The present work describes the possibility of using pervaporation to recover the tea aroma compounds from tea aroma condensate generated in the manufacturing of tea or instant tea, as well as directly from tea extract. Eight compounds that make a significant contribution to tea aroma, namely, trans-2-hexenal, linalool, cis-3-hexenol, 3-methylbutanal, 2-methylpropanal, benzyl alcohol, phenylacetaldehyde, and β-ionone, were studied in this work. Permeation studies for all of these compounds with poly(octyl methyl siloxane) (POMS) and poly(dimethylsiloxane) (PDMS) membranes in a batch-type vacuum pervaporation system were carried out, first, in their aqueous solutions (binary mixtures); second, in a model solution containing all of the abovementioned compounds; and last, with an actual tea extract. In this work, mainly the effect of the feed concentration on the organic flux and separation factor was studied. The permeation studies with the mixture revealed that β-ionone, trans-2-hexenal, linalool, cis-3-hexenol, and 3-methylbutanal offered very good selectivity, whereas phenylacetaldehyde, 2-methylpropanal, and benzyl alcohol gave moderate selectivity. The results indicate that pervaporation is an attractive technology for the recovery of tea aroma compounds from tea aroma condensate as it (i) yields good separation and (ii) operates under mild conditions. However, it should be noted that, because the selectivity offered by pervaporation varies considerably from compound to compound, attempts to concentrate a solution of volatiles to a high degree can result in significant alteration in the profile of the aroma. Thus, the commercial utility of this approach will need to be ascertained on a case-by-case basis.

Citric acid is one of the organic acids for which the world market is growing every year. This article describes equilibria and kinetic studies for the extraction of citric acid by Alamine 336 with methyliso-butylketone (MIBK) as diluent. The theory of extraction accompanied by a chemical reaction has been used to obtain the intrinsic kinetics of extraction of citric acid by Alamine 336 in MIBK. The reaction has been found to be first order in both Alamine 336 and citric acid with a rate constant of 0.013 m 3 kmol −1 s −1 .

An attempt has been made to investigate the effect of the presence of a helical coil, used in specific cases to increase the heat-transfer rate, on the critical impeller speed (N SG ) for a solid suspension in a sparged stirred tank reactor. It has been observed that the coil disturbs the flow pattern generated by the impeller, consequently affecting the critical impeller speed. The critical impeller speed increases with an increase in the superficial gas velocity (investigated in the range of 0.52−9.74 mm s-1). For the small-size solids (<150 μm), typical of the industrial catalyst size and the range of solid loading investigated (0.5−2 wt %), the six-bladed downflow-pitched (45°) turbine was found to be the most efficient impeller in terms of power required for a solid suspension.