Abstract

In this study dehydroxylation of alunite was studied. On the basis of thermogravimetricresult and SO2 loss, dehydroxylation of alunite occurs from 508 to 577C. In this temperature range, temperature and time as well as their interactionhave the greatest effect on alunite conversion(dehydroxylation) with99.85% contribution, while the contribution of particle size was only 0.11 %.Dehydroxylation increased with time up to a maximumand reached a plateau beyond that time. The time required (tmax)for maximum dehydroxylation (i.e. maximum conversion)forvarious temperatures was different and showed decreasing trend with increasing temperature. Kinetic studies below tmax showed that dehydroxylation of alunite followsAvrami-Erofeev models with different reaction indexes. In the temperature range of 508-534C, dehydroxylation occurs according to the following model: While in the 534-575 Ctemperature range the following model is applicable: