Application of recycled ferric chloride for alkalinity regulation of bauxite residue

Abstract Bauxite residue is the biggest environmental issue for the alumina industry, and alkalinity regulation is the key step to treat this kind of solid waste. In this work, recycled ferric chloride, generated from the resource recycling process of bauxite residue, was applied to regulate the alkalinity of bauxite residue. The results show that the pH value of the leachate decreased from 11.38 to 7.06 under the optimal condition (solid-to-liquid ratio 400 g/L, Fe3+ concentration 10 g/L, reaction temperature 25 °C and reaction time 1 h). Most alkaline components in the bauxite residue can be neutralized after two dealkalization stages. Fe3+ showed a preferential exchange capability to Na + than Ca2+, and the exchanged Ca2+ was also beneficial for the alkalinity regulation process. The elution solution may be used as the raw material for chlor-alkali industry. Furthermore, evaluation of the revegetation potential showed that the dealkalized bauxite residue was suitable for the growth of Lolium perenne. In summary, utilization of recycled ferric chloride to regulate the alkalinity of bauxite residue offers an economical and environmentally friendly way for large-scale bauxite residue disposal.