In this paper, a powerful photocatalyst based on carbon nanocomposite is developed in order to obtain a new material applicable in water treatment and especially for the discoloration of effluents used in the textile industry. For that, TiO2- graphene nanocomposites have been successfully synthesized by a mixture of Functionalized Graphene Sheet (FGS) and tetrachlorotitanium complexes to form FGS-TiO2 nanocomposite. In the presence of an anionic surfactant, we used a new chemical process to functionalize graphene sheets in order to make them an excellent medium for blocking and preventing the aggregation of TiO2 nanoparticles. The components of these nanocomposites are characterized by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), which confirms the successful formation of the FGS-TiO2 nanocomposite. It was found that the TiO2 nanoparticles were dispersed uniformly on the graphene plane which possesses better charge separation capability than pure TiO2. The FGS-TiO2 nanocomposites exhibited higher photocatalytic activity compared to pure TiO2 for the removal of three dyes: such as Methylene Blue (MB), Bromophenol Blue (BB) and Alizarin Red-S (AR) in water. The removal process was fast and more efficient with FGS-TiO2 nanocomposite in daylight (in the absence of UV irradiation) compared to pure TiO2 nanoparticles without and under UV in all pH range.

The inhibition effect of the invasive brown seaweed Sargassum muticum extract (ESM), harvested from the Atlantic coast of Morocco, against the corrosion of carbon steel (CS) in 1 M HCl medium was studied for the first time using gravimetric, electrochemical and surface techniques. The methanolic crude extract of Sargassum muticum (ESM) is rich in alginate biopolymer. The evaluation corrosion tests showed that this algal extract acts as a good mixed corrosion inhibitor for CS substrate in 1 M HCl since inhibition efficiency of 97% was reached with 1 g/L of ESM at 303 K. AC impedance findings showed that the seaweed extract adding in the corrosive electrolyte increases the polarization resistance and conversely decreases the charge capacitance at the interface. Adsorption of ESM on the substrate surface followed the Langmuir adsorption isotherm. X-ray photoelectron spectroscopy analyses (XPS) demonstrated that the corrosion inhibition mechanism of CS substrate in 1 M HCl environment by the investigated algal extract is typical of the chemisorption process and the protective barrier is mainly formed by the adsorbed biological macromolecules.

The residue of alginate extraction from the invasive brown seaweed Sargassum muticum harvested from the Moroccan Atlantic coast was tested as biosorbent for hexavalent chromium removal. The results revealed that biosorption of Cr(VI) was highly pH dependent, favoring higher chromium removal at very low pH values. Langmuir and Freundlich adsorption isotherms were applied to fit the experimental data. The results demonstrated that the equilibrium data were well fitted by Langmuir isotherm model. The maximum uptake capacity for Cr(VI) was about 34.8 mg/g. The kinetic studies showed that biosorption process can be described perfectly by a pseudo-second-order model. Functional groups on the biomass surface, responsible of adsorption phenomenon, have been successfully evidenced by the use of attenuated total reflectance Fourier transform infrared spectroscopy. The results gave evidence that the residue of alginate extraction from S. muticum could be an appropriate low-cost biosourced material for removing hexavalent chromium from aqueous solutions.

The corrosion inhibition efficiency of newly synthesized 3,5-diaryl-4-amino-1,2,4-triazole derivatives was investigated for mild steel corrosion in 1.0 M HCl medium using weight loss quantum chemical calculations and Monte Carlo simulations. It was found that the studied compounds exhibit a very good performance as inhibitors for mild steel corrosion in 1.0 M HCl. The results show that the inhibition efficiency increases with decreasing temperature and increasing concentration of inhibitors. The kinetic parameters such as E a, ΔH a, and ΔS a were evaluated. It was found that the adsorption for these inhibitors on the mild surface obeys the Langmuir adsorption isotherm at all studied temperatures and the adsorption isotherm parameters (K ads, ΔG ads°, ΔH ads°, and ΔS ads°) were determined and discussed. The values of inhibition efficiency for all triazoles followed the order 3-APAT < 4-APAT < 4-DTAT < 4-MAT < 3,4-MAT. The 3,4-methoxyphenyl substituted triazole (3,4-MAT) exhibited the highest inhibition efficiency of 98.5% at concentration of 1 × 10–4 M. Quantum chemical calculations using the Density Functional Theory (DFT) were performed on the 3,5-diaryl-4-amino-1,2,4-triazole derivatives in an attempt to correlate the corrosion inhibition properties of these 1,2,4-triazole derivatives with their calculated quantum chemical parameters. Furthermore, Monte Carlo (MC) simulations were applied to search for the most stable configuration and adsorption energy for the interaction of inhibitors on Fe (110)/30 H2O interface. A good correlation was observed between the Monte Carlo calculations and experimentally inhibition efficiency data.

