A process that causes crusts to form inside teapots could also help clean nickel-borne contamination from seawater, according to a new study from the South Pacific island of New Caledonia.
        Nickel mining is the main industry in New Caledonia; the tiny island is one of the largest metal producers in the world. But a combination of large open pits and heavy rainfall has resulted in large amounts of nickel, lead and other metals ending up in the waters around the islands. Nickel pollution can be detrimental to human health as its concentration in fish and shellfish increases as you move up the food chain.
       Marc Jeannin, an environmental engineer at the University of La Rochelle in France, and his colleagues at the University of New Caledonia at Nouméa wondered if they could use the cathodic protection process, a technique used to combat corrosion of marine metal structures, to get some nickel from water.
        When a weak electric current is applied to metals in seawater, calcium carbonate and magnesium hydroxide precipitate out of the water and form lime deposits on the surface of the metal. This process has never been studied in the presence of metallic impurities such as nickel, and the researchers wondered if some nickel ions might also be trapped in the precipitate.
        The team threw a galvanized steel wire into a bucket of artificial seawater that had NiCl2 salt added to it and ran a mild electric current through it for seven days. After this short period, they found that as much as 24 percent of the nickel originally present was trapped in scale deposits.
        Jannen says it can be an inexpensive and easy way to remove nickel contamination. “We can’t completely eliminate pollution, but that could be one way to limit it,” he said.
        The results were somewhat random, as the elimination of pollution was not one of the goals of the original research program. Janine’s main research is focused on developing ways to combat coastal erosion: he studies how lime deposits buried in a wire mesh on the ocean floor can act as a kind of natural cement, helping to stabilize deposits under dykes or on sandy beaches.
        Jannin started a project in New Caledonia to determine if the network could capture enough metal contamination to help study the site’s history of nickel contamination. “But when we discovered that we could capture large volumes of nickel, we started thinking about possible industrial applications,” he recalls.
        The method not only removes nickel, but a host of other metals as well, says environmental chemist Christine Orians of the University of British Columbia in Vancouver. “Co-precipitation is not very selective,” she told Chemistry World. “I don’t know if it will be effective at removing enough toxic metals without removing potentially beneficial metals like iron.”
        Jeanning, however, is unconcerned that the system, if deployed on a large scale, will remove vital minerals from the ocean. In experiments that removed only 3 percent of calcium and 0.4 percent of magnesium from the water, the iron content in the ocean is high enough to not have much of an effect, he said.
        Specifically, Jeannin suggested that such a system could be deployed at high nickel loss locations such as the port of Noumea to help reduce the amount of nickel ending up in the ocean. It does not require much control and can be connected to renewable energy sources such as solar panels. Nickel and other contaminants caught in scale can even be recovered and recycled.
       Jeanning said he and his colleagues are working with companies in France and New Caledonia to develop a pilot project to help determine whether the system can be deployed on an industrial scale.
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