Zeolite for Radiocesium Farmland Decontamination

Q: If I spread zeolite on farmland, does it remove the radioactive cesium from the soil?

No. ¹³⁷Cs is a radionuclide with a half-life of about 30 years, and zeolite cannot eliminate the radioactivity itself. Clinoptilolite is a transfer-suppression aid that captures exchangeable Cs⁺ in the soil solution at ion-exchange sites with high Cs⁺ selectivity, thereby lowering plant availability (transfer to crops). In a paddy-field trial near Fukushima (Goto & Inagaki, 2015), brown rice from plots treated with zeolite plus potassium fertilizer showed radiocesium dropping from 17 Bq/kg in the control to 5–6 Bq/kg.

Q: Cesium is an anion, so can a negatively charged framework like zeolite adsorb it?

Cesium is not an anion; it is a monovalent cation (Cs⁺). As an alkali metal, cesium behaves as a monovalent cation in soil, which fits well with the cation-exchange mechanism of clinoptilolite's negatively charged framework. By contrast, for anions/oxyanions such as phosphate, fluoride, or arsenic, unmodified clinoptilolite adsorbs anions weakly because of its negative framework, so metal (Ca/La/Fe·Al) or surfactant modification (SMZ) is effectively a prerequisite. Cs⁺, however, is selectively exchanged in the natural state without such modification. That said, co-existing cations such as Ca²⁺, Mg²⁺, and K⁺ compete for the Cs⁺ sites.

Q: Why is it recommended to use it together with potassium (K) fertilizer?

Crop roots cannot distinguish between K⁺ and Cs⁺, which have similar chemical properties, so when soil K is deficient they take up Cs⁺ instead. Filling the soil's exchangeable K to a sufficient level makes the crop preferentially absorb K and suppresses Cs transfer. In the Fukushima paddy trial, the zeolite's effect was interpreted as arising mainly from adsorbing ammonium and potassium ions, preventing leaching and runoff of nitrogen and potassium from the plow layer and thereby maintaining K nutritional status. Therefore, combination with K nutrition management is recommended over zeolite alone.

Q: Which particle size (mesh) should be used on farmland?

For plow-layer mixing, Powder (100 mesh), which has a large contact area with the soil, is generally considered, while for packed-bed treatment passing leachate through drainage channels or collection wells, Fine–Coarse Granule (8×14–30×50 mesh) with good water permeability is suitable. Please refer to the application-based product selection guide.

Q: Is there a risk that fixed cesium transfers back to crops?

Clinoptilolite retains Cs⁺ selectively even under excess Na⁺ conditions, but Cs⁺ release may increase as the concentrations of Ca²⁺, Mg²⁺, and K⁺ rise (Dyer et al., 2018). Therefore, after application, the transfer factor (TF) trend should be checked through monitoring of crops, soil, and drainage, and K nutrition and pH must be managed throughout the cultivation period. Measurement-based safety management should, as a rule, follow the standards of nuclear and agricultural authorities.

Q: Can I receive a sample for testing?

Yes. KMIZEOLITE supports sample provision to verify transfer-suppression efficiency. On the sample request page, please provide the target soil's radiocesium concentration, exchangeable K, and desired particle size. We do not handle radioactive materials themselves; simulated (stable Cs) and actual-soil trials must be conducted at licensed facilities.

Radiocesium Farmland Contamination: What Is the Problem?

Radiocesium (¹³⁴Cs, ¹³⁷Cs) released by nuclear power plant accidents or nuclear-test fallout deposits onto farmland topsoil together with rainfall. In particular, ¹³⁷Cs has a long half-life of about 30 years, so once deposited it remains in the plow layer for decades and transfers from soil to crops. In one paddy field in Minamisoma near Fukushima, total radiocesium in the plow layer (15 cm) was measured at about 2,600 Bq/kg (¹³⁴Cs 1,137 Bq/kg + ¹³⁷Cs 1,428 Bq/kg), which led to cropping restrictions and full pre-shipment inspection (Goto & Inagaki, 2015).

Topsoil stripping and removal—excavating and carting away the topsoil—imposes heavy cost and waste-soil disposal burdens on large sites. For this reason, field farming-based transfer suppression, which binds cesium within the soil into a form difficult for plants to take up and thereby lowers the crop transfer factor (TF), is being considered as a realistic alternative, and here cation-exchanging minerals such as zeolite are used as soil amendments. The key is not to "remove" the cesium but to keep it from "going into the crop." Because effectiveness varies greatly with the soil's exchangeable potassium level, pH, and clay mineral composition, review at the material-selection stage is important.

Why Clinoptilolite Is Considered for Cesium Transfer Suppression

As an alkali metal, cesium behaves in soil as a monovalent cation (Cs⁺) and exists as exchangeable cesium adsorbed onto the negative charge of soil colloids and as water-soluble cesium dissolved in the soil solution. Natural clinoptilolite, based on its negative framework and cation-exchange capacity (CEC 1.6–2.0 meq/g), captures this exchangeable and water-soluble Cs⁺ by ion exchange. Importantly, clinoptilolite retains Cs⁺ selectively even when large amounts of Na⁺ coexist. The clinoptilolite used in the Sellafield SIXEP process has been reported to selectively extract 20 mol of Cs⁺ even under conditions where 7.5×10⁵ mol Na⁺, 6.5×10³ mol Mg²⁺, and 5×10³ mol Ca²⁺ coexist (Dyer et al., 2018).

The story is different, however, if the target is anions/oxyanions (phosphate, fluoride, arsenic, boron, nitrate, etc.). Unmodified clinoptilolite adsorbs anions weakly because of its negative framework, so metal (Ca/La/Fe·Al) or surfactant modification (SMZ) becomes effectively a prerequisite. But because cesium is a monovalent cation, it works by cation exchange in its natural state without such modification—a decisive advantage of this application. It is a target to which the cation-exchange logic applies exactly.

Structurally, uniform micropores of 4.0–7.0 Å and a specific surface area of 40.0 m²/g provide adsorption sites, and a stable pH range of 3.0–10.0 keeps the framework from collapsing in soils ranging from acidic to weakly alkaline. KMIZEOLITE's clinoptilolite is 97% pure, mined and processed at the Amargosa Valley mine in Nevada, USA, and being a natural mineral, it poses a low risk of secondary contamination even if it remains in the soil. The GRAS basis for soil-application use is summarized as 21 CFR 182.2729 (the general-use designation, not the animal-feed intake use).

In a cultivation trial that divided a paddy field 20.8 km from the Fukushima Daiichi plant into six plots and applied zeolite and potassium chloride (KCl), the radiocesium in brown rice was highest in the control at 17 Bq/kg, but in plots treated with zeolite plus potassium fertilizer it dropped to 5–6 Bq/kg. The researchers interpreted the zeolite's effect as arising mainly from adsorbing ammonium and potassium ions, preventing leaching and runoff of nitrogen and potassium from the plow layer (Goto & Inagaki, 2015, DOI:10.1007/978-4-431-55558-2). In other words, direct fixation of cesium and suppression of uptake competition through maintenance of K nutrition operate together.

KMIZEOLITE Key Properties

Item	Value
Clinoptilolite purity	97%
Cation Exchange Capacity (CEC)	1.6–2.0 meq/g
Specific surface area	40.0 m²/g
Pore diameter	4.0–7.0 Å
Stable pH range	3.0–10.0
Hardness	4.0–5.0 Mohs
Thermal stability	700°C
Specific gravity	1.89
Bulk density	45–54 lbs/ft³
Certifications	OMRI KMI-10365, FDA GRAS (21 CFR 182.2729), TSCA, EN-71-3

Radiocesium Farmland Application Examples (Transfer-Suppression Focused)

Below are representative scenarios in which clinoptilolite is considered as a soil amendment on radiocesium-contaminated farmland, along with typical operating conditions. The actual application rate must be finalized through field trials based on the soil's radiocesium concentration, exchangeable K level, and clay composition.

