Abstract
The elimination of free fatty acids (FFA) from biodiesel is usually performed in industrial practice using different units for neutralization with caustic, washing and drying of the fuel. However, adjustment of the free fatty acids can be performed in only one operation using bleaching tanks and commercial adsorbents. In this work, purification of crude biodiesel fuel from palm fatty acid distillate (PFAD) has been done by employing dry washing method for the removal of FFA using modified potato and cassava starch and compared with commercial magnesium silicate. The molar ratios of KOH/starch in modified potato and cassava, i.e. 0.10:1, 0.15:1 and 0.25:1 were obtained by varying concentrations of KOH: starch samples. The morphology, crystal structures, surface area and pore size of the adsorbents were characterized by scanning electron microscopy (SEM), X-ray diffraction method (XRD) and Brunauver-Emmett-Teller technique (BET). The adsorption efficiency of the synthesized adsorbents in biodiesel was studied by varying dosage of adsorbents for 50 g of biodiesel at 30 oC for 30 min. The results showed that the modified potato and cassava at 0.25:1 KOH/starch molar ratio at room temperature presented the highest efficiency in adsorption of residual FFA at 69.46 % and the highest adsorption capacity of modified cassava and potato starch was 233 mg and 228 mg of FFA per gram of adsorbent. The comparison of dry washing with commercial magnesium silicate, presented good efficiency in the removal of FFA and depicted similar behaviour independent of the kind of adsorbent employed.
