Sustainable Iron-Making Using Oxalic Acid: The Concept, A Brief Review of Key Reactions, and An Experimental Demonstration of the Iron-Making Process

摘要

Global iron and steel production continues to expand. The iron-making industry is, however, one of the main contributors to global warming due to its reliance on fossil fuel-based high temperature processes. Therefore, alternative green approaches to iron-making are highly desired. Herein, we propose a new concept of iron-making, which consists of a sequence of known reactions: the dissolution of iron from iron ore using oxalic acid to obtain a Fe(III) oxalate aqueous solution, followed by the photochemical reduction of Fe(III) oxalate to Fe(II) oxalate as a solid precipitate, and the pyrolytic reduction of Fe(II) oxalate to metallic iron. By harnessing the chemical characteristics of oxalic acid and iron oxalates, the method is expected to produce high-quality iron at low temperatures. Moreover, the recovery of carbon oxides, generated during iron-making, for the synthesis of oxalic acid enables the iron-making without having carbon in the stoichiometry. The present study explains the key chemical concepts of the process, experimentally demonstrates the iron-making, and discusses the challenges and barriers to industrial application. In the experiment, according to the proposed scheme, three different iron sources were successfully converted into metallic iron. The yield and quality (purity) of the iron product depended on the metallic composition of the feedstock. In the absence of impurity metals, near-complete recovery of pure iron was possible. Alkaline earth and transition metals were identified as impurities that affected process performance and product quality. The iron dissolution needed a relatively long reaction time to achieve sufficient conversion under the conditions employed in this study, rendering it a rate-determining step that influenced overall iron productivity.