Abstract
The iron leaching by acid treatment of Shirasu, glassy volcanic ash abundant in South Kyushu, has been studied in an attempt to convert it into a ceramic raw material. The effects of leaching temperature and particle size of Shirasu were studied. The rate of leaching was high in the early stage, levelling off with time. The amount of leached iron increased with increasing acid concentration and was highest with HCl, followed by H2SO4 and HClO4 in the order stated. The rate of leaching increased with increasing temperature but no tempeature effect was observed after the extended heating. The reduction in particle size resulted in the enhanced iron leaching and also in the dissolution of Shirasu particles. The surface area, determined by the BET (N2) adsorption method, increased with increasing leaching time. The residual iron content after leaching was not reduced below 0.9wt%, probably because of the inert nature of glassy particles.
