Molecular modeling of cationic dyes adsorption on agricultural Algerian olive cake waste

International audienceIn this research, the adsorption isotherms of Methylene Blue (MB) and Basic Yellow 28 (BY28) on agricultural Algerian olive cake waste (AAOCW) were modeled at molecular level using statistical physics and COSMO–RS theories. This molecular modeling aimed to demonstrate an alternative way to describe the interactions between dyes and adsorbents. The adsorption equilibrium isotherms of MB and BY28 on AAOCW were constructed at different temperatures. The statistical physics model was used to quantify the number of adsorbed dye molecules per site, the anchorage number, the receptor sites density, the adsorbed quantity at saturation, the concentration at half saturation and the molar adsorption energy. The COSMO–RS theory was used to quantify the interaction energies Electrostatic, hydrogen bonding and Van der Waals. σ–Profile and σ–potential were calculated to show the ability of each of the two dyes to interact with every adsorbent site. It was demonstrated that statistical physics and COSMO–RS theories are confident ways to elucidate the interactions between dye molecules and adsorbent surface at a molecular level. © 2018 Elsevier B.V

Computational study of acid blue 80 dye adsorption on low cost agricultural Algerian olive cake waste Statistical mechanics and molecular dynamic simulations

International audienceThe present study is focused on the adsorption of acid blue 80 dye on a low-cost sorbent, i.e. agricultural Algerian olive cake waste. FTIR analysis of the sorbent shows that the main compositional fractions are cellulose (cellobiose), hemicelluloses (xylose) and lignin. Batch isotherm studies are carried out under different experimental conditions in terms of temperature and pH. A subsequent FTIR spectrum analysis of the spent sorbent is adopted for a phenomenological interpretation of adsorption. Experimental adsorption isotherms show the presence of two steps, depending on the dye concentration. Adsorption isotherms are interpreted by statistical physics as well by molecular dynamics simulations. Based on statistical physics approach, a heterogeneous Bimodal-Gauss monolayer model is developed to evaluate the adsorption energy distribution and the isosteric heat of adsorption (Qst). The evaluations of adsorption energy distribution and Qst show that the interactions between adsorbent and adsorbate have greater magnitude than the adsorbate-adsorbate ones and aggregates of dye molecules are formed during the adsorption process. Furthermore, the heterogeneity of adsorbent is evaluated according the modeling approach showing that the temperature catalyzes the heterogeneity of surface and then different kinds of interaction occur during adsorption process. These interactions were identified by molecular simulations as Hydrogen, Van der Waals and electrostatic bonds. Finally, simulations results allow highlighting the lignin as the main compositional fraction of the sorbent responsible for adsorption of the investigated dye. © 201