Plow-layer mixing (in-situ): Spread powdered zeolite on the topsoil (0–15 cm plow layer) and rotary-mix it to fix exchangeable Cs⁺ and suppress crop transfer. As in the Fukushima trial, combination with K fertilizer such as potassium chloride is key
K nutrition management aid: The zeolite adsorbs and slow-releases ammonium and potassium, reducing K leaching from the plow layer and inducing the crop to preferentially absorb K⁺ instead of Cs⁺
Revegetation / fallow-land stabilization: Mixed into cropping-restricted farmland or non-agricultural revegetation sites to suppress both plant transfer and surface runoff of cesium
Drainage / collection post-treatment: Passing leachate and drainage discharged from contaminated farmland through a granular zeolite packed bed (column) to adsorb and treat dissolved Cs⁺
Pilot application: Pre-verifying the transfer-factor (TF) reduction effect using simulated cesium (stable Cs) or actual-soil trials at licensed facilities

Recommended Particle Size and Product Specifications

For plow-layer mixing, Powder (100 mesh), which has a large contact area with the soil, is considered, and for leachate/drainage packed beds, Fine–Coarse Granule with good water permeability is suitable. Refer to the table below to select the product group that matches your application.

Product group	Mesh	Particle size	Representative uses
Powder	100 mesh or finer	<150μm	Pozzolan, feed, powder adsorption
Fine Granule	30×50 mesh	0.3–0.6mm	Water treatment, filtration, soil
Medium Granule	14×40 mesh	0.4–1.4mm	Filter media, bedding, litter
Coarse Granule	8×14 mesh	1.4–2.4mm	Swimming pools, de-icing, large-scale filtration
Extra Coarse	4×8 mesh	2.4–4.8mm	Packed beds, air scrubbers

→ View products by mesh size · Application-based product selection guide

Pilot Testing and Field Review Points

When applying zeolite to radiocesium-contaminated farmland, the following items must be checked together.

Soil diagnosis: Measure exchangeable K, clay mineral composition, and pH along with total radiocesium concentration (¹³⁴Cs, ¹³⁷Cs). Transfer suppression is an approach that lowers the plant-available (exchangeable) fraction rather than the total amount
Combination with potassium nutrition: Because crop roots cannot distinguish K⁺ from Cs⁺, Cs uptake increases when exchangeable K is deficient. Review the combined effect with K fertilizer application such as KCl rather than zeolite alone
Application-rate optimization: Through batch and field trials for each soil condition, compare the transfer-factor (TF) reduction against cost to determine the appropriate application amount. As in the Fukushima case, it is effective to design it together with the K fertilizer dose
Co-existing cation competition: When the concentrations of Ca²⁺, Mg²⁺, and K⁺ are high, they compete for the Cs⁺ exchange sites and Cs release may increase (Dyer et al., 2018), so verify performance in the actual soil matrix
Long-term stability: Monitor the radiocesium trend in crops, soil, and drainage over multi-year cultivation, and continuously manage K nutrition and pH to confirm the persistence of the transfer-suppression effect
Regulatory compliance: Handling of radioactive materials follows the standards and licensing of nuclear and agricultural authorities. Simulated and actual-soil trials must be conducted at licensed facilities, and expert review must always precede them

An overall review of radioactive-waste treatment using zeolites was compiled by Jimenez-Reyes et al. (2021) (DOI:10.1016/j.jenvrad.2021.106610), and a practical approach using geomaterials (including zeolite) to decontaminate radiocesium contaminants in agricultural areas was reported by Ito et al. (2021) (DOI:10.15669/fukushimainsights.vol.4.100).

