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Regarding enormous expansion of bacterial contamination as well as their increase resistivity to commonly used disinfectants, there is a great demand for antibacterial material, which will not be based on organic compounds. Among various inorganic substances, environmentally friendly, low-cost and chemically stable ZnO and TiO2 demonstrate considerable antibacterial activity.This work primarily focuses on idea of developing novel disinfectant based on both, ZnO and TiO2, which would integrate all the worthy properties of both oxides. For that matter, titanium(IV) butoxide was dissolved in a solution of zinc acetate following with the ammonia addition until pH value was 8.5. Half of the initial solution was hydrothermally treated, dried and calcined at 500 (H-ZnTi-500) and 800°C (H-ZnTi-800). Two other samples (ZnTi-500 and ZnTi-800) were obtained from the other half of the initial solution which was directly dried and calcined under the same conditions. The samples were characterized by XRD including Rietveld refinement, FESEMand TG/DTA. Antibacterial activity was examined towards Gram-positive S. aureus and Gram-negative E. coli .The results showed that only ZnTi-800 consisted of pure Zn2TiO4 (Fd-3m) while Zn TiO was the major phase in three other samples. In the case of samples calcined at 500 °C, traces of ZnO were found. H-ZnTi-800 contained three phases: Zn2TiO4, ZnO and Zn2Ti3O8 (P4332). Cubic Zn2TiO4 contains two cation sites: tetrahedrally coordinated Zn at 0,0,0 and octahedral site at 5/8,5/8,5/8 shared between Zn and Ti. The calculated a-parameters of all obtained Zn2TiO4 as well as Zn–O and Zn/Ti–O bond distances were independent of synthesis. At 500 °C nanocrystalline Zn2TiO4 were obtained with the crystallite sizes 26 and 71 nm for H-ZnTi-500 and ZnTi-500, respectively, while microcrystalline phases were obtained at 800 °C with the crystallite sizes larger than 110 nm. The soft agglomerates consisted of smaller particles were obtained at 500 °C comparing to samples at 800 °C having more compact agglomerates.The best antibacterial activity with high reduction in the number of bacteria cells (87.6 % of E. coli and 63.4 % of S. aureus) was exhibited by the ZnTi-500. It means that the purity of samples, crystallite size and softness of agglomerates, influence antibacterial activity and that optimal level of all factors should be reached since ZnTi-500 was almost pure with sufficiently small crystallites and soft agglomerates.

Adsorption of the antibiotic ciprofloxacin (CIP) from an aqueous solution by calcium- rich clinoptilolite (CLI) was investigated. Obtained results showed that natural CLI possesses a high adsorption efficiency in the removal of CIP at 283, 288 and 293 K and at pH= 5. Adsorption kinetics studied for the initial CIP concentrations of 15–75 mg 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 aluminosilicate lattice of CLI and the cationic form of CIP accompanied by an ion-exchange reaction. The CIP saturated CLI was successfully regenerated by a cold atmospheric pressure plasma treatment.

Silanization of the natural and synthetic zeolites as well as their use as adsorbents for removing arsenic(III) oxyanions from wastewater are the topic of this paper. Two types of zeolite were used: natural zeolite-clinoptilolite from Zlatokop deposit, Vranjska Banja, Serbia, previously converted to H+-form and synthetic zeolite, mordenite. The modification was performed with solution (3-aminopropyl) triethoxysilane (APTES). The presence of APTES on the surface of zeolite was confirmed using TG/DSC and FTIR analysis. The results showed that natural aminosilane-modified zeolite has a higher adsorption capacity for arsenic(III) oxyanions compared to mordenite prepared in the same way. The kinetic data follow the Lagergren pseudo-second-order model. This model implies a chemical interaction between AsO33–- ions and functional groups on the silanized zeolite surface. 9th Croatian-Slovenian-Serbian Symposium on Zeolites, 23rd-25th September 2021, Split, Croatia

In this study the employment of non-equilibrium plasma processing for regeneration of spent natural zeolite-clinoptilolite adsorbent was investigated in order to recover its adsorption properties. The antibiotic ciprofloxacin was used as a model persistent pollutant. Treatments of the spent clinoptilolite were performed in a surface dielectric barrier discharge operating in air. High-voltage sine signal was supplied to the square-shaped segmented upper electrode separated 2 mm from the lower electrode which served as a sample holder. Simple geometry in the plasma source design allowed scaling up the device in order to study the effect of electrode surface to the zeolite treatment. Recovery of the adsorption potential up to 70% was achieved after 20 minutes of the treatment in the first regeneration cycle. High recovery rates were also obtained in subsequent cycles showing non-equilibrium plasma is a prospective method for recycling the used adsorbent material.

Composites based on natural zeolite – clinoptilolite and thymol were prepared using two different approaches: 1) wet impregnation (WI) and supercritical solvent impregnation (SSI). The SSI was more superior since it yielded the composite with higher amount of thymol and with stronger thymol-clinoptilolite interactions than WI. The composites exhibited antibacterial activity towards Gram-negative bacteria Escherichia coli and Grampositive bacteria Staphylococcus aureus suggesting its applicability for disinfectant purposes.

Bacterium Acinetobacter baumannii is an opportunistic pathogen of great clinical significance. Clinically significant A. baumannii isolates have been recorded in wastewaters, natural aquatic habitats and soils contaminated by human waste. The aim of this study was to investigate the potential application of unmodified (NZ) and Ag-modified (AgNZ) natural zeolitized tuff to remove A. baumannii from natural soil. Pure culture of pandrug-resistant A. baumannii was suspended in spring water and inoculated into 100 g of fresh alkaline red palaeosol, which was supplemented with 1 wt.% of NZ or AgNZ. The abundance of A. baumannii was monitored on CHROMagar Acinetobacter at 36 °C/24h, while total heterotrophic bacteria were monitored on Nutrient agar 22 °C/72h. A. baumannii successfully survived 50 days in soil with the addition of NZ. The AgNZ showed a strong bactericidal activity, after only 1h exposure (removal of 6.8±0.1 log CFU/g). The abundance of native heterotrophic bacteria was reduced by AgNZ for 2.6±0.1 log CFU/g, but a large portion of the population remained viable (4.1±0.2 log CFU/g). AgNZ is a promising material for the bioremediation of soil contaminated with hospital pathogen A. baumannii. The application of AgNZ does not influence the population of native heterotrophic bacteria in soil, which makes it acceptable for use in real environment.

Fleksotisak je tehnika tiska koja je još u razvoju. Svojom ekspanzijom na tržište fleksotisak konkurira ostalim tehnikama tiska, jer nudi nižu cijenu i veću brzinu izrade tiskovne forme, dok kvalitetom tiska ne zaostaje u toj mjeri da gubi na konkurentnosti. Premda je našao primjenu u različitim domenama grafičke proizvodnje, fleksotisak se specijalizirao kao ambalažni tisak. U ovom radu su obrađene konstrukcije strojeva u fleksotisku kakve danas nalazimo na tržištu uz prethodno opisane opće karakteristike te tehnike tiska.