With some 300,000 hazardous-waste sites scattered across the United States, cleaning up contaminated soil and groundwater is a daunting challenge. Chemical engineer Michael Wong is taking on toxic waste with tiny particles that can break down organic pollutants more quickly, and perhaps less expensively, than existing technologies.
Each particle measures just four nanometers across and consists of a gold granule spotted with palladium. The nanoparticles’ high surface-area-to-volume ratio enables them to split chemicals faster than larger particles could, but their real advantage lies in their unique combination of metals. Palladium on its own does an adequate job of breaking down toxic chemicals such as trichloroethylene (TCE), an industrial degreaser that is linked to cancer and contaminates 60 percent of sites overseen by the U.S. Environmental Protection Agency’s Superfund project. But spotting the palladium on gold has a synergistic effect: the combination particles catalyze the removal of chlorine atoms from TCE molecules 100 times as fast as palladium particles alone.
Wong is already developing ways to incorporate his nanoparticles into filters for treating contaminated groundwater. To keep the particles in place, he has designed a method of growing them directly on the inner walls of hollow fiber tubes. He plans to test the system in the field this fall.