→ View TDS (Technical Data Sheet) · View MSDS (Material Safety Data Sheet)

Radiocesium Farmland Decontamination FAQ

If I spread zeolite on farmland, does it remove the radioactive cesium from the soil?

No. ¹³⁷Cs is a radionuclide with a half-life of about 30 years, and zeolite cannot eliminate the radioactivity itself. Clinoptilolite is a transfer-suppression aid that captures exchangeable Cs⁺ in the soil solution at ion-exchange sites with high Cs⁺ selectivity, thereby lowering plant availability (transfer to crops). In a paddy-field trial near Fukushima (Goto & Inagaki, 2015), brown rice from plots treated with zeolite plus potassium fertilizer showed radiocesium dropping from 17 Bq/kg in the control to 5–6 Bq/kg.

Cesium is an anion, so can a negatively charged framework like zeolite adsorb it?

Cesium is not an anion; it is a monovalent cation (Cs⁺). As an alkali metal, cesium behaves as a monovalent cation in soil, which fits well with the cation-exchange mechanism of clinoptilolite's negatively charged framework. By contrast, for anions/oxyanions such as phosphate, fluoride, or arsenic, unmodified clinoptilolite adsorbs anions weakly because of its negative framework, so metal (Ca/La/Fe·Al) or surfactant modification (SMZ) is effectively a prerequisite; Cs⁺, however, is selectively exchanged in the natural state without such modification. That said, co-existing cations such as Ca²⁺, Mg²⁺, and K⁺ compete for the Cs⁺ sites.

Why is it recommended to use it together with potassium (K) fertilizer?

Crop roots cannot distinguish between K⁺ and Cs⁺, which have similar chemical properties, so when soil K is deficient they take up Cs⁺ instead. Filling the soil's exchangeable K to a sufficient level makes the crop preferentially absorb K and suppresses Cs transfer. In the Fukushima paddy trial, the zeolite's effect was interpreted as arising mainly from adsorbing ammonium and potassium ions, preventing leaching and runoff of nitrogen and potassium from the plow layer and thereby maintaining K nutritional status. Therefore, combination with K nutrition management is recommended over zeolite alone.

Which particle size (mesh) should be used on farmland?

For plow-layer mixing, Powder (100 mesh), which has a large contact area with the soil, is generally considered, while for packed-bed treatment passing leachate through drainage channels or collection wells, Fine–Coarse Granule (8×14–30×50 mesh) with good water permeability is suitable. Please refer to the application-based product selection guide.

Is there a risk that fixed cesium transfers back to crops?

Clinoptilolite retains Cs⁺ selectively even under excess Na⁺ conditions, but Cs⁺ release may increase as the concentrations of Ca²⁺, Mg²⁺, and K⁺ rise (Dyer et al., 2018). Therefore, after application, check the transfer-factor (TF) trend through monitoring of crops, soil, and drainage, and manage K nutrition and pH throughout the cultivation period. Measurement-based safety management should, as a rule, follow the standards of nuclear and agricultural authorities.

Can I receive a sample for testing?

Yes, KMIZEOLITE supports sample provision to verify transfer-suppression efficiency. On the sample request page, please provide the target soil's radiocesium concentration, exchangeable K, and desired particle size. We do not handle radioactive materials themselves; simulated (stable Cs) and actual-soil trials must be conducted at licensed facilities.

Inquiries and Sample Requests

If you are considering applying zeolite in the field of radiocesium farmland decontamination, please contact us through the channels below.

Notice

Whether the application is appropriate may vary depending on field conditions, regulations, and test results. Before actual application, testing and review tailored to the field conditions must always be carried out first. Zeolite should be understood not as an all-in-one solution for radiocesium contamination but as a material that complements existing farming measures such as K nutrition management.

Zeolite for Radiocesium Farmland Decontamination (Crop Transfer Suppression)