Abstract for presentation at Chemeca 2005

Lactic acid has extensive uses in the food and chemical industry. Lately, its use in producing biodegradable polymer makes the extraction of lactic acid more important. In this report the separation characteristics of extraction of lactic acid is examined by (i) liquid-liquid equilibrium experiments and (ii) by using a hydrophobic microporous hollow-fibre membrane module (HFMM). Firstly, equilibrium experiments were conducted and values of the distribution co-efficient (defined as a ratio of the concentration of lactic acid extracted over that remaining in the aqueous solution) were obtained as a function of the main operating variables, e.g., solvent type, carrier/solvent ratio, feed pH. The best system for extraction at pH 4.5 was determined as 10-20 wt% tri-octyl amine (TOA) dissolved in 80 wt% tri-butyl phosphate (TBP) with a value for the distribution co-efficient of 8.11. This system and other two systems: TOA in Oleyl alcohol (OA) and TOA in Shellsol TK were used for extraction study in the hollow-fibre module. The module was operated with the feed solution (flowing inside the fibres) and the organic phase (flowing on the shell side) recirculated at various flow rates. A maximum extraction of 93% was achieved for extraction with 10% TOA in TBP at a flow of 15 L/h within a processing time of 5-6 hrs. There was no significant change in the extraction from the synthetic broth (compared to the pure lactic acid solution) and the percentage extracted in both cases was about 90%. Lactose and salts such as sodium chloride, potassium phosphate and magnesium sulphate did not affect the extent of extraction.