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Electrically controlled ion exchange offers a greener way to treat wastewater

| By Chemical Engineering

Researchers at Pacific Northwest National Laboratory (PNNL; have demonstrated a new process for treating water contaminated by toxic perchlorate ions, found in drinking water in 35 U.S. states. As in conventional treatment methods, the process uses ion exchange to separate the ion from water. However, instead of regenerating the resin with an acid, PNNL’s process uses an electric current for regeneration, thus eliminating large quantities of secondary waste.

The process relies on an electrically conductive polymer, such as polypyrrole; by application of a positive charge to the polymer, the negatively charged ions are selectively attracted to the polymer (diagram). When the resin is loaded, an electric current is applied, which releases the captured ions. The "resin" is made by depositing a thin film of polymer – by electrodeposition and in situ polymerization – onto a matrix of carbon nanotubes, creating a porous, conductive nanocomposite with a high surface area.

The technology can also be adapted for removing cations, such as cesium and chromium ions, from water. The technology is available for licensing and joint research through Battelle (Columbus, Ohio;, which operates PNNL for the U.S. Dept. of Energy (DOE; Washington, D.C.).