An Electrochemical Method for the Formation of Magnetite Particles*

ABSTRACT

Magnetite has been widely used in numerous industrial processes and environmental applications. The conventional method for the production of magnetite particles, based on the mixing of ferrous and ferric ions at a 1 : 2 molar ratio, produces high-pH secondary wastewater that requires further treatment. This study investigates an alternative approach based on electrochemical reactions for the production of magnetite particles, a process in which ions of iron are produced by carbon steel electrodes and pure magnetite particles are formed through electrochemical reactions under favorable conditions. To better understand the mechanisms involved, experiments were conducted to examine the effects of various electrolytes—such as those of NaCl, CaCl₂, MgCl₂, and CuCl₂ —and various operating conditions—including temperature and applied voltage—on the formation of magnetite particles. It was observed that magnetite could form in NaCl solutions in the presence or absence of Mg²⁺ and Ca²⁺ ions, while only insignificant quantities of magnetite particles were observed in tap water and CuCl₂ solutions. A mechanistic study of magnetite formation based on the E-pH diagram is presented, and the reactions involved are identified.

Keywords:

• Magnetite
• Electrocoagulation
• Electrochemical precipitation

ACKNOWLEDGMENT

Support for this research was provided by the National Science Foundation through a Career Award (BES-9702356 to S.Y.), and by the Environmental Management Science Program, Office of Environmental Management, and the Division of Chemical Sciences, Office of Basic Energy Sciences, US Department of Energy, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. The authors are also thankful to Dr. Marsha K. Savage for editing the manuscript. * The submitted manuscript has been authored by a contractor of the US Government under contract DE-AC05-00OR22725. Accordingly, the US Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US Government purposes.