Activated Carbon vs Zeolite for Ammonia

Ammonia is a small polar molecule, and plain carbon adsorbs mainly by non-polar physical attraction. That single fact decides most of this page.

Plain activated carbon is the weakest of the three common options for ammonia. For ammonia in water, zeolite is the conventional specification. For ammonia in air, phosphoric-acid impregnated carbon is usually the stronger route. For a real-world mixed odor — a litter box, a waste bin, an enclosed pen — no single adsorbent is the right answer and the construction matters more than the grade.

Granular activated carbon mesh, the carbon media with a measured ammonia figure — **Plain activated carbon** — granular carbon mesh. Strong on mercaptans and VOCs, comparatively weak on ammonia.

Zeolite filter media pads on a polyester nonwoven base — **Zeolite media** on polyester nonwoven. The polar adsorbent; the conventional specification for ammonia in water.

Pelletized activated carbon, the base form for impregnated grades — **Impregnated activated carbon**. The phosphoric acid grade reacts with ammonia rather than holding it.

Three adsorbents, three mechanisms

The three routes work by different mechanisms, and that is what decides the answer rather than any headline number:

Plain activated carbon holds molecules physically, in a large non-polar pore network. That rewards molecules which are large, heavy and non-polar — solvents, mercaptans, most VOCs. Ammonia is small, light and polar: it enters the pores easily and leaves just as easily.
Zeolite is a hydrated alkali or alkaline-earth aluminosilicate whose framework carries a charge. That charge, not pore volume, is what gives it affinity for small polar molecules such as ammonia and the ammonium ion.
Impregnated activated carbon carries a reagent that reacts with the target gas instead of merely holding it. The phosphoric acid grade is acidic, so it targets basic contaminants — ammonia and the amine family.

Why the mechanism decides the answer, not the grade. Plain carbon rewards molecules that are large, heavy and non-polar; ammonia is small, light and polar, so it enters and leaves just as easily. Zeolite holds it by charge instead.

This also explains why a media datasheet can look excellent and still disappoint on ammonia. Iodine number and benzene adsorption measure pore volume and non-polar capacity. Neither one tells you what the media will do with ammonia.

Quick selection summary

If the project needs	Evaluate first	Why
Ammonia or ammonium removal in water — aquarium, pond, water treatment	Zeolite media	Polar adsorbent; this is the conventional specification and where most zeolite demand sits
Ammonia or amines in air — enclosed pet products, waste handling, gas-phase odor control	Phosphoric acid impregnated carbon	Chemical reaction rather than physical adsorption, so it is less dependent on long contact time
A mixed household or animal odor — ammonia plus sulfur compounds plus general VOCs	A layered construction, not one adsorbent	Zeolite is weak exactly where carbon is strong; substituting one for the other usually makes the product worse

This is a starting point, not a performance ranking. Final selection has to be checked against the contaminant, its concentration, the airflow, the depth available in the housing and the complete filter design.

Adsorbent 01 — Plain activated carbon

Supplied as nonwoven, fiber felt and cloth, foam or granular media. Our published series values include activated carbon fiber felt and cloth at iodine 850–1800 mg/g and felt 0.8–4.5 mm, activated carbon nonwoven at carbon ≥50% and 1–30 mm, and granular carbon mesh at carbon ≥80% with 1200 g/m² at 5 mm.

Its strengths are mercaptans, sulfur odor, solvents and mixed VOCs. On ammonia it is comparatively weak. That is a property of the mechanism, not of the grade — a higher iodine number does not convert a non-polar adsorbent into a polar one.

One exception worth knowing. Our granular activated carbon mesh (model SY-GAC-2003) is the single product in our range with a measured ammonia figure: ammonia adsorption ≥20% by weight, alongside carbon content ≥80%, iodine value >1000 mg/g and 1200 g/m² at 5 mm. That figure is measured by a static saturated-vapor method — a 0.5 g sample cut to 5 × 5 mm, dried at 120 °C for 15 minutes and cooled for 15 minutes, then held in saturated ammonia vapor at 25 ± 1 °C for 75 minutes and weighed to 0.001 g, in duplicate. The test report is available on request. It carries far more carbon per unit area than a bonded-powder media, which is why it is the carbon media used where ammonia is part of the duty.

