Thermally activated seawater neutralised red mud used for the removal of arsenate, vanadate and molybdate from aqueous solutions

The effectiveness of using thermally activated hydrotalcite materials has been investigated for the removal of arsenate, vanadate, and molybdate in individual and mixed solutions. Results show that increasing the Mg,Al ratio to 4:1 causes an increase in the percentage of anions removed from solution. The order of affinity of the three anions analysed in this investigation is arsenate, vanadate, and molybdate. By comparisons with several synthetic hydrotalcite materials, the hydrotalcite structure in the sea-water neutralised red mud (SWN-RM) has been determined to consist of magnesium and aluminium with a ratio between 3.5:1 and 4:1. Thermally activated seawater neutralised red Mud removes at least twice the concentration of anionic species than thermally activated red mud alone, due to the formation of 40-60% Bayer hydrotalcite during the neutralisation process. (C) 2009 Elsevier Inc. All rights reserved.