The mechanism of citric acid and oxalic acid on dissolution of high-silicon iron tailings

Abstract

In the indoor static environment, citric acid and oxalic acid, two kinds of low molecular weight organic acids were used to dissolve silicon and iron, which were two valuable elements in iron tailings. The results showed that the iron tailings used in this study were high silicon type iron tailings with 76.1 % silicon content and 11.31 % iron content. Both acids were soluble to ferrosilicon, but their solubility to iron was higher. Compared with the two, oxalic acid had stronger silicon solubility, reaching 35.98 μg/mL after 24d. The solubility of citric acid to iron was stronger, reaching 483.51 μg/mL after 24d. The dissolution of silicon and total iron in iron tailings by oxalic acid, citric acid and mixed acid conforms to first-order kinetics and belongs to surface dissolution reaction. After the dissolution of oxalic acid, silicon and iron ions might exist in the form of metasilic acid, iron oxalate and trioxalate potassium ferrite. Oxalic acid reacted with Fe to precipitate, which might be the reason for the higher Fe in the solution. The silicon and iron ions after citric acid dissolution might exist in the form of ferric citrate, ferric citrate complex, ferrous hexafluorosilicate, and more Fe products might be the reason for the higher Fe in the solution.