Controlled-Release Fertilizers Using Zeolites

Controlled-Release Fertilizers Using Zeolites

The U.S. Geological Survey (USGS) has experimented with zeolites to help control the release of fertilizer nutrients in soil. The use of soluble fertilizers can lead to water pollution and to wasted nutrients. Nitrogen, for example, can leach into ground and surface waters, especially in sandy soils, and phosphate may become fixed and unavailable to plants, especially in tropical soils. Zeolites are porous minerals with high cation-exchange capacity that can help control the release of plant nutrients in agricultural systems. Zeolites can free soluble plant nutrients already in soil, and may improve soil fertility and water retention. Because zeolites are common, these unique minerals could be useful on a large-scale in agriculture.

USGS research has experimented with zeolites applied to several different fertilizers including controlled-release nitrogen, controlled-release phosphorous fertilizers, and in the release of trace nutrients.

Controlled-Release Nitrogen Fertilizer

Urea is one of the most common nitrogen fertilizers. It is very soluble in water, and can be leached through the root zone. In addition, urea is converted into ammonium ions by an enzyme found in most soils. Soil bacteria then convert these ammonium ions into readily leachable nitrate ions. Using zeolitic rocks in fertilizer can help prevent these nutrient losses.



A controlled-release nitrogen (N) fertilizer can be produced by heating zeolite rock chips to about 400oC to drive out all zeolite and pore water, which is replaced with molten urea. The urea crystallizes at about 132oC. The rate of nitrogen release from the zeolitic rock is slowed in three ways: (1) by containing urea in the rock pores and zeolite crystals, thus preventing the leaching of urea from the root zone; (2) by slowing the conversion of urea by soil enzymes, thus delaying the formation of ammonium ions; and (3) by taking up ammonium ions onto exchange sites in the zeolite, thus protecting them from nitrifying bacteria. Potassium-saturated zeolite prepared by the above method contains approximately 17 wt. percent elemental N. The rate of N release can be controlled by changing the size of the rock chips.

Controlled-Release Phosphorous Fertilizers

Phosphate (H2PO4) can be released to plants from phosphate rock (P-rock) composed largely of the calcium phosphate mineral apatite by mixing the rock with zeolite having an exchange ion such as ammonium. The approximate reaction in soil solution is as follows: (P-rock) + (NH4-zeolite) = (Ca-zeolite) + (NH4+) + (H2PO4-).

The zeolite takes up Ca2+ from the phosphate rock, thereby releasing both phosphate and ammonium ions. Unlike the leaching of very soluble phosphate fertilizers (for example, super-phosphate), the controlled-release phosphate is released as a result of a specific chemical reaction in the soil. As phosphate is taken up by plants or by soil fixation, thechemical reaction releases more phosphate and ammonium in the attempt to reestablish equilibrium. The rate of phosphate release is controlled by varying the ratio of P-rock to zeolite. Phosphorus is also released from the rock by the lowering of soil pH as ammonium ions are converted to nitrate.



Controlled-release fertilizers were tested in greenhouse pot experiments with sorghum-sudangrass using NH4-saturated zeolite (clinoptilolite) and P-rock with a phosphate application rate of 340 mg P per kg soil, and zeolite/P-rock ratios ranging from 0 to 6. Total phosphate uptake and phosphate concentration measured for the grass were related linearly to the zeolite/P-rock ratio, and yields summed over four cuttings were as much as four times larger than control experiments.

Release of Trace Nutrients

Experiments indicate that zeolite in soil can aid in the release of some trace nutrients and in their uptake by plants. The release of phosphorus, potassium (K), manganese (Mn), zinc (Zn), iron (Fe), and copper (Cu) was enhanced by the presence of zeolite in a neutral soil. The concentration of Cu and Mn in sudangrass (in mg/kg) was significantly related to the zeolite/P-rock (x) in experimental systems that used two different NH4-saturated clinoptilolites, two different soils, and two different forms of P-rock.

Potential Harmful Effects

Zeolites can be harmful as well as helpful to plant growth. For example, zeolites with sodium as the chief exchange ion can be toxic to plants, and K-, Ca-, and NH4-poor zeoIites can scavenge these ions from soil solutions and thereby limit plant growth when used in soils that are deficient in these nutrients. These negative results emphasize the need to use appropriate zeolites during agricultural experimentation.

