Mercury pollution has been a serious problem in the Republic of Ghana, located in West Africa, and a group of Japanese NPO and researchers have started providing support by providing Japanese smelting technology that does not use mercury to prevent mercury exposure. The group is aiming to provide the technology as early as possible, as global awareness of the need to protect against mercury is growing since the implementation of the Minamata Convention on Mercury.
Gold is one of Ghana’s main exports and it has many mines across the country. According to Tokuaki Tanzawa, Director General of NPO Nihon to Ghana Kakehashi no Kai, which means build bridges between Japan and Ghana, and Agyeman Siaw, Associate Professor of Tokyo University of Agriculture and Technology, small-scale mines use cheap mercury to manually separate the gold from the ore.
Miners mix the mercury into the ore with their bare hands, create a gold-mercury amalgam, and then heat the amalgam over an open flame to vaporize the mercury to separate the gold. It is said that this toxic smelting method is rampant in small illegal mines run by Chinese operators.
Professor Izumi Watanabe of Tokyo University of Agriculture and Technology (Environmental Contamination and Toxicology) and others surveyed the soil of these small mines in southwest Ghana and found high mercury concentrations up to tens of times higher than normal levels. There have been increasing reports of severe skin disease among residents who live near the mines, raising suspicions of a link.
The miners are typically impoverished young people who are processing gold without any knowledge of the dangers of mercury poisoning. “High levels of mercury are detected in vegetables and river fish. Locals are at risk of serious health hazards if nothing is done,” warns Professor Watanabe.
Tanzawa is particularly interested in the smelting technology developed in 1992 by Yukimichi Nakao, former chief research scientist at the National Institute of Advanced Industrial Science and Technology. He has been working to start a feasibility project using this technology in a mine in Ghana by establishing a dedicated research center, partnering with academia based in southeast Ghana.
This refining technique uses an organic solvent made of melted iodine and iodine compounds. Although gold is a stable element that is hard to melt, this solvent melts the metal easily. Gold was extracted at a rate exceeding 99% in an experiment using this method with gold ore found in Japan.
“Iodine is safe and easy to use. We still need to do a cost feasibility study but it is promising as an alternative to mercury,” says Nakao.
The Minamata Convention on Mercury, which came into effect on August 16, is a global treaty to protect human health and the environment from the adverse effects of mercury, and it includes a target to curb the use of mercury in small-scale mines. Although Ghana ratified the treaty in March, it has yet to implement concrete measures.
“If this mercury-free gold processing method is adopted in Ghana, it can act as a model case for other emerging economies. I am driven to find funding for further research,” says Tanzawa, who is calling for the cooperation of companies and other organizations.