Abdellah Elmchaouri

Characterization of the dealumination effect into H faujasites by adsorption: Part 1. The water molecule as a structural aluminum ion selective probe

The adsorption and desorption isotherms of water vapor are drawn at 25°C for dealuminated HY zeolites upon framework Si/Al ratio. The isotherms are compared to that of the parent NaY zeolite studied in a wide range of temperatures and filling coefficients (0.03 < θ < 1). The isotherm changes in shape from type I to type IV with an hysteresis loop changing from type H4 to type H2, as the Si/Al ratio increases. The Polanyi—Dubinin theory is used to determine the volume accessible to water. It decreases with increasing Si/Al ratios, down to zero at a Si/Al ratio of 35. Such a result is accounted for by the adsorption on the hydrophillic centers, which are the cations (H+) associated with the structural aluminum ions, each cation being coordinated on average by 9 H2O.

Equilibrium and thermodynamic investigation of methylene blue adsorption on thermal- and acid-activated clay minerals

Abstract The use of a natural Moroccan clay as an adsorbent for removal of the cationic dye methylene blue from aqueous solutions has been investigated. The starting material was activated by thermal treatment and by acid leaching with nitric acid in order to obtain samples with modified adsorption properties. The effect of the experimental conditions on the adsorption behaviour was studied by varying the treatment temperature from 373 to 1,073 K in the case of the thermally treated solids, the nitric acid concentration for the acid-activated solids and the adsorption temperature from room temperature to 368 K for both these solids. Data obtained from further batch studies were analysed using the Freundlich, Langmuir and Toth isotherm equation models. The thermodynamic parameters of the adsorption process were calculated, and the resulting Gibbs free energy indicated its spontaneity. The adsorption capacity of the clay materials makes them suitable as a low cost alternative for the removal of cationic dye...

Study of the Pore Network of Dealuminated Faujasites by Water Vapor Adsorption

Summary The adsorption and desorption isotherms of water vapor are drawn at 25°C for dealuminated HY zeolites upon framework Si/Al ratio. The isotherms are compared to that of the parent NaY zeolite. The isotherm changes in shape from the type I to the type IV with an hysteresis loop changing from the type H 4 to the type H 2 , as increases the Si/Al ratio. The POLANYI-DUBININ theory is used to determine the micropore volume accessible to water. It decreases with increasing Si/Al ratios, down to zero at a Si/Al ratio of 35. Such a result is accounted by the adsorption on the hydrophilic centers which are the cations (H + ) associated with the structural aluminium ions, each cation being coordinated by 8H 2 O.

Removal of Tetrachloroethylene from Aqueous Solutions by Adsorption on Clay Minerals

The objective of this study was to assess the adsorption capacity of Moroccan stevensite for the removal of tetrachloroethylene from aqueous solutions. The mechanism of adsorption of tetrachloroethylene was studied in terms of pseudo-first-order and pseudo-second-order kinetic models by applying the Freundlich, Langmuir and Sips isotherm models to the equilibrium adsorption data. A maximum adsorption capacity of 284 mg/g at equilibrium was achieved, which indicates that the stevensite can be considered an efficient and suitable adsorbent for the removal of tetrachloroethylene from water systems and wastewaters.