Drum leaching tests in iron removal from quartz using oxalic and sulphuric acids

Abstract

A study has been made of a leaching process to remove iron from quartziferous industrial minerals using oxalic and sulphuric acid in a drum reactor. The experimental work was necessary because of the paucity of literature on the use of oxalic acid in the treatment of industrial minerals containing iron as an impurity. The positive effect of oxalic acid on the iron extraction yield is clearly observed during leaching in a drum reactor. Iron extraction yields of 35–45% are obtained on treating the quartz with 3 kg/t oxalic acid and 2 kg/t sulphuric acid at 90°C for 4–5 h. Under the same conditions but without oxalic acid the iron extraction yield ranges from 3 to 9%, depending on the sulphuric acid content. Chemical and mineralogical analyses were run on the ore to ascertain where the iron compounds occur on the different mineral components. These analyses were carried out on an as-is sample and on three other samples obtained by magnetic separation. The experimental results indicate that 52% of the iron is found in the mica fraction. These results explain why the maximum iron extraction yield is only 35–45%. A flow-sheet of the process is proposed together with a rough material balance in order to estimate oxalic acid, sulphuric acid and water consumption.