Search

This work describes the synthesis and application of a novel magnetic metal-organic framework (MOF) [([Fe.sub.3][O.sub.4]-2,5-dimercapto-1,3,4-thiadiazole)/[Cu.sub.3] [(benzene-1,3,5-tricarboxylate).sub.2]] to preconcentrate trace amounts of Cd(II), Pb(II), and Zn(II) ions. A Box-Behnken design was used to find the parameters affecting the preconcentration procedure through response surface methodology. Three variables including sorption time, amount of the magnetic sorbent, and sample pH were selected as affecting factors in the sorption step, and four parameters including type, volume, concentration of the eluent, and elution time were selected in the elution step for the optimization study. These values were 33 mg, 11 min, 5.7 EDTA, 4.3 mL, 0.64 mol [L.sup.-1] EDTA solution, 16 min, for amount of the magnetic sorbent, sorption time, sample pH, type, volume, and concentration of the eluent, and elution time, respectively. Following the sorption and elution steps, the ions were quantified by FAAS. The limits of detection were 0.10, 0.15, and 0.75 ng [mL.sup.-1] for Cd(II), Zn(II), and Pb(II) ions, respectively. The relative standard deviations (RSD) of the method were less than 8.3% for five separate batch experiments in the determination of 25 µg [L.sup.-1] of Cd(II), Zn(II), and Pb(II) ions. The sorption capacity of the magnetic MOF nanocomposite was 155 mg [g.sup.-1] for Cd(II), 173 mg [g.sup.-1] for Pb(II), and 190 mg [g.sup.-1] for Zn(II). Finally, the magnetic MOF nanocomposite was successfully applied to rapidly extract trace amounts of heavy metal ions in baby food samples. Key words: magnetic metal-organic frame work nanocomposite, heavy metal ions, extraction, baby food samples. Les presents travaux decrivent la synthese et l'application d'un nouveau reseau metallo-organique [([Fe.sub.3][O.sub.4]-2,5-dimercapto-1,3,4-thiadiazole)/[Cu.sub.3][(benzene-1,3,5-tricarboxylate).sub.2]] en vue de la preconcentration des ions de Cd(II), de Pb(II) et de Zn(II) a l'etat de trace. Nous avons utilise un plan d'etude de Box-Behnken afin de trouver, au moyen de la methodologie de surface des reponses, les parametres influant sur la procedure de preconcentration. Trois variables, soit le temps de sorption, la quantite de sorbant magnetique et le pH de l'echantillon, ont ete selectionnees comme facteurs d'influence dans l'etape de sorption et quatre parametres, soit le type, le volume, la concentration, l'eluant et le temps d'elution, ont ete selectionnes dans l'etape de l'elution aux fins d'etude de l'optimisation. Les valeurs de la quantite de sorbant magnetique, de temps de sorption, de pH de l'echantillon, de type, de volume et de concentration de l'eluant, et de temps d'elution etaient respectivement 33 mg, minutes, 5,7, EDTA, 4,3 mL, solution d'EDTAa 0,64 mol [L.sup.-1] et 16 minutes. Apres les etapes de sorption et d'elution, les ions ont ete quantifies par spectrometrie d'absorption atomique a atomisation par flamme (FAAS). Les limites de detection etaient respectivement 0,10, 0,15 et 0,75 ng [mL.sup.-1] pour les ions de Cd(II), de Zn(II) et de Pb(II). Les coefficients de variation (CV) de la methode etaient inferieurs a 8,3% dans les cinq series d'experiences ayant permis de doser les ions de Cd(II), de Zn(II) et de Pb(II) a 25 µg [L.sup.-1]. La capacite de sorption du reseau metallo-organique nanocomposite magnetique etait de 155 mg [g.sup.-1] pour le Cd(II), de 173 mg [g.sup.-1] pour le Pb(II) et de 190 mg [g.sup.-1] pour le Zn(II). Enfin, le reseau metallo-organique nanocomposite magnetique a ete utilise avec succes pour extraire rapidement les metaux lourds presents a l'etat de trace dans des echantillons d'aliments pour nourrisson. [Traduit par la Redaction] Mots-cles: reseau metallo-organique nanocomposite magnetique, ions de metaux lourds, extraction, echantillon d'aliments pour nourrisson., Introduction Heavy metals are toxic pollutants that exist widely in wastewaters, and their presence concerns industries and environmental organizations all over the world. Most of these pollutants are severely toxic [...]

