□ A research team led by Professor Seongkyun Kim of the Department of Physics and Chemistry, the Daegu Gyeongbuk Institute of Science & Technology (DGIST; President Kunwoo Lee), successfully developed a solar-powered artificial plant device and rapidly purified soil contaminated with radioactive cesium. This device, which mimics plant transpiration, can collect cesium in leaves and purify it using sunlight alone without electric power or additional water. It is highly applicable on site as it is not necessary to scoop up and clean the soil, unlike traditional devices.
□ As radioactive cesium (Cs⁺) has a long half-life, it remains in the environment for a long time. It is also highly soluble in water and spreads easily in the environment. Once it enters the body, it can build up in muscles and bones and cause cancer or organ damage. In fact, in the aftermath of the Fukushima nuclear accident in Japan in 2011, imports of Japanese vegetables and seafood were "above the cesium threshold" and were accordingly stopped or destroyed. While contaminated water can be purified with an adsorbent, it is a global challenge to purify soil as there is no alternative to scooping up and purifying the soil.
□ Technology to purify contaminated soil based on the use of natural plants has been studied for a long time. It is based on the principle that plants suck in pollutants with their roots and collect the pollutants in their leaves or stems. This method, however, takes a lot of time, does not have a high elimination rate, and is highly influenced by weather and climate conditions. Most of all, radioactive material must be eliminated quickly for safety, and it is difficult for plants to do so as they grow slowly. Another downside is that the contaminated plants themselves become radioactive waste and require additional treatment.
□ To overcome these limitations, the research team led by Professor Seongkyun Kim developed an artificial plant device that simulates plant transpiration. The device uses solar energy to quickly absorb contaminated water from the soil. It picks up only radioactive cesium and accumulates it in its leaves. Pure water evaporates, and the evaporated water returns to the soil through the recovery system. Therefore, it is not necessary to replenish the water.
□ As the absorbed cesium remains in the leaves, the device can be reused repeatedly as long as the leaves are replaced after purification. Furthermore, an acidic substance can be used to wash the used leaves to take the cesium out, and the adsorbent can be recycled multiple times, which reduces costs and the environmental burden.
□ The research team experimented with soil contaminated at various concentrations of cesium and found that this technology reduced the concentration of cesium in the soil by more than 95% within 20 days. It greatly accelerated the purification process, which usually takes months. The technology can be used to restore soil in agricultural land or accident sites severely contaminated by radioactive cesium. It is powered by solar energy alone, and it does not require electricity or additional water. Hence, it is highly applicable on site.
□ "While radioactive cesium contamination causes a much more serious problem in soil than in water, there has been no proper method to purify it so far," said Professor Seongkyun Kim. "This study holds significance as it demonstrates the possibility of purifying contaminated soil based on solar energy by mimicking natural plants and simply installing the device without any other equipment."
□ Soobin Kim, a PhD student in the Department of Physics and Chemistry, DGIST, participated in this study as the first author, and it was published online on Aug 25, 2025, in Environmental Science & Technology, an international environmental sciences journal.