This paper investigated the catalytic effect of inorganic elements in ash on bio-oil thermal conversion process (pyrolysis and gasification). Bio-oil with a natural ash contents of 0.05 wt.% and bio-oil added with 3 wt.% of ash were explored. The influence of ash content of the bio-oil conversion on char, tar and gas yields were investigated over a wide range of temperature from 500 degrees C to 1200 degrees C. A Horizontal Tubular Reactor (HTR) is used for pyrolysis process and an Entrained Flow Reactor (EFR) is used for gasification process. The experimental results showed that ash seems to favor re-polymerization reactions that lead to an increase in char yield and causing a decrease in the yield of gas while an increase was a priori expected.

The corrosion inhibition efficiency of 3,7-dimethyl-1-(prop-2-yn-1-yl)quinoxalin-2(1H)-one (DPQO) on carbon steel in 1.0M HCl solution has been investigated using, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), weight loss, and scanning electron microscopy (SEM) methods. The results showed that the inhibition efficiency of DPQO increased with the inhibitor concentration but decreased with temperature. Polarization studies revealed that DPQO acts as a mixed-type inhibitor at 308K. The inhibitor adsorption on the steel surface obeyed the Langmiur isotherm and the thermodynamic parameters (Kads, ΔGadsο) were calculated and discussed. The corrosion process in 1.0M HCl in the absence and presence of DPQO followed first-order kinetics. Activation parameters of the corrosion process (Ea, ΔHa and ΔSa) were also calculated from the corrosion rates. SEM results supported the adsorption conclusions. Quantum chemical calculations have been performed using DFT and several quantum chemical indices of DPQO were calculated and correlated with its inhibitive effect.

Full factorial experimental design technique was used to study the main effects and the interaction effects between operational parameters in the photocatalytic degradation of oxalic acid in a batch photo-reactor using TiO2 aqueous suspension. The important parameters which affect the removal efficiency of oxalic acid such as agitation, initial concentration, volume of the solution and TiO2 dosage were investigated. The parameters were coded as X1, X2, X3 and X4, consecutively, and were investigated at two levels (−1 and +1). The effects of individual variables and their interaction effects for dependent variables, namely, photocatalytic degradation efficiency (%) were determined. From the statistical analysis, the most effective parameters in the photocatalytic degradation efficiency were initial concentration and volume of solution. The interaction between initial concentration, volume of solution and TiO2 dosage was the most influencing interaction. However, the interaction between agitation, initial concentration and volume of solution was the least influencing parameter.

Synthesis and physico-chemical characterization of a pure magnesium phosphate (MgP) prepared by coprecipitation, and MgP modified by introduction of cobalt-molybdenum (4-12 wt.% of MoO3 with the Co/Mo ratio fixed at 0.5) have been carried out. The structural properties of these catalysts were characterized by X-ray diffraction, their textural properties were determined by N-2 adsorption-desorption isotherms and the dispersion of cobalt-molybdenum was studied by XPS spectroscopy. Their acid properties have been investigated by in situ FT-IR spectroscopy of adsorbed molecules, often, 2,6-dimethylpyridine (pK(a) = 6.7), pyridine (pK(a) = 5.3). Co-Mo incorporation leads to a modification in the MgP acid-base properties, especially on the acid sites type and number. Thus, lower loading of cobalt-molybdenum species decreased the number of strong Lewis acid sites whereas higher loading increased it. It was found that Lewis acid sites on magnesium phosphates play an important role in the isomerization of 3,3-dimethylbut-1-ene.The 3,3-dimethylbut-1-ene (33DMB1) conversion increases with the reaction temperature from 493 to 653 K for MgP, but decreases after 573 K for MgP supported by Co-Mo. A linear relationship between both types of acid sites and conversion values was found. The deactivation of the catalysts appears at high reaction temperature (> 573 K). (C) 2010 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.

