Search

Due to the development of resistance to antimicrobial agents, bacterium Acinetobacter baumannii is nowadays a leading cause of nosocomial outbreaks. Clinically relevant A. baumannii outside hospital settings including natural soils affected by human waste represents a public-health risk for humans and animals. The aim of this study was to investigate the potential of metal-loaded zeolites to eliminate viable A. baumannii from artificially contaminated natural soils. A. baumannii isolate was subjected to the activity of natural zeolitised tuff (NZ) and Cu-modified (CuNZ) or Ag-modified zeolite (AgNZ) in wet, slightly acidic terra rossa and slightly alkaline red palaeosol. A. baumannii survived in terra rossa and red palaeosol supplemented with 1 wt% of NZ for seven days and four months, respectively. The addition of 1 wt% of CuNZ to terra rossa and red palaeosol shortened the survival of A. baumannii to three and 14 days, respectively. The addition of 0.1 wt% of AgNZ to both soils resulted in complete removal of viable A. baumannii within 1 h of contact, while the total native heterotrophic bacterial counts remained high. Since AgNZ is prepared with a simple modification of cost-effective and environmentally friendly natural zeolite, it is a promising material for the remediation of soils contaminated with pandrug-resistant A. baumannii.

The use of natural zeolite clinoptilolite in preparing photocatalysts and its function in photocatalysis are discussed in this review. The importance of advanced oxidation processes (AOPs) and the potential of heterogeneous photocatalysis in removing environmental pollutants are emphasized. The review focuses on the synergistic effects of clinoptilolite with semiconductors (TiO2, ZnO, CuO, SnO2, and NiO) to prepare stable and active photocatalysts, highlighting recent advancements in this field. It explores clinoptilolite's structural characteristics, highlighting its microporous nature, adaptable framework, and improved textural properties due to acid and alkali treatments. Particle size, crystal phase, and calcination temperature are three key synthesis parameters that affect photocatalytic activity and are highlighted in the discussion of these parameters and their methods. A discussion is held regarding the processes and mechanisms of photocatalytic degradation of different organic compounds under varying irradiation conditions, including UV, visible, and ambient sunlight. Clinoptilolite is vital in improving supported semiconductor oxides' photocatalytic efficiencies, which aid in pollutant degradation and environmental remediation. [ABSTRACT FROM AUTHOR]

Adsorptive, catalytic, and antibacterial properties of clinoptilolite-rich tuffs (ZT) are presented here. ZT transformed into Fe-containing ZT (Fe-ZT) removes various organic and inorganic anions from water. Fe-ZT, which contains selenium, is beneficial for growing Pleurotus ostreatus mushrooms. The fungi convert inorganic Se from Fe-ZT into a more useful organically bonded form. ZT and Fe-ZT as supplements retain nitrogen and potassium in sandy, silty loam and silty clay soils. ZT shows an affinity toward toxic metal cations, which are essential for cleaning contaminated water. The adsorption of atenolol, acetylsalicylic, and salicylic acid onto M-ZT (M–Cu2+, Mn2+, Ni2+, or Zn2+) from water solutions suggests that both the natures of M and pharmaceuticals have a significant impact on the adsorption mechanism and determine the adsorption capability of the ZT. ZT is an excellent carrier for ultrafine (2–5 nm) nano oxide particles, which have been shown to have catalytic activity in different chemical processes and photodegradation reactions of organic pollutants. ZT can also be transformed into SO4-SnO2-ZT, which is catalytically active as a solid acid. M-ZT is an effective carrier of valuable bacteria. Ag-ZT possesses beneficial bactericidal activity in disinfecting water and soil remediation. [ABSTRACT FROM AUTHOR]

The multidrug resistant bacteria Acinetobacter baumannii cause serious hospital infections. Commercial poly(vinyl chloride) (PVC) used for endotracheal tubes was modified in order to obtain the composite with antibacterial effect towards clinical isolate of A. baumannii ST145. The composites were prepared by addition of different amounts of copper-containing zeolite tuff (CuZ) and by successive impregnation with D-Tyrosine (D-Tyr) solution. The composites which were obtained by addition of CuZ (CuZ-PVC) only did not exhibit antibacterial effect. The impregnation of the CuZ-PVC by D-Tyr resulted in an antibacterial effect which is explained by a synergistic effect of CuZ and D-Tyr. Rheological tests confirmed that the modification of PVC by CuZ does not affect its processability and reformability. [Projekat Ministarstva nauke Republike Srbije, br. 172018]

In this work, different metal oxides (MO) supported on two types of zeolites: 1) natural clinoptilolite (NZ) and 2) synthetic zeolite, ZSM-5 were prepared and tested as catalysts in the fast pyrolysis of hardwood lignin. NZ was modified with the CaO and MgO by a simple two steps procedure consisting of an ion exchange reaction and a subsequent calcination at 773 K. The synthetic ZSM-5 was modified with several MO species (Ni, Cu, Ca, Mg) by a wet impregnation and calcination at 873 K. Тhe prepared catalysts were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDS) and measurement of specific surface area (BET method). Acid sites were characterized and quantified by pyridine (py) absorption using Fourier transform infrared spectroscopy (FTIR). The catalysts exhibit catalytic activity depanding on modification, reaction temperature and of the MO contents. The highest yield of useful phenol in bio-oil was obtained with NiO/ZSM-5 (34.8 wt.%) which exhibits the highest specific surface area and the highest concetration of Brönsted and Lewis acid sites. The studied catalysts did not increase significantly the content of polycyclic aromatic hydrocarbons (PAHs) and heavy compounds compared to non-catalytic experiment. [Projekat Ministarstva nauke Republike Srbije, br. 172018]

The natural zeolitic tuff from the Zlatokop mine (Vranjska Banja deposit) has been investigated as a starting material for obtaining a low cost adsorbent for the removal of nitrate from water media. The tuff riched with zeolite - clinoptilolite was modified by simple procedures by several oxides: iron(III), manganese(IV) and magnesium in order to make clinoptilolite surface accessible for binding the nitrate ions. The obtained oxide-modified zeolite samples were characterized by scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDS), powder X-ray diffraction (PXRD), infrared spectroscopy (FTIR) and by measurement of specific surface area. The effects of the adsorbent dosage (0.5, 1.0, 1.5 and 2.0 g), temperature (25, 35 and 45 °C) and initial nitrate concentration (C0= 100, 200 and 300 mg dm-3) on the binding efficiency were also studied. For all adsorbents the efficiency increases with temperature. The type of oxides effects the adsorption mechanism and Fe(III) oxide modified zeolite exhibits the best binding ability. For this adsorbent the adsorption kinetics was studied and found that it is best represented by the pseudo-second-order model. [Projekat Ministarstva nauke Republike Srbije, br. 172018]

Due to the development of resistance to antimicrobial agents, bacterium Acinetobacter baumannii is nowadays a leading cause of nosocomial outbreaks. Clinically relevant A. baumannii outside hospital settings including natural soils affected by human waste represents a public-health risk for humans and animals. The aim of this study was to investigate the potential of metal-loaded zeolites to eliminate viable A. baumannii from artificially contaminated natural soils. A. baumannii isolate was subjected to the activity of natural zeolitised tuff (NZ) and Cu-modified (CuNZ) or Ag-modified zeolite (AgNZ) in wet, slightly acidic terra rossa and slightly alkaline red palaeosol. A. baumannii survived in terra rossa and red palaeosol supplemented with 1 wt% of NZ for seven days and four months, respectively. The addition of 1 wt% of CuNZ to terra rossa and red palaeosol shortened the survival of A. baumannii to three and 14 days, respectively. The addition of 0.1 wt% of AgNZ to both soils resulted in complete removal of viable A. baumannii within 1 h of contact, while the total native heterotrophic bacterial counts remained high. Since AgNZ is prepared with a simple modification of cost-effective and environmentally friendly natural zeolite, it is a promising material for the remediation of soils contaminated with pandrug-resistant A. baumannii. [ABSTRACT FROM AUTHOR]

Antibacterial activity of a natural zeolite, clinoptilolite (Z), enriched with about 0.4-0.5 mmol of Ag (Ag-Z), Cu (Cu-Z) or Zn (Zn-Z) was tested toward two strains of Gram-negative bacteria - Escherichia coli and Acinetobacter baumannii - in natural seawater from Adriatic Sea (Croatia). The Ag-Z and Cu-Z exhibited bactericidal activity toward E. coli and A. baumannii after 3 and 6 h of exposure, respectively. The Zn-Z showed antibacterial activity toward both strains, but lacking the bactericidal effect even after 24 h of exposure. All studied samples released metal cations in seawater. Concentration of Ag and Zn leached from Ag-Z and Zn-Z was higher than maximum allowable concentrations (MAC) for drinking water, whereas concentration of Cu was below MAC. Due to high concentration of Na+ in seawater (about 1.2 g Na+ dm-3) an ion-exchange process can be responsible for the leaching of the studied cations. The lowest extent of leaching from Cu-Z was ascribed to different position and geometry of sites occupied by Cu(II) in the clinoptilolite lattice. The antibacterial activity of M-Z was attributed to the metal cations leached from the zeolite lattice into seawater. The obtained results indicate that Cu-Z can be considered as a promising disinfectant for treatment of seawater. [ABSTRACT FROM AUTHOR]

The adsorption of the antibiotic ciprofloxacin (CIP) from an aqueous solution by natural zeolite, the calcium-rich clinoptilolite (CLI), and magnetite-coated CLI (MAG-CLI) was investigated. Both CLI and MAG-CLI showed a high adsorption affinity towards CIP at 283, 288 and 293 K at a pH of 5. Adsorption kinetics studied for the initial concentrations of 15–75 mg CIP dm−3 follow Lagergren's pseudo-second order equation and the adsorption is best represented by the Langmuir model. The adsorption mechanism involves strong electrostatic interactions between negatively charged aluminosilicate lattice and the cationic form of CIP accompanied by an ion-exchange reaction. Magnetite coverage (approx. 12 wt.%) induces magnetism, which can facilitate the separation process. The coverage does not influence the adsorption activity of CLI. The leaching test showed that the MAG coating protects the adsorbent from CIP leaching. This is ascribed to interactions between the CIP carboxyl groups and magnetite nano-particles. Antibacterial tests showed strong antibacterial activity of the ciprofloxacin-containing adsorbents towards pathogenic E. coli and S. aureus. [ABSTRACT FROM AUTHOR]