A Massachusetts-based company is looking to mine wastewater in Arizona as a potential source of valuable copper.
SiTration is running two pilot projects in Arizona this year, hoping to pull copper from wastewater from a historic mining operation in the Globe-Miami mining district. The tests follow similar tests in Australia. The company hopes to produce two tons of copper in a two-month period during one of the pilot tests.
Wastewater from copper mining often contains “significant” amounts of the metal, Smith said. But the mineral has been historically difficult to access. Worldwide, Smith said, there’s roughly $100 billion worth of copper trapped in liquid waste. Forty percent of that is in the American Southwest.
The price of copper surged to
about $6 per pound this year, more than double the price in 2020, according to the Federal Reserve Bank of St. Louis.
Demand for copper is growing, driven by global electrification, including grid improvements, and solar panel and wind turbine development, as well as the semiconductor industry and data centers. Just one hyperscale data center requires roughly 50,000 tons of copper to build the facility alone, not to mention any power generation or transmission needed for the facility, Smith said.
But as demand is projected to grow, supply is expected to shrink, Smith said. The highest-quality and most accessible copper deposits are being used up, and establishing new mines can be capital and time intensive.
“Twenty years to bring online a new copper mine, that’s not fast enough to address this really quick supply-demand gap that’s growing,” Smith said.
The pilot project will be conducted at the Copper Cities mine, which produced roughly 900 million pounds of copper during its lifespan, according to Kevin Ramsay, BHP's general manager of legacy assets.
The Globe-Miami mining district first gained attention for its silver deposits in the 1800s, Ramsay said. But as the country electrified in the early 1900s, copper became king. The Copper Cities mine was first developed at the start of the 20th century, and a productive copper deposit was found in the 1950s.
BHP took over management of the mine in 1996, when it acquired the previous owner. While production stopped in the 1980s, monitoring and environmental management of the site has continued.
Roughly 300 million gallons of copper-laced water are still stored on site, collected in what appears to be a shallow lake. When rain or snowmelt and natural inflow interact with materials that have sulfur in them, the reaction creates acid rock drainage, Ramsay said, which can't be released into the environment.
"The pilot will help us progress a technology that, if we can deploy on a bigger scale, absolutely has some potential to shift the way that we do water management at this and other sites, because it may enable you to move towards more recovery and remediation of water simultaneously," Ramsay said.
SiTration uses two processes to separate valuable copper from water and other mining waste byproducts. A silicon filter uses channels, roughly 100,000 thinner than a human hair, to separate out a concentrate copper and other substances and clean water from mining wastewater.
The copper can then be separated from the concentrate left behind using electricity using a process called electroplating, which is already used in conventional copper mining to separate copper from ore. The Copper Cities pilot will rely on electroplating.
“You’re using electricity to directly extract these metals from a liquid stream,” Smith said. “And so, we do that from waste.”
But the material of the electrode and the process used by SiTration are more efficient and durable than normal. The system can extract copper from less concentrated solutions at a rate that is still profitable, Smith said. For each kilogram of copper extracted, the process uses about three to four kilowatt hours — which Smith said is five to six times more energy efficient than producing a kilogram of copper with conventional mining techniques like smelting.
The end product doesn’t require any additional processing before it can be sold to the market. Then, the modular treatment system can be moved to the next site.
“Especially in geographies like Arizona, where there is a high density of these legacy sites and a lot of copper available for harvesting from these legacy pits, it’s a great strength to be able to uproot these things and move them around in a very versatile, very nimble way,” Smith said.
Alaina Mencinger covers energy, tech and utilities for the Arizona Republic. Reach her at Alaina.Mencinger@usatodayco.com.
This article originally appeared on Arizona Republic: Company bets it can strike it rich from copper in Arizona wastewater