In this paper we describe the synthesis and characterization of the acido–basic properties of catalysts containing varied amounts of vanadium supported on ZrO2. The preparation of the zirconia was carried out using a hydrolysis method and the vanadium was introduced by impregnation with a porous volume in several stages, followed by calcinations under air at a temperature of 723K. The obtained samples are characterized by adsorption–desorption of nitrogen and infrared spectral analysis of different species formed by acidic and basic probes. This adsorption on the surface of these compounds has been studied in order, in the hand to investigate information on their surface acidity and in the other hand to know particularly the nature and strength of acidic and basic sites. Among the molecular probes, we used carbon monoxide, carbon dioxide, pyridine and 2,6-dimethylpyridine. The adsorption of CO has shown that contrary to pure zirconia and oxidized V2O5/ ZrO2, the reduced V2O5/ ZrO2 samples favour the formation of CO co-ordinated on Lewis acidic sites of reduced V2O5 species (CO on V4+ or V3+). We also observe the creation of Brønsted acidic sites by means of the incorporation of vanadium.

By hydrolysis of an ethanolic gallium nitrate solution, gamma-Ga2O3 was prepared as a single-phase polymorph having a specific surface area of 160 m2 g(-1). Surface acidity and basicity of this material was studied by IR spectroscopy, using pyridine, 2,6-dimethylpyridine, acetonitrile, and carbon dioxide as spectroscopic probe molecules. For comparison, a gamma-Al2O3 sample having a surface area of 290 m2 g(-1) was also studied. On partially hydroxylated gamma-Ga2O3, the main O-H stretching bands were found at 3693 (sharp) and at 3660-3630 cm(-1) (broad), and the material proved (by adsorbed dimethylpyridine) to have a weak Brønsted acidity. Surface Lewis acidity of gamma-Ga2O3 was revealed (mainly) by adsorbed pyridine, which gave the characteristic IR absorption bands of Lewis-type adducts at 1612, 1579, 1488, and 1449 cm(-1) (values noted under an equilibrium pressure of 1 Torr at room temperature); the corresponding Lewis acid centers (coordinatively unsaturated Ga3+ ions) were found to be weaker, although more abundant, than those present on the surface of gamma-Al2O3 (unsaturated Al3+ ions). Another significant difference between gamma-Ga2O3 and gamma-Al2O3 is the smaller thermal stability of pyridine and 2,6-dimethylpyridine Lewis adducts formed on the gallium oxide. The surface basicity of gamma-Ga2O3 was studied by using carbon dioxide and deuterated acetonitrile as IR probe molecules. Adsorbed CO2 gave carbonate and hydrogen-carbonate surface species similar to those formed by gamma-Al2O3. Adsorbed acetonitrile gave rise to acetamide species, which revealed the basic character of surface O2- ions. These acetamide species were found to be more abundant on gamma-Ga2O3 than on gamma-Al2O3.

A series of sulphated binary oxides ZrO2-TiO2 (10 wt% SO42-) Was prepared by simultaneous hydrolysis of zirconium n-propylate and titanium n-propylate, followed by calcination at 450degreesC. The sulphatation was performed before hydrolysis by addition of H2SO4 to Ti and Zr mixed alkoxides solutions. The so-obtained mixed catalysts are amorphous, and they present a high specific surface area. Their infrared spectra present one band at 1380 cm(-1) indicating the presence of surface sulphate species while another one at 1140 cm(-1) is characteristic of bulk-like sulphate species. The thermal stability of the latter is higher than that of the surface species. Moreover their amount sharply decreases with the introduction of TiO2. Infrared spectra of adsorbed pyridine on these oxides showed that the surface sulphate species creates Bronsted acidity.

