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Reducing CO2 emissions from industrial sectors and motor vehicles is currently receiving much attention. There are different strategies for CO2 capture, one of which is using calcium oxide (CaO). In our proposed carbon dioxide cycle, limestone is first calcined to get CaO, which is then used to capture CO2 by converting it to CaCO3. Next, the released CO2 could be converted to different organic matter by different sequestration techniques. For this purpose, CaCO3 discs have been prepared by compression molding to investigate the effect of sintering temperature on the mechanical and chemical properties of CaO carbonation reaction. The aim of this work is to fill the knowledge gap for the effect of the contact profile between CO2 gas and CaO disc, particularly the effect of reducing the void fraction of CaO on the rate of carbonation reaction. It was found that the flexural strength of the CaO discs was influenced by several factors, such as the calcination temperature, duration of calcination, and pressing pressure. The carbonation step indicated that both CO2 and H2O are reacting with CaO simultaneously and progressively, with the progressive reaction of H2O and CO2 being a favorable route. The carbonation process happens as a surface reaction-controlled process followed by a slower internal diffusion-controlled process. Additionally, a kinetic study of the competing reactions indicated that two factors are controlling the process: diffusion of gases through the pores and then the reaction rate. Furthermore, our data showed that the CO2 uptake rate was 1352.34 mg/g CaO, indicating that 566.34 mg of CO2 was adsorbed inside the pores of the CaO disc. Based on these results, we propose a new mechanism of the sequence of the competing reactions. In summary, the CaO discs revealed a significant removal of CO2 from stack gases, which will be suitable for removing CO2 from exhaust gases generated by industrial processes and other sources of emissions such as vehicles and ships.

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The study of the adsorption efficiency of new carbon/CNT composites was undertaken to remove a cationic dye, Rhodamine B (RhB), from dye-contaminated wastewater. Indeed, we investigated the effect of different experimental parameters such as time, initial concentration of dye and temperature on the adsorption of RhB by the carbon composites (KS44-0 and KS44-20). The results showed that the adsorption uptake increased with the initial concentration and solution temperature while maintaining a relatively constant pH. The presence of the carbon nanotubes provided more active sites for dye removal and improved the adsorption behavior of Rhodamine B dye. The analysis of the experimental data was conducted using model equations, such as Langmuir, Freundlich and Temkin isotherms. As regards the Freundlich isotherm model, it was the best fit for the equilibrium data obtained from the experiments. The applicability of the pseudo-second-order equation could be explained assuming that the overall adsorption rate is limited by the rate of adsorbate transport that occurs on the pore surfaces of adsorbents. Furthermore, the intraparticle diffusion and Bangham models were used to investigate the diffusion mechanism of RhB absorption onto carbon composites. They showed that multiple adsorption stages occurred simultaneously via pore surface diffusion. Concerning the thermodynamic parameters (∆G°, ∆H°, and ∆S°), they were calculated and explained in the mean of the chemical structure of the adsorbate. Negative standard Gibbs free energy change values (ΔG°ads) at all temperatures suggested that the adsorption process was spontaneous, and the positive values of the standard enthalpy change of adsorption (∆H°ads) revealed the reaction to be endothermic. The values of standard enthalpy (ΔH°ads) and activation energy (Ea) indicated that the adsorption process corresponds to physical sorption. The mechanisms for the removal of Rhodamine B dye from wastewater using carbon composite were predicted. RhB is a planar molecule that is readily adsorbed, in which adsorbed molecules are bound by hydrophobic or other weak interactions due to the π-π interactions between the dyes' aromatic backbones and the hexagonal skeleton of graphite and carbon nanotubes. Thus, the graphite carbon/carbon nanotube composite is believed to play a major role in organic pollutant reduction.

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Thermal Energy Storage (TES) technologies based on Phase Change Materials (PCMs) with small temperature differences have effectively promoted the development of clean and renewable energy. The organic phase change materials are most commonly used in latent heat TES (LHTES). Nevertheless, the trend of this type of material limits their applications because of their low thermal conductivities and liquid leakage over the phase transition process. Copper oxide (CuO) microparticles served as an additive to enhance thermal performance and a series of shape-stabilized composite PCMs (SSPCMs) were prepared by physical impregnation. The composites were characterized for their micro-morphology, chemical structure, thermal degradation stability and thermal energy storage performance with the aid of SEM, FT-IR, ATG, infrared thermography (IRT) and DSC, respectively. To obtain the maximally efficient energy storage capacity, the mass fraction of Hex (PCM) was found to be 75%, with a good form stability, which surmounts almost all mass fraction values reported in the literature. The ATG curves of all PCM composites revealed that addition of CuO has increased the onset degradation temperature and the maximum weight loss temperature. During the heating and cooling processes, leakage and impairment of the composite PCM were not detected. Significant enhancement in melting time and larger heat storage capacity were observed when 15% CuO was added to the SSPCM as revealed by IRT. The DSC results of the SSPCM composite indicated that the presence of CuO microparticles in PCM composites reduces the supercooling effect during the phase change process and increases the energy storage/release capacity with suitable phase change temperatures for building TES applications.

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Due to the high crystallinity and natural abundance, the crystal structures of native cellulose allomorphs have been theoretically studied until today, but some details remain to be deciphered. In this work, research was extended on the visualization and quantification of intermolecular interactions related to hydrogen bonds and van der Waals interactions in cellulose crystals Iα and Iß based on previous studies. For each allomorph, the crystal structure has been described by two models of hydrogen bonding networks designated here as (A) and (B). This network diversity is due to the location of the hydrogen atoms of two disordered positions in the hydroxyl groups O6 and O2. Hirshfeld surface analysis (3D) was used to visualize the fidelity of intermolecular interactions O-H⋯O (involving O2 and O6) in the different cellulosic structural models Iα and Iß. Two-dimensional fingerprint plots were used to identify the individual type of intermolecular contact and its impact on crystal packaging by graphical representation. A crystal contact study using the enrichment ratio was performed to investigate the tendency of intermolecular interactions to form the crystalline packing. The control of O-H⋯O inter-chain interactions in each type of network shows that hydrogen bonding is more favored in the model (A) than in the model (B).

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The hydrolysis of three alkoxysilane coupling agents, gamma-methacryloxypropyltrimethoxysilane (MPS), gamma-aminopropyltriethoxysilane (APS), and gamma-diethylenetriaminopropyltrimethoxysilane (TAS), was carried out in an ethanol/water (80/20) solution and followed by 1H, 13C, and 29Si NMR spectroscopy, which showed that its rate increased in the order MPS < APS < TAS. The formation of the silanol groups was followed by their self-condensation to generate oligomeric structure. APS and MPS only gave soluble products, whereas colloidal particles precipitated in the medium when TAS was hydrolyzed. Pristine and hydrolyzed MPS were then adsorbed onto a cellulose substrate and thereafter a thermal treatment at 110-120 degrees C under reduced pressure was applied to the modified fibers to create permanent bonding of the coupling agent at their surface.

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