In this work the influence of citric, acetic and oxalic acids on the extraction of nanometric silica from rice hull was studied. The experimental conditions of extraction, such as pressure and acid concentration, were also studied. According to the pore size evaluated by N2 adsorption (BET method), the specimens were classified as mesoporous. Comparisons between different types of acids used were performed by evaluation of the specific surface area of the silica obtained. Acetic acid showed the best performance, resulting in silica with a specific surface area of 271 m²/g. Citric acid showed the best result in terms of purity, 99.96%.
rice hull; silica; mesoporous; specific surface area
