Cleantech
New MIT Technology Could Revolutionize Wastewater Treatment

MIT has developed a new technology that could revolutionize wastewater treatment and water purification. Providing an alternative to more energy- and chemical-intensive alternatives, MIT’s new method is capable of removing even extremely low levels of pollutants from water.

The technology was developed by MIT postdoc Xiao Su, Ralph Landau, Professor of Chemical Engineering T. Alan Hatton and five others at MIT and at the Technical University of Darmstadt in Germany.

The new approach relies on an electrochemical process to selectively remove organic contaminants such as pesticides, chemical waste products and pharmaceuticals, even when they are present in small but dangerous concentrations. It also eliminates problems present in other more traditional methods, including acidity fluctuations and losses in performance resulting from competing surface reactions.

Current systems for dealing with such dilute contaminants are expensive and have limited effectiveness at low concentrations and often require high voltages that tend to produce side reactions. These processes also are hampered by excess background salts.

In the new system, the water flows between chemically treated, or “functionalized,” surfaces that serve as positive and negative electrodes. Electrode surfaces are coated with Faradaic materials, which can undergo reactions to become positively or negatively charged. These active groups can be tuned to bind strongly with a specific type of pollutant molecule, which was demonstrated with ibuprofen and various pesticides. The researchers found that this process can effectively remove such molecules even at parts-per-million concentrations.

Not only are side reactions completely eliminated in the new process, but the asymmetric systems also allow for simultaneous selective removal of both positive and negative toxic ions at the same time, as the team demonstrated with the herbicides paraquat and quinchlorac.

According to Xiao Su, the same process could also be applied to the recovery of high-value compounds in a chemical or pharmaceutical production plant, where they might otherwise be wasted.

“The system could be used for environmental remediation, for toxic organic chemical removal, or in a chemical plant to recover value-added products, as they would all rely on the same principle to pull out the minority ion from a complex multi-ion system,” Su added.

The system is inherently highly selective, but in practice it would likely be designed with multiple stages to deal with a variety of compounds in sequence, depending on the exact application.

“Such systems might ultimately be useful,” he suggests, “for water purification systems for remote areas in the developing world, where pollution from pesticides, dyes, and other chemicals are often an issue in the water supply. The highly efficient, electrically operated system could run on power from solar panels in rural areas for example,” said Su.

MIT’s work, which is outlined in the journal Energy and Environmental Science, has already received recognition from the J-WAFS Solutions and Massachusetts Clean Energy Catalyst competitions and researchers last year received the MIT Water Innovation Prize. The research team has also applied for a patent on the new process.

“We definitely want to implement this in the real world,” said Hatton.