Study on the formation mechanism of silica gel and influence on the mineral dissolution during bauxite residue acid leaching

Bauxite residue contains about 5%–10% silica, easily dissolves and forms silica gel during acid leaching. This increases the difficulty of sample handling and solid-liquid separation. In this paper, the formation mechanism of silica gel and its influence on the mineral dissolution during bauxite residue acid leaching were investigated. The results revealed that the preferential dissolution of alkaline minerals released silicon, leading to the formation of silica gel. The formation of silica gel mainly hindered the further dissolution of hematite, but had little impact on other phases in the bauxite residue. The silica gel exhibited a strong affinity for the hematite, and most of the them wrapped around the surface of the hematite, blocking its contact with hydrochloric acid.