In this study

we investigated the essential role of feed solution pH so as to gain insights into the transport mechanisms of succinic acid concentration by osmotically-driven forward osmosis (FO) process. FO performances including water flux and bidirectional transport of succinate and chloride anions were systematically examined using cellulose triacetate-based FO membrane. Additionally

real seawater was explored as draw solution. Experimental results revealed that the pH-dependent speciation of succinic acid can affect the FO performances. Ionization of succinic acid at higher solution pH enhanced the osmotic pressure of feed solution

thus leading to lower water flux performance. A strong effect was pointed out on the succinate rejection for which nearly 100% rejections were achieved at pH above its pK

a2

value. The rejection of succinate increased in the following order of chemical form:C

2

H

4

C

2

O

4

H

2

C

2

H

4

C

2

O

4

H

-

C

2

H

4

C

2

O

4

2-

. With real seawater as the draw solution

low to moderate wat

er fluxes (4 L·m

-2

·h

-1

) were observed. The divalent succinate anion was highly retained in the feed side despite differences in the succinic acid feed concentration at pH of approximately 6.90.