The factors were studied in the effect of solvent, concentration of
sulfuric acid, time and temperature. The result showed that 3% wt
of activated bentonite could adsorb 64.37 % (w/w) of soap and
exhibited acid value of purified biodiesel as 0.29 (mg KOH/g oil).
In addition, the specific surface area of activated bentonite was
increased from 48 to 55 m2 g-1. The quality of purified biodiesel
met the requirement of biodiesel standards (ASTM D974).
Therefore, activated bentonite revealed more environmental
friendly in biodiesel purification than water washing because there
is no wastewater generated.