Source : http://www.usgs.gov

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ZEO Health Zeolite

The Cleaning Process of ZEO Health Zeolite

We start with the cleanest zeolite on earth mined specifically for human consumption (the only mine in the world that does this). The zeolite is then intensely washed with purified water and prepared to ensure a standardized cat-ion capacity and clean cage. The zeolite is then put through rigorous quality control tests to ensure its quality and safety is maintained for human consumption. It is thoroughly dried and then MICRONIZED to the smallest powdered particle size thus allowing it to penetrate throughout the body and even through the blood brain barrier to safely remove disease causing toxic heavy metals that include lead, mercury, cadmium, arsenic, nickel, barium and other toxic chemicals.

Milled vs. Micronized Zeolite

Another characteristic of a low grade zeolite has to do with the way it is processed. When zeolite rocks are “milled”, they are grinded to powder. This is normally takes place at the mine and it the cheaper way to create powder. The problem with the milling process is that it crushes the zeolite cage structure rendering the zeolite un-absorbable in the body and largely ineffective for human consumption. “Micronization” is the only way to make powdered zeolite and maintain the benefits of the cage structure.



The micronization process is an expensive quality control. When faced with the choice of milling the zeolite at the mine or shipping it out to a specialty micronization plant, many zeolite companies choose to mill the zeolite. All Zeo Health Ltd. zeolite is micronized with the strictest quality controls and highest standards for human consumption.

Refference : http://www.zeolite.com

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Use Zeolite for Water Treatment

The high cation exchange capacity (C.E.C.) of GSA zeolites combined with their selective affinity for specific cations make them uniquely suited to various applications in water treatment. These natural zeolites have been shown to be effective in industrial and municipal waste water systems. The following is a listing of those cations which can be removed from various effluents by GSA zeolites under the proper conditions:

Rb+ Li+ K+ Cs+ NH+4

Na+ Ag+ Cd+2 Pb+2 Zn+2

Ba+2 Sr+2 Cu+2 Ca+2 Hg+2

Mg+2 Fe+3 Co+3 Al+3 Cr+3

One of the first full scale projects to incorporate natural zeolites in a municipal tertiary water treatment system was built for the Tahoe Truckee Sanitation Agency. This system, designed by CH2M Hill, utilizes zeolite as an ion exchange medium for the removal of ammonium (NH+4). The municipal effluent containing ammonium is passed through the natural zeolite which adsorbs the ammonium ion. The efficiency of ammonium removal is dependent upon temperature, water quality, and rate of flow. Regeneration of the natural zeolite bed for reuse is achieved by passing a brine solution through it. The regenerant then is passed through a stripping unit and the ammonium is converted into ammonium sulfate, and sold as a fertilizer.


A pilot project near Denver, Colorado, is now using natural zeolites for the removal of ammonium in a potable water system. Similar systems are now in production which remove various pollutants including heavy metals and radioactive ions from industrial effluents.

One alternative to a typical tertiary water treatment plant is to apply effluents over natural soils. The soil filters the pollutants from the water as it gradually percolates to the natural ground-water table which may be recovered from wells for reuse. The soil, as an ion exchange medium, is regenerated by way of crop production capable of removing many of the pollutants. A major limitation of such systems is the requirement for percolation which typically necessitates the use of a sandy soil type not ideal for ion exchange. The low cation exchange capacity of these sandy soil can then be enhanced through the addition of GSA zeolites which will not impede percolation. Tests of such a system were carried out by Dr. Ian Pepper of the University of Arizona. In these tests, a turf grass was used to regenerate the system and adequate efficiencies of pollutant removal were found to be attainable. Additions of natural zeolites in these systems may be found to favorably improve the sequestering of heavy metals. Further testing is required to fully demonstrate this possibility.

Systems for the specific removal of cations from industrial wastes utilizing natural zeolites as a component of the filter medium have been commercialized. These systems have successfully recovered precious metals from plating operations as well as basic industrial pollutants from effluents.

Reference : http://www.gsaresources.com

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