Homogenous UV/Periodate Process for the Treatment of Acid Orange 10 Polluted Water

The photoactivated periodate (UV/IO4−) process is used to investigate the degradation of acid orange 10 (AO10) dye. The photodecomposition of periodate ions produces highly reactive radicals (i.e., •OH, IO3•, and IO4•) that accelerate dye degradation. Increasing the initial concentration of periodate to 3 mM enhances the dye removal rate, but over 3 mM periodate, the degradation rate slows down. On the contrary, increasing initial dye concentrations reduces the degradation performance. pH is the most critical factor in AO10 breakdown. Salts slow down the degradation of the dye. However, UV/IO4− is more efficient in distilled water than natural water. Even at low concentrations, surfactants may affect the dye’s decomposition rate. The addition of sucrose reduced the breakdown of AO10. Although tertbutanol is a very effective •OH radical scavenger, it does not affect the dye breakdown even at the highest concentrations. Accordingly, the AO10 degradation is a non-•OH pathway route. According to retrieved data, the photoactivated periodate method eliminated 56.5 and 60.5% of the initial COD after 60 and 120 min of treatment time; therefore, it can be concluded that the UV/IO4− system may treat effluents, especially those containing textile dyes

Mechanism of implantation of size-selected clusters into graphite

An analytical approach is proposed to investigate the mechanism of implantation of size selected clusters into graphite, in order to explain the origin of linear variation of measured penetration depth with momentum or energy of incident cluster. In agreement with experimental observations, the cluster experiences, during its penetration, a force which consists in a component proportional with cluster velocity and a constant component. Expressions of these forces were obtained in the frame work of this approach. Regardless of whether the cluster breaks down into single atoms on the surface or not, there is evidence for existence of a wave generated under impact of cluster on the surface. Under the assumption that the cluster does not break up at impact on the surface, the penetration depth depends on the cross-section between the cluster and the surface, the cluster velocity and the properties of graphite. When the cluster fragments upon the impact on the surface, the generated wave is followed by a collective motion (“collective cascade”) of displaced atoms of target, including the constituents of cluster themselves, due to the transfer of cluster momentum. Thus, it is these displaced atoms which penetrate in the medium. During this collective penetration, some constituents of cluster can reach a certain depth which may be considered as the range of the deepest implanted constituents of cluster. It is shown that, the depth of penetration depends on the initial radius of cluster, its velocity and the properties of graphite. In addition, the depth varies non linearly with cluster velocity, for small clusters (n ≤ 7), while for large clusters (n ≥ 13), it varies (i) linearly with cluster velocity (or momentum) when the force proportional with speed of cluster is dominant. (ii) Linearly with the square of cluster velocity (or energy) if the constant force becomes dominant. It is shown that, a mechanism based on a collective motion of displaced atoms including the constituents of cluster themselves, induced by transfer of cluster momentum to the medium, permits to explain the behavior of measured depth of implanted clusters into graphite. This collective motion involves only one free parameter for all clusters of the same nature which are used as projectiles in the same experiment

Investigation of dry reforming of methane over Mo-based catalysts

An investigation of methane dry reforming over Mo–Ni based catalysts is carried out in a fixed bed catalytic reactor at different temperatures. Two Mo–Ni catalysts supported on alumina are prepared with 20%Mo–10%Ni and 20%Mo–2%Ni, respectively, in which the nickel is used for its highly resistance at high temperature during dry reforming of methane (DRM) reaction. Experimental results shows that an increase in temperature favours the CH4 conversion and determined a higher H2/CO ratio. A small amount of deposited coke is observed because of the abundant presence of CO2 in the reaction medium and only for 2% Ni catalysts. A kinetic model is proposed for the DRM with Mo–Ni based catalysts, in which the reaction mechanism routes and the operating conditions such as the reaction temperature and the CH4/CO2 molar ratio are accounted for. The results of the mathematical model allow a consistent description of the experimental data, in terms of gas outlet composition. The absence of the methane decomposition reaction, responsible of carbon deposition that is known to lead to catalyst deactivation, is the main result that is adequately predicted by the model

Numerical study of sorption-enhanced methane steam reforming over Ni/Al2O3 catalyst in a fixed-bed reactor

