Residual glycerol was kindly supplied by a soybean oil-based
biodiesel manufacturing plant (Passo Fundo, Brazil). The biodiesel
production in this plant is obtained by transesterification of
degummed soybean oil using methanol or sodium methylate in the
reaction. The composition of the residual glycerol was analysed and
contained (as mass fraction): 81.8% glycerol, 5.82% ashes, 6.00%
NaCl, 11.7% moisture, 0.6% monoacylglycerols, and pH 5.37