The crude glycerol was obtained from the biodiesel production
which was prepared from base catalyzed trans-esterification
reaction of soya bean oil, with KOH as base catalyst (Jiangsu Kate
New Energy Co., Ltd, China). Crude glycerol was dilute with
deionized water at a ratio of 3:1 (v/v) to reduce its viscosity. The
pH was adjusted to about 4 with 85% phosphoric acid. Then the
acid-treated glycerol was centrifuged at 5000 rpm, followed by
collection of the middle layer (glycerol and water). Methanol was
removed by atmospheric distillation at 75 C. After the distillation,
a filtration was carried out to remove the crystallized phosphate
salts.
After the aforementioned pre-treatment, the compositions of
crude glycerol obtained were 80.1% (w/w) glycerol, 13.4% (w/w)
water, 3.7% (w/w) phosphate salts, 1.0% (w/w) free-fatty acids
and 1.8% (w/w) other compositions.