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Kenitra, Morocco

Fayoud N.,University Hassan asablanca | Tahiri S.,Chouaib Doukkali University | Alami Younssi S.,University Hassan asablanca | Albizane A.,University Hassan asablanca | And 3 more authors.
Desalination and Water Treatment | Year: 2015

The purpose of this work is to establish the optimal experimental conditions for the removal of methylene blue (MB-as model basic dye) from aqueous solution by adsorption onto four agro-based materials, namely, cedar sawdust, pine sawdust, wheat straw, and Provence cane Arundo donax. Results show that an increase in acidity or ionic strength of the medium has generally a negative effect on the discoloration yield. From the data of pH effect, there is no need to change the initial pH of the MB solution to be treated. Equilibrium was reached after 20−30 min of agitation when cedar sawdust, pine sawdust, and Provence cane are used as adsorbents. However, in the case of wheat straw, an agitation for 40 min is required. The pseudo-second-order model was found as the best to explain the adsorption kinetics effectively. The adsorption may be controlled by external mass transfer followed by intra-particle diffusion mass transfer. The adsorption equilibrium data were fitted well by the Langmuir isotherm and the maximum adsorption capacity was estimated to be about 100, 71.4, 143, and 91 mg g−1 for cedar sawdust, pine sawdust, straw, and Provence cane, respectively. For all the adsorbents tested, adsorption decreases with the increase in solution temperature. The values of the thermodynamic parameters of each system adsorbent/MB indicated that adsorption is a spontaneous and exothermic process. The comparison of the characteristics of the supernatants recovered after adsorption shows clearly that cedar sawdust leads to the production of a liquid with minimum values of turbidity, conductivity, and permanganate index. © 2015 Balaban Desalination Publications. All rights reserved. Source

Ettayfi A.,University Hassan asablanca | Moubah R.,University Hassan asablanca | Boutahar A.,University Hassan asablanca | Boutahar A.,CNRS Neel Institute | And 2 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2015

Polycrystalline La0.67Sr0.33MnO3 (LSMO) powders were prepared by solid-state reaction, and their structural, magnetic, magnetocaloric, and critical exponent properties have been investigated. X-ray diffraction has shown that the sample is polycrystalline with a rhombohedral (R-3c) structure. Scanning electron microscopy has revealed that the surface of the sample is chemically homogeneous. The samples undergo a second-order magnetic transition from a ferromagnetic to a paramagnetic state with a Curie temperature of 361 K. The maximum entropy change is determined to be 274 J/kg K for a magnetic field change of 0–5 T. For the same applied field, the adiabatic temperature change and relative cooling power are found to be 1.75 K and 242 J/kg, respectively. These values are compared with those reported in the literature. It is concluded that large grain sizes are mandatory in order to obtain high magnetic refrigeration efficiency in LSMO-based compounds. Moreover, it is shown that the critical exponent values are in agreement with those of the long-range mean field model. © 2015 Springer Science+Business Media New York Source

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