Treated Carbon Cloth Electrode Sets Cesium Removal Record at 1,173 mg/g

The problem with radioactive cesium is its mobility. Cesium-137, a byproduct of nuclear fission, dissolves readily in water and spreads through aquatic systems with few natural barriers. Its 30-year half-life means it persists in contaminated environments long after the incidents - reactor accidents, research facility discharges, ordinary nuclear plant operations - that release it. Removing it efficiently and durably from wastewater has been a practical challenge with direct public health consequences.

Prussian blue, the iron cyanide compound most people know as a pigment, turns out to be a remarkably effective cesium trap. Its crystalline structure contains cavities sized almost perfectly for cesium ions. The material is relatively nontoxic, chemically stable, and highly selective - it captures cesium in preference to competing ions like sodium and potassium, which are present in far greater concentrations in most wastewater streams. The problem has been practical: Prussian blue typically comes as a powder, which requires additional processing steps to deploy in treatment systems, adding cost and complexity.

The Wettability Barrier

One approach to solving the handling problem is to deposit Prussian blue directly onto a conductive electrode substrate, enabling electrochemical control of adsorption and desorption. Carbon cloth is an attractive substrate - it is conductive, commercially available, and structurally robust. But it has a significant drawback: it is inherently hydrophobic. Water does not spread evenly across its surface, which means the electrolyte solution needed to deposit Prussian blue also does not spread evenly. The result is patchy, inconsistent Prussian blue coating that underperforms in actual cesium removal.

The team led by Professor Jum Suk Jang at Jeonbuk National University addressed this directly. They subjected carbon cloth to acid treatment at 60 degrees Celsius. The process removes some graphitic carbon from the surface and introduces oxygen-containing functional groups - hydroxyl, carbonyl, carboxyl - that make the surface hydrophilic. Water now spreads evenly, and so does the electrolyte during Prussian blue electrodeposition.

The resulting electrode - designated PB-ACC, for Prussian blue on acid-treated carbon cloth - showed significantly improved wettability and homogeneous Prussian blue distribution compared to untreated controls. Electrochemical characterization confirmed enhanced activity and reduced ion diffusion resistance.

Record Adsorption Performance

In testing, PB-ACC achieved a cesium adsorption capacity of 1,173 milligrams per gram within three hours. That figure, reported in the Chemical Engineering Journal (Volume 527, January 2026), exceeds previous records for Prussian blue-based materials. The comparison matters because Prussian blue has been studied extensively as a cesium adsorbent - improving on the best prior results requires a genuine advance in material design, not simply different test conditions.

The system also demonstrated high selectivity for cesium ions in the presence of competing ions, an important practical requirement since real wastewater is not a pure cesium solution. And when tested across repeated adsorption-desorption cycles - the key metric for real-world deployability - PB-ACC maintained approximately 97 percent cycling efficiency. This long-term stability is where many promising laboratory adsorbents fail when scaled toward application.

The electrochemical control mechanism provides an additional operational advantage over purely passive adsorption systems: by applying a voltage, operators can switch the electrode between adsorption and desorption modes on demand, allowing the captured cesium to be concentrated and managed as a distinct waste stream rather than requiring the entire electrode to be replaced.

Context: Why Cesium Removal Matters Now

Nuclear energy generates roughly 10 percent of global electricity and is attracting renewed investment as a low-carbon power source. That makes effective radioactive waste management more, not less, important. Even under normal operating conditions, nuclear facilities generate wastewater containing radionuclides. Accidental releases - the Fukushima disaster remains the most significant recent example - can produce far larger contamination challenges. Cesium-137 was among the primary radionuclides released at Fukushima in 2011, and decontamination of affected water has remained an ongoing challenge.

A cesium removal technology that combines high capacity, rapid kinetics, reusability, and selectivity addresses real operational needs. The PB-ACC electrode meets all four criteria in laboratory testing.

What Remains to Be Demonstrated

The experiments were conducted under controlled laboratory conditions, not in actual nuclear facility wastewater, which may contain a broader range of competing ions, organic compounds, and other contaminants. Scale-up from laboratory electrode to treatment-scale system involves engineering challenges that this study did not address. The long-term performance of the acid-treated carbon cloth substrate under sustained electrochemical cycling, over months or years rather than the cycle counts tested here, also requires further evaluation. Commercial viability will ultimately depend on cost comparisons with existing treatment technologies at industrial scale.