Correlation between eletrokinetic mobility and ionic dyes adsorption of Moroccan stevensite

This study aims at establishing a correlation between the electrical charge of Moroccan stevensite particles and ionic dyes adsorption. The electrophoretic mobility, (Ue), of the stevensite particles in water, was measured at pH 2.5–12 by microelectrophoresis. At pH between 2.5 and 8, Ue remained constant (Ue = − 1.6 10− 8 m2/(V s)), as resulting from the permanent charge of the clay mineral planar surfaces. At pH > 8, the magnitude of electrophoretic mobility increased (Ue = − 2.7 10− 8 m2/(V s)) due to the deprotonation of silanol groups on the surfaces. The anionic Orange G adsorption at the clay mineral–water interface was negligible whereas the methylene blue cations were strongly adsorbed due to the electrostatic attraction

Synthesis, characterization and photocatalytic activity of TiO2 supported natural palygorskite microfibers

This study deals with the synthesis of TiO2 supported Moroccan palygorskite fibers and their use as photocatalyst for the removal of Orange G pollutant from wastewater. The TiO2-palygorskite nanocomposite synthesis was accomplished according to a colloidal route involving a cationic surfactant as template (hexadecyltrimethylammonium bromide) assuring hence organophilic environment for the formation of TiO2 nanoparticles. The clay minerals samples were characterized before and after functionalization with TiO2. Anatase crystallizes above ca. 450 °C and remarkably remains stable up to 900 °C. In contrast, pure TiO2 xerogel obtained from titanium tetraisopropoxide (TTIP) showed before calcination a nanocrystalline structure of anatase. By increasing the temperature, anatase readily transforms into rutile beyond 600 °C. The remarkable stability at high temperature of anatase particles immobilized onto palygorskite microfibers was due to the hindrance of particles growth by sintering. Homogeneous monodisperse distribution of anatase particles with an average size of 8 nm was found by TEM and XRD onto palygorskite fibers. This anatase particle size remains below the nucleus critical size (ca. 11 nm) required for anatase–rutile transition. The TiO2 supported palygorskite sample annealed in air at 600 °C for 1 h exhibits the highest photocatalytic activity towards the degradation of Orange G compared to nanocomposite samples prepared under different conditions as well as pure TiO2 powders obtained from the xerogel route or commercially available as Degussa P25

Multiaxial fatigue behavior of 2618 aluminum alloy

The purpose of the present research project is to study multiaxial fatigue behavior of 2618 alloy. The influence of mean stress on the fatigue behavior under tension and torsion is particularly investigated. Fatigue tests under combined tensile-torsion, in or out of phase, as well as combined tensile-torsion-internal pressure tests have also been conducted. Multiaxial fatigue results are analyzed according to Fatemi-Socie criterion to predict the fatigue life

A novel microstrip low pass filter based on ring topology

This paper describes the design of a new configuration of a low pass filter (LPF). This filter structure is based on a ring topology. The proposed LPF is miniature and low cost because it is mounted on FR4 substrate. The validation of this circuit into simulation was based on many optimization methods integrated in ADS "Advanced Design System" and some tuning methods. At the end, the fabrication and the test of the final circuit permits to have a good agreement between simulation and measurement results reaching a low pass behavior. The proposed filter has an area of 25x25 mm2, with a cutoff frequency of 2GHz and good performances in term of insertion losses, which are around -0.127 dB in the whole bandwidth and a high stopband

Supported Photocatalyst Based on CuO–TiO2/Palygorskite Nanocomposite Material for Wastewater Treatment

This study deals with the immobilization of mixtures of two semiconductor oxides CuO and TiO2 on fibrous palygorskite clay mineral in order to evaluate their photocatalytic activity for removing Orange G dye as model pollutant from aqueous solutions. The elaboration of CuO–TiO2/Palygorskite nanocomposites was carried out by impregnation with Cu2+ of before hand synthesized TiO2 supported palygorskite (Pal) followed by air annealing for 5 h at 550 °C. In the composite materials, different CuO to CuO + TiO2 molar ratios were used in order to obtain a CuO content in the range 13–30 mol.%. XRD, SEM and TEM equipped with elemental EDS analysis are concordant for showing the crystallization of anatase TiO2 along with CuO whose average size of nanoparticles (NPs) are in the range 6 to 20 nm as determined by TEM. By increasing the CuO content the average size of this oxide remains constant at about 10 nm while that of TiO2 NPs is slightly decreasing from 8.4 to 5.1 nm. Both oxide NPs were successfully attached on palygorskite fibers where they form CuO–TiO2 heterojunctions (grain boundaries like). The CuO–TiO2/Pal supported photocatalyst containing 23% of CuO was found to be the most photoactive material but itremained less active than TiO2/Palygorskite supported photocatalyst. The photocatalytic activity of the mixed nanocomposites is not readily correlated with only one of their main features as CuO content or the average crystallite size of functional oxides indicating that if there are synergistic effects there are also antagonistic effects in particular for high CuO contents

Electrokinetic and ionic dyes adsorption studies of Moroccan stevensite Jbel Rhassoul clay

This study aims at establishing correlation between the nature of electrical charge of morocan stevensite Jbel Rhassoul clay particles and ionic dyes adsorption phenomenon. The electrical charges of the clay mineral particles were assessed by measuring zeta potential (z) using micro electrophoresis technique. Measurements were carried out onto aqueous clay dispersions by varying the pH in the range 2.5 – 12 with additions of HCl or NaOH. On the whole, the electrical charges of stevensite particles remain negative in the whole pH range. Nevertheless, depending on the pH values, two behaviours were observed. For pH ranging from 2 to around 8, the negative electrical charge remains constant (z = - 20 mV) and corresponds to permanent charges of basal surfaces formed of –O-Si-O- groups insensitive to pH variation. Beyond pH = 8, the electrical charge increases (z = - 35 mV) as a result of deprotonation of silanol edge groups. Ionic dyes adsorption experiments show that anionic orange G adsorption is negligible whereas that of cationic methylene blue is greater due to columbic interactions. In accordance with eletrokinetic measurements, the methylene blue adsorption capacity onto stevensite particles significantly increases beyond pH » 8 due to the increase of the whole electrical charge of stevensite particles evolved by silanol edge sites deprotonation

Photocatalytic activity of TiO2/stevensite nanocomposites for the removal of Orange G from aqueous solutions

TiO2/stevensite nanocomposite photocatalysts were synthesized by a solvothermal method using TiCl3/HCl as reactants and the stevensite clay mineral extract as support. The prepared photocatalyst samples were then characterized using various techniques such as X-ray diffraction (XRD), Infrared spectroscopy (IR) and Transmission Electron Microscopy (TEM). The Points of Zero Charge (PZC) of the various samples were evaluated by titration of the non-modified and the Ti-modified clay aqueous dispersions, with cationic surfactant solutions. The photocatalytic activity of the resulting nanocomposites samples were evaluated for the removal of Orange G (OG) from aqueous solution as a model dye pollutant. The data indicate that the formation of Na+-stevensite by the TiO2 particles leads to TiO2/stevensite nanocomposites having higher specific surface areas and mesopore volumes, and lower PZC values. Further, the photocatalytic activity was found to be greater for the TiO2/stevensite nanocomposites having the greatest Ti amount, as compared to a pure TiO2 sample, and increased with the increase of the TiO2 amount in the TiO2/stevensite nanocomposites