We demonstrated the surface composite character down to the nanometer scale of SiO(2)-CeO(2) composite high surface area materials, prepared using 5 nm colloidal CeO(2) nanoparticle building blocks. These materials are made of a homogeneous distribution of CeO(2) nanoparticles in thin layers of SiO(2), arranged in a hexagonal symmetry as shown by small-angle X-ray scattering and transmission electron microscopy. Since the preparation route of these composite materials was selected in order to produce SiO(2) wall thickness in the range of the CeO(2) nanoparticle diameter, these materials display surface nanorugosity as shown by inverse chromatography. Accessibility through the porous volume to the functional CeO(2) nanoparticle surfaces was evidenced through an organic acid chemisorption technique allowing quantitative determination of CeO(2) surface ratio. This surface composite nanostructure down to the nanometer scale does not affect the fundamental properties of the functional CeO(2) nanodomains, such as their oxygen storage capacity, but modifies the acid-base properties of the CeO(2) surface nanodomains as evidenced by Fourier transform IR technique. These arrays of accessible CeO(2) nanoparticles displaying high surface area and high thermal stability, along with the possibility of tuning their acid base properties, will exhibit potentialities for catalysis, sensors, etc.

Adsorption of CS2 on a series of metal oxides (Al2O3, ZrO2, ZnO and CeO2) activated at 723 or 973K was studied at room temperature by FT-IR spectroscopy. In addition to hydrogen thiocarbonate and carbonate species, a new species, characterized by bands in the 1200–1000cm−1 range, was evidenced. Its amount increased by increasing activation temperature of metal oxides. Co-adsorption experiments of CS2 with either CO2 or pyridine showed that its adsorption sites are mainly those giving rise to bidentate carbonates from CO2. Experiments on ZrO2 preechanged by H218O confirmed CS2 adsorption on basic O2− sites. Xanthate (COS2)2− species formation was proposed. Results were compared with metal oxide basicity and a nice agreement was observed. However, on ceria, carbonates formation easily occurred from CS2 adsorption, even at room temperature, suggesting that CS2 can probe both surface basicity, through the intensity of bands due to xanthate species, and surface oxygen mobility, involved in the surface transformation of xanthate into carbonate species.

Sulfate species formed by heating SO2 in excess of O2 at 723K on TiO2, ZrO2, Al2O3 and Al2O3 promoted by Fe, Cu, Ni, Mo, W or V were studied by FT-IR spectroscopy. The presence of Ni, Cu or Fe enhance sulfate formation on the alumina support. The sulfated samples were then heated under H2S at different temperatures. It was found that sulfate species on TiO2 and ZrO2 were much more easily reduced than those on alumina. The presence of promoting elements on alumina increased the sulfate reducibility. CS2 hydrolysis was also performed at 593K, on pure and promoted aluminas. Under flow of CS2+H2O, alumina was more active than Cu/Al2O3 and Fe/Al2O3. However, in more realistic conditions, e.g. in presence of SO2 and/or O2, addition of H2S to the flow maintained the activity of Cu and Fe doped catalysts with time-on-stream whereas that of pure Al2O3 drastically decreased, in agreement with H2S sulfates reduction results. The inactivity of Mo, W or V/Al2O3 samples toward CS2 hydrolysis was explained involving the acidity induced by these promoters.

The mixed oxides ZrO2 -TiO2, Al2O3 - ZrO2, Al2O3 - TiO2 have been prepared by simultaneous hydrolysis of alkoxide solutions of the corresponding elements. The obtained mixed oxides display a homogeneous composition and a high surface area. The characterization of acidic and basic properties of the various samples has been performed by FT-IR spectroscopy using the adsorption of specific probe molecules (carbon dioxyde, pyridine). The results show that acidity increases whereas basicity decreases as a fonction of TiO2 for ZrO2 - TiO2 and Al2O3 -TiO2. The maximum of acidity corresponds to a composition of 84 % and 50 % of TiO2 respectively. In contrast to these two systems, Al2O3 - ZrO2 exhibits no particular propertie which indicates weak interactions between the individual oxides.