Environmental Aspects on the Use of Bayer's Process Bauxite Residue in the Production of Ceramics

Abstract

Bauxite Residue (BR) is the main waste generated during the alumina-producing Bayer process. With the aim to utilize BR in the production of traditional ceramics, the potential impact such a use might have on the leaching behaviour and radioactivity levels of the final products was investigated. Leaching behaviour of Cr, Ni and V on calcined BR was studied according to the maximal availability test, NEN 7341. Firing atmosphere, firing temperature and soaking time were the investigated parameters. Results demonstrate that the soluble fraction of Cr is higher for oxidizing atmosphere whereas the soluble fraction of V and Ni increases for inert and reducing atmosphere, respectively. For assessing radioactivity, the activity concentrations of 226Ra, 40K, and 232Th were determined by means of gamma ray spectroscopy. For an excess gamma dose less than 1mSv/a, the maximum quantity of BR that can be introduced replacing the raw materials ranges from 14wt.% up to 100wt.%, depending on the type of product and the extent of use in the dwelling.