The present work deals with the Sorption-Enhanced Methane Steam Reforming (SE-MSR), an interesting and energy-efficient hydrogen production route with in situ CO2 capture. A computational fluid dynamics (CFD) model for an industrial-scale fixed-bed reactor, with Ni/Al2O3 as catalyst and CaO as an adsorbent for CO2 capture, is developed taken into consideration also the coke deposition. Temperature is shown to be the key parameter of the SE-MSR chemical process at large scales. H2 production is constant and maximum until the saturation of CaO sorbent occurs, after which the concentrations of all the other compounds start to vary, and the efficiency of the process begins to drop. When the exothermic carbonation reaction stops, an alteration of the thermal regimes is observed. The absence of the contribution of the exothermic carbonation reaction results in a decrease of the temperature, which in turn determines a lower conversion of CH4 and H2O, according to the endothermic reforming reactions. The maximum H2 outlet mole fraction (dry basis) is 0.8, and it occurs in the presence of CO2 sorption; the value drops to 0.42 once the adsorbent reaches its maximum conversion degree. The molar selectivity in hydrogen relative to the quantity of CH4 fed to the reactor is of the order of 1.75 (with CO2-capture) and 0.8 (without CO2 capture). The molar fluxes obtained and the kinetics of the system model show the excellent choice of the operating conditions of the catalyst to produce a large quantity of hydrogen as well as of the adsorbent, which eliminates the CO2 responsible of coke deposition

Physicochemical Properties and Atomic-Scale Interactions in Polyaniline (Emeraldine Base)/Starch Bio-Based Composites: Experimental and Computational Investigations

The processability of conductive polymers still represents a challenge. The use of potato starch as a steric stabilizer for the preparation of stable dispersions of polyaniline (emeraldine base, EB) is described in this paper. Biocomposites are obtained by oxidative polymerization of aniline in aqueous solutions containing different ratios of aniline and starch (% w/w). PANI-EB/Starch biocomposites are subjected to structural analysis (UV-Visible, RAMAN, ATR, XRD), thermal analysis (TGA, DSC), morphological analysis (SEM, Laser Granulometry), and electrochemical analysis using cyclic voltammetry. The samples were also tested for their solubility using various organic solvents. The results showed that, with respect to starch particles, PANI/starch biocomposites exhibit an overall decrease in particles size, which improves both their aqueous dispersion and solubility in organic solvents. Although X-ray diffraction and DSC analyses indicated a loss of crystallinity in biocomposites, the cyclic voltammetry tests revealed that all PANI-EB/Starch biocomposites possess improved redox exchange properties. Finally, the weak interactions at the atomic-level interactions between amylopectin-aniline and amylopectin-PANI were disclosed by the computational studies using DFT, COSMO-RS, and AIM methods. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Synthesis and characterization of Layered Double Hydroxides aimed at encapsulation of sodium diclofenac: Theoretical and experimental study

The main objective of the paper is to study the encapsulation/adsorption of sodium diclofenac (Na-DIC) on hydrotalcite cationic clays (i.e., Layered Double Hydroxides, LDHs) by ion exchange and adsorbent reconstruction mechanisms. The encapsulation/adsorption method is generally used to modify some drugs' physicochemical characteristics, such as unpleasant odors, low solubility, high volatility, etc. LDHs are synthesized and characterized by different techniques (SEM, DRX, FTIR, BET, and ATG). Na-DIC adsorption capacity onto calcined LDH (CLDH) is determined (with maximum value in between 195 and 211 mg/L in the range 25–45 °C), together with the effect of the main operating parameters (adsorbent mass, pH, initial concentration of Na-DIC, and temperature). A statistical physics derived adsorption model allows a correct interpretation of experimental data and indicates that multiple molecules' vertical adsorption per active site occurs. Kinetic tests showed that the Pseudo First order (PFO) model correctly describes the Na-DIC adsorption kinetics on LDH at different temperatures, indicating the pore diffusion as the primary resistance mechanism and an activation energy of +34.56 kJ/mol (physical adsorption). HOMO and LUMO obtained from quantum chemical calculations confirm the ability of Na-DIC to receive electrons from LDH, indicative of polar adsorption (ΔNmax = 1.9). Adsorption is also simulated by Monte Carlo method, which allows determining the Na-DIC/CLDH configuration corresponding to the lowest total energy. The value of the adsorption energy confirms a strong interaction between the DIC and the CLDH. In conclusion, LDH clays show great potential as adsorption support and encapsulation medium, which could be proficiently used also to remove Na-DIC from wastewater. Na-DIC is adsorbed onto calcined hydrotalcite by the reconstruction method, which is explained by the so-called “memory effect” of hydrotalcite