The goal of this work is to study the purification of biodiesel from waste frying oil (WFO) using rice husk ash (RHA) at concentrations of 1%, 2%, 3%, 4% and 5% (w/w) and compare it with two other different puri- fication methods, the traditional acid solution (1% aqueous H3PO4) and with the commercial adsorbent MagnesolÒ 1% (w/w). The structure and composition of the RHA were studied to better understand its properties as an adsorbent. In a concentration of 4%, the RHA showed excellent results for removal impu- rities from biodiesel. The high concentration of silica in its composition and the presence of meso and macropores can explain its high capacity of adsorption. Thus, the RHA, that is a byproduct of the rice pro- cessing, can appear as an alternative material for biodiesel purification.