Zeolites are porous minerals with high absorbency and ion-exchange capacity. Their molecular structure is a dense network of AlO₄ and SiO₄ that generates cavities where water and other polar molecules or ions are inserted/exchanged. Even though there are several synthetic or natural occurring species of zeolites, the most widespread and studied is the naturally occurring zeolite clinoptilolite (ZC). ZC is an excellent detoxifying, antioxidant and anti-inflammatory agent. As a result, it is been used in many industrial applications ranging from environmental remediation to oral applications/supplementation in vivo in humans as food supplements or medical devices. Moreover, the modification as micronization of ZC (M-ZC) or tribomechanically activated zeolite clinoptilolite (TMAZ) or furthermore as double tribomechanically activated zeolite clinoptilolite (PMA-ZC) allows improving its benefits in preclinical and clinical models. Despite its extensive use, many underlying action mechanisms of ZC in its natural or modified forms are still unclear, especially in humans. The main aim of this review is to shed light on the geochemical aspects and therapeutic potentials of ZC with a vision of endorsing further preclinical and clinical research on zeolites, in specific on the ZC and its modified forms as a potential agent for promoting human brain health and overall well-being.

Unique and outstanding physical and chemical properties of zeolite materials make them extremely useful in a variety of applications including agronomy, ecology, manufacturing, and industrial processes. Recently, a more specific application of one naturally occurring zeolite material, clinoptilolite, has been widely studied in veterinary and human medicine. Due to a number of positive effects on health, including detoxification properties, the usage of clinoptilolite-based products in vivo has increased enormously. However, concerns have been raised in the public about the safety of clinoptilolite materials for in vivo applications. Here, we review the scientific literature on the health effects and safety in medical applications of different clinoptilolite-based materials and propose some comprehensive, scientifically-based hypotheses on possible biological mechanisms underlying the observed effects on the health and body homeostasis. We focus on the safety of the clinoptilolite material and the positive medical effects related to detoxification, immune response, and the general health status.

Many industries discharge wastewater from processing into surface and underground waterways, and then, these waste waters must therefore be treated in order to remove heavy metals. The most common treatment used is the activated carbon adsorption, a particularly competitive and effective process; however, the use of activated carbon is not suitable due to the high costs. Then, in order to minimize processing cost, recent investigations have been focused on the use of low-cost adsorbents as zeolites. In particular, clinoptilolite is known to have high selectivity for certain heavy metals. In this paper, the capability of clinoptilolite as a low-cost adsorbent for the removal of zinc and cadmium ions from wastewater was analyzed in a batch system. Preliminary characterization was performed on adsorbent material in order to evaluate the chemical-physical structure. Tests in batch for analyzing adsorbing capacity of clinoptilolite were carried out varying zinc and cadmium concentrations between 10 and 200 mg/L with different amounts of sorbent in the solution (10-60 g/L). For both zinc and cadmium ions, complete adsorption was reached when the concentration was equal to 10 mg/L and adsorption capacity decreased increasing metals amount. In particular, clinoptilolite permitted high Cd²⁺ abatement, probably due to its greater affinity with adsorbent in the single system. Binary system was then analyzed, and, contrary to previous tests, the adsorbent in the simultaneous presence of the two metals demonstrated a greater affinity toward zinc, showing a higher percentage of absorption, due to a different absorption mechanism in the presence of two ions.

Objectives: A tribomechanically activated clinoptilolite (natural aluminosilicate mineral) has been used to increase growth in meat-producing animals, as an adjuvant in cancer therapy, and a heavy metal remover in humans. Because of its unique cation exchanging and chelating properties, we hypothesized that clinoptilolite may be beneficial for the treatment of dyslipidemia in the manner similar to bile acid sequestrants. Thus, specific aims of this pilot study were to orally administer clinoptilolite in different doses and granule size combinations to determine magnitude and time profile of changes in blood lipids.

Design: A phase I/IIa prospective, open-label, uncontrolled, dose/granule size-ranging study (treatment phase 8 weeks, follow-up 6 weeks). Blood lipids were examined every 2 weeks.

Settings: Outpatient clinic of a university-affiliated hospital.

Subjects: Forty-one subjects (all white, mean age 57.6 ± 6.8 years, 17 women) with blood lipids above the normative limits divided into three groups.

Intervention: A tribomechanically activated clinoptilolite was administered in three dose/grind combinations: 6 g/day of fine grind (6gF), 6 g/day of coarse grind (6gC), and 9 g/day of coarse grind (9gC).

Outcome measures: Blood concentrations of total cholesterol (TC), low-density lipoprotein cholesterol (LDLc), high-density lipoprotein cholesterol (HDLc), and triglycerides (TG).

Results: For the 3 groups combined, all lipid fractions significantly improved after 8 weeks of treatment (20-25%, p < 0.001), which reversed to baseline after 6 weeks of clinoptilolite withdrawal. Early (week 2) and the most pronounced decrease in TC and LDLc was observed in the 6gF group (19% and 23% in week 8, respectively), with no difference in HDLc and TG between the three dose/grind groups. No side effects were reported.

