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Ceramic membrane pretreatment of monosodium glutamate isoelectric supernatant to facilitate (NH4)2SO4 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 (NH4)2SO4. 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 (NH4)2SO4. This paper reports on investigations of the electrodialysis process for (NH4)2SO4 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, ΔTMP = 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