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Sustainable Chemistry: An Even Darker Shade of Green

Innovative EPA researcher taps everyday tools and plants to develop environmentally friendly ways to make chemicals and nanomaterials.

A microscope

EPA researcher Dr. Rajender Varma has given new meaning to the phrase “reading the tea leaves” through his visionary development of new, green ways to synthesize chemicals and nanomaterials from things such as microwave ovens, magnets, and natural antioxidants found in coffee, vitamins, grape husks left over from winemaking operations, and, of course—tea.

Varma and his team have developed dozens of new and patented methods for the chemical industry and others to make compounds in environmentally friendly ways.

Working at an EPA research laboratory dedicated to tapping the principles of green chemistry and engineering to advance sustainability, Varma’s team is developing benign nanomaterials to replace conventional catalysts, substances that initiate or speed up chemical reactions but do not themselves change during the reaction. Catalysts can be expensive, dangerous if not handled properly, and may end up as waste products that must be treated and/or disposed of carefully. In contrast, Varma has created iron-based magnetic nanomaterial-based catalysts that are easily recycled.  

By building nanomaterial-based catalysts with a core of iron and coating them with other metals, the catalyst can be separated using a simple magnetic field and then re-used, avoiding the use of hazardous substances while creating virtually no waste. “I often feel these methods plagiarize Nature because our approaches mimic what nature does so elegantly in biological systems,” Varma says.

Varma’s group has also pioneered a new method of synthesizing nanoparticles. Instead of using a typical “top-down” approach that relies on large energy inputs and toxic solvents to break down larger materials, Varma and his colleagues employ a simple “bottom-up” method that assembles nanomaterials at the molecular level. This novel approach avoids the use of hazardous reducing agents, and instead employs benign metallic salts (such as iron salts), water, and polyphenols from plant materials (tea, coffee, and red grapes) to act as reducing or capping agents to prevent nanomaterials from aggregating into larger clumps during the production process.  

Varma’s innovative methods for coating iron nanomaterials are earth-friendly in both their production and degradation processes, allowing them to be used for environmental remediation operations, even to clean up pesticides from soils near crops.  

Working with the Connecticut-based firm VeruTEK, Varma and his EPA colleagues have played an important role in developing and commercializing green remediation technologies. VeruTEK has used this approach for degradation of pollutants in water. The technology can also be applied directly to soil, where it forms nanomaterials that breakdown organic toxicants. The iron-based, phenolic-coated nanomaterials naturally degrade, so they can be left in place once applied, offering an attractive alternative to standard cleanup methods of extracting and hauling away contaminated soils for offsite cleaning before they are trucked back in and replaced.

Not surprisingly, Varma’s work has attracted significant attention from the scientific community and beyond. He has briefed U.S. Congressional staff and the President of India in addition to lecturing in Chile, China, India, Peru, and Venezuela. He pointed out that developing countries are immensely interested in methods that allow them to “leapfrog” by circumventing older technologies and embracing more efficient ones, such as when governments encourage the establishment of cell phone networks, allowing them to skip costly and disruptive installations of telephone poles and overhead wires in areas that previously had no telecommunications technology.

The nanocatalysts that Varma’s team produces can be safely recycled and may be used over and over, and can even be utilized for clean-up operations using visible light from the sun. According to Varma, “this process allows for a little darker shade of green” as we transition to practices for more sustainable chemical manufacturing and use. “In addition to its monitoring and compliance efforts, hopefully EPA can be a beacon to others in developing sustainable methods going forward,” Varma says.

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