Conclusions: These pilot results suggest that oral administration of clinoptilolite may improve lipid profile in individuals with dyslipidemia, which warrants further investigations.

The aim of this study was to prepare and characterize highly porous clinoptilolite/poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) composite scaffolds. Scaffolds with different clinoptilolite contents (10% and 20%) were fabricated with reproducible solvent-free powder compression/particulate leaching technique. The scaffolds had interconnective porosity in the range of 55-76%. Clinoptilolite/poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) scaffolds showed negligible degradation within eight weeks and displayed less water uptake and higher bioactivity than poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) scaffolds. The presence of clinoptilolite improved the mechanical properties. Highest compressive strength (5.6 MPa) and modulus (114.84 MPa) were reached with scaffold group containing 20% clinoptilolite. In vitro protein adsorption capacity of the scaffolds was also higher for clinoptilolite/poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) scaffolds. These scaffolds had 0.95 mg protein/g scaffold adsorption capacity and also higher osteoinductivity in terms of enhanced ALP, OSP activities and intracellular calcium deposition. Stoichiometric apatite deposition (Ca/P=1.686) was observed during cellular proliferation analysis with human fetal osteoblasts cells. Thus, it can be suggested that clinoptilolite/poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) composite scaffolds could be promising carriers for enhancement of bone regeneration in bone tissue engineering applications.

Natural clinoptilolite (Clin) was modified with iron oxide using three different methods including precipitation, wet-impregnation and ion-exchange and then the modified adsorbent with highest As(V) removal efficiency was encapsulated into Alginate by a simple cross-linking method to obtain Fe-Clin granules. The surface morphology and chemical composition of the Fe-Clin sorbents were characterized by scanning electron microscope and X-ray diffraction analysis. The selected Fe-Clin powders and granules possessed enhanced affinity towards the highly toxic arsenic pollutant in a very short time. Batch adsorption experiments showed that the Fe-Clin adsorbent can be widely used within a wide range of pH (2-9). In addition, to reach a high removal percentage (over 90%) of As(V), the optimum dosage of powder and granule shaped adsorbents was obtained as 0.1 and 0.6 g L^-1, respectively. Both adsorbents could successfully remove As(V) in a very short amount of time as 20 and 30 min in the case of powders and granules, respectively. The maximum adsorption capacity of Fe-Clin granules evaluated by using Langmuir adsorption isotherm was found to be 11.17 mg g^-1. By testing the granules in a circulated fluidized column experiment, it was demonstrated that Fe-Clin granules could remove As(V) up to an acceptable level (93%) within 10 min. This study demonstrates that Fe-Clin granules, obtained by exploiting natural clinoptilolite, iron oxide and alginate, are efficient, sustainable and fairly cheap adsorbents for the removal of arsenate from the aquatic environment in a very short contact time.

Carcinogenic polycyclic aromatic hydrocarbons (PAHs) are widespread in the environment. In this study, the removal of PAHs from aqueous media was assessed using samples of clinoptilolite, a natural zeolite, pre-treated with 1 mol/L of NaCl, (Na pre-treated clinoptilolite, NC). Samples (10 g) of NC were separately modified with 5, 2, 2, and 20-mmol/L solutions of cetylpyridinium chloride (CPC), didodecyldimethyl ammonium bromide (DDAB), hexadecyltrimethylammonium bromide (HDTMA), and tetramethyl ammonium chloride (TMA) surfactants as potential cost-effective adsorbents. The kinetics, optimal sorbent dosage, and competitive effects were evaluated through batch adsorption tests using deionised water spiked with five PAHs (anthracene (50 μg/L), fluoranthene (100 μg/L), fluorene (100 μg/L), phenanthrene (100 μg/L), and pyrene (100 μg/L)). The surfactant non-modified (NC) and TMA-MC (modified clinoptilolite) exhibited PAH removal of <66% from the spiked concentration in aqueous solution, while CPC-MC, DDAB-MC, and HDTMA-MC achieved removal rates of >93% for the five PAHs after 24 h at a solid:liquid ratio of 1:100. The remaining concentrations of anthracene and fluoranthene were below 3 μg/L, and that of fluorene was <6 μg/L, lower than the water quality criteria of British Columbia, Canada, for protecting aquatic life. However, HDTMA-MC retained >83% of the fluorene. Over 80% of all PAHs were absorbed within 15 min for the CPC-MC and DDAB-MC, and the maximum adsorption was reached in <2 h. Three kinetic models were applied assuming pseudo-first-order, pseudo-second-order, and intra-particle equations, and the results were well-represented by the pseudo-second-order equation. The PAH sorption results indicated that the adsorption mechanism is based on PAH hydrophobicity, and π-π electron-donor-acceptor interaction with surfactant. CPC and DDAB with two long chain hydrocarbons had more PAH adsorption than HDTMA with one, and TMA with no long chain hydrocarbons (DDAB-MC > CPC-MC > HDTMA-MC ≫ TMA-MC > NC). With a solid:liquid ratio of 1:200, over 90%, 80%, and 70% of the anthracene, fluoranthene, and pyrene were adsorbed by the CPC-MC, DDAB-MC, and HDTMA-MC, respectively.