Ceramic membrane pretreatment of monosodium glutamate isoelectric supernatant to facilitate (NH 4 ) 2 SO 4 recovery by electrodialysis

BACKGROUND: The large output of monosodium glutamate in China has produced huge amounts of isoelectric supernatant containing 40–60 g L −1 (NH 4 ) 2 SO 4 . With the increasing national emphasis on environmental protection and recycling, it is necessary to find a cost‐effective and environment‐friendly alternative to recover the (NH 4 ) 2 SO 4 . This paper reports on investigations of the electrodialysis process for (NH 4 ) 2 SO 4 recovery from isoelectric supernatant pretreated by ceramic membrane. RESULTS: For ceramic membrane pretreatment, the optimal pore size chosen was 0.2 µm. After a 250 min run, permeate flux was still maintained at 90 L m −2 h −1 ( v = 2.8 m s −1 , Δ TMP = 0.12 MPa, concentration factor = 7). Meanwhile, the total solids and proteins content in condensed supernatant were high, up to 78 g L −1 and 24 g L −1 , respectively, which greatly favors future cell protein harvest. With the chosen current density of 17 mA cm −2 , the energy consumption and time for six consecutive batches for electrodialysis were 2.6–2.7 kW h kg −1 sulfate and ∼100 min, based on ∼80% ammonium sulfate recovery from pretreated isoelectric supernatant. CONCLUSION: Ceramic membrane pretreatment was shown to be a promising pretreatment strategy, applicable to the electrodialysis process to recover ammonium sulfate from isoelectric supernatant produced during monosodium glutamate production. Copyright © 2008 Society of Chemical Industry