4. Conclusions
In the present study, activated bentonite could be used as an adsorbent for biodiesel purification. The adsorption efficiency of activated bentonite was considerably improved after modification by activating with 0.1 M H2SO4/EtOH at 60 °C for 12 h. The activated bentonite (3% wt) could absorb 64.37 % (w/w) of soap and the acid value of purified biodiesel was 0.29 (mg KOH/g oil) which met the requirement of biodiesel standard (ASTM D974: acid value