Recovery of Oxalic Acid from Oxalic Acid Leaching of Diatomaceous Earth by use of Electrodialysis

• Published in: Shigen to sozai Vol. 111; no. 8; pp. 569 - 574
• Main Authors: TAKAHASHI, Hiroshi, KIDA, Shigenobu, KIKUCHI, Ken-ichi, SUGAWARA, Takuo
• Format: Journal Article
• Language: English; Japanese
• Published: The Mining and Materials Processing Institute of Japan 1995
• Subjects: Diatomaceous Earth; Electrodialysis; Ion-Exchange Membrane; Iron (II)-Oxalate; Membrane Separation; Oxalic Acid
• ISSN: 0916-1740; 1880-6244
• DOI: 10.2473/shigentosozai.111.569

Electrodialyses of a model solution, oxalic acid-iron (II) oxalate mixture, and a real leaching solution were investigated focusing on the removal of iron from the solution for effective recovery of oxalic acid from oxalic acid leaching of diatomaceous earth. Two types of dialyzers, having 5 compartments, were used: with a desalting compartment (the center one) divided with both of a cation-exchange membrane and an anion-exchange membrane (A-C type), and with the same compartment arrays divided with only cation-exchange membranes (C-C type). The fluxes of various ionic species through the membranes were examined in the both types of dialyzers varying the concentrations of iron and oxalic acid. Iron was effectively removed as iron-dioxalate ion and as ferrous ion through the anion-exchange membrane and cation-exchange membrane, respectively. In the A-C type dialyzer, the removal rate through the former was considerably higher than that through the latter. The total removal rate of iron attained about 90% at 24hr; however, 30% of oxalic acid was lost through the anion-exchange membrane. In the C-C type dialyzer, oxalic acid loss was negligibly small, whereas the iron removal rate was lower than that in the A-C type dialyzer. A real leaching solution showed almost the same permea-, tion characteristics in dialysis as that of the model solution. No poisonous effect was observed for membranes during the dialysis. The dialysis characteristics described above were explained through the ionic species concentration-profiles calculated by the dissociation equilibria for oxalic acid and iron (II)-oxalate.