mohammad khodadadi-moghaddam

This study initially investigated sugar production through a Formose Reaction (FR) using methanol as a solvent and an aerosil (fumed silica) as a catalyst. The products observed in the reaction medium were 2,3-dihydroxypropanal (glyceraldehyde) and 1,2-ethanediol (ethylene glycol). The results showed that if the target of the reaction is to produce glyceraldehyde (GA) and ethylene glycol (EG), the aerosil is a better option as a catalyst in the FR. Finally, the Molecular Dynamic (MD) simulation of 2,3-dihydroxypropanal adsorption was investigated on montmorillonite (MMT) as a mineral adsorbent. MD simulation indicated that the adsorption of GA molecule at the MMT-water interface occurred due to the oxygen of the carbonyl group. The Radial Distribution Function (RDF) of the solvent around the main atoms of GA and the Root-Mean-Square Deviation (RMSD) were calculated from the MD simulation results using Gaussian and LAMMPS software. The RDF results showed a weak hydrogen bond between oxygen atoms of the hydroxyl group and solvent molecules. Moreover, the solvent molecules had no significant influence on the behavior of tetrahedral carbons of GA, indicating that the oxygen atom of the carbonyl group had a higher ability to form a hydrogen bond with water compared to the other atoms. The RMSD of carbonyl oxygen, carbonyl carbon, hydroxyl oxygen, and tetrahedral carbon increased during a simulation time of 20 ns, respectively. Evaluation of the mean distance of calcium atom at the surface of MMT and different atoms of GA showed that the GA molecule was chemically adsorbed on the surface of MMT by oxygen of carbonyl. The mean distances of C-tetrahedral, C-carbonyl, O-hydroxyl, and O-carbonyl in the GA structure from the surface of MMT (distance from calcium ions) were estimated to be 3.8, 3.2, 3.0, and 2.6 Å, respectively.

In the present study, natural and synthetic adsorbents were used to remove nickel ions through the adsorption process. First, TiO2 nanoparticles (NPs) were prepared through the sol-gel method. The synthesized samples were then characterized using X-ray diffraction spectroscopy (XRD), Fourier transform-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption/desorption isotherms (BET). The influences of different operational parameters including adsorbate content, pH, adsorbent concentration, contact time, ionic strength, and stirring speed were also explored. According to the results, the pseudo-second-order kinetic model showed the best performance in evaluating the experimental data when using both adsorbents. The adsorption of nickel cations by the thin film membrane on the surface of TiO2 NPs is a rate-determining step of the removal reaction. The removal rate constants of nickel ions from aqueous solutions by TiO2 NPs and pomegranate peel were evaluated to be 0.013 and 0.018 g mg-1 min-1, respectively. The thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy were also determined. Nickel removal processes in all cases were endothermic and spontaneous. The removal mechanism also followed physical adsorption. Equilibrium data were fitted with Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models. The results showed that the adsorption of Ni2+ on TiO2 NPs and pomegranate peel followed Freundlich and Temkin isothermal models, respectively. Based on the calculated removal percentage, TiO2 is a better adsorbent for removing Ni2+ from the aqueous medium as compared to pomegranate peel.

In the present paper, the Formose reaction to produce polyols in methanol solvent in the presence of an aerosil (fumed silica) catalyst is first investigated. The mechanism of Formose reaction is actually the same aldol condensation that occurs in an alkaline media and is accelerated by the presence of a heterogeneous catalyst. The products observed in the reaction medium are ethylene glycol and glyceraldehyde. Finally, the selectivity of the synthesis of these products was compared and evaluated with the two corresponding products synthesized through the Formose reaction in aqueous solvent. The present study shows that in the presence of fumed silica catalyst in aqueous solvent, the production of ethylene glycol decreases with increasing pH from 7.6 to 9.3, while the conversion of ethylene glycol to glyceraldehyde increases. As a result, the amount of ethylene glycol in the reaction mixture decreases at alkaline pHs compared to neutral pHs; in contrast, the selectivity of the reaction to the production of glyceraldehyde increases. Changing the solvent from water to methanol also reduces production efficiency. Therefore, it indicates the low selectivity of the methanolic medium compared to the aqueous medium to produce two products, 1,2-ethanediol and 2,3-dihydroxypropanal.

