Élimination du colorant basique « Bleu de Méthylène » en solution aqueuse par l’argile de Safi

Ce travail porte sur l’étude de l’adsorption du colorant bleu de méthylène, colorant cationique utilisé dans la teinture du coton, du bois et de la soie sur l’argile brute et purifiée de la région de Safi (Maroc). Les essais d’adsorption ont montré que l’équilibre s’établit au bout de 20 minutes. Différents paramètres expérimentaux ont été analysés : pH, masse d’adsorbant et concentration initiale en colorant. Les résultats expérimentaux ont montré que l’adsorption du colorant bleu de méthylène sur l’argile brute et purifiée dépend du pH de la solution et de la concentration initiale en colorant.La capacité d’adsorption a été déterminée en utilisant les isothermes de Langmuir et Freundlich. La capacité maximale d’adsorption de l’argile brute est de 50 mg•g-1, celle de l’argile purifiée est de 68,5 mg•g-1. La cinétique d’adsorption du bleu de méthylène a été étudiée en utilisant les équations du pseudo-premier-ordre et pseudo-second-ordre. L’adsorption du colorant bleu de méthylène sur l’argile brute et purifiée peut être décrite par une cinétique du pseudo-second-ordre. L’effet de la température sur l’adsorption du colorant a été également étudié et les paramètres thermodynamiques ont été déterminés.This study reports the adsorption of methylene blue dye, a cationic dye used in dyeing cotton, wood and silk, on the crude and purified clay from Safi (Morocco). The adsorption experiments demonstrated that adsorption equilibrium is established after 20 minutes. Various experimental parameters were analyzed: pH, adsorbent mass, initial dye concentration. The experimental results showed that adsorption of methylene blue onto crude and purified clay is related to the pH of the solution and the initial dye concentration.The adsorption capacity was determined using the Langmuir and Freundlich isotherms. The monolayer adsorption capacity for methylene blue dye is 50 mg per g of crude clay while the monolayer adsorption capacity on purified clay is 68,5 mg per g clay. The adsorption kinetics of methylene blue were studied using the equations of the pseudo-first-order and pseudo-second-order reactions. The kinetics of adsorption of methylene blue dye onto the crude and purified clay can be described by a pseudo-second-order model. The effect of temperature on the adsorption of the dye was also evaluated and the thermodynamic parameters were determined

Particle swarm optimization for beamforming design in a cognitive radio

Beamforming is essential for improving transmission in wireless sensor networks (WSNs), particularly in cognitive radio networks (CRNs) with several secondary users (SU) equipped with transmitting antennas. Optimizing beamforming while minimizing interference with primary users (PU) is of great interest. This study proposes an improved particle swarm optimization (PSO) algorithm to enhance beamforming performance. This approach aims to maximize the power of the beam directed to the SU receiver while controlling interference in the PU protection region. The results show that this algorithm constantly improves beam focus and signal-to-noise ratio to effectively optimize beamforming. Firstly, beam focusing becomes narrower as the number of antenna elements increases, generating optimal transmission conditions. Secondly, the algorithm achieves a considerable improvement in signal-to-noise ratio as the number of antenna elements increases. Furthermore, optimization performance improves as the number of antenna elements increases, as shown by the best fitness values. The simulations also illustrate the performance of the proposed method

Adsorption of BR46 dye using raw and purified clay

The adsorption behaviour of Basic Red 46 (BR46) from aqueous solution onto raw (RA) and Purified (PA) natural adsorbent samples was investigated as a function of parameters such as initial dye concentration, contact time and temperature. The Langmuir, Freundlich and Dubinin– Radushkevich (D–R) adsorption models were applied to describe the equilibrium isotherms. The Langmuir monolayer adsorption capacities of RA and PA were estimated at 54 mg/g and 72 mg/g, respectively. The mean adsorption energy derived from D–R isotherm for the PA and the RA showed that the type of adsorption of dye molecules on these materials may be defined as physical adsorption for the PA and ion-exchange processes for the RA. The adsorption rate was fast and the equilibrium was achieved within 20 min at the room temperature. The pseudo-first-order and pseudo-second-order kinetic were used to describe the kinetic data and rate constants were evaluated. The trend of the correlation coefficients values (r²) were pseudo-second-order > pseudo-first-order. Thermodynamic parameters were also evaluated and revealed that the adsorption process is exothermic in nature. The quite high adsorption capacity of PA will provide an important advantage for using of this material in basic dye solution.

Reactions oscillantes en electrocatalyse: etudes electrochimique et spectroscopique de l'oxydation du formaldehyde sur le rhodium

SIGLEINIST T 72999 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Performance Evaluation of LMS and CM Algorithms for Beamforming

In this paper, we compare the performances of the least mean square (LMS) and constant modulus (CM) algorithms for beamforming. Our interest in these algorithms finds its origins in their reliability as a source-receiver pair. In addition, their use brings a great frequency of diversity even to respond quickly to the increasing spectral demand. The results suggest that the greater the number of elements in the antenna, the better the directivity for both LMS and CM. We also note that a judicious choice of the control parameter mu leads to a better speed of convergence for the two algorithms. Let us note, however, that LMS is more efficient. Our simulations show that in an environment affected by white Gaussian noise, LMS is more robust than CM. This confirms the theoretical result due to the fact that LMS uses a sequence for learning. Performance analyses of the two techniques are simulated in the MATLAB environment

Performance Evaluation of LMS and CM Algorithms for Beamforming

In this paper, we compare the performances of the least mean square (LMS) and constant modulus (CM) algorithms for beamforming. Our interest in these algorithms finds its origins in their reliability as a source-receiver pair. In addition, their use brings a great frequency of diversity even to respond quickly to the increasing spectral demand. The results suggest that the greater the number of elements in the antenna, the better the directivity for both LMS and CM. We also note that a judicious choice of the control parameter mu leads to a better speed of convergence for the two algorithms. Let us note, however, that LMS is more efficient. Our simulations show that in an environment affected by white Gaussian noise, LMS is more robust than CM. This confirms the theoretical result due to the fact that LMS uses a sequence for learning. Performance analyses of the two techniques are simulated in the MATLAB environment.</jats:p