Granular Agrochemical & Microbial Slow-Release Carrier Zeolite

Q: Why is zeolite suitable as a carrier for granular agrochemicals and microbial products?

Natural clinoptilolite is a mineral with a three-dimensional porous structure featuring a specific surface area of about 40m²/g and a pore diameter of 4.0–7.0Å. It acts as a carrier that loads active ingredients onto its pores and surface and then releases them slowly. Its good inter-particle flowability makes it easy to handle as a carrier and filler for dust and granular formulations, and with a pH stability range of 3.0–10.0 and thermal stability up to 700°C, it remains stable throughout formulation processing. However, zeolite should be understood not as a pesticide that delivers active ingredients directly, but as an inert porous carrier that assists loading and slow release. Changing the excipient of a registered pesticide is a separate regulatory matter.

Q: Which active ingredients load well onto a zeolite carrier? Are anionic pesticides possible?

Unmodified clinoptilolite carries a negative framework charge, so it loads ammonium, some cationic active substances, and hydrophilic molecules well, but because of this negatively charged surface, phosphate-based, some anionic, and oxyanion active ingredients adsorb weakly. To load and slowly release anionic pesticides and nutrients, an SMZ (Surfactant-Modified Zeolite) modified with a metal (Ca·La·Fe·Al) or a quaternary ammonium surfactant is effectively a prerequisite. Bansiwal et al. (2006) reported that a surfactant-modified zeolite loaded phosphate and functioned as a slow-release phosphorus fertilizer. Therefore, you should select an unmodified or modified carrier according to the charge characteristics of the active ingredient.

Q: How do you set the carrier particle size and loading ratio?

For dust and wettable powder fillers, Powder (100 mesh, <150μm) is standard, while soil-applied granules use Fine to Medium Granule (0.3–1.4mm) as the carrier aggregate. The active-ingredient loading ratio and the filler ratio relative to the carrier vary with the physical properties of the active ingredient, the target release rate, and the formulation specification, so they must be determined through loading and dissolution testing at the formulation design stage. There is no generalized single blend ratio; it is safer to first confirm homogeneity and the release curve with a small batch.

Q: How does this connect to organic input or food/feed certification?

KMI natural zeolite holds OMRI Listed (KMI-10365) and FDA GRAS (general use 21 CFR 182.2729) status. However, the registration and certification of the final product (pesticide granule or microbial product) in which it is used as a carrier is separate from the certification of the carrier mineral, and crop protection registration rules and eco-friendly input standards must be met separately. If you are considering it as a carrier for animal feed intake, also confirm that the feed additive GRAS provision (21 CFR 582.2729) applies.

What the Carrier Determines in Granular Formulations

In agrochemical and biological-input formulations such as soil-applied granules (GR), dusts (DP), wettable powders (WP), and soil microbial products, the active ingredient usually accounts for only a single-digit to a few-tens-of-percent share, while most of the rest is filled by the carrier and filler. The carrier is not merely bulk-filling material; it is a key excipient that adsorbs and loads the active ingredient to disperse it homogeneously, governs the release rate in the soil after application, and determines particle flowability, disintegration, and dust generation.

Particularly in soil-applied granules, if the active ingredient is released all at once, the initial efficacy is strong but persistence is poor and leaching and volatilization losses increase. Conversely, if release is too slow, efficacy onset is delayed. The core performance demanded of a carrier is therefore loading capacity through sufficient specific surface area and porosity, together with controlled release behavior matched to the physical properties of the active ingredient. Compared with traditional carriers such as clay, diatomite, and talc, zeolite—a porous aluminosilicate—is a candidate that can target both requirements at once.

How Zeolite Works as a Carrier

Natural clinoptilolite is a mineral whose crystal framework contains micropores 4.0–7.0 Å in size connected in three dimensions, reaching a specific surface area of about 40 m²/g. This porous structure acts as a "storage–release matrix" that loads active-ingredient molecules and ions into and onto its pores, then releases them gradually as soil moisture and ionic environments change. The negative charge carried by the framework creates a cation-exchange capacity of CEC 1.6–2.0 meq/g, firmly capturing positively charged active ingredients and nutrients such as ammonium (NH₄⁺) by ion exchange and releasing them slowly.