Adsorbent 02 — Zeolite media

Zeolite loaded onto a polyester nonwoven base, supplied by the roll or die-cut to your part. Thickness 1–20 mm. Two grades: a beige fibrous natural zeolite and a grey powdered zeolite bonded to the nonwoven base. Because the zeolite sits on a nonwoven carrier, it cuts, folds and die-cuts the same way filter cotton does, with no separate handling on your line.

Target compounds are ammonia, nitrogen oxides, nitrogen- and sulfur-group compounds and general malodor. Most zeolite demand sits in water — aquarium and pond filtration, and water-treatment stages where ammonium is the target — and it is also specified for enclosed pet products where urine odor is the complaint.

We do not publish an adsorption capacity figure for zeolite media. Capacity depends on the grade, the loading, humidity and contact time, and we would rather send you material to test than quote a number we cannot stand behind. Full specifications: zeolite filter media.

Adsorbent 03 — Impregnated activated carbon

Impregnation adds a reagent that reacts with the target gas. The rule is chemical, not commercial — an acidic impregnant for a basic gas, an alkaline impregnant for an acidic one. We produce two grades, at an impregnation load of 5–10% by weight, on a coal or coconut-shell base:

Phosphoric acid (H₃PO₄) — acidic, so it targets ammonia, amines and general nitrogen-group odor. This is the ammonia grade.
Sodium carbonate (Na₂CO₃) — alkaline, so it targets hydrogen sulfide, sulfur dioxide and acid gases generally.

We publish no removal efficiency, capacity or breakthrough figure for either grade. We have not measured them under conditions we could hand you. The wider industry also offers potassium hydroxide, sulfur, silver, potassium iodide and permanganate impregnations; we do not produce those and would rather say so than take an enquiry we cannot fill. Full specifications: impregnated activated carbon.

Ammonia adsorbent comparison

	Plain activated carbon	Zeolite	H₃PO₄-impregnated carbon
Mechanism	Physical adsorption in non-polar pores	Polar adsorption on a charged aluminosilicate framework	Chemical reaction with the impregnant
Ammonia and amines	Comparatively weak	Strong — this is what it is specified for	Strong — the grade exists for basic gases
Mercaptans, H₂S, sulfur odor	Strong	Weak	Use the Na₂CO₃ grade instead
Solvents and mixed VOCs	Strong	Weak	Unimpregnated media is the better answer
Usual duty	General air and odor work	Water, aquarium, pond, ammonium	Gas-phase ammonia and amines
Supplied forms	Nonwoven, felt, cloth, foam, granular	On polyester nonwoven, 1–20 mm, cuttable and foldable	Granular, or carried on media we convert
Published ammonia figure	Only on granular carbon mesh: ≥20% wt, report on request	None published	None published

The table compares mechanisms and supplied forms, not measured performance. The absence of a comparable ammonia test on all three products prevents a complete numerical ranking, and we have not run one under conditions we could hand you.

Air or water? This question usually decides it

The most useful splitting question is not "which is better" but "where is the ammonia". In water, zeolite is the conventional and usually correct specification. In air, impregnated carbon is more often the stronger route, with zeolite used where a polar adsorbent is wanted in a thin, cuttable, low-cost sheet.

The second question is depth. Contact time is set by the depth available and the face velocity through it, and contact time frequently decides the result more than the adsorbent grade does. There is no point specifying the strongest adsorbent in a build the fan cannot push air through.

A litter box makes both molecules

Cat urine odor is ammonia. Fecal odor is mercaptans. A covered litter box produces both at once, which is why "carbon or zeolite" is the wrong question for that product — the usual answer is a construction that carries both, sized to the depth the housing actually has. The same applies to waste bins, enclosed pens and small air modules.

