Arsenic Trioxide Leaching and Scorodite Crystallization in Methanesulfonic Acid

ABSTRACT

Arsenic, one of the most toxic elements, is a byproduct generated from metallurgical processes of arsenic-containing ores. Arsenic can be formed into an arsenic trioxide as a byproduct during the decopperization in electro-refining process when processing high arsenic-bearing copper minerals. However, arsenic trioxide has a very high arsenic mobility, so it requires to be re-dissolved and immobilized into scorodite (FeAsO₄▪2H₂O). In this study, methanesulfonic acid (MSA) was tested for both arsenic trioxide leaching and scorodite precipitation. Arsenic trioxide leaching tests showed the arsenic extraction of 80% at 21°C in MSA with H₂O₂ as an oxidant within 6 hours. Meanwhile, arsenic precipitation tests were conducted to achieve above 95% arsenic removal within 6 hours by the formation of scorodite at an initial pH of 0.5 and temperature of 80°C. In addition, coarser scorodite particles were formed in higher temperature and lower solution pH. The optimum condition for scorodite crystallization in MSA medium can be suggested to be at 80°C with the initial pH of 0.5.

KEYWORDS:

• Methanesulfonic acid
• scorodite
• decopperization
• arsenic trioxide leaching
• arsenic precipitation
• arsenic ferrihydrite

Acknowledgments

Authors, Junmo Ahn and Jiajia Wu, sincerely appreciate Freeport-McMoRan Copper & Gold’s support to the Department of Mining and Geological Engineering at the University of Arizona. A portion of their graduate assistantship was subsidized by Freeport-McMoRan Foundation through the Sustaining 21st Century Mining Education in Arizona program. The corresponding author, Dr. Jaeheon Lee, also would like to express his gratitude to Freeport-McMoRan and SME foundation for their support to SME Career Development Grant as a recipient of the program.

Disclosure statement

No potential conflict of interest was reported by the author(s).