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) (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 mu m. After a 250 min run, permeate flux was still maintained at 90 L m(-2) h(-1) (v = 2.8 m s(-1), Delta 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 similar to 100 min, based on similar to 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. (C) 2008 Society of Chemical Industry.