Researchers at Rice University and Vanderbilt University have developed an electrochemical wastewater treatment technology that simultaneously removes salt and selectively recovers valuable metals. This approach could reduce treatment costs and improve water reuse in industrial sectors such as electronics manufacturing and metal processing.
The new approach, described in the journal Nature Water, uses a process known as electrochemical ion pumping (EIP) to address two persistent challenges in industrial wastewater: high salinity and dissolved toxic metals. Existing treatment systems typically handle these contaminants separately, often requiring multiple treatment steps and producing hazardous brines or metal-laden sludge.
The research team, led by Shihong Lin, associate professor of civil and environmental engineering at Rice University, demonstrated that EIP can be programmed to desalinate wastewater while selectively recovering dissolved metals such as copper.
“Conventional desalination technologies such as reverse osmosis can remove salts, but they do not selectively separate valuable or toxic metal ions from background salts,” Lin said in a statement from Rice University. “Meanwhile, chemical precipitation can remove metals, but it relies on added chemicals and often produces hazardous sludge.”
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The system relies on electrically controlled electrodes that temporarily capture ions from wastewater before releasing them into a separate receiving stream. By carefully adjusting the electrode voltage, researchers can determine whether specific metal ions are transferred into the receiving stream or remain trapped on the electrode for later recovery.
Unlike conventional electrosorption systems that require switching between adsorption and regeneration stages, the new process changes only the electrical circuit, allowing ions to move continuously through the system without interrupting operation.
“Conventional electrosorption systems typically require the feed and receiving solutions to be switched between adsorption and regeneration steps,” Lin said. “Our method replaces that physical solution switching with rapid changes in the electrical circuit, allowing ions to move continuously in one direction through the system.”
Laboratory testing with synthetic wastewater containing sodium and copper showed the technology removed 90% of dissolved salt while retaining nearly all of the copper on the electrode instead of allowing it to enter the concentrated brine.
Researchers also tested the process using a more complex wastewater containing copper, nickel and sodium. By adjusting the electrode voltage in a five-electrode EIP stack, they selectively captured copper while allowing nickel and sodium to continue through the desalination pathway.
After four hours of operation, researchers said the system removed 85% of the dissolved salt and more than 92% of both copper and nickel from the wastewater. Nearly all of the copper remained on the electrode, while almost all of the nickel was transferred into the receiving stream. The recovered copper reached approximately 96% purity relative to nickel.
“Our results showed that EIP can be tuned to decide where different ions go during treatment,” Lin said in a news release. “Some metals can be captured on the electrode, while salts and other ions can continue through the normal desalination pathway.”
The researchers say the technology could be particularly valuable for industries seeking to recycle water while recovering commercially valuable metals. By preventing target metals from entering mixed brine streams, the process could reduce downstream purification requirements and hazardous waste generation while producing concentrated metal recovery streams after electrode regeneration.
The latest study builds on the research team’s earlier work establishing the electrochemical ion pumping concept and advancing its desalination capabilities, extending the technology to perform simultaneous desalination and selective metal recovery within a single electrochemical platform.
The research was supported by the U.S. National Science Foundation and the Office of Naval Research.
