Researchers have developed a new technology that targets and captures copper in contaminated wastewater.
Decontaminating wastewater polluted with heavy metals is complex, expensive, and usually involves a slow-paced process. Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory have developed a material that targets and captures copper ions from wastewater with unmatched precision and speed. Their prototype exhibits how metals could be sourced from water while providing a more affordable water treatment solution.
“Today’s water treatment systems are ‘bulk separation technologies’ – they pull out all solutes, irrespective of their hazard or value,” says Peter Fiske, co-author of the research. “Highly selective, durable materials that can capture specific trace constituents without becoming loaded down with other solutes, or falling apart with time, will be critically important in lowering the cost and energy of water treatment. They may also enable us to ‘mine’ wastewater for valuable metals or other trace constituents.”
Called ZIOS (zinc imidazole salicylaldoxmine), the crystalline material is inspired by how bacterial cells select specific metals to regulate their metabolism. The material’s durability allows it to be used in acidic water sourced from a copper mine. The copper can be removed once it fills up the material, which can be reused. Scientists chose copper because it’s easier to target.
A schematic diagram (left) shows a ZIOS network and an SEM (scanning electron microscopy) image of a ZIOS-copper sample on a silicon wafer. (Image Credit: Berkeley Lab)
“It’s kind of like a crystal sponge,” says Jeff Urban, senior author of the journal article. “When you put it into water, it opens up. Instead of grabbing everything, this is a sponge that’s very specific to copper because of the size of the pores and the stickiness of the pores for copper.”
ZIOS consists of tiny channels that expand when the material is submerged in water. When these channels widen, water molecules can flow through the structure. From there, a chemical reaction occurs, which binds the material with copper ions that are present in the liquid.
In their X-ray experiments, the scientists discovered that the material is extremely selective when it binds to copper ions in water that has the same pH levels as mining wastewater. It does this with remarkable efficiency. “ZIOS has a high adsorption capacity and the fastest copper adsorption kinetics of any material known so far – all in one,” Jeff Urban, senior author, said.
The team says ZIOS is capable of selectively trapping copper ions at 30 to 50 times the speed of existing state-of-the-art solutions. It also stays incredibly stable after being immersed in water for up to 52 days. When it’s removed from the water, it returns to its original size in one nanosecond.
According to the team, ZIOS is a type of blueprint for wastewater treatment. This is the first technology that’s capable of removing heavy metal ions with atomic-level precision. It can also be designed to capture other metals in water.
“We view this as kind of a template for an overall strategy for doing targeted and precision separations,” Urban says. Eventually, wastewater treatment plants could use filters to capture various materials at the same time, putting each material in a different channel. It could also become the source for new materials without the environmental impacts of mining.
This new technology is quicker and less expensive than other techniques that remove pollutants. “The starting materials are cheap,” he says. “And it has a good lifetime, so you’re not paying to replace it.”
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