Separation of ethylene glycol solution by vacuumT. Mohammadi*, M. A k b a r a b a d i

The feasibility of VMD for concentration of ethylene glycol (EG) from a used coolant liquid is presented. VMD experiments were performed with water-EG mixtures using a flat-sheet polypropylene membrane at various temperatures and recirculation rates. Results show that the membrane almost completely rejects EG and the desired concentration was achieved. This is due to the vapor pressure of EG being negligible compared to that of water. Increasing temperature and recirculation rate increased flux with no effect on EG rejection. Increasing o f feed flow rate higher than 0.67 had no strong effect on permeate flux.

VMD is able to recover EG concentration in used coolant liquids, although it needs a temperature gradient, which requires energy consumption. Nevertheless, VMD for this application may be competitive in some circumstances; for instance, if a source of waste heat is available. The non-linearity o f flux behavior is related to the temperature polarization and concentration polarization effects, and the latter is very important, especially at higher concentrations. In all experiments the permeate was almost distilled water. This is due to the fact that vapor pressure of EG is negligible compared with that of water; as a result, the membrane almost completely rejects EG in the range of the temperatures and concentrations tested. It was shown that increasing the feed flow rate higher than 0.67 L/min has no effect on permeate flux.