Study on the Recovery of Polyethylene Glycol in Spent Liquid from Aqueous Two-phase Extraction

The recovery and recycling of polyethylene glycol(PEG) in spent liquid from aqueous two phase extraction were studied in order to reduce the cost,chemical oxygen demand(COD) discharge,and precede the application of aqueous two phase extraction in industry.The spent upper phase from the aqueous two-phase system composed of polyethylene glycol(PEG) and ammonium sulfate was used for the recovery of PEG.Hydrogen peroxide(H2O2) was used for decolorization,and the optimal decolorization was reached at the H2O2 concentration of 6%,lasting for 4 h.Salting out was used for concentration,the optimal salt was sodium sulpham,and its optimal amount was 3 g/10 mL spent liquor.Further,acid washing and alkaline washing was employed for clearing the insoluble impurities.The characteristic of recycled PEG was that appearance was light yellow cereus,conductivity was 10.8 μs/cm,freezing point was 37～40 ℃,pH(5% solution) value was 6.33 and there was no significant difference with pure PEG.