Back extraction of propionic acid from loaded organic phase

Study of back extraction and hence regeneration of the acid from the loaded organic phase is essential for the design of a complete reactive extraction process. In this paper, the backextraction of propionic acid from the loaded organic phase (tri-n-octylamine (TOA)+diluent) was studied using different techniques, like, temperature and diluent swing, using NaOH or trimethyl amine. It was found that temperature swing regeneration could result in recovery as high as 88% of acid in two stages from organic phase, TOA+MIBK. However, from TOA+alcohols, the recovery by this technique was average. Diluent swing is not successful in efficiently recovering acid from the organic phases employed. NaOH, in stoichiometric ratio, could completely recover the acid, but in the form of sodium propionate. The 100% acid recovery was accomplished using trimethylamine (TMA), when used in stoichiometric ratio slightly higher than (1:1). Along with the complete recovery acid can be easily separated from TMA as the base is volatile. Kinetics of backextraction of propionic acid using TMA was also studied and it was found to be fast. (C) 2010 Elsevier Ltd. All rights reserved.