ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Direct electrochemical reduction of red mud to metallic iron in alkaline media with process performance and preliminary techno-economic assessment

Franky Michael Hamonangan Siagian, Vincent Sutresno Hadi Sujoto, Muhammad Stally Argha Pradipta, Panut Mulyono, Ferian Anggara, Widi Astuti, Gyan Prameswara, Rosy Amalia Kurnia Putri, and Himawan Tri Bayu Murti Petrus

Department of Chemical Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia

E-mail: bayupetrus@ugm.ac.id

Received: 28 January 2026  Accepted: 23 March 2026

Abstract:

Red mud, a highly alkaline residue generated from the Bayer process, represents both an environmental burden and a potential secondary resource due to its high iron oxide content. This study investigates the recovery of zero-valent iron (ZVI) from red mud via direct electrochemical reduction in concentrated NaOH solution. Electrolysis experiments were conducted in a three-electrode configuration at current densities ranging from 189 to 755 A/m² and temperatures from 30 to 110 °C to elucidate the effects of operating conditions on iron deposition and competing reactions. The highest iron yield and current efficiency (41.2%) were achieved at a current density of 755 A/m² and 110 °C after 6 h of electrolysis, yielding 1.718 g of metallic iron. Cyclic voltammetry analysis confirmed that hematite reduction occurs at cathodic potentials below − 1.1 V vs. Hg/HgO. At the same time, hydrogen evolution becomes significant at more negative potentials, acting as a parasitic reaction that limits faradaic efficiency during prolonged operation. SEM–EDS characterisation revealed dense dendritic iron deposits composed of micron-scale nodules, indicating diffusion-limited growth under strong cathodic polarisation. In addition to process performance evaluation, a preliminary techno-economic assessment at laboratory scale was performed. The results indicate that the proposed electrochemical route incurs lower capital and operational expenditures than laboratory-scale blast furnace/direct reduction analogues, primarily due to lower operating temperatures and the absence of high-temperature gas-handling systems. Overall, red mud electrolysis offers a low-temperature, modular pathway for iron recovery, supporting sustainable, circular metallurgical waste valorisation.

Keywords: Red mud; Electrochemical reduction; Iron recovery; Hydrogen evolution; Alkaline electrolysis

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04838-x

Chemical Papers 80 (7) 7583–7597 (2026)