An NJIT Water Treatment Specialist Wins an Edison Patent Award

In daily battles with pathogens, legacy chemicals from long disappeared factories and a growing array of micropollutants, water treatment systems are often handicapped by clogged membrane filters. Replacing them regularly is both laborious and expensive.

“Membrane filters are easily clogged when bacteria, natural organic matter and insoluble solids block their pores, aging and damaging them. They must be cleaned by intensive backwashing, sometimes involving strong chemicals,” said Wen Zhang, an associate professor of civil and environmental engineering who designs novel reactive membrane systems that degrade contaminants not captured or removed by standard filtration. 

Zhang recently won a Thomas A. Edison Patent Award from the R&D Council of New Jersey for a novel technology that combats what’s known in the industry as membrane fouling. His revolutionary technology uses microwave irradiation to catalyze reactions on the membrane surfaces, producing high-temperature hot spots and reactive radicals that rapidly degrade pollutants, kill microbes and mitigate membrane clogging.

Zhang was among 14 organizations and 57 researchers honored at the 43rd Edison Patent Awards in November. His technology is the first to use microwaves to enhance catalytic reactions during membrane filtration. It has proved capable of destroying refractory micropollutants such as PFAS and viruses in both water and in airborne droplets.

His device is a microwave chamber with filtration membranes placed inside, which have embedded metal oxides as catalysts that facilitate chemical reactions with the water being treated when they are irradiated. The whole device can be as small as a kitchen microwave oven or as large as a trailer, depending on the treatment capacity and other factors.

Zhang’s Sustainable Environmental Nanotechnology and Nanointerfaces Laboratory creates devices that employ filters with functionalized membranes, where membrane surfaces are coated with contaminant-degrading nanoparticles or nanomaterials as catalysts that are activated by microwaves or electrochemistry. Once activated, the membranes serve as a highly reactive barrier to destruct water pollutants on contact, providing a self-cleaning filtration system that also mitigates membrane fouling issues. 

In addition to microwave-activated membranes, he has also developed reactive electro-chemical membrane systems that are activated by DC power sent to the membrane surface and photocatalytic reactive membranes activated by external UV or visible light irradiation.

The micropollutants he treats, including chemicals in organophosphate flame retardants, pesticides, herbicides, pharmaceuticals and personal care products, don’t degrade naturally. Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS), chemicals used for six decades in the aerospace, automotive, construction and electronics industries as protective coatings to resist heat, oil, stains, grease and water, for example, are increasingly detected in many water sources and contaminated sites. PFAS molecules are composed of a chain of linked carbon and fluorine atoms that have strong bonds.

Traditional filtration technologies, such as microfiltration, do not remove micropollutants efficiently as their small size allows them to penetrate membrane pores. Reverse osmosis (RO) and nanofiltration effectively remove them, but are hampered by membrane fouling and high operational costs. For example, RO consumes high energy (~1 kilowatt-hour per cubic meter of water) and generates high-strength brines containing concentrated residual chemicals such as PFAS, as the process does not degrade pollutants. The disposal of these concentrated residuals or RO retentate is expensive and itself potentially polluting.

“Water pollution is increasingly complex, thus pushing us to think about the next generation of water treatment solutions,” said Zhang. “With our new technologies, we aim to reduce the burden downstream at water plants, while providing individual users access to safe drinking water.”