Glauconite, a natural mineral, serving the soil and the environment.
From geological raw material to functional natural material
Y. Kozub
Geologists have long been familiar with glauconite, yet today interest in it increasingly extends beyond the scope of classical mineralogy. The reason is simple: the properties of this natural iron- and potassium-bearing phyllosilicate make it valuable for several fields simultaneously—water purification, pollutant immobilization, land reclamation, soil improvement, and the development of new mineral and organo-mineral materials for agriculture.
A classic review in *Earth-Science Reviews* previously highlighted the need for precision regarding the term “glauconite.” Green glauconite grains found in sedimentary rocks do not always consist of a single mineral. Their structure, potassium content, proportion of swelling layers, cation-exchange capacity, and other characteristics can vary significantly depending on the conditions of their formation. (ScienceDirect)
This is also fundamentally important for practical application. There is no such thing as an abstract, generic “glauconite”; technological characteristics must be determined for raw material from a specific deposit.
A recent 2024 review in *Applied Clay Science*, focusing specifically on the agricultural application of glauconite, confirms the growing interest in glauconite-bearing rocks as sources of potassium and trace elements, as well as bases for creating more complex fertilizers and materials for restoring soil fertility. (ScienceDirect)
Glauconite as part of a natural mineral system
For practical application, interest lies not only in high-purity concentrates but also in natural glauconite-bearing rocks.
This is precisely the approach taken in our research on glauconite rocks from the “Adamivka II” deposit. The experiments utilized unbeneficiated and unactivated quartz-glauconite sands with a glauconite content of up to 40% and a particle size of less than 0.5 mm.
This aspect is of practical significance. If a natural material exhibits beneficial properties without complex chemical modification, it potentially simplifies the technology for large-scale application and reduces raw material preparation costs.
At the same time, this does not imply that glauconite beneficiation or activation is unnecessary; it all depends on the specific objective. For applications such as highly selective sorption, water purification, or the creation of specialized composites, modification can significantly enhance performance. Recent international studies, for instance, demonstrate the potential of mechanical, thermal, chemical, and composite modification of glauconite. (ScienceDirect)
Thus, it is more accurate to speak not of “better glauconite,” but rather of the suitability of a specific glauconite raw material for a particular technological task.
Why glauconite can function as a sorbent
The sorption activity of glauconite is linked to its mineral structure, surface active sites, and ion-exchange capacity. When the mineral comes into contact with an aqueous solution, various processes can occur simultaneously: surface adsorption, ion exchange, complex formation, and other forms of substance binding.
This has been clearly demonstrated with heavy metals.
In a classic study published in *Water Research*, the sorption of Cd(II), Pb(II), and Zn(II) by Lithuanian glauconite was investigated. The authors established the dependence of sorption on concentration, ionic strength, and pH, finding that the relative metal-binding capacity followed the sequence Pb > Cd > Zn. (ScienceDirect)
Later, Franus, Bandura, and Madej investigated natural glauconite in both static and dynamic systems in the journal *Minerals*. In batch experiments, the sorption capacity sequence was Pb > Cd > Zn > Cu, with pH, contaminant concentration, and contact conditions playing significant roles. (MDPI)
Thus, the sorption properties of glauconite are not merely a theoretical assumption but a phenomenon confirmed by various research groups across different glauconite materials.
