(371d) Membrane Fouling Mechanism in Ultrafiltration of Succinic Acid Fermentation Broth

Succinic acid (1, 4-butanedioic acid) is identified as an important building-block chemical which can be used for the synthesis of high value-added derivatives, such as 1, 4-butanediol (BDO), g-butyrolactone (GBL), tetrahydrofuran (THF), N-methyl-2-pyrrolidone (NMP), 2-pyrrolidone (2-Pyrr), succinimide, succinic esters, etc. Great efforts have been made to develop biotechnology methods to produce succinic acid from renewable resources since last decade.

However, fermentation process is still not economically feasible, mainly due to the low succinic acid concentration in the fermentation broth, and the high cost of succinic acid separation and purification. Considerable efforts have been made to improve the succinic acid concentration in the fermentation broth and several possible operation units such as adsorption, extraction and electrolysis have been investigated for the recovery of succinic acid.

In this study, fouling mechanisms of different membranes were fist studied in treating succinic acid fermentation broth during ultrafiltration process. The membrane fouling mechanism was studied during dead-end ultrafiltration. Different membranes were used and two models were applied to analyze the fouling mechanism. Resistance-in-series model was applied to determine the main factor that caused the operation resistance. Results indicated that most membranes tended to be fouled by cake layer or concentration polarization. Hermia’s model, which is composed of four individual sub-models, was used to analyze the predominant fouling mechanism. Results showed that the fouling of RC 10kDa and PES 30kDa was controlled by the complete blocking mechanism, while PES 100kDa was controlled by the intermediate blocking and PES 10kDa was controlled by cake layer. This conclusion was also proved by SEM photos. Membrane characteristics were monitored before and after ultrafiltration by AFM and goniometer. Both contact angle and roughness of most membranes increased after ultrafiltration.