3. Preparation of POFA
Two different POFA were used: fresh POFA
(FPOFA) and POFA burned in muffle furnance
(BPOFA) (Carbolite CWF1100, England) at 550
o
C for 12 h.
4. Chemical compositions in POFA
The chemical compositions of FPOFA and BPOFA
were determined using X-ray fluorescence
spectrometer (PW 2400, PHILIPS, Netherlands) .
5. Threating with adsorbents
The adsorbents were added individually to the used
frying oil 2% w/v then stirred for 15 min at
105
o
C and filtered through Whatman
No. 1 filter paper.