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Think at the nanoscale, act globally

Wei-xian Zhang’s technologies are cleaning up pollution on three continents.

Wei-xian Zhang, professor of civil and environmental engineering, was working in his lab, pondering oil spills in the gulf of Mexico and in Dalian, China, when a call came from Hoboken, New Jersey. A pedestrian had smelled fumes in one of the city’s brownstone neighborhoods. Police had discovered heating oil gushing from a corroded tank beneath the sidewalk in front of a house.

Zhang, who applies nanotechnology solutions to some of the world’s most notorious environmental disasters, knew time was of the essence. The leak had to be stopped and the oil removed before it spread farther into the soil and groundwater.

Workers remove algae from China’s Lake Tai.

Ten years ago, Zhang recalled as he drove to Hoboken, a construction crew would have rushed to the scene to perform an intervention as elaborately choreographed, and almost as dated, as the million-dollar brownstone’s ornate facade. Inch by inch, workers would have jacked the house off its foundation. A backhoe would have dug up the tainted soil to a depth of dozens of feet, and a line of trucks would have hauled it to a landfill. Workers would have refilled the foundation with fresh dirt before lowering and resecuring the house. The entire process would have taken weeks or months.

Zhang found these excavations fascinating to watch – “like a fossil dig,” he says – but decided there had to be a smarter way to decontaminate soil and groundwater. A decade ago, he took particles of iron measuring 50 nanometers in diameter, or about 1,000 times thinner than a human hair, and coated them with infinitesimal dots of palladium. He spent 30 minutes drilling a 3-inch hole, then pumped the nanoparticles into the soil and groundwater.

The nanoparticles spread quickly through the narrow pathways of soil and sediment. The greater proportional surface afforded by the particles’ tiny size gave the catalyst an unprecedented degree of contact and reactivity with toxins. The agile nanoparticles “chased” the contaminants in the water and converted them into harmless compounds.

“Only a few pounds of the nanomaterials, versus a ton of larger compounds, make sweeping changes in cleaning contaminated environments.” —Better World Report

Lehigh licensed the commercial rights to the nanoparticles to several companies, including the global engineering firm Golder Associates and local start-up Lehigh Nanotech LLC of Bethlehem, Pa. To date, the nanoparticles have remediated more than 50 toxic waste sites in 10 states and in Europe and Asia. They have decontaminated soil and groundwater in one-tenth the time, and at a much greater economy of scale, than traditional cleanup methods. At landfills, factories, gas stations, dry-cleaning shops and military sites, they have removed pesticides, vinyl chloride, TCE, chromium and other toxins.

“This revolutionary breakthrough in nanotechnology is helping clean up hazardous waste sites faster and more economically than ever before,” said Better World Report, a publication of the Association of University Technology Managers, which named lehigh Nanotech one of the nation’s top 25 technology-collaboration stories in 2008.

“It takes only a few pounds of the nanomaterials, versus a ton of larger compounds, to make sweeping changes in cleaning up contaminated environments.”

A green role for scrap metal
Mot all environmental challenges, says Zhang, are suited to nano-solutions.

In 2002, Zhang received a call from an industrial wastewater treatment plant in the Taopu Industrial District of Shanghai. Zhang knows the area well; he earned his bachelor’s degree from Shanghai’s Tongji University, one of China’s top engineering schools.

“China is experiencing serious environmental problems,” says Zhang. “The area around Shanghai has 6,000 industrial parks. Many of them are huge, and they generate a tremendous amount of industrial wastewater.”

The Taopu facility was using traditional biological methods, called activated sludge, to treat wastewater from chemical, materials and pharmaceutical companies. Zhang and his collaborator, Luming Ma, professor of environmental engineering at Tongji, identified two challenges. Biological microorganisms effectively treat municipal wastewater but not the compounds in industrial wastewater, many of which are loaded with toxic metals and synthetic organic chemicals. and the iron nanoparticles from Zhang’s lab that could remove those toxins were too expensive – at about $50 a pound – for a large, 13-million-gallon-a-day treatment plant in a developing country like China.

Zhang and Ma thought of the countless pieces of cheap scrap metal being generated by nearby factories. With its composition of zero valent iron (ZVI) – iron that has not been oxidized, he and Ma reasoned, the scrap metal could pretreat the industrial wastewater. after the iron degraded the toxic chemicals, the wastewater could be treated a second time with biological methods.

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