The current study describes the investigation of the adsorption NO, N2O, and NO2 on haeckelite boron nitride nanotube doped with Si (Si-doped haeck-BNNT) by means of density functional theory calculation (DFT). The obtained results confirmed the energetic stability of the optimized geometries and revealed that the adsorption of the gas molecules with the nanotube sidewall is a spontaneous process. The calculated work function of Si-doped haeck-BNNT in the presence of gas molecules is greater than that of a bare Si-doped haeck-BNNT sheet. The energy gap of the Si-doped haeck-BNNT is sensitive to the adsorption of the gas molecules, which implies possible future applications in gas sensors. For most of the adsorption configurations studied, the adsorption energies for the SiB-doped haeck-BNNT are higher than those for SiN-doped haeck-BNNTones. The N2O gas molecule is totally dissociated into N2 and O species through the adsorption process, while the other gas molecules retain their molecular forms. Thus, the SiN-doped haeck-BNNT is a likely catalyst for dissociation of the N2O gas molecule. Our findings divulge promising potential of the doped haeck-BNNT as a highly sensitive molecular sensor for NO and NO2 detection and a catalyst for N2O dissociation. [ABSTRACT FROM AUTHOR]

In this computational inspection, influences of substituted aluminum(s) on the vibrational frequency, infrared (IR) spectroscopy, atomic polar tensor (APT) charge, and electrostatic potential (ESP) map, along with atoms in molecules (AIM) analysis of C20 fullerene and its C20‐nAln derivatives (where n = 1–5) are investigated using B3LYP/6‐311 + G*, B3LYP/6‐311++G**, M06‐2X/6‐311++G**, B3PW91/6‐311 + G*, and B3LYP/AUG‐cc‐pVTZ. IR spectroscopy emerges that exclusive of C15Al5, the other optimized structures are global minimum without imaginary frequency. Substituting C20 to C20‐nAln heterofullerenes leads to higher APT charge distribution upon surfaces of heterofullerenes than unsubstituted species. Accordingly, the highest negative and positive APT charges on carbon and aluminum atoms of C15Al5 suggest that these sites can be attacked more readily by electrophilic and nucleophilic regents, that is, may act as the Lewis acid or Lewis base centers. This species is including five alternative aluminum heteroatoms in equatorial position and can be suitable hydrogen storage. AIM analysis of the studied C20‐nAln derivatives implies the highest ρ(r) of 0.083 a.u., the highest negative ∇2ρ(r) of −0.084 and −0.085 a.u. and the highest positive G(r)/V(r) of 4.86 and 4.69 a.u. at bond critical point of CAl bond with the strongest covalent property in the most stable C19Al1 and C17Al3 species, respectively, between studied structures. [ABSTRACT FROM AUTHOR]

DFT calculations are utilized to compare and contrast the substituted aluminum—heterofullerenes, C20-nAln (with n = 1–5) from thermodynamically view point, at density functional theory (DFT). Vibrational frequency analysis confirms that apart from C15Al5, all studied species are true minima. Considering the optimized geometries shows that all heterofullerenes are isolated-pentagon cage and none collapse to open deformed as segregated structure. The highest binding energy (5.56 eV/atom) and absolute heat of atomization (3323.68 kcal mol−1) reveals open-shell C19Al1 as the most stable thermodynamic heterofullerene. The most NICS (0) (isotropic and anisotropic parameters, −49.58 and − 46.47 ppm, respectively) introduces closed-shell C18Al2-2 as the most aromatic structure. Also, closed-shell C16Al4-1 heterofullerene emerges with the most polarizability (307.71 a.u.) and hence activity to interact with the surrounding polar species. The lowest and the highest charge transfer on the surfaces of C20 and C16Al4-2 without weak Al—Al bond, as the worst and the best candidate, respectively, provokes further investigation on impossible and possible application for hydrogen storage, respectively. We wish that the present survey will stimulate new experiments. [ABSTRACT FROM AUTHOR]