Table 1. What has been confirmed by research on glauconite to date
| Direction | What is shown | Practical significance |
|---|---|---|
| Heavy metals | Sorption of Pb, Cd, Zn, Cu | Water purification, barrier materials, remediation |
| Radiocesium | Selective binding of Cs by glauconitic sands | Geochemical and protective barriers |
| Ammonium | Removal of NH₄⁺ via ion exchange | Water purification, nitrogen compound control |
| Phosphates | Sorption by natural and modified glauconites | Eutrophication control |
| Pesticides | Sorption of a number of organic pesticides in our model experiments | Remediation potential of contaminated sites |
| Soil nutrition | Slow release of K and changes in K, P, Ca, and Mg in the soil | Use as a mineral soil amendment |
International research extends beyond heavy metals. Experiments have demonstrated a high affinity of glauconite sands for radiocesium, leading authors to consider them as a potential additional geological sorption barrier. (ScienceDirect)
Current research also covers the sorption of ammonium, phosphates, fluorides, and other pollutants. For instance, a 2024 study in *Desalination and Water Treatment* investigated natural, thermally treated, and microwave-treated glauconite for the removal of phosphates and ammonium nitrogen. The results showed that the treatment method significantly alters the material’s selectivity. (ScienceDirect)
This underscores a key point: the properties of natural raw materials can not only be utilized but also technologically directed.
Original research: glauconite and pesticide residues
A specific area of our work focused on the issue of sites where unusable or banned pesticides had been stored for many years.
The problem associated with such sites does not end with the removal of containers or the decommissioning of the storage facility; residual amounts of toxic substances can remain in the soil and migrate via groundwater and surface water.
In the study of glauconite rock from the “Adamivka II” deposit, model solutions were prepared for nine pesticides belonging to various groups: DDT, HCH, Tilt, Baytan, Chlorophos, DDVP, Actellic, Decis, and Cymbush.
Glauconite rock samples weighing 10, 50, and 100 g were added to 1,000 ml of the model solution. The mixture was agitated for five minutes and allowed to stand for 24 hours, after which residual pesticide concentrations were determined using chromatography.
The results demonstrated significant differences in sorption depending on the specific substance.
Table 2. Maximum uptake of the studied pesticides in the model experiment.
Pesticide
Maximum recorded absorption, %
Source: experimental data by Yu.B. Kozub and Yu.I. Fedoryshyn; the values are presented for specific experimental model conditions.
In the case of DDT and DDVF, complete removal from the solution under experimental conditions was observed even at the lowest quantity of the rock material tested. For other substances, efficiency depended on the amount of sorbent used.
It is important to highlight a scientific caveat regarding this result: it does not imply that the application of glauconite will automatically ensure 100% removal of the respective pesticide from actual field soil.
Soil is far more complex than a model aqueous solution. It contains organic matter, colloids, various minerals, microorganisms, and plant roots, while pH, moisture levels, and temperature are constantly fluctuating.
Therefore, the data obtained should be viewed as evidence of the sorption potential of the specific glauconite rock and as a basis for subsequent laboratory, vegetation, and field trials.
Results in this area were also presented in the paper “Hygienic Assessment of the Sorption Properties of Glauconitolite Regarding Pesticides of Various Chemical Groups” by S.T. Omelchuk, A.K. Manenko, S.I. Matysik, N.A. Khopiak, H.M. Tkachenko, L.V. Khabrovska, Yu.B. Kozub, and Yu.I. Fedoryshyn, published in 2010 in the *Scientific Bulletin of the O.O. Bogomolets National Medical University* (Irbis NBUV).
Glauconite — not just a sorbent
It is here that another important aspect of this natural material becomes apparent.
For most conventional sorbents, their function ends with the binding of the pollutant. Once the material is saturated, a new challenge often arises: how to remove, regenerate, or dispose of the sorbent.
In the case of glauconite-based materials, a different model is potentially feasible—particularly when dealing with soil: after performing its sorption or buffering function, the mineral component can remain part of the soil’s mineral system. However, the safety of such an approach must be determined by the nature of the specific pollutant, the strength of its binding, and the results of desorption studies.
Our research on pesticides led to the conclusion that a natural glauconite mixture could be used without prior enrichment or activation, and we noted the absence of desorption under the conditions studied.
Nevertheless, it is advisable to verify this premise for each pollutant individually—incorporating long-term experiments, cyclic wetting and drying, pH variations, and bioavailability assessments.
And what happens to glauconite in agricultural soil?
International field studies offer an interesting answer.
