Defect Formation, T-Atom Substitution and Adsorption of Guest Molecules in MSE-Type Zeolite Framework—DFT Modeling

We used computational modeling, based on Density Functional Theory, to help understand the preference for the formation of silanol nests and the substitution of Si by Ti or Al in different crystallographic positions of the MSE-type framework. All these processes were found to be energetically favorable by more than 100 kJ/mol. We suggested an approach for experimental identification of the T atom position in Ti-MCM-68 zeolite via simulation of infrared spectra of pyridine and acetonitrile adsorption at Ti. The modeling of adsorption of hydrogen peroxide at Ti center in the framework has shown that the molecular adsorption was preferred over the dissociative adsorption by 20 to 40 kJ/mol in the presence or absence of neighboring T-atom vacancy, respectively.

Abnormal retention of s-triazine herbicides on porous graphitic carbon

Porous graphitic carbon (PGC) is a widely used stationary phase for reversed-phase high-performance liquid chromatography (HPLC) that allows separation of structurally similar compounds retained in mixed form on a flat graphite surface. Such a stationary phase can be used in analytical chemistry to provide good separation and selectivity in pesticide monitoring. In this article, we studied the chromatographic behavior of five common triazine herbicides (simazine, atrazine, desmetryn, propazine, prometryn) on PGC vis-à-vis octadecyl-functionalized silica gel (ODS). It was found that the herbicides studied have an abnormal elution order on PGC compared to ODS. PGC was also characterized by higher selectivity of analyte separation. This behavior of triazine herbicides on PGC cannot be explained either with the help of existing theory or by mathematical modeling of adsorption processes on graphite. Therefore, we have proposed a possible retention mechanism, explaining the effects observed, due to the shielding of the amino group in the triazine ring by alkyl substituents, which decreases the “polar retention effect” of PGC. Satisfactory separation efficacy was obtained with the proposed analytical method, using convenient UV-detection and without resort to laborious techniques such as HPLC coupled with mass spectrometry.

The use of Biomaterials as Adsorbents for Removing Colorants from Aqueous Solution Case of Straw with Respect to Methylene Blue

In the following study, we have tested Straw as a biomaterial for removing methylene blue (MB) by adsorption. The characterization of the adsorbent was carried out by scanning electron microscopy coupled with EDX (SEM), infra-red spectroscopy with Fourier transform and the point of zero charge (PZC). The studied variables are: the mass of adsorbent, the initial concentration of dye, the contact time, pH and temperature. Kinetic data were modeled by equations pseudo first order and pseudo-second order, and revealed that the adsorption of MB on the straw pseudo second order for initial dye concentration. The MB adsorption isotherms on straw were analyzed by models of Langmuir and Freundlich. The modeling of adsorption isotherms obtained good agreement with the model of Freundlich.

Modeling of adsorption of aluminum on macrocyclic porphyrins H2TPP and H2TTPP: Phenomenological investigation of aluminum (Ⅲ)-porphyrin complex at the molecular level

The authors have requested that this preprint be removed from Research Square.

Modeling of adsorption of aluminum on macrocyclic porphyrins H2TPP and H2TTPP: Phenomenological investigation of aluminum (Ⅲ)-porphyrin complex at the molecular level

The authors have requested that this preprint be removed from Research Square.

A thermodynamic modeling of 2-bed adsorption desalination to promote main equipment performance

Adsorption desalination utilizes the discrete adsorption of the water vapor from the evaporator, and is capable of being discharged to the condenser. This study illuminated an advanced cycle of mass and heat recovery among beds, condensers, and evaporators. Morover, the thermodynamic modeling of Adsorption Desalination Systems (ADS) under different operating conditions was investigated. Furthermore, its effect on the evaporator vapor production and the water vapor adsorption and desorption in the adsorption beds were accounted for. Parenthetically, the mathematical model of ADS thermodynamics was validated with the experimental data. Besides, the advanced ADS modeling was conducted via mass and heat recovery among beds, condensers, and evaporators. In addition to the amount of the desalinated water, the time history chart of the equipment applied in the process with and without the thermal and mass recovery is also illustrated. Finally, under such operating conditions, the SDWP (Specific Daily Water Production) advanced ADS is 153% higher than conventional ADS.