In the present paper, the Formose reaction is investigated to produce polyols in the presence of two different catalysts at different pHs. The Formose reaction mechanism is the same as aldol condensation, which occurs in alkaline media and is accelerated by the presence of a heterogeneous catalysis. The products observed in the reaction medium are ethylene glycol, and glyceraldehyde. The present study shows that in the presence of fumed silica catalyst, increasing the pH from 7.6 to 9.3 reduces the production of ethylene glycol; however, it increases the conversion of ethylene glycol to glyceraldehyde. As a result, the amount of ethylene glycol in the reaction mixture decreases compared with neutral pHs. Nevertheless, the selectivity of the reaction to the production of glyceraldehyde increases. The same result can be observed when using montmorillonite as another heterogeneous catalyst. The difference is that the montmorillonite catalyst has less ability to accelerate the reaction than fumed silica. Also, at pH around 9 and above, practically no product is observed in the reaction medium.

This study focuses on the utilization of ZnO (as synthetic) and mango peel (natural adsorbent)  to remove blue 221 dye from aqueous solutions. First, ZnO nanoparticles (NPs) were synthesized and detected using the descriptor-based techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), N2 adsorption/desorption isotherms (BET), and X-ray diffraction (XRD). Various operational parameters including adsorbent concentration, pH, adsorbent dose, contact time, and stirring speed were investigated. The obtained kinetic results demonstrated great compatibility of the pseudo-second-order model with the experimental data. The effects of thermodynamic parameters were calculated to confirm the endothermic, spontaneous and physical nature of adsorption process. Langmuir and Freundlich isotherm models were utilized to fit the obtained equilibrium data. Freundlich model was found sufficient to explain the adsorption of blue 221 dye by ZnO NPs and mango peel. The results indicated that the ZnO NPs performed better in blue 221 dye removal as compared with mango peel. The mean size of ZnO NPs was found to be 22.16 nm. The specific surface area of ZnO NPs was obtained 26.85 m2.g-1 and pore volume and pore-size were 0.0581 cm3.g-1 and 1.22 nm, respectively. The maximum adsorption capacity of blue 221 dye on ZnO NPs and mango peel was estimated as 133.33 and 476.19 mg.g-1, respectively.

In this research, adsorption of six tri-bisphenol-A-diglycidyl ether oligomers on montmorillonite are investigated using molecular dynamics simulation method at  298, 323, and 348k. At the beginning of the simulation, the distance between oligomers and Montmorillonite is set greater than cut-off distance; but, the distance between oligomer chains is smaller than the cut-off distance. During the simulation, the oligomer chains are adsorbed on the surface and after temperature and pressure equilibration, sampling is done for data analysis. The results show that the adsorption of oligomer chains on Montmorillonite is done via etheric Oxygens of oligomer chains. The etheric oxygen has a partial negative charge and reacts sufficiently with positive calcium ions of Montmorillonite. The result of this interaction is the strong adsorption of oligomer chains on Montmorillonite. Increasing temperature causes an increase in distance between adsorbed oligomer chains, but, does not strong effect on adsorption of chains on surface.

Photocatalytic reduction of carbon dioxide to formaldehyde was investigated on four semiconductor photocatalysts (FeS, FeS/FeS2, NiO and TiO2). The reaction was carried out in continues flow of CO2 gas bubbled into the reactor. Semiconductor photocatalysts were characterized by X-Ray diffraction (XRD) and Diffuse Reflectance Spectroscopic (DRS) methods. Sulfide ion was used as hole scavenger. The results show that the TiO2 has greater photocatalytic activity compared to the other photocatalysts, for example, maximum formaldehyde concentration were 720 and 380 ppm on TiO2 and NiO, respectively. Addition of carbonate ion causes an increase (around two times) in the concentration of formaldehyde. The yield of the formaldehyde decreased with decreasing concentration of the sulfide ion and the pH of the reaction mixture (from 700 ppm to 500 ppm). This investigation demonstrates that under ultraviolet radiation, carbon dioxide can be reduced to formaldehyde on semiconductor photocatalysts. This reaction could have been a possible chemical route to photosynthesis on the early Earth.