ice husk ash was successfully as an adsorbent for purifying biodiesel from waste frying oil showing efficiency in the adsorp- tion of organic and inorganic impurities of biodiesel. The results were similar to that presented by MagnesolÒ or acid solution. Although the RHA has lower specific surface than MagnesolÒ, in the RHA the surface is predominantly in large pores allowing get- ting hold large molecules making easy the diffusion of the species to be adsorbed. The high silica content of RHA, which also accounts for its high adsorptive capacity, was confirmed by EDS and FTIR analysis.
The main advantage of using the RHA is in the use of an agro- industrial waste pollutant which, after use, can be reused as a soil corrective due to its content of biodegradable organic matter (bio- diesel, glycerin and residual oil) and potassium (catalyst).