2.6. Ultrafiltration study
The permeation flux and rejection ratio of the membranes were
measured by UF experimental equipment as shown in Fig. 1. The
effective ultrafiltration area of PVDF membranes and PVDF–PVP
membranes was 78.5 cm2. Generally, membrane samples were
pre-pressured initially at 0.3 MPa with DI water or oil waste water
for 5 h before the measurements. Then the pressure was maintained
to 0.3 MPa and the ultrafiltration experiments began.
The stable permeation flux at the end of 1 h is referred to as initial
flux (J0) and calculated by Eq. (2). Permeate solution containing
oil were extracted by 25 ml CCl4 and the CCl4-rich phase was analyzed
for oily concentration using a novel infrared oil content analyzer
with the scanning wavelength from 3.20 to 3.55 lm.
Rejection ratio (RR) is defined by Eq. (3):