Effect of Ammonium- and Phosphonium-Based Ionic Liquids on the Separation of Lactic Acid by Supported Ionic Liquid Membranes (SILMs)

Abstract

Biodegradable polymers have attracted much attention from an environmental point of view. Optically pure lactic acid that can be prepared by fermentation is one of the important raw materials for biodegradable polymer. The separation and purification of lactic acid from the fermentation broth are the major portions of the production costs. We proposed the application of supported ionic liquid membranes to recovering lactic acid. In this paper, the effect of ionic liquids, such as Aliquat 336, CYPHOS IL-101, CYPHOS IL-102, CYPHOS IL-104, CYPHOS IL-109 and CYPHOS IL-111 on the lactic acid permeation have been studied. Aliquat 336, CYPHOS IL-101 and CYPHOS IL-102 were found to be the best membrane solvents as far as membrane stability and permeation of lactic acid are concerned. CYPHOS IL-109 and CYPHOS IL-111 were found to be unsuitable, as they leak out from the pores of the supported liquid membrane (SLM), thereby allowing free transport of lactic acid as well as hydrochloric acid. CYPHOS IL-102 was found to be the most adequate (Permeation rate = 60.41%) among these ionic liquids as far as the separation of lactic acid is concerned. The permeation mechanisms, by which ionic liquid-water complexes act as the carrier of lactate and hydrochloric acid, were proposed. The experimental permeation results have been obtained as opposed to the expected values from the solution-diffusion mechanism.

Separation of Lactic Acid through Polymer Inclusion Membranes Containing Ionic Liquids

“…Lactic acid was successfully permeated to the stripping phase. We also observed that the pH decrease in the feed solution was smaller than that for SILM [6]. In the following, we examine the effects of various factors on permeation and membrane stability.…”

“…Cyphos 6 ] were synthesized according to the method described in a previous paper (5). For the conversion of Aliquat 336 in bicarbonate, iodide, nitrate, thiocyanate, hydrogen sulfate, dihydrogen phosphate, and bromide forms, it was contacted with each concentrated sodium salt solution to form partially anion-exchanged Aliquat 336, according to the procedure presented by Kyuchoukov et al (13).…”

“…However, many papers characterize SILMs as more stable than SLMs. Fortunato et al (8) reported the retention of [C 4 mim][PF 6 ] in membrane pores for 230 h without leaking using water as a feed= receiving phase. However, because dissolution of Aliquat 336 in water was reported to be not negligible (9), the loss of ILs from the membrane pore is of particular concern.…”

“…A number of processes for lactic acid recovery have been studied, including solvent extraction, adsorption, direct distillation, and electrodialysis (1)(2)(3)(4). In our previous studies, supported liquid membranes (SLM) based on ionic liquids (ILs) such as Aliquat 336 and Cyphos IL -101 were proposed for lactic acid separation (5,6) and lactate was successfully permeated through supported ionic liquid membranes (SILMs) using a hydrochloric acid solution as a stripping agent. The main problem for SLM operation is the membrane instability caused by the loss of the membrane solution from the membrane pore.…”

“…In our previous studies (5,6) using SILM, Aliquat 336, Cyphos IL -101 and -102 were suitable ILs for the separation of lactate. In the present study, we used [C n mim][PF 6 ], which gave the stable SILM mentioned above, in addition to these above ILs as a lactate carrier. Pereria et al reported that carriers with partially positively charged atoms with partially negatively charged chlorine atoms in PVC can act as a successful plasticizer with PVC-based PIMs (12).…”