Rice hull charcoal for adsorption of cesium and strontium in aqueous solution

Abstract

The adsorption capacity of rice hull charcoal for cesium and strontium in aqueous solution was examined. Rice husk carbonized at various temperatures was added to aqueous solutions of cesium and strontium and stirred, whereupon, samples carbonized at 400°C adsorbed cesium, and those carbonized at 800°C adsorbed strontium. In view of this result, it was inferred that the mechanisms of adsorption of cesium and strontium on rice hull charcoal are different. FTIR analysis and Boehm titration results indicated that charcoal carbonized at 400°C had acidic functional groups. In addition, the pH of the rice hull charcoal carbonized at high temperature tended to be higher, which is attributed to precipitation of inorganic substances such as potassium on the surface of rice hull charcoal. Pore distribution measurements showed that many mesopores were formed in rice hull charcoal carbonized at 800°C. It was concluded that cesium adsorbs primarily on acidic functional groups on the surface of rice hull charcoal and strontium undergoes ion exchange with potassium, or adsorbs on mesopores.