Modeling biosorption of Cr(VI) onto Ulva compressa L. from aqueous solutions

International audienceThe marine biomass Ulva compressa L. (ECL) was used as a low-cost biosorbent for the removal of Cr(VI) from contaminated aqueous solutions. The operating variables were optimized: pH ∼ 2, initial concentration of 25 mg/L, solid/liquid ratio of 6 g/L and a temperature of 50 °C, leading to an uptake elimination of 96%. A full factorial experimental design technique enabled us to obtain a mathematical model describing the Cr(VI) biosorption and to study the main effects and interactions among operational parameters. The equilibrium isotherm was analyzed by the Langmuir, Freundlich and Dubinin–Radushkevich (D-R) models; it has been found that the adsorption process follows well the Langmuir model. Kinetic studies showed that the pseudo-second order model describes suitably the experimental data. The thermodynamic parameters indicated an endothermic heat and a spontaneity of the Cr(VI) biosorption onto ECL

Ni-exchanged cationic clays as novel heterogeneous catalysts for selectiveethylene oligomerization

International audienceMontmorillonite rich clays, including bentonite, acid washed clay (K10) and Al-pillared clay were exchangedwith nickel in order to prepare novel heterogeneous catalysts for the ethylene oligomerization. The catalyticproperties were examined in flow mode (p =3.0 MPa, T=150–350 °C), and the results were related to thetextural and acidic characteristics of the catalysts. Due to higher surface area and mesoporous volume, as well asmoderate acidity, Ni-exchanged K10 exhibited superior catalytic behaviour compared to others catalysts. Ni-K10was very active (TOF =570 h−1), stable (high conversion during 20 h on stream), and highly selective to linearC4 and C6 olefins