Absorption of hydrogen sulfide and carbon dioxide in exfoliated graphene oxide (EGO)−water and synthesized silica (SS)−water nanofluids in a bubble column was investigated. Oxygen group functionalities and silanol groups were detected on the surface of EGO and SS nanoparticles, respectively. Due to the adsorption of H 2 S by these functionalities in EGO and SS nanoparticles, the mass transfer coefficient, k L , increased more than 500% and 200% relative to the based fluid, respectively. The EGO−water nanofluid significantly absorbs H 2 S while CO 2 absorption is diminished to zero in nanoparticle mass fractions higher than 0.02 wt %, because oxygen groups on the EGO surface attract H 2 S but repel CO 2 molecules. However, SS nanoparticles attract both CO 2 and H 2 S due to hydrogen bonding between gas molecules and hydrogen atoms in the silanol groups.

Nanoparticles addition is a novel technique for enhancement of mass transfer in absorption process. A bubble column was used for investigation of hydrogen sulfide (H2S) absorption process. Silica and exfoliated graphene oxide (EGO) were used for preparation of nanofluids used as hydrogen sulfide absorbent. The absorption rate of hydrogen sulfide deteriorated by addition of 14 nm silica nanoparticles to water, while EGO–water nanofluid augmented hydrogen sulfide absorption relative to the base fluid. EGO–water nanofluid with 0.02% wt EGO enhanced absorption rate by 40%. For greater mass percentages of EGO in water, the absorption rate was reduced. It is concluded that EGO–water nanofluid is suitable for H2S absorption. Grazing is the main reason for mass transfer enhancement in EGO–water nanofluids. Mathematical modeling was developed for predicting the effective absorption ratio. The maximum deviation of model predictions from the measurements is 13%.

No abstract

The solubility of loxoprofen as a nonsteroidal anti-inflammatory drug (NSAID) is measured at various temperatures (308, 318, 328, and 338 K) and pressures (12,16,20,24,28,32,36, and 40 MPa) in supercritical carbon dioxide (SC-CO 2 ). The solubility data were measured using a gravimetric-based approach and revealed the solubility range of 1.35 × 10 −5 to 1.28 × 10 −3 based on the mole fraction of loxoprofen. The results revealed that solubility can be significantly enhanced from 1.04 × 10 −5 to 1.28 × 10 −3 (mole fraction basis) for the isotherm at 338 K because of the effect of temperature which can boost the pressure effect on solubility enhancement, at pressures greater than crossover (around 20 MPa for the case of loxoprofen). Moreover, the experimental data points were modeled using five different density-based correlations including Chrastil, Garlapati and Madras, Mendez-Santiago and Teja (MST), Bartle et al., and Kumar and Johnston (K−J) models because measuring the solubility of loxoprofen in entire required ranges of pressure and temperature is impossible or expensive similar to the other pharmaceuticals. The results of modeling revealed that one can correlate the loxoprofen solubility data with an accuracy of about 9.2% (Mendez-Santiago−Teja), 10.7% (Bartle et al.), 7.1% (Kumar and Johnstone), 12.7% (Chrastil), and 12.7% (Garlapati and Madras) based on average absolute relative deviation percent (AARD %).

No abstract