Nanotechnology on the agenda

Professor Jaehong Kim

Originally from Korea, Yale University Professor Jaehong Kim gave a plenary keynote at the IWA Leading Edge conference held there in May/June 2023 in the city of Daegu. Here, he outlines his research area of nanotechnology.

By Erika Yarrow-Soden

IWA’s 18th Leading Edge Conference on Water and Wastewater Technologies (LET) was held in Daegu, in South Korea, from 29 May to 2 June 2023, and marked the 20th anniversary of the series.

The series is held in a different country every year, and is designed to be the place where new ideas are introduced and the opportunity is provided to interact with the ‘best of the best’. This makes LET the global conference where new insights are shared into the pioneering science, technological innovation and leading practices that are shaping major transformation in the water sector.

Contributing to this dynamic environment of innovation and knowledge transfer, Professor Jaehong Kim, Henry P Becton Sr, Professor of Engineering in the School of Engineering and Applied Science at Yale University in the USA, gave a plenary keynote presenting recent outcomes of his research on developing ultrafiltration-based advanced oxidation platforms for organic pollutant degradation in complex wastewater matrices.

Kim is a specialist in the environmental application of nanomaterials, the development of photoluminescence/photocatalysis technology for environmental and energy applications, and the development of membrane processes and materials. This edition of LET had particular significance for him, as he originally comes from Korea, receiving his BS and MS degrees in chemical and biological engineering from Seoul National University in South Korea. His presentation focused on his work to develop a water treatment membrane with a catalytic function.

Ultrafiltration membrane is typically used to remove particulate and organic pollutants from water through size exclusion. Things that are bigger than the pore of the membrane are rejected to produce clean water, but that means small organic pollutants found in water can pass through the membrane. Even with reverse osmosis, which is the tightest membrane, the smallest hydrophilic and neutral molecules can pass through. Kim’s research looks at the potential for a catalytic function to be added to the membrane treatment so that organics are not just removed through size exclusion, but are chemically destroyed during the filtration.

The heterogeneous advanced oxidation processes (AOPs) that Kim is researching enable the destruction of aqueous organic pollutants via oxidation by reactive oxygen species, such as hydroxyl and sulphate radicals. However, practical treatment scenarios suffer from the low availability of short-lived radicals in aqueous bulk because of mass transfer limitations and quenching by water constituents such as natural organic matter (NOM) and carbonate. Kim has been exploring ways to overcome these challenges by loading various catalysts within the pores of a ceramic ultrafiltration membrane, resulting in an internal heterogeneous catalytic reaction that can efficiently degrade organics in complex water matrices.

With radicals confined inside the nanopores below 20 nm, a critical length scale that exerts a nanoconfinement effect, these membrane reactors nearly completely removed various organic pollutants through single-pass treatment with water fluxes equivalent to a retention time of a few seconds. These membranes, with a pore size that removes most NOM, selectively exposed smaller organics to radicals within the pores under confinement and showed excellent resiliency to representative water matrices. Moreover, these membranes exhibited sustained AOPs over long-term operation and could be regenerated for multiple cycles because of oxidative removal of foultants on the membrane surface and pore walls.

Kim explains: “My presentation included quite a lot on the nanoconfinement effect. The radicals’ lifetime is very short. Their concentration diminishes very fast from the catalyst surface where they are generated. This is a distance dependent phenomenon. In other words, the oxidation efficiency depends on how far the pollutant is from the surface. That’s the reason we introduced this catalyst inside the pore, so that the distance would be fixed. This means the radicals cannot move and are consumed in a short distance. Consequently, the pollutants that pass through the membrane pore are inevitably exposed to radicals and consequently destroyed.”

Kim aims to apply this technology for use in a modular system that is suitable for commercialisation. It is likely to be too costly for large-scale municipal water treatment, industrial combined sewage/water treatment or desalination, as it is difficult to engineer at scale and the catalyst doesn’t last indefinitely. However, Kim sees the potential for this technology to be used in small modular systems for niche applications for the treatment of highly concentrated, highly polluted water. As such, he sees opportunities for the technology to address the needs of the oil and petrochemical industries, for example.

“If you are talking about large-scale municipal treatment, there is little room for nanotechnology to replace conventional treatment processes, simply because of cost ineffectiveness,” says Kim. “But there are many other cases where water treatment would be required to this level, especially treatment of industrial wastewater for recycling and process water that often has a very specific quality requirement that may not be achieved by conventional treatment. The opportunities lie where high-quality processing is required, even though this technology is fairly expensive.”

As the technology develops there could even be potential for it in low income or developing country settings if, for example, it is used to enhance other technologies, or if longer-term performance can be considered rather than initial costs.

Kim’s research is ongoing, with some applications at pilot stage, so LET provided the perfect opportunity for him to share this advancing technology with experts from across the globe. He says: “LET was educational, delightful, and inspiring. It is one of the major conferences in the water industry and offers a global platform where experts and stakeholders in the sector can come together to discuss and explore emerging technologies and innovations. It gave me the opportunity to meet colleagues and industry leaders who had a practical view of the industry.

“I was deeply honoured to give a plenary keynote. Daegu is promoting itself as a water hub and Korea has been investing a lot in the water industry. I was pleased to see a successful LET hosted by my home country.” •

For your diary – LET 2024 in Essen, Germany

Following the success of LET 2023, IWA looks forward to hosting its 19th Leading Edge Conference on Water and Wastewater Technologies on 24-28 June 2024, in Essen, Germany. With its rich history and reputation as an environmental hub, Essen promises to be an ideal host for this prestigious event. Join us to learn about the latest advances in water and wastewater treatment, be inspired by our speakers, and network with the leading lights of the water sector. Find out more at: