Lactic acid recovery from dilute fermentation broths is a growing
requirement due to the increasing demand for pure lactic acid. Reactive
extraction is proposed as an alternative to conventional methods of recovery,
since the selectivity of separation is remarkably enhanced in reactive extraction.
The aim of this study is to perform the equilibrium studies for the recovery
of lactic acid from its synthetic aqueous solutions (not from real fermentation
broths) by reactive extraction and investigate the effects of various parameters
such as initial lactic acid concentration in the aqueous phase (0.25 - 1.3 M),
initial pH of the aqueous phase (2 &ndash / 6), organic phase extractant concentration
(0.1 &ndash / 0.5 M), type of the extractant (chloride, hydrogensulphate and hydroxide salts of tri-n-octylmethylammonium) and the type of diluent (oleyl alcohol or
octanol).
The results of the experiments showed that the degrees of extraction
decreased with increasing use of diluent with the extractant and increasing initial
lactic acid concentration of the aqueous phase. Highest degrees of extraction
were achieved for undiluted extractants. The performance of the diluents were
investigated by performing extraction experiments with solutions of TOMAC in
oleyl alcohol or octanol at different pH values and it was observed that octanol
had a higher solvating power than oleyl alcohol especially at lower aqueous
phase pH values. Higher extraction efficiencies were obtained for TOMAC
dissolved in octanol rather than oleyl alcohol. Initial aqueous pH of 6 was
identified as the optimum pH for the extraction, also due to its being equal the
average fermentation pH for the extractions with Lactobacillus species.
Among the different salts of tri-n-octylmethylammonium, hydroxide salt
exhibited the highest degrees of extraction (83% with undiluted TOMA(OH) and
78% with 0.5 M TOMA(OH) in octanol for the extraction of 0.316 M lactic acid
solutions).
The present work is the first step in the design of an industrial reactive
extraction process that is going to attempt forward and backward extraction of
lactic acid simultaneously in a hollow fiber membrane module that is going to be
attached to the lactic acid fermentor to achieve continuous product recovery.
The equilibrium data obtained from this study can be combined with the kinetic
studies as the next step of designing a separation module.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/1120781/index.pdf |
| Date | 01 August 2003 |
| Creators | Acan, Basak |
| Contributors | Gurkan, Turker |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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