Darka Marković

Sonophotocatalytic degradation of dye C.I. Acid Orange 7 by TiO2 and Ag nanoparticles immobilized on corona pretreated polypropylene non-woven fabric.

This study discusses the possibility of using corona pre-treated polypropylene (PP) non-woven fabric as a support for immobilization of colloidal TiO2 and Ag nanoparticles in order to remove dye C.I. Acid Orange 7 from aqueous solution. Dye removal efficiency by sonocatalysis, photocatalysis and sonophotocatalysis was evaluated on corona pre-treated fabric loaded with TiO2 nanoparticles, corona pre-treated fabric double loaded with TiO2 nanoparticles and corona pre-treated fabrics loaded with TiO2 nanoparticles before and after deposition of Ag nanoparticles. In addition, the stability of PP non-woven fabric during these processes was investigated. The substrates were characterized by SEM, EDX and AAS analyses. The change of the dye concentration was evaluated by UV-VIS spectrophotometry. Unlike sonocatalysis and photocatalysis, complete dye removal from both solution and non-woven fabric was obtained already after 240-270 min of sonophotocatalysis. Corona pre-treated PP non-woven fabric loaded with Ag nanoparticles prior to deposition of TiO2 nanoparticles provided excellent degradation efficiency and superior reusability. Sonophotocatalytic degradation of dye in the presence of all investigated samples was the most prominent in acidic conditions. Although this nanocomposite system ensured fast discoloration of dye solution, