Published: October 27, 2011
Abstract: The motivation for this study was to find a possible economic alternative for the residual Rice Husk Ash (RHA) as well as a way to mitigate the growing environmental problem in Southern Brazil (illegal deposition of exceeding rice husks and RHA). For this, an investigation was carried out into the preparation of two kinds of xerogel silicas from micronised rice husk ash and their utilisation as additives in the cultivation of rice. The effect of the parameters of silica extraction was evaluated by means of Response Surface Methodology and the maximal yields were 96 and 98%. The silicas were characterised in terms of their chemical composition, particle size distribution and surface area. High values for specific surface area, 183.73 and 232.42 m2 g-1 and mean particle size of 67.93 and 28.41 μm, were found for the potassium-and sodium-based silicas, respectively. The effect of Si on rice production was studied under conditions of soil samples containing low concentrations of Si, with addition of 0, 100, 200 and 400 kg Si ha-1. The Si content of the soil samples increased with the increase in the dose of both silicas, causing an increase in grain yield.