This slow-release mechanism is supported by research in the fertilizer and pesticide fields. Rashidzadeh et al. (2015, Polymer Bulletin) reported that a hydrogel/clinoptilolite nanocomposite-coated fertilizer simultaneously improved the slow-release behavior of the active ingredient and water retention, while Eliaspour et al. (2024, IJPSS) outlined an approach using modified clinoptilolite as a slow-release fertilizer and soil conditioner. As a broad review continuing Mumpton's classic work, Li et al. (2011, Advances in Agronomy) examined how the porous and exchange properties of zeolite contribute to nutrient loading and slow release.

However, there is a clear limitation depending on charge characteristics. Because unmodified clinoptilolite carries a negative framework charge, anionic and oxyanion active ingredients (phosphates, some herbicidal and insecticidal components, boron, fluorine, arsenic, nitrate compounds, etc.) are electrostatically repelled and load weakly. In such cases, an SMZ (Surfactant-Modified Zeolite) whose surface is modified with a metal cation (Ca·La·Fe·Al) or a quaternary ammonium (such as HDTMA) surfactant is effectively a prerequisite. Bansiwal et al. (2006, J. Agric. Food Chem.) experimentally showed that a surfactant-modified zeolite loaded phosphate and functioned as a slow-release phosphorus fertilizer. In other words, anionic ingredients must be approached through adsorption via surface modification rather than cation-exchange logic.

KMIZEOLITE's natural clinoptilolite has a purity of 97% and is mined and processed at the Amargosa Valley mine in Nevada, USA. With a pH stability range of 3.0–10.0, thermal stability of 700°C, and a hardness of 4.0–5.0 Mohs, it remains stable across formulation processes such as grinding, granulation, and drying. As a non-toxic mineral, it is also favorable to microbial survival, so it is considered as a carrier for soil microbial products as well.

KMIZEOLITE Key Properties

Property	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
pH stability 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, TSCA, EN-71-3

Carrier & Filler Application Examples

Below are representative ways in which a zeolite carrier is considered in crop protection and soil microbial product formulations.

Soil-applied granule (GR) carrier aggregate: A granular formulation using Fine to Medium Granule as the aggregate to load and slowly release cationic active ingredients. It is designed to release gradually with soil moisture after application.
Dust and wettable powder filler: Using 100mesh powder as a filler to disperse the active ingredient homogeneously and secure flowability and metering precision.
Soil microbial product (inoculant) carrier: A non-toxic mineral carrier that loads microbes and spores into its porous structure for protection and slow release. Microbial viability and moisture-content control are key review items.
SMZ-modified anionic carrier: For anionic components such as phosphates, an SMZ modified with Ca/La/Fe·Al or a surfactant must be used as the carrier for loading and slow release to work.
Formulation pilot batch: The stage of measuring loading ratio, homogeneity, dissolution (release) curve, and disintegration in a small batch before full production to finalize the blend ratio.

Recommended Particle Size and Product Specifications

For dust and wettable powder fillers, Powder (100 mesh), which is favorable for homogeneous dispersion, is standard, while Fine to Medium Granule (0.3–1.4mm) is selected as the carrier aggregate for soil-applied granules. Combine particle sizes according to the target release rate and formulation specification. Refer to the table below to select the product line that suits your use.

Product line	Mesh	Particle size	Typical use
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 filtration
Extra Coarse	4×8 mesh	2.4–4.8mm	Packed beds, air scrubbers

→ View products by mesh size · Product selection guide by application

Formulation Design and Review Points

When applying zeolite as a carrier and filler, the following items must always be checked together.

