Adsorbent Zeolite for Transformer Insulating Oil & PCB Waste-Oil Spill Containment

Q: Does zeolite decompose or remove PCBs (polychlorinated biphenyls)?

No. Zeolite does not chemically decompose PCBs. PCBs are persistent organic pollutants (POPs), and zeolite (especially organically modified material) only serves a containment and sorption-support role: it physically traps the oil phase in which the PCBs are dissolved and slows the spread of free oil. Waste transformer oil suspected of containing PCBs must be classified as designated waste (or PCB-containing waste) under waste-management and persistent-pollutant-management regulations and processed through authorized routes such as high-temperature incineration; the sorbent is a temporary containment measure, not a final disposal.

Q: Which particle size (mesh) is suitable for spill containment?

For temporary spill-response and support layers that are scattered on the floor to rapidly absorb free oil while maintaining air and water permeability, Coarse–Extra Coarse Granule (4×8–8×14 mesh) with good water permeability is generally considered; for post-treating spill water and washing fluids in a column, Fine–Medium Granule (14×40–30×50 mesh) with a larger contact surface is used. Please refer to the product selection guide by application.

Q: How should spent zeolite that has absorbed oil be handled?

Spent sorbent that has absorbed insulating oil or PCBs may be classified as designated waste depending on the nature of the absorbed contaminant, and if PCBs are present it must follow PCB-containing waste handling standards (high-temperature incineration, etc.). On-site landfilling or reuse at one's discretion is prohibited; the material must be disposed of through an authorized processor after waste analysis. It is advisable to design the disposal route and costs together before application.

Q: Can I get a sample for testing?

Yes, KMIZEOLITE supports the provision of samples to verify oil-sorption capacity and containment suitability. On the sample request page, please specify the target oil type (mineral/synthetic insulating oil), whether PCBs are present, and your desired particle size.

Transformer Insulating Oil & PCB Spills: What Is the Problem?

In substations, power-receiving equipment, and industrial transformers, mineral-based or synthetic insulating oil is used for insulation and cooling. When insulating oil leaks due to equipment aging, damage, or overheating, or due to accidents during transport and replacement, it spreads across floors, soil, and stormwater drains, causing soil and water contamination. In particular, transformers manufactured before the 1980s sometimes used PCBs (polychlorinated biphenyls) in their insulating oil or were cross-contaminated, so waste transformer oil becomes subject to strict handling under persistent-pollutant-management and waste-management regulations, depending on the results of PCB content analysis.

PCBs are persistent organic pollutants (POPs) that undergo almost no natural decomposition and have high bioaccumulation potential, so in the event of a spill the primary task is containment to immediately stop the spread of free oil, and the secondary task is final disposal through an authorized route after absorption and recovery. Granular adsorbent minerals are considered here as a temporary spill-response and support medium, but it must first be made clear that a sorbent is only a containment aid and is not a treatment technology that removes or decomposes PCBs.

Why Zeolite Is Considered for Spill Containment — and Its Limitations

Granular natural clinoptilolite is a porous mineral with physical absorption and support characteristics that trap fluids in its capillary and pore structure, so it can be scattered at a spill site as a temporary oil-absorbing support medium in place of soil or sand to slow the spread of free oil. However, there is a decisive limitation. Natural (unmodified) clinoptilolite has a hydrophilic framework surface, so it has a high affinity for water and a limited absorption affinity for non-polar hydrocarbons (insulating oil and grease). Therefore, to use it as a serious oil sorbent, making the surface hydrophobic through surfactant modification (organozeolite/SMZ) or hydrophobic coating with PEG, silicone, etc. is effectively a prerequisite. Explaining oil adsorption in terms of cation-exchange logic is inappropriate; oil is held not by ion exchange but by surface hydrophobicity and pore capillarity.

Szala et al. (2015, Fuel Processing Technology) reported that organically modified clinoptilolite has improved petroleum-compound sorption performance compared with unmodified material (DOI:10.1016/j.fuproc.2016.04.015), and Dabizha (2025) showed that clinoptilolite mechanochemically modified with polyethylene glycol (PEG) functions as an oil sorbent (DOI:10.17586/2220-8054-2025-16-5-640-649). In addition, Anagnostopoulos et al. (2019) evaluated the crude-oil adsorption potential of natural clinoptilolite under seawater conditions (DOI:10.4236/nr.2019.1010020). In common, oil-adsorption performance depends heavily on surface modification, oil type, and temperature, so a direct oil-sorption test with the target insulating oil must be conducted before adoption.

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 (21 CFR 182.2729), TSCA, EN-71-3

The CEC and specific surface area values above are indicators for cationic contaminants (heavy metals, ammonium); because non-polar insulating-oil adsorption depends on surface hydrophobicity, they do not guarantee the oil-sorption performance of unmodified product. For oil applications, the possibility of modification and the oil-sorption test results must be confirmed separately.

Spill-Containment Application Examples (Focused on Temporary Response & Support)

Below are representative scenarios in which granular clinoptilolite is considered for responding to transformer insulating oil and PCB-bearing waste-oil spills. All are containment and support uses that slow the spread of free oil; final disposal must be carried out as a separate process.

