An environmentally friendly design for low-grade diasporic-bauxite processing

A new environmentally friendly design for low-grade diasporic-bauxite processing which is different from the Bayer and sintering processes was proposed in this paper. In the redesign of alumina production technology, a mixture of bauxite ore and sodium hydroxide solution was heated at a higher temperature for the purpose of complete decomposition of bauxite. The products were then extracted by water; the resulting sodium aluminate solution was further purified and used for the gibbsite precipitation, the residue being reacted with a caustic liquor to recover sodium oxide and alumina. The experimental results show that during the new process bauxite decomposition rates approach 100% and the residues can be easily recovered. When diasporic ores with mass ratio of alumina to silica of approximately 5:1 are treated, total alumina recovery efficiency of 86% and a sodium oxide presence below 1.5% in the final red mud will be achieved. This new design surpasses previous approaches in terms of high resource efficiency and low environmental impact. (C) 2009 Elsevier Ltd. All rights reserved.