Membrane contactor for reactive extraction of succinic acid from aqueous solution by tertiary amine

A hollow fibre membrane contactor (HFMC) made of microporous, hydrophobic, polypropylene (PP) fibres was used for removing dissolved succinic acid (SA) from aqueous streams. The Liquicel^® HFMC module was operated in the liquid–liquid extraction (LLE) mode with aqueous SA as the feed solution. The aqueous feed was prepared by dissolving measured amounts of SA in deionised water, with concentrations varying from 5000 to 59 000 ppm. Two different types of organic extractant solutions were chosen to extract SA from aqueous streams: (a) 30% tripropylamine (TPA) dissolved in 1-octanol and (b) 30% trioctylamine (TOA)–TPA mixture in a 2:8 weight ratio and dissolved in 1-octanol. The aqueous feed was circulated through the lumens of the hollow fibres, and the extractant solution was passed through the shell side (i.e., inside the shell) of the HFMC module. Both liquids flowed counter-currently within the HFMC module and were recirculated continuously. Conditions such as SA-water flow rate, organic phase flow rate, and initial SA-water concentration were selected as the operating variables. The complexation reaction of SA with the amine was assumed at the aqueous–organic interface on the lumen side. The complex thus formed first diffused through the membrane pores filled with the organic phase (hereafter “organic-filled membrane pores”) and was subsequently swept by the organic liquid flowing through the shell side of the module. The HFMC was observed to be highly efficient in removing SA from water, and a removal efficiency of more than 95% was obtained. A mathematical analysis was performed by considering the transport of SA molecules through the bulk aqueous phase and within the organic-filled membrane pores. The results of the model simulation were shown to be in agreement with the experimental data.