What to send before requesting a sample

Copy this into your email. Unknown items can be left open for discussion instead of estimated — the contaminant and the available depth are usually enough for a first recommendation.

Target contaminant or odor source: [ammonia, sulfur/mercaptan, mixed VOC, or just describe the smell]
Air or water: [gas-phase or liquid-phase duty]
Part dimensions: [L × W × thickness, or roll width and media thickness — a drawing, DXF or a photo with a ruler also works]
Depth available in the housing: [maximum media thickness that fits]
Airflow and pressure-drop limit: [if known]
Current part: [the media or component you buy today, if there is one]
Quantities: [sample quantity, and estimated annual volume]

Frequently asked questions

Is zeolite better than activated carbon?

Not in general — only for specific molecules. Zeolite is stronger on ammonia and ammonium because it is a polar adsorbent. It is weaker than activated carbon on mercaptans, solvents and mixed VOCs. Substituting zeolite for carbon, rather than using it alongside carbon, usually makes a product worse.

Can I just use a higher iodine number carbon for ammonia?

No. Iodine number measures pore volume and non-polar adsorption capacity. Ammonia is a small polar molecule, so a higher iodine number does not change the mechanism that makes plain carbon comparatively weak on it.

Which impregnated carbon grade removes ammonia?

The phosphoric acid grade. An acidic impregnant targets basic contaminants such as ammonia and amines. The sodium carbonate grade is the opposite case — it targets acid gases such as hydrogen sulfide and sulfur dioxide.

Do you publish an ammonia adsorption figure?

For one product. Our granular activated carbon mesh is specified at ammonia adsorption ≥20% by weight, measured by a static saturated-vapor method at 25 ± 1 °C with a 75-minute exposure, in duplicate; the test report is available on request. We publish no ammonia capacity figure for zeolite media or for either impregnated grade, because we have not measured them under conditions we could hand you.

Can one media handle both cat urine odor and fecal odor?

The two odors are different molecule families — ammonia and mercaptans — and no single adsorbent is strong on both. The usual answer is a layered construction sized to the depth available in the housing rather than a single material.

Data sources, test methods and limitations

Every figure above is a published specification from our own product pages — a product-series reference, confirmed per grade and order, not a measurement of your finished part. Adsorption performance is not a property of the material alone: it moves with inlet concentration, humidity, temperature, contact time and bed depth. A figure measured on another company's rig at another company's inlet concentration tells you very little about your duty.

A number quoted without its test conditions is not a specification. When a supplier gives you one, ask which standard, what concentration, what face velocity and what humidity. Here are ours, so you can hold us to the same rule:

Iodine value — sample cut to 2 × 2 mm and dried at 105–110 °C for 2 hours; 0.2 g and 0.5 g portions weighed to 0.0001 g, each dosed with 50.00 ml of 0.1 mol/L iodine solution; shaken 10 minutes at 240–270 strokes per minute, centrifuged 5 minutes at 2000 rpm; 10.00 ml of the supernatant back-titrated with 0.1 mol/L sodium thiosulfate to a starch endpoint.
Benzene adsorption — static saturated-vapor method: 0.5 g cut to 5 × 5 mm, dried at 120 °C for 45 minutes and cooled 15 minutes, held in saturated benzene vapor at 25 ± 1 °C for 3 hours, weighed to 0.001 g, in duplicate.
Ammonia adsorption — the same static method with a 15-minute dry and a 75-minute exposure at 25 ± 1 °C, in duplicate.

These are gravimetric saturation figures, not breakthrough or removal-efficiency figures, and they are measured on the material rather than on a finished filter. They tell you how the media ranks; they do not tell you how long your part will last.

We make the carbon media — activated carbon and activated carbon fiber — in our own plant, and we convert all three materials into finished parts there. The zeolite mineral itself is bought in and coated onto its nonwoven carrier in the same factory. Because we supply all three, we have no commercial reason to push one adsorbent over another — and we will say when the cheaper build is the right one.