(385c) Clarification of Succinic Acid Fermentation Broth By Ultrafiltration and the Membrane Fouling Mechanism

Ultrafiltration was investigated to clarify succinic acid fermentation broth in consideration of integrating fermentation and separation process and removal the product in situ. Different membranes(PES 100kDa, PES 30kDa, PES 10kDa and RC 10kDa) were used and two models were applied to analyze the fouling mechanism. Results indicate that ultrafiltration is feasible in clarifying succinic acid fermentation broth. Almost all the microorganism cells (99.6%) were removed from the fermentation broth. Proteins were also removed effectively by all membranes selected in this study. The removal rate was 79.86% for PES 100kDa, 86.43% for PES 30kDa, 86.83% for PES 10kDa, and 80.06% for the RC 10kDa. After ultrafiltration, clearer permeate was obtained comparing with the centrifugation. Among all tested membrane, PES 10kDa gave the best results which showed relative higher initial flux (18.86 L/m2 h), highest protein removal rate (87%), and less flux drop rate. Resistance-in-series model was applied to determine the main factor that caused the operation resistance. Results showed that most membranes selected in this study 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 for the used membranes. 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 analyzed before and after ultrafiltration by AFM and goniometer. Both contact angle and roughness of most membranes increased after ultrafiltration.