Silica with a high surface area is a good compound to be used as adsorbent or support for catalysts. Also, the reactivity of silica is directly related to its surface area. The BET-specific surface area and pore volume of RHA (at optimized conditions) and nanosilica are given in Table 5. A major contribution to the high surface area is that the organic matter has been broken up during the thermal decomposition of RH′, thus leaving a highly porous structure. The increasing pore volume in nanosilica confirms this phenomenon.