A sonochemical method was employed in the synthesis of nickel aluminum layered double hydroxides (NiAl-LDH) and the materials were used as adsorbents for the removal of the reactive azo dye, Remazol Brilliant Violet (RBV-5r). The experimental data obtained for microstructure were compared and both the arrangement and orientation of the intercalated dye species were examined using molecular dynamics (MD) simulations. The obtained materials were characterized by X-ray diffraction (XRD), nitrogen sorption (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transformation infrared spectroscopy (FTIR). The adsorption characteristics were studied in a batch process by optimizing different parameters such as calcination temperature, contact time, initial dye concentration, solution pH, and solution temperature. NiAl-LDH material synthesized by sonochemical (SC) methods and calcined at 250 °C (NiAl-C250SC) showed the best dye removal efficiency (100% removal in 6 min) with an adsorption capacity of 150 mg/g at 25 °C and at pH = 6. The reusability of the dye loaded material was investigated by replicating the adsorption−desorption cycle. The results show that the material could regenerate without significant loss of the adsorption capacity. The regenerated adsorbent showed 95.9%, and 95.7% of the initial adsorption capacity after the first and the second regeneration cycles, respectively. XRD and FTIR results for LDH before and after the dye adsorption showed removal of the dye is due to intercalation of the organic dye molecule into the LDH structure where a net increase in the basal spacing from 7.48 to 8.71 Å is observed. Molecular dynamics (MD) simulations further suggest that the dye molecules arrange in the interlayer space as a monolayer with the main axis horizontal to the layer plane. The calculated d-spacing values were in good agreement with the experimental results.

Cobalt doped cryptomelane type manganese oxide (K-OMS-2) microwires had been successfully synthesized and characterized. Their catalytic activity was tested in an oxidation reaction with benzyl alcohol as the substrate and the cobalt doped OMS-2 materials showed 100% selectivity towards benzyl aldehyde with a conversion of 55%. The cobalt doped OMS-2 materials were also investigated as a desulfurization sorbent in a fixed bed reactor at 250ºC where high sulfur sorption capacities (49.4 g sulfur/100 g sorbent) were observed. Here, the structure controlled synthesis was performed using a facile one step microwave assisted hydrothermal method (MWHY) associated with a rapid temperature ramping (200ºC/min). The structural effects induced by the compositional control of transition metal dopants on the cryptomelane (space group I4/m) body centered tetragonal structure were identified with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD and TEM results showed that the systematic variance of the cobalt content was accompanied by a stepwise lattice expansion of (110) plane from 6.70 to 7.43 Å. The XRD, high resolution TEM (HRTEM)/TEM, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) data suggested that the assynthesized cobalt doped OMS-2 materials were also crystalline with no segregated metal oxide impurities. The uniform morphology of the metal doped OMS-2 materials was observed by the field-emission scanning electron microscopy (FESEM), whereas energy-dispersive X-ray (EDX) analysis confirmed the successful incorporation of metal dopant into the OMS-2 structure.Inductively coupled plasma atomic emission spectroscopy (ICP-AES) showed a higher degree of doping (Co/Mn = ~0.26) associated with MWHY method over conventional methods. On the other hand, TGA demonstrated that the as-synthesized materials were more thermally unstable than their undoped counterparts. The observed structural and chemical characteristics upon doping with some metal cations were explained by the Jahn-Teller distortion.

Mesoporous cobalt oxides (M-Co-X, X = 150, 250, 350, 450°C) with tunable porosity and crystallinity were synthesized based on an inverse micelle soft template method. They are the members of recently discovered University of Connecticut (UCT) mesoporous materials. The M-Co-X materials were investigated as desulfurizing sorbents in a fixed bed reactor in the temperature range of 25−250°C. A considerably high sulfur sorption capacity was observed even at room temperature (13.4 g S/100 g sorbent), and very high values were observed in the temperature range of 175−250°C (65.0−68.9 g S/100 g sorbent). The sulfided materials were further analyzed with LA-XRD, WA-XRD, N 2 sorption studies, FESEM, FESEM-EDX, TEM, FETEM-EDX, TGA, and TPO. The M-Co-250 material reached 100% theoretical sulfur capacity at 150°C. The presence of interconnected intraparticle voids and surface exposed particles were found to be the critical factors determining the ability of H 2 S to diffuse in the sorbent. The mesostruture of the M-Co-X material was preserved even after sulfidation. Other mesoporous metal oxides synthesized by the same method (Cr 2 O 3 (UCT-37), CuO (UCT-11), Mn 2 O 3 (UCT-1), and Fe 2 O 3 (UCT-5)) also showed sulfur capacities of 2−200 times more than the corresponding nonporous materials.

We report the synthesis of ordered mesoporous NiAl mixed metal oxides (MMOs) from NiAl-layered double hydroxides (LDHs) through a soft template method using pluronic-F127 as the structure-directing agent. Ordered mesopores were obtained by the thermal decomposition of as-synthesized LDHs at different temperatures. The effects of the pluronic-F127 amount and the calcination temperature on the pore size distribution of the MMO were investigated. NiAl MMOs exhibited excellent catalytic activity in the Knoevenagel condensation of benzaldehyde with acidic methylene group-containing malononitrile. Finally, the dependence of the catalytic activity on the surface properties of NiAl MMOs was investigated. The pore diameter and the pore volume of NiAl MMOs were well correlated with the performance of the catalysts. MMO obtained from the calcination of NiAl-F127(3%)LDH at 750 °C for 5 h gave the highest conversion (>99%) in the Knoevenagel condensation in 30 min. The optimum pore diameter for the model reaction described here was 7.7 nm, which gave rise to more than 99% conversion with 100% selectivity. Ethanol gave the best conversion at 60 °C. The regenerated catalyst showed 93.0 and 89.0% of the initial catalytic activity after the first and the second regeneration cycles, respectively.

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