed ethynylation of acyl chlorides, aryl iodides and bromides was demonstrated by palladium-catalyzed cross-coupling reaction of N-t-butyl-Sb-ethynyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azastibocine under mild conditions. Optimization and generalization of the hypervalent antimony-mediated coupling reaction are presented in detail. Single-crystal X-ray analysis of the N-methyl-1,5-azastibocine revealed that the remarkable reactivity enhancement of the azastibocine was derived from elongation of the antimony–ethynyl carbon bond originated from Sb–N intramolecular non-bonding interaction. [Copyright &y& Elsevier]

Exploiting the full potential of copper-based nanoparticles in the activation of peroxymonopersulfate (PMS) is a great challenge due to their insufficient dispersity and electronic properties. We report here a novel iron‑nitrogen co-doped carbon nanotube (FNC) modified with a Cu 2 O nanocomposite (Cu 2 O/FNC) that exhibits ultrahigh catalytic performance in the activation of PMS to degrade fluconazole (~95%). Catalytic performance evaluation illustrated that Cu 2 O/FNC also has wide pH applicability (3.0–11.0), long-term stability and excellent adaptability. In addition, luminescent bacteria toxicity tests confirm that Cu 2 O/FNC/PMS significantly reduced the acute biotoxicity of various recalcitrant pollutants (reduced by 45–83%). By identifying the reactive oxygen species (ROS) and catalytic performance for various pollutants, we propose that pollutants that interact weekly with activators are mostly destroyed by sulfate radicals and hydroxyl radicals, whilst both radical and non-radical routes were involved in the degradation of pollutants that were easily adsorbed. By modifying Cu 2 O with FNC, several crucial properties such as the specific surface area, surface defects, active sites and the charge transfer rate were significantly improved, leading to excellent catalytic performance for pollutant removal. Finally, a reasonable reaction mechanism is advanced for the fluconazole degradation pathway. This study not only develops a novel PMS oxidation system for fluconazole degradation, but also provides a new strategy to improve the reactivity and applicability of PMS activators by combining radical and non-radical activation pathways. Unlabelled Image • FNC was used to enhance the electronic characteristics of Cu 2 O nanoparticles. • Cu 2 O/FNC showed much higher reactivity for activating PMS to degrade FLC. • The application potential of the Cu 2 O/FNC catalysts was evaluated in detail. • FLC degradation pathway and PMS activation mechanism are proposed. [ABSTRACT FROM AUTHOR]

• Ce was used to enhance the surface characteristics of Cu-based materials. • Cu-Ce bimetallic catalyst showed much higher reactivity for FLC degradation. • The relationship between catalyst activity and structure was investigated in detail. • Mechanism of Cu-Ce composite catalyzed Fenton reaction is proposed. In order to fully exploit the potential of Cu-based Fenton systems, Ce was utilized to modify the Cu-based catalysts through one-pot synthesis. A typical antifungal drug, fluconazole (FLC), was selected as the target pollutant to evaluate the reactivity of as-synthetic Cu-Ce bimetallic catalysts. Evaluation test results indicated Ce 5% CuO y bimetallic materials exhibit the most excellent catalytic activity. Compared to copper monometallic catalyst, its fluconazole degradation efficiency and TOC removal rate are increased by 20% and 15%, respectively. Ce 5% CuO y also possess wide pH applicability (3.0–9.0) and maintain high activity after 4 runs. Radical quenching experiments and fluorescent probes tests showed that hydroxyl radicals (OH) played a dominant role in the degradation of FLC. The various characterization illustrated that Ce doping (2.5–5 at%) significantly improved the properties related to catalytic activity, such as morphology Cu(I) ratio, specific surface area, interface electron transfer rate and unpaired electron content. In particular, the increase in the unpaired electron content and Cu(I) ratio endow more electron-rich centers and active sites on the composite surface, which facilitates the H 2 O 2 to receive electrons and decompose into OH. Finally, the degradation intermediates during fluconazole oxidation were identified by LC/MC. [ABSTRACT FROM AUTHOR]

• V was used to fine-tune the surface characteristics of monometallic Cu catalysts. • Cu-V bimetallic catalysts showed much higher Fenton activity for FLC degradation. • A OH surf reaction mechanism for Cu-V bimetallic catalysts Fenton was investigated. • The application potential of the Cu-V bimetallic catalysts was evaluated in detail. In this study, a novel Cu-V bimetallic catalyst (CuVOx) with abundant surface defects was successfully synthesized by hydrothermal method. Degradation experiment of emerging pollutant fluconazole confirmed that CuVOx exhibited higher catalytic activity, wider pH applicability and more satisfactory reusability than monometallic copper compounds. Electron paramagnetic resonance and radical quenching tests indicated that surface hydroxyl groups play a crucial role in the degradation of contaminants. By the introduction of vanadium into copper-based materials, several surface properties that are closely related to the reactivity of the copper catalysts such as adsorption capacity, surface defects, and active sites concentration were improved. It was also found that the electron-rich center around Cu/V active sites and surface oxygen vacancies are responsible for the rapid dissociation of H 2 O 2 and the efficient catalytic oxidation of fluconazole in CuVOx Fenton system. We also applied CuVOx Fenton to the degradation of various refractory organic pollutants, further confirming its excellent removal and detoxification efficiency for organic pollutants in the aquatic environment. [ABSTRACT FROM AUTHOR]