Surface Interactions during the Removal of Emerging Contaminants by Hydrochar-Based Adsorbents.

The aim of this work was to test activated carbons derived from hydrochars produced from sunflower stem, olive stone and walnut shells, as adsorbents for emerging contaminants in aqueous solution, namely fluoxetine and nicotinic acid. The adsorption capacity was determined by the chemical nature of the adsorbents, namely the presence of specific functional groups and their positive or negative ionization in aqueous solutions and also by steric factors. The activated carbons produced by air showed a higher adsorption capacity of fluoxetine, whilst the samples produced by carbon dioxide activation were more useful to remove nicotinic acid. In general, surface acidity was advantageous for fluoxetine adsorption and detrimental for nicotinic acid removal. The adsorption mechanisms involved in each case were discussed and related to the adsorbents characteristics. The maximum adsorption capacity, Q0, given by the Langmuir model was 44.1 and 91.9 mg g-1 for fluoxetine and nicotinic acid adsorption, respectively.

Removal of amitriptyline from simulated gastric and intestinal fluids using activated carbons.

In this work, the adsorption behavior of a tricyclic antidepressant, amitriptyline hydrochloride, onto several activated carbons (ACs) is reported. The adsorption was done using in vitro simulated gastric and intestinal fluid at 37°C to test the performance of the carbons as treatment in overdose cases. The tested materials were one commercial AC (carbomix) and two ACs produced in our laboratory. The highest adsorption capacity was achieved by carbomix, followed by the laboratory-made carbons that still have a very good performance with adsorption capacity up to 120 and 100 mg/g for the gastric and intestinal fluids, respectively.

Systems involving hydrogenated and fluorinated chains: volumetric properties of perfluoroalkanes and perfluoroalkylalkane surfactants.

As part of a combined experimental and theoretical study of the thermodynamic properties of perfluoroalkylalkanes (PFAAs), the liquid density of perfluorobutylpentane (F4H5), perfluorobutylhexane (F4H6), and perfluorobutyloctane (F4H8) was measured as a function of temperature from 278.15 to 353.15 K and from atmospheric pressure to 70 MPa. The liquid densities of n-perfluoropentane, n-perfluorohexane, n-perfluorooctane, and n-perfluorononane were also measured at room pressure over the same temperature range. The PVT behavior of the PFAAs was also studied using the SAFT-VR equation of state. The PFAA molecules were modeled as heterosegmented diblock chains, using different parameters for the alkyl and perfluoroalkyl segments, that were developed in earlier work. Through this simple approach, we are able to predict the thermodynamic behavior of the perfluoroalkylalkanes, without fitting to any experimental data for the systems being studied. Molecular dynamics simulations have also been performed and used to calculate the densities of the perfluoroalkylalkanes studied.

Viscosity of liquid perfluoroalkanes and perfluoroalkylalkane surfactants.

As part of a systematic study of the thermophysical properties of two important classes of fluorinated organic compounds (perfluoroalkanes and perfluoroalkylalkanes), viscosity measurements of four n-perfluoroalkanes and five perfluoroalkylalkanes have been carried out at atmospheric pressure and over a wide range of temperatures (278-353 K). From the experimental results the contribution to the viscosity from the CF(2) and CF(3) groups as a function of temperature have been estimated. Similarly, the contributions for CH(2) and CH(3) groups in n-alkanes have been determined using literature data. For perfluoroalkylalkanes, the viscosity results were interpreted in terms of the contributions of the constituent CF(2), CF(3), CH(2), and CH(3) groups, the deviations from ideality on mixing hydrogenated and fluorinated chains, and the contribution due to the formation of the CF(2)-CH(2) bond. A standard empirical group contribution method (Sastri-Rao method) has also been used to estimate the viscosities of the perfluoroalkylalkanes. Finally, to obtain molecular level insight into the behavior of these molecules, all-atom molecular dynamics simulations have been performed and used to calculate the densities and viscosities of the perfluoroalkylalkanes studied. Although both quantities are underestimated compared to the experimental data, with the viscosities showing the largest deviations, the trends observed in the experimental viscosities are captured.