Adsorption Behavior and Mechanism of Antibiotic Sulfamethoxazole on Carboxylic-Functionalized Carbon Nanofibers-Encapsulated Ni Magnetic Nanoparticles.

In this work we developed a one-step process for synthesizing carboxylic-functionalized carbon nanofibers (CNFs)-encapsulated Ni magnetic nanoparticles (Ni@CNFs) that exhibit an excellent magnetic response and a large content of hydrophilic carboxylate groups with a negative charge (RCOO(-)) on the carbon surface. The carbon-encapsulated magnetic Ni nanoparticles could be rapidly separated from water, and they showed high efficiency for adsorption of the antibiotic sulfamethoxazole (SMX) in aqueous solution. The adsorption of SMX on Ni@CNFs as a function of pH was investigated, and the greatest adsorption occurred at pH 7.0. The adsorption isotherms for SMX on Ni@CNFs depended on different pH values. A Monte Carlo simulation was used to probe the relationship between molecular conformation and π-π interaction. The high adsorption of SMX on Ni@CNFs at pH 7.0 could be ascribed to deprotonated SMX being easily converted to a planar-like conformation, thereby resulting in the formation of π rings that were approximately parallel to the graphite surface and that enhanced strong π-π interaction. Electrostatic and π-π interactions both contributed to deprotonated SMX adsorption at pH 7.0, and they influenced the adsorption isotherm toward the Freundlich model. However, in weakly acidic environments (pH 2.0 and 4.0), the electrostatic interaction alone could induce an adsorption pattern that was similar to the Langmuir model.

Effects of potassium on Ni-K/Al2O3 catalysts in the synthesis of carbon nanofibers by catalytic hydrogenation of CO2.

Commercially available Ni/Al(2)O(3) samples containing various concentrations of potassium were used to achieve carbon deposition from CO(2) via catalytic hydrogenation. Experimental results show that K additives can induce the formation of carbon nanofibers or carbon deposition on Ni/Al(2)O(3) during the reverse water-gas shift reaction. This work proposes that the formation rate of carbon deposition depends closely on ensemble control, suggesting that the ensemble size necessary to form carbon may be approximately 0.5 potassium atoms. The results of CO(2) temperature-programmed desorption provide strong evidence that the new adsorption sites for CO(2) created on Ni-K/Al(2)O(3) closely depend upon the synthesis of carbon nanofibers. It is found that some potassium-related active phases obtained by calcination and reduction pretreatments can participate in the carbon deposition reaction. The formation pathway for carbon deposition suggests that the main source of carbon deposition is CO(2) and that the pathway is independent of the reaction products CO and CH(4) in the reverse water-gas shift reaction.

Unravelling the mechanisms behind mixed catalysts for the high yield production of single-walled carbon nanotubes.

The use of mixed catalysts for the high-yield production of single-walled carbon nanotubes is well-known. The mechanisms behind the improved yield are poorly understood. In this study, we systematically explore different catalyst combinations from Ni, Co, and Mo for the synthesis of carbon nanotubes via laser evaporation. Our findings reveal that the mixing of catalysts alters the catalyst cluster size distribution, maximizing the clusters' potential to form a hemispherical cap at nucleation and, hence, form a single-walled carbon nanotube. This process significantly improves the single-walled carbon nanotube yields.

Properties of Cu(thd)2 as a precursor to prepare Cu/SiO2 catalyst using the atomic layer epitaxy technique.

The new Cu/SiO2 catalyst is developed by the atomic layer epitaxy (ALE) method. The ALE-Cu/SiO2 catalyst with high dispersion and nanoscale Cu particles appears to have very different catalytic properties from those of the typical Cu-based catalysts, which have satisfactory thermal stability to resist the sintering of Cu particles at 773 K. Due to the formation of small Cu particles, the ALE-Cu/SiO2 can strongly bind CO and give high catalytic activity for CO2 converted to CO in the reverse water-gas-shift reaction. The catalytic activity decreases in the order of 2.4% ALE-Cu/SiO2 =... 2% Pt/SiO2 > 2% Pd/SiO2 > 10.3% IM-Cu/SiO2.