Photo credit: Manuel/Adobe Stock
The Global Environment Facility is helping countries worldwide meet deadlines set by the Minamata Convention on Mercury for the elimination of the deadly neurotoxin from everything from healthcare and mining to chemical production.
One of the most pressing is the pledge to phase out mercury from the manufacturing of caustic soda and chlorine – two workhorse chemicals essential for everything from water treatment to the creation of life-saving medicines – by the end of 2025.
To help Mexico do this, a GEF-funded project is supporting the country as it converts its sole remaining mercury-cell chlor-alkali plant – one of only a handful still in operation today – and addresses contamination linked to this century-old production technique.
In mercury-cell chlor-alkali production, widely used since the 1890s, an electrical current is run through a vat of salt water with a layer of mercury at the bottom. The current breaks the water into chlorine and an amalgam of sodium and mercury. The amalgam is then subjected to a second reaction, which yields hydrogen and sodium hydroxide – or caustic soda. The mercury is freed up for reuse.
Despite a sharp fall in the number of mercury-cell plants since Minamata came into force in August 2017, the chlor-alkali sector remains a significant user of mercury, responsible for 1.4 tons of annual mercury emissions since 2020.
Cleaning up the process globally is vital since even small amounts of the silvery mineral – ranked by The World Health Organization as one of the world’s 10 most harmful substances – endangers the health of workers, surrounding communities, and ecosystems.
The project ‘Eliminate mercury use and adequately manage mercury and mercury wastes in the chlor-alkali sector in Mexico’ is working with the government and conglomerate CYDSA to convert the company’s mercury-cell plant in Coatzacoalcos, in the southeastern state of Veracruz, to a greener and less-costly method that relies on ion-exchange membranes.
Critically, the UN Environment Programme-managed initiative is also providing needed expertise for the safe clean-up of mercury waste at the sites of both the Coatzacoalcos plant and CYDSA’s already-converted facility in the northeastern city of Monterrey.
While the converted plant will use far less energy and cost less to run, the conversion, the clean-up of both sites, and the transfer of the mercury waste to environmentally safe long-term storage facilities will require both expertise and considerable capital investment.
Work will not focus solely on the chlor-alkali industry, however. By its end, the project aims to transform Mexico’s approach to all hazardous substances and wastes.
Expert teams will work with the government to create and distribute a good practice guide for the monitoring and management of all chemical plants and contaminated sites, with a chapter dedicated to mercury-cell chlor-alkali facilities.
They will also assess all laws, policies, and practices related to chemical and waste management: from collection and treatment to disposal and storage.
The project’s final phase will focus on communicating the valuable lessons garnered from the plant conversion and the site decontaminations to the rest of the nation – and the rest of world.
This will not only benefit countries working to free their chlor-alkali production from mercury, it will help make the process of decommissioning all types of hazardous chemical facilities in Mexico more efficient and effective.
