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pore volume and especially the surface basic properties induced by the introduction of N atoms. However, its preparation requires severe conditions, long time and is somewhat dangerous (e.g. explosive), limiting its applications in practice. For these reasons, this work intends to use N-doped carbon xerogel (N-CX), which can be easily prepared with a similar procedure as that of carbon xerogel [ 27 ], [ 28 ], as base adsorbent and studies its ability for the adsorption removal of MC-LR from aqueous solution. Results indicate that the N-CX is efficient for adsorption
Soybean curd is a very popular food containing high-quality protein, polyunsaturated fats, vitamins, minerals and other nutrients. This study aims to prepare porous soybean curd xerogels via a vacuum freeze drying method and uses them as adsorbents to remove congo red from aqueous solutions. The morphology and functional groups of the soybean curd xerogels were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The adsorption properties of congo red onto the soybean curd xerogels were carried out through investigating the infl uencing experimental parameters such as the drying method, solution pH, adsorbent dose, contact time and temperature. The results showed that the adsorption isotherm data were fitted well to the Freundlich isotherm. Adsorption kinetics of congo red onto the soybean curd followed the pseudo-second-order kinetic model. The thermodynamic parameters, such as ΔG0, ΔH0 and ΔS0, were also determined.
In this work ternary bioactive glasses with the molar composition 63 % SiO2, 28 % CaO, and 9 % P2O5 have been prepared via sol-gel processing route leading to xerogel or aerogel glasses, depending on the drying conditions. Two types of drying methods were used: atmospheric pressure drying (evaporative), to produce xerogels, and supercritical fluids drying, to obtain aerogels. Both dried gels were subjected to heat-treatment at three different temperatures: 400, 600 and 800 ºC in order to the removal of synthesis byproducts and structural modifications. The resulting materials were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and differential thermal analysis (DTA), and by in vitro bioactivity tests in simulated body fluid. The influence of the drying and the sintering temperature of their structure, morphology, and bioactivity of the final products were evaluated. The results show a good bioactivity of xerogel and aerogel bioactive glass powders with the formation of an apatite layer after one day of immersion in SBF solution for aerogel bioactive glass powders and a particle size less than 10 nm. An apatite layer formed after 3 days in the case of xerogel bioactive glass powders and a particle size around 100 nm.
Carbon xerogels (CXs) synthesized from resorcinol and formaldehyde under different pH conditions were investigated. Both the textural and surface properties of the CXs depend closely on the pH used in the synthesis procedure. Concerning the texture, the mesoporous surface area (Smeso) increases and the micropore volume (Vmicro) decreases as the pH increases; concerning the surface chemistry, surface oxygen functional groups were easier to be created (by O2) on CX synthesized at lower pH. Application of these CXs as support of gold catalysts was also studied. Results showed that the oxygen activated CX that was synthesized at moderate pH (i.e., pH 6.0) was the most favorable support for gold catalysts used in selective oxidation of benzyl alcohol by molecular oxygen in liquid phase, due to the adequate amounts of surface oxygen functional groups created on the surface.
duction (TPR), and hydrogen chemisorption. The activity of these catalysts was
studied for the stoichiometric reduction of NO by methane. The decomposition
of NO and methane oxidation were also used as a test reaction. Catalyst prepared
by wet impregnation method using Pd(C5H7O2)2 and alumina xerogel presented
the best performance for the studied reaction. The activity of Pd/alumina cata-
lysts for NO-CH4 reaction is related to the facility for reduction/oxidation of the
metal. This property is affected by the nature of the support as well as the metal
edge) wherein the metal atoms are octacoordinated with a distorted square-antiprismatic geometry.
In a sol-gel treatment the amorphous xerogel obtained from 1 was transformed into a nano-crystalline
product at 600 ◦C while the xerogel of Gd(OPri)3 under similar conditions required a heat treatment
up to 900 ◦C for the same development.
Key words: Gadolinium, iso-Propoxy, Hydroxo Ligands, Acetylacetonato, Gd2O3
The synthesis and characterisation of suitable mol-
ecular precursors for sol-gel/hydrothermal processes
is of great importance for the
reported the preparation of transparent titania xerogel-monolith by controlling the hydrolysis of this precursor through the intermediate of the esterification reaction between acetic acid and methanol [ 17 ]. This method takes substantial time (90 days) to obtain a transparent monolithic gel. The number of papers on the chemical modification of titanium alkoxide with acetic acid is undergoing an exponential increase. As often occurs in the case of an explosively growing subject, a certain degree of confusion is present in the literature. This is mainly due to the