Temporary oil-absorbing support layer: Immediately after a spill, granular zeolite is spread on the floor or soil surface to first absorb free oil and delay surface spreading of the oil. Depending on the oil type, consider using it together with modified material or a dedicated oil sorbent
Secondary containment dike & trench filling: Granular material fills temporary dikes or trenches around the transformer's oil-retaining curb and collection sump to provide a first barrier before spilled oil reaches the stormwater drains
Leachate & washing-fluid post-treatment column: Oil-bearing aqueous solution generated after washing and cleaning the spill area is passed through a column packed with (modified) zeolite to adsorb residual oil and VOCs
VOC & vapor suppression aid: Considered as a cover and barrier aid that suppresses volatile organic vapors in temporary storage areas (see Asgharzadeh et al. 2025 on VOC adsorption by surfactant-modified clinoptilolite)
Pilot oil-sorption test: Verify the oil-sorption capacity for the target insulating oil and the need for modification in advance with a small sample

Recommended Particle Size and Product Specifications

For floor scattering, support layers, and containment-dike filling, Coarse–Extra Coarse Granule (4×8–8×14 mesh), which has good water and air permeability and rapidly absorbs free oil, is generally considered; for post-treating leachate and washing fluids in a column, Fine–Medium Granule with a larger contact area is used. Refer to the table below to select the product group suited to your application.

Product Group	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, litter, bedding
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 · Product selection guide by application

Pilot Testing and On-Site Review Points

When applying zeolite to respond to transformer insulating oil and PCB-bearing waste-oil spills, the following items must always be checked together.

PCB content analysis: Above all, first analyze the PCB concentration of the target insulating oil. If PCBs are present, the entire sorbent and spent material is classified as PCB-containing waste and the handling standards change completely
Need for surface modification: Unmodified clinoptilolite is hydrophilic, so its oil absorption is weak. Test directly with the target oil type whether to apply hydrophobic modified material such as organozeolite/SMZ or PEG, and its oil-sorption capacity
Containment vs. treatment distinction: Zeolite is a containment and support medium that slows the spread of free oil, not a treatment technology that decomposes PCBs or oil. Design the final disposal route, such as recovery and incineration, together from the outset
Spent-material disposal route: Determine in advance whether the spent sorbent that has absorbed oil and PCBs qualifies as designated waste, the authorized processor and high-temperature incineration route, and the disposal cost
Work safety & environment: Monitor VOC vapor inhalation, inflow into stormwater drains, and secondary spreading into soil and groundwater, and establish a system for combined use with response materials (booms, pads)
Regulatory compliance: Review in advance the requirements under persistent-pollutant-management, waste-management, and soil-environment-conservation regulations and the suitability of the material. Specialized engineering and environmental consulting review must precede any application

Meanwhile, Camenzuli & Freidman (2015), which reviewed in-situ remediation technologies for oil-contaminated sites in cold and remote regions, addressed how zeolite-type sorbents can be considered as containment and barrier options in environments where pump and power infrastructure is limited (DOI:10.3402/polar.v34.24492).

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

Transformer Insulating Oil & PCB Spill-Containment FAQ

Does unmodified clinoptilolite absorb transformer insulating oil well?

Natural (unmodified) clinoptilolite has a hydrophilic framework surface, so it has a high affinity for water and only a limited affinity for non-polar hydrocarbons (insulating oil). Therefore, to use it as an oil sorbent, making the surface hydrophobic through surfactant modification (organozeolite/SMZ) or hydrophobic coating with PEG, etc. is effectively a prerequisite. Szala et al. (2015) and Dabizha (2025) reported that organic and mechanochemical treatment improves the petroleum-compound sorption capacity of clinoptilolite. Unmodified material is best regarded as a physical containment and support medium that limits the spread of a spill.

Does zeolite decompose or remove PCBs (polychlorinated biphenyls)?

No. Zeolite does not chemically decompose PCBs. PCBs are persistent organic pollutants (POPs), and zeolite (especially organically modified material) only serves a containment and sorption-support role: it physically traps the oil phase in which the PCBs are dissolved and slows the spread of free oil. Waste transformer oil suspected of containing PCBs must be classified as designated waste (or PCB-containing waste) under waste-management and persistent-pollutant-management regulations and processed through authorized routes such as high-temperature incineration; the sorbent is a temporary containment measure, not a final disposal.

Which particle size (mesh) is suitable for spill containment?

For temporary spill-response and support layers that are scattered on the floor to rapidly absorb free oil while maintaining air and water permeability, Coarse–Extra Coarse Granule (4×8–8×14 mesh) with good water permeability is generally considered; for post-treating spill water and washing fluids in a column, Fine–Medium Granule (14×40–30×50 mesh) with a larger contact surface is used. Please refer to the product selection guide by application.

How should spent zeolite that has absorbed oil be handled?

Spent sorbent that has absorbed insulating oil or PCBs may be classified as designated waste depending on the nature of the absorbed contaminant, and if PCBs are present it must follow PCB-containing waste handling standards (high-temperature incineration, etc.). On-site landfilling or reuse at one's discretion is prohibited; the material must be disposed of through an authorized processor after waste analysis. It is advisable to design the disposal route and costs together before application.

Can I get a sample for testing?

Yes, KMIZEOLITE supports the provision of samples to verify oil-sorption capacity and containment suitability. On the sample request page, please specify the target oil type (mineral/synthetic insulating oil), whether PCBs are present, and your desired particle size.

Inquiries and Sample Requests

If you are considering applying zeolite in the field of transformer insulating oil and PCB waste-oil spill containment, please contact us through the channels below.

Notice

Whether the application is suitable may vary depending on site conditions, regulations, and test results. Before actual application, test review suited to the site conditions must always be conducted first. Zeolite is not a cure-all for PCB and oil spills; it is more appropriately understood as a containment and support material that slows the spread of free oil, and final disposal must be carried out separately through an authorized route.