Confirm active-ingredient charge characteristics: Cationic and hydrophilic components suit unmodified clinoptilolite, but phosphate-based and anionic/oxyanion components effectively require SMZ modification. Do not expect anionic loading from cation-exchange logic.
Measure loading ratio and release curve: Quantitatively measure the active-ingredient loading ratio and dissolution (release) behavior in a small batch. There is no generalized single blend ratio; it varies with component properties and the target release rate.
Particle size, homogeneity, and dust: Select 100mesh for dusts and Granule for granules, and check homogeneous mixing, disintegration, and dust generation together.
Microbial-product viability: When used as an inoculant carrier, verify how moisture content, pH, and sterilization processes affect microbial survival. Zeolite itself is non-toxic and favorable to survival.
Registration and certification consistency: Changing the excipient (carrier) of a registered pesticide, eco-friendly input standards, and whether OMRI (KMI-10365) applies are separate regulatory matters. For animal feed intake use, also confirm the feed additive GRAS (21 CFR 582.2729).
Process stability: Check whether the carrier withstands without denaturation within the grinding, granulation, and drying process temperatures (thermal stability 700°C) and pH range (3.0–10.0).

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

Granular Carrier FAQ

Why is zeolite suitable as a carrier for granular agrochemicals and microbial products?

Natural clinoptilolite is a mineral with a three-dimensional porous structure featuring a specific surface area of about 40m²/g and a pore diameter of 4.0–7.0Å. It acts as a carrier that loads active ingredients onto its pores and surface and then releases them slowly. Its good inter-particle flowability makes it easy to handle as a carrier and filler for dust and granular formulations, and with a pH stability range of 3.0–10.0 and thermal stability up to 700°C, it remains stable throughout formulation processing. However, zeolite should be understood not as a pesticide that delivers active ingredients directly, but as an inert porous carrier that assists loading and slow release. Changing the excipient of a registered pesticide is a separate regulatory matter.

Which active ingredients load well onto a zeolite carrier? Are anionic pesticides possible?

Unmodified clinoptilolite carries a negative framework charge, so it loads ammonium, some cationic active substances, and hydrophilic molecules well, but because of this negatively charged surface, phosphate-based, some anionic, and oxyanion active ingredients adsorb weakly. To load and slowly release anionic pesticides and nutrients, an SMZ (Surfactant-Modified Zeolite) modified with a metal (Ca·La·Fe·Al) or a quaternary ammonium surfactant is effectively a prerequisite. Bansiwal et al. (2006) reported that a surfactant-modified zeolite loaded phosphate and functioned as a slow-release phosphorus fertilizer. Therefore, you should select an unmodified or modified carrier according to the charge characteristics of the active ingredient.

How do you set the carrier particle size and loading ratio?

For dust and wettable powder fillers, Powder (100 mesh, <150μm) is standard, while soil-applied granules use Fine to Medium Granule (0.3–1.4mm) as the carrier aggregate. The active-ingredient loading ratio and the filler ratio relative to the carrier vary with the physical properties of the active ingredient, the target release rate, and the formulation specification, so they must be determined through loading and dissolution testing at the formulation design stage. There is no generalized single blend ratio; it is safer to first confirm homogeneity and the release curve with a small batch.

How does this connect to organic input or food/feed certification?

KMI natural zeolite holds OMRI Listed (KMI-10365) and FDA GRAS (general use 21 CFR 182.2729) status. However, the registration and certification of the final product (pesticide granule or microbial product) in which it is used as a carrier is separate from the certification of the carrier mineral, and crop protection registration rules and eco-friendly input standards must be met separately. If you are considering it as a carrier for animal feed intake, also confirm that the feed additive GRAS provision (21 CFR 582.2729) applies.

Inquiries and Sample Requests

If you are considering zeolite for granular agrochemical and microbial slow-release carrier applications, please contact us through the channels below.

Notes

Applicability may vary depending on site conditions, regulations, and test results. Before actual application, formulation and dissolution testing and registration/regulatory review must always be carried out first. Zeolite should be understood not as a universal solution in this field, but as a porous carrier that assists the loading and slow release of active ingredients.