The formation of interstellar organic molecules: H2C3O a DFT and ELF theoretical study

15 pags., 12 figs., 9 tabs., 1 app.This quantum study at B3LYP/6-311 ++ G (d, p) with ELF analysis were performed in order to understand the formation of propynal and cyclopropenone, two molecules detected in the interstellar medium. The formation of these molecules is supposed to be through reactions between carbon monoxide (CO) and acetylene (C2H2) in the cold conditions of interstellar clouds. All the structures, reagents, products and transition states, have been optimized and the geometrical parameters are given as well as the dipole moments. The reaction paths are elaborated and discussed here using the IRC method implemented in the Gaussian program. The determined activation energies allow an estimation of the rate constants. The ELF analysis performed here seems to be a valuable tool for screening the evolution of the bonds during the formation processes. The two reactions probably occur in one step. The propadienone, another possible isomer, has been also studied. It is formed through a third reaction. A stable triplet ground state of this molecule, the thermodynamic consideration and a small dipole moment can explain the fact that it is not detected yet in the interstellar medium. M06-2X and WB97XD functional were also used for comparing results.This project has received funding from CSIC iCOOP 2018 program under the reference number COOPB20364 and from the Ministerio de Educación y FP (Spain) under grant number (FIS2016-76418-

Fish scale of Sardina pilchardus as a biosorbent for the removal of Ponceau S dye from water: Experimental, designing and Monte Carlo investigations

International audienceIn this work, the removal of the hazardous Ponceau S dye (PS) from aqueous solutions was investigated using Fish Scale (FS) of Sardina pilchardus as low-cost adsorbent. Different relevant factors such as contact time, initial pH, initial PS concentration, biosorbent dose and temperature were examined to evaluate their effects. The optimization of these factors was performed with a Central Composite Design (CCD). Optimized parameters (pH = 2.1, [PS] = 35 mg L−1, m(FS) = 250.0 mg, V = 200 mL and T = 303 K) were found with the maximum of 96.58% PS loading onto FS. The kinetics results show that the pseudo-first-order model gave a better fit than the pseudo-second-order model. Freundlich isotherm gave a better fit than Langmuir model. The thermodynamic factors, such as Gibb's free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) have been calculated. The biosorption was found to be a spontaneous and endothermic process. The desorption of PS from exhausted biosorbent was investigated in alkaline solution. Furthermore, Monte Carlo (MC) and radial distribution function (RDF) simulations were achieved to obtain a better understanding of biosorption mechanism of PS on both collagen and hydroxyapatite (HDA) which are the main constituents of FS. The results showed that PS presented a better biosorption on collagen than on the HDA surface. The biosorption of PS onto studied surfaces was spontaneous, characterized highly by chemical interactions and slightly by physical ones. Since FS is a low-cost marine waste, it presents interesting perspectives in the treatment of contaminated wastewaters on a large-scale

Optimization of cadmium ions biosorption by fish scale from aqueous solutions using factorial design analysis and Monte Carlo simulation studies

International audienceThis work investigated cadmium ions biosorption on Fish scales (FS) of Sardina pilchardus. Different relevant parameters such as initial pH in the range 2.14-7.76, initial cadmium concentration from 35 to 150 mg L-1, and biosorbent dose in the range 50-300 mg L-1, were examined. The effect of these parameters on the cadmium removal was analyzed and optimized using full factorial design methodology and the analysis of variance. The kinetics were modelized for pseudo-second order and pseudo-first order models. Results showed that the pseudo-second order kinetic gave the best fit for equilibrium data. The biosorption isotherms were investigated for Freundlich and Langmuir models. Langmuir isotherm model gave the best fit and led to a maximum biosorption capacity of Cd(II) on FS of 52.08 mg g-1. The results indicated that FS of was effective in the removal of cadmium ions. Optimum Cd(II) removal of 88.2 % was calculated for pH 3, 75 mg L-1 of Cd(II) and 250 mg L-1 of FS. Monte Carlo simulation was used as relatively greener pathway to study the biosorption behavior of Cd(II) ions onto FS. It showed that the interaction Cd(II) - hydroxyapatite was more favored than Cd(II) - collagen