Activated Carbons Obtained from Rice Husk: Influence of Leaching on Textural Parameters

Abstract

Activated carbons obtained from rice husk exhibit low specific surface areas when physical activation is applied due to its high silica content. The purpose of this work was to improve textural parameters of powdered activated carbons obtained from rice husk. To avoid the negative influence of the raw material ash content, a leaching step was included in the preparation process. Hydrofluoric acid, in two concentrations (25 and 50 wt %), was used as leaching agent and applied in different stages of the process. Physical activation using water vapor as activating agent was applied. Specific surface area and porosity were evaluated from nitrogen adsorption data. When a leaching step was included, specific surface area values between 700 and 1200 m2/g were obtained. These values are higher than that corresponding to the activated carbon prepared from rice husk not treated with acid (290 m2/g). Pore size distribution depends on the step sequence of the preparation process and on the HF concentration.

Application studies of activated carbon derived from rice husks produced by chemical-thermal process—A review

“…Activated carbons obtained from rice husks exhibit low specific surface areas when physical activation is applied due to its high silica content [32]. In physical activation, the gasification of a char with gases, the char is reacted at high temperature (usually above 800°C) with steam, carbon dioxide, or a mixture of these.…”

“…Activated carbons obtained from rice husk exhibit low specific surface areas when physical activation is applied due to its high silica content [32]. By physical activation with employing CO 2 , steam or air, The scanning electron micrographs (SEM) of the rice husk and the prepared activated carbons are illustrated in Figs.…”

“…In the former carbonization is followed by the activation of the resulting char at elevated temperature in the presence of suitable oxidizing gases such as carbon dioxide, steam, air or their mixtures; in the second one, carbonization and activation are performed in a single step, using a chemical agent [32] such as KOH, NaOH, H 3 PO 4 , ZnCl 2 etc. In comparison to physical activation, chemical activation provides two important advantages.…”

“…The major constituents of rice husk are cellulose, hemicellulose, lignin, and mineral components. The content of each of them depends on rice variety, climatic conditions, and even the geographic localization of the culture [32].…”

Effective and highly recyclable ceramic membrane based on amorphous nanosilica for dye removal from the aqueous solutions

“…Rice husk is costless and a widely available agricultural waste which is produced from the processing and refining of rice (Wang et al, 2014). Usually, in many countries, most of the rice husk produced is either burnt producing rice husk ash or dumped as waste (Deiana et al, 2008). About 75-90% of rice husk is organic matters such as cellulose and lignin and the rest (10-25%) are mineral components such as silica, alkalis and trace elements depending on rice variety, soil chemistry, climatic conditions, and even geographic location of growth (Carmona et al, 2013).…”