In the present study, supercritical solvent impregnation (SSI) has been applied to incorporate thymol into bio-composite polymers as a potential active packaging material. Thymol, a natural component with a proven antimicrobial activity, was successfully impregnated into starch-chitosan (SC) and starch-chitosan-zeolite (SCZ) films using supercritical carbon dioxide (scCO₂) as a solvent. Experiments were performed at 35 °C, pressures of 15.5 and 30 MPa, and an impregnation time in the range of 4–24 h. The highest impregnation yields of SC films with starch to chitosan mass ratios of 1:1 and 1:2 were 10.80% and 6.48%, respectively. The addition of natural zeolite (15–60%) significantly increased the loading capacity of films enabling thymol incorporation in a quantity of 16.7–27.3%. FTIR and SEM analyses were applied for the characterization of the films. Mechanical properties and water vapor permeability of films before and after the impregnation were tested as well. Thymol release kinetics in deionized water was followed and modeled by the Korsmeyer-Peppas and Weibull model. SCZ films with thymol loading of approximately 24% exhibited strong antibacterial activity against E. coli and methicillin-resistant Staphylococcus (S.) aureus (MRSA).

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.

Hospital wastewaters can become a route for dissemination of antibiotic-resistant bacteria to the environment if not properly treated. Some of these bacteria are able to survive conventional disinfection treatments (e.g. chlorination, UV irradiation), which evokes the need for novel disinfection methods. The metal-exchanged zeolites were tested as novel antibacterial agents for wastewater treatment. The natural zeolite clinoptilolite enriched with silver (AgNZ) showed far better antibacterial activity towards hospital pathogenic bacterium Acinetobacter baumannii when compared with copper-exchanged zeolite (CuNZ), with minimal bactericidal concentration of 0.25–2 (AgNZ) compared with 32–64 mg L−1 (CuNZ) in a batch system and respective log 5.6 reduction compared with log 0.5 reduction in a flow system with pure bacterial culture. In the flow system with real effluent wastewater from the treatment plant, the removal of carbapenem-resistant bacteria using AgNZ was 90–100% during the 4 days of the experimental run. These results indicate that the AgNZ efficiently removes pathogenic bacteria from the wastewater, including A. baumannii, and is promising as a disinfectant material in a bead filter system.

Copper flotation tailings (FTs), resulting from the separation and beneficiation processes of ores, are a significant source of environmental pollution (acid mine drainage, toxic elements leaching, and dust generation). The most common disposal method for this industrial waste is dumping. However, due to their favorable physical and chemical properties—the high content of aluminosilicate minerals (60–90%)—flotation tailings can be effectively treated and reused through geopolymerization technology, thereby adding value to this waste. The objective of this study was to evaluate the potential of utilizing the geopolymerization of FTs to produce sustainable materials. Geopolymers based on natural zeolite (NZ), sodium-modified natural zeolite (NaZ), and fly ash (FA) were prepared using 20%, 35%, and 50% of FTs, activated with a 10 M NaOH solution. The study investigated the influence of Ca/Si, Si/Al, and Na/Al molar ratios on the structural, thermal, and mechanical properties (XRD, TG/DTG and unconfined compressive strength, UCS), and contaminant immobilization (TCLP method) of geopolymers. Geochemical modeling via the PHREEQC program was employed to interpret the results. The findings indicated that the UCS value decreased in zeolite-based geopolymers as the content of FT increased due to the inertness of the tailings and the low calcium content in the system (Ca/Si ≤ 0.3), in contrast to the FA-based geopolymer. The highest UCS of 44.3 MPa was recorded in an FA-based geopolymer containing 50% flotation tailings, with optimal molar ratios of 0.4 for Ca/Si, 3.0 for Si/Al, and 1.1 for Na/Al. In conclusion, the geopolymerization process has been determined to be a suitable technological approach for the sustainable treatment and reuse of FTs.