Permeation study on the hollow-fiber supported liquid membrane for the extraction of Cobalt(II)

The transport of Co(II) through hollow-fiber-supported liquid membrane containing di-(2-ethylhexyl) phosphoric acid (D2EHPA) diluted in kerosene was examined. The mass transfer rate, expressed as permeability, P, focused on diffusion through the aqueous layer in the feed solution, the organic layer and the aqueous layer in the stripping solution. Experiments were performed as a function of aqueous feed solution velocity (100-500 ml/min), carrier concentration (0.1-20% v/v), aqueous stripping solution velocity (100-1,000 ml/min) and feed concentration (100-1,000 ppm) with 0.1 M HCl in the product phase. pH of the feed solution was 5.0. The measured permeabilities were compared to generally accepted mass transfer correlations. The validity of the prediction was evaluated with the experimental data, and the data were found to tie in well with the theoretical values. The model is the reported describing that the rate limiting step in the transport of the ion was the diffusion through both aqueous films, feed and stripping, whereas the organic resistance of the membrane was negligible. From this study, the model has good potential for the prediction of permeability of Co(II).     

Decision tree models for characterizing smoking patterns of older adults

The main objective of the present paper is to characterize smoking behavior among older adults by assessing the psychological distress, physical health status, alcohol use, and demographic variables in relations to the current smoking. We targeted 466 senior American smokers who are 65 years of age or older from the 2006 National Survey on Drug Use and Health (NSDUH, 2006). We employed a decision tree algorithm to conduct classification analysis to find the relationship between the average numbers of cigarette use per day. The results showed that the most important explanatory variable for prediction of the average number of cigarette use per day is the age when first started smoking cigarettes every day, followed by education level, and psychological distress. These results suggest that social workers need to provide more customized and individualized intervention to older adults.     

Separation of radioactive metal ions by hollow fiber-supported liquid membrane and permeability analysis

Extraction and stripping of uranium ions from nitrate media using a hollow fiber liquid membrane contactor was studied. In this study, tri-butyl phosphate (TBP) diluted in kerosene was used as extractant and sodium hydroxide was applied as a stripping solution. Uranium ions were extracted using TBP 5%(v/v) by rejecting thorium ions into raffinate with a maximum percentage of extraction for the uranium being 67%. The mathematical model was focused on the extraction side of the liquid membrane system. The permeability for each concentration of HNO₃ was investigated by mass transfer theory. When the concentration of HNO₃ increased, more uranium ions were extracted; however, when the concentration of uranium and thorium in the feed solution was increased, the percentage of extraction and stripping slightly decreased because the permeability decreases when the concentration of the feed solution increases due to membrane fouling and concentration polarization.     

Evaluation of chromatographic separation of free lutein and fatty acids in de-esterified marigold lutein

In this study, chromatographic purification of de-esterified marigold lutein was evaluated to obtain high purity free lutein. The quantification and identification of fatty acid in the de-esterified marigold lutein, which have not been reported before, were determined. The amount of fatty acid, mostly palmitic acid, was 49.12 mg/g oleoresin. The separation of free lutein and fatty acid was then performed. The high purity and recovery of free lutein were observed to be 99.2% and 95.2%, respectively, for the suitable chromatographic separation condition, i.e., step-gradient of hexane-ethyl acetate mixture at 85:15 v/v in the first 12 min, followed by 70:30 v/v.     

Mass transfer modeling of membrane carrier system for extraction of Ce(IV) from sulfate media using hollow fiber supported liquid membrane

A theoretical and experimental study on the extraction and stripping of Ce(IV) ions from sulfate media using microporous hydrophobic hollow fiber supported liquid membrane has been performed. The experiments were made in the recycling mode. Tri-n-octylamine (TOA) was used as extractant diluted in kerosene and sodium hydroxide was use as strip solution. The mathematical model focused on the extraction side of a liquid membrane system. The aqueous feed mass transfer coefficient (k_i) and the organic mass transfer coefficient (k_m) which were calculated from the model were 9.47 X 10^-2 and 6.303 cm/s, respectively. Therefore, the rate controlling step is the diffusion of the cerium complex across a liquid membrane. In addition, the mass transfer modeling was performed and the validity of the developed model was evaluated with experimental data and found to tie in well with the theoretical value when the concentration of TOA was higher than 5% (v/v).     

Selective recovery of palladium from used aqua regia by hollow fiber supported with liquid membrane

This research study was aimed at recovering palladium from used aqua regia by means of a hollow fiber thoroughly supported with liquid membrane. The liquid membrane, consisting of two extractants—thioridazine HCl and oleic acid-solubilized in chloroform—was used to coat the rmcroporous hollow fiber throughout. Sodium nitrite, a stripping agent, which was fed through the shell side, flowed counter-currently with the feed solution fed via the tube side. The following factors were investigated: the concentrations of the two extractants and of sodium nitrite, the pH of used aqua regia, the flow rates of both the feed and stripping solution, and the number of runs in the hollow fiber module. It was found that after a 30-mmute operation, 29.10% of palladium ion was optimally recovered at 0.0005-M thioridazine and 0.05-M oleic acid. With reference to the precious metals recovered, the following order was recorded: Pd(II)>Pt(IV)>Cu(II)>Au(III). It was observed that synergistic extraction could be gained at the concentration level of the extradants, regulated in the experiment. The liquid membrane system had long-term stability and even after the third run, it could still recover palladium up to 65%.     

Chromatographic modeling of free lutein derived from marigold flowers

Abstract

In this study, mass transfer of free lutein derived from marigold in a chromatographic process was mathematically modeled. The required model parameters were first determined. The adsorption isotherm was determined from experimental adsorption study using batch method, while the overall mass transfer and axial dispersion coefficients were determined from appropriate empirical equations. The adsorption isotherm was found to be Langmuir and was applied to three mathematical models: ideal model, equilibrium–dispersive model, and transport model. From the results, the transport model was able to the most reasonably describe the mass transfer behavior of free lutein in both linear and nonlinear ranges of concentration. The optimum mobile phase velocity, determined numerically, was 0.16?cm/s.