In a study published in 2019 in *Applied Clay Science*, glauconite material was evaluated in the cultivation of durum wheat. The authors reported increased yields, changes in soil physicochemical properties, and the gradual release of potassium: the K₂O content in the glauconite decreased by approximately 24% over a single growing season. This led to the material being considered a potential slow-release source of potassium. (ScienceDirect)
Even more interesting is a two-year study on oats published in the journal *Agronomy*. Following a single application of glauconite material at a rate of 200 g/m² (equivalent to 2 t/ha), the effect was observed in the second season as well. The average oat yield was 147.5 kg/ha in the experimental group compared to 133.7 kg/ha in the control group—an increase of approximately 10.4%. (MDPI)
Fig. 1. Example of the residual effect of glauconite material in a field experiment with oats.
Oat yield in the second season
Average yield in the control and glauconite variants
Rundmin, Banerjee & Makarov, Agronomy, 2020. Glauconite material application rate: 2 t/ha.
The figures from this study cannot be mechanically applied to other soil types, other glauconite deposits, or different application rates. Furthermore, they should not be extrapolated—without specific testing—to complex products in which glauconite is merely one component.
However, the result is conceptually significant: glauconite in the soil can remain an active part of the system for more than one growing season. (MDPI)
Sorbent or fertilizer? Framing the question this way is too narrow.
In my view, the potential of glauconite lies precisely in its multifunctionality.
Table 3. Functional role of glauconite raw material
| Property | Possible result | Area of application |
|---|---|---|
| Sorption surface | Binding of a portion of the pollutants | Water purification, barrier materials, remediation |
| Cation exchange | Interaction with ions in the soil solution | Soil, water |
| Potassium in the structure | Gradual release of part K | Agronomy |
| Mineral matrix | Formation of multicomponent materials | Fertilizers, sorbents |
| Interaction with water | Impact on the course of processes in the soil system | Arid and degraded soils |
| Modifiability | Change in selectivity and sorption capacity | Specialized technologies |
A recent 2024 review by Dasi, Rudmin, and Banerjee moves in essentially the same direction: the authors consider not only the direct application of glauconite materials but also the prospect of developing more complex compositions and nanocomposite fertilizers based on them. (ScienceDirect)
It is precisely here that geology begins to transition into materials science, agroecology, and biotechnology.
From Sorption to Soil Remediation
However, there is a fundamental limitation.
Binding a pollutant does not equate to restoring the soil.
Sorption can reduce a substance’s mobility or its concentration in the aqueous phase. Yet, healthy soil is a far more complex system. Its functioning depends on structure, organic matter, water dynamics, microbiota, vegetation cover, nutrient availability, and many other factors.
Therefore, I envision the future of glauconite not so much in the mass application of a single mineral to solve every problem, but rather in the development of integrated technologies where each component performs a specific function.
The mineral component can interact with the soil solution and pollutants. The organic component contributes to structure formation and the carbon environment. The biological component supports microbial processes. The plant completes the system through the rhizosphere, root exudates, nutrient uptake, and the production of new organic matter.
It is in this way that a natural mineral ceases to be merely a raw material and becomes a functional link in the restoration of the soil ecosystem.
Our research findings and results from the international scientific community indicate that glauconite warrants significantly greater attention.
Its sorption properties have been confirmed across various classes of substances—ranging from metals and radiocesium to nitrogen and phosphorus compounds. Our experimental studies have further demonstrated the high potential of the “Adamivka II” quartz-glauconite rock regarding a range of pesticides in model aqueous systems.
Concurrently, field studies by other research groups suggest that glauconite materials can serve as a slow-acting mineral soil component. (ScienceDirect)
However, the most promising next step appears to be shifting from the study of a single glauconite property to managing the complex system comprising “mineral–organic matter–water–microorganisms–plant.”
It is precisely this transition—from raw natural material to soil remediation technology—that the subsequent articles in this series will address.