Mhamed Taibi

Bio: Mhamed Taibi is an academic researcher from École Normale Supérieure. The author has contributed to research in topics: Thin film & Raman spectroscopy. The author has an hindex of 18, co-authored 111 publications receiving 1095 citations. Previous affiliations of Mhamed Taibi include Institut Galilée & Centre national de la recherche scientifique.

Structure and DC conductivity of lead sodium ultraphosphate glasses

Abstract: Glasses of (0.40−x)Na2O−xPbO−0.60P2O5 system with (0⩽x⩽0.40) molar fraction have been prepared with a conventional melting procedure. Their physical, thermal and spectroscopic studies such as density, molar volume, glass transition temperature, ionic conductivity and infrared spectroscopy have been investigated. The density and thermal stability of theses glasses increase with the substitution of PbO for Na2O. The ionic conductivity increases substantially with increasing concentration of sodium oxide and diminishes with increasing PbO content. Fourier-transform infrared spectroscopy reveals the formation of POPb bonds in theses glasses. The formation of POPb bonds which replace PO−…Na+ bonds is in accordance with variations of glass transition temperature (Tg), molar volume (Vm) and ionic conductivity (σ). The former bonds are the origin of the partial glass-forming ability of Pb2+.

Application of geopolymers for treatment of water contaminated with organic and inorganic pollutants: State-of-the-art review

Abstract: This study aims to provide a state-of-the-art review on application of geopolymer (inorganic polymer) materials for treatment of waters and wastewaters contaminated with organic pollutants (such as dyes), and inorganic pollutants (such as heavy metals). Geopolymer materials possess good surface and interface properties for immobilization, encapsulation, and adsorption of pollutants from waters and wastewaters. Special focus is given to available studies conducted over the last ten years (2010–2020) to draw an in-depth knowledge on the formulation and characterization of geopolymers as efficient, environmentally-friendly low-cost adsorbents for elimination, decontamination, and purification of inorganic and organic hazardous pollutants from aqueous environments. The ability of geopolymer materials to remove hazardous compounds from aqueous mediums and wastewaters was assessed to be comparable to that of other composites. The nature, mechanism of adsorption, and interaction between adsorbents (geopolymers) and adsorbates (dyes and heavy metals) are investigated by the isotherm and kinetic models, respectively. The thermodynamic study between geopolymers and pollutants was also evaluated to assess the feasibility and favorability of the adsorption process. Most kinetic and isothermal studies showed that the adsorption of heavy metal ions and dyes (cationic and anionic) on geopolymers synthesized by different aluminosilicate sources are described by pseudo-second-order and Langmuir models, respectively. Future studies could target the improvement of geopolymers capabilities, to be applied to other pollutants, such as herbicides and pesticides, as well as monitoring their efficiency in remediation processes, such as photo-degradation, encapsulation, and immobilization.

Preparation, Characterization, and Application of Metakaolin-Based Geopolymer for Removal of Methylene Blue from Aqueous Solution

Abstract: Metakaolin-based geopolymers are aluminosilicate materials that can be used as cationic dye adsorbents in aqueous system treatment. Our aim in this paper is to study the ability of geopolymer powder produced from metakaolin and alkaline activators to act as an adsorbent to remove methylene blue (MB). The solid materials were systematically analyzed by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectrometery (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and the point of zero charge. XRF, FTIR, XRD, SEM, and EDX analyses confirmed the formation of a geopolymer composite by geopolymerization reaction. The influence of various experimental factors such as geopolymer dosage, pH, initial dye concentration, contact time, and temperature was assessed. Adsorption isotherms were evaluated by Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms. Kinetics data were studied using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The thermodynamic parameters, namely, Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°), were determined. The results indicated that the maximum decolorization was found in high pH values. The collected isotherm data were best fitted by the Langmuir isotherm, and the maximum adsorption capacity of dye onto the geopolymer was 43.48 mg/g. The experiment kinetics followed the pseudo-second-order kinetic models. The thermodynamic results demonstrated that the adsorption of the obtained material occurs spontaneously as an endothermic process. The results confirmed that the prepared adsorbent can be used for remediation of water contaminated by MB dye.

An Advanced Ni–Fe Layered Double Hydroxide Electrocatalyst for Water Oxidation

Abstract: Highly active, durable, and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions, including water-splitting and rechargeable metal–air batteries. Here, we report the synthesis of ultrathin nickel–iron layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multiwalled carbon nanotubes (CNTs). Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-LDH. The crystalline NiFe-LDH phase in nanoplate form is found to be highly active for oxygen evolution reaction in alkaline solutions. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for oxygen evolution than commercial precious metal Ir catalysts.

Lanthanide-Containing Light-Emitting Organic-Inorganic Hybrids: A Bet on the Future

Abstract: Interest in lanthanide-containing organic-inorganic hybrids has grown considerably during the last decade, with the concomitant fabrication of materials with tunable attributes offering modulated properties. The potential of these materials relies on exploiting the synergy between the intrinsic characteristics of sol-gel derived hosts (highly controlled purity, versatile shaping and patterning, excellent optical quality, easy control of the refractive index, photosensitivity, encapsulation of large amounts of isolated emitting centers protected by the host) and the luminescence features of trivalent lanthanide ions (high luminescence quantum yield, narrow bandwidth, long-lived emission, large Stokes shifts, ligand-dependent luminescence sensitization). Promising applications may be envisaged, such as light-emitting devices, active waveguides in the visible and near-IR spectral regions, active coatings, and bio-medical actuators and sensors, opening up exciting directions in materials science and related technologies with significant implications in the integration, miniaturization, and multifunctionalization of devices. This review provides an overview of the latest advances in Ln(3+)-containing siloxane-based hybrids, with emphasis on the different possible synthetic strategies, photoluminescence features, empirical determination.

Chapter 155 Rationalization of crystal-field parametrization

Abstract: Publisher Summary This chapter describes the symmetry aspects of the crystal field and the parametrization of the energy level scheme. It provides an overview of the experimental data of trivalent lanthanide ions doped into crystalline host matrices. The selection rules for induced electric dipole (ED) and magnetic dipole (MD) transitions for systems with even or odd numbers of f electrons in different site symmetries are presented. Methods for the assignment of crystal-field levels are discussed and the determination of phenomenological crystal-field parameters is described. Such a set of crystal-field parameters in combination with a suitable set of free-ion parameters allows calculating crystal-field energy levels and reconstructing the energy diagram of the 4fn configuration. In this way, it is not only possible to check the validity of the crystal-field model but also to get information about energy levels, which cannot be detected experimentally.