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Silica from rice straw for nitrates absorption

ESTECHfunctionalized silicanitrates removalrice straw ashsilica


The patent describes the production of functionalized silica, obtained from the ashes resulting from the energy recovery process of rice straw, for its use as an adsorbent bed in filters used for the removal of nitrates in contaminated water. The nitrate adsorption values ​​achieved are between 60% and 80%.

Technical features

The invention describes a process for the adsorption of nitrates in water using functionalized silica from rice straw ash. The methodology comprises three main steps: the obtainment of rice straw ash, the extraction of silica from ashes and its activation. Rice straw ashes are obtained by a controlled temperature combustion. The extraction and activation of silica is carried out using acid (first step) and alkaline (second step) reagents. Lastly, the product is filtered, and active silica is obtained in the form of white powders.

Possible Applications

  • • Nitrate adsorption in water, for well water for consumption
    • Future applications with other negative ions that act as pollutants



• Reduction of rice straw residues and the problems derived from its current treatment
• Cleaner activation treatment than traditional ones affecting operating times and efficiency
• Nitrate adsorption values higher than the current ones