Performance assessment of the MOF adsorbent MIL-101 for removal of gaseous benzene and toluene: kinetic column modeling and simulation studies of fixed-bed adsorption.

The adsorbent MIL-101, a metal-organic framework material, was synthesized, characterized, and tested for removal of relatively low concentrations of benzene and toluene adsorbates (200 ppm) from a gas phase in a continuous flow system. Breakthrough studies were modeled based on Thomas, Yoon-Nelson, Yan, Clark, Bohart-Adams, bed-depth service time, modified dose response, Wolborska, and Gompertz in the continuous fixed-bed operation. Through statistical analysis, it was determined which type of regression is most suitable for the studied models, linear or nonlinear. By comparing the values of error functions, it was possible to infer that the Thomas model is the best match for the experimental breakthrough curves for benzene (with maximum solid-phase concentration qT=126,750 mg/g) and the Gompertz model for toluene (parameter ß=0.01 min-1). Overall, when compared to the model parameters of the linear regression, those obtained through nonlinear regression show a stronger correlation with the results found experimentally. Thus, this type of regression is more suitable for the adsorption model analysis. The liquid film and intraparticle diffusion analysis was described, and it was suggested that both types of diffusion contribute to the adsorption mechanism of benzene and toluene on MIL-101. As for the isotherms, the adsorption process was better fitted by the Freundlich isotherm. The reusability of MIL-101 after six cycles was 76.5% for benzene and 62.4% for toluene, indicating that MIL-101 was a better adsorbent for the removal of benzene in comparison with toluene.

Isotherm, kinetic, and thermodynamic studies for dynamic adsorption of toluene in gas phase onto porous Fe-MIL-101/OAC composite.

In the present paper, micro-mesoporous Fe-MIL-101/OAC composite using in situ incorporation of Fe-MIL-101 into oxidized activated carbon was synthesized and characterized by XRD, FT-IR, SEM, EDS, and BET techniques. The adsorption performances of toluene onto adsorbents in the gas phase were studied using a laboratory-scale dynamic adsorption system under moist ambience. The toluene adsorption capacity of Fe-MIL-101/OAC composite and Fe-MIL-101 were 127 and 97.6 mg g-1, severally. Results revealed that the larger pores in micro-mesoporous Fe-MIL-101/OAC enhanced the molecular diffusion rate. The findings indicated that micro-mesoporous structures played key roles in the capture of toluene molecules. The initial toluene concentration positively affected on toluene adsorption capacity while temperature and humidity negatively affected on toluene adsorption capacity. The Langmuir model and the pseudo-second-order kinetics model described better adsorption process of Fe-MIL-101/OAC composite. Thermodynamic findings determined that toluene adsorption over Fe-MIL-101/OAC was spontaneous, exothermic physisorption. The regeneration of the composite was still up to 72.6% after six cycles. The micro-mesoporous Fe-MIL-101/OAC composite proposes a promising support for the high toluene removal for future. Graphical abstract.

Stability of beta-lactoglobulin A in the presence of sugar osmolytes estimated from their guanidinium chloride-induced transition curves.

The stabilizing role of Trehalose, Sucrose, Sorbitol and Mannitol as sugar osmolytes and polyols on beta-lactoglobulin A (beta-lgA) against its chemical denaturation at pH 2.0 and 25 degrees C has been explored by means of UV-vis spectroscopy. It has been observed that DeltaG (D) (o) of beta-lgA in the presence of 10% (w/v) Trehalose, Sucrose, Sorbitol and Mannitol is increased. We report that the functional dependence of DeltaG (D) of proteins in the absence and the presence of sugar osmolytes on denaturant concentration is linear. Trehalose is found to induce remarkable stability of beta-lgA against chemical denaturation. Furthermore, we assumed sugar osmolytes do not affect the secondary and tertiary structures of the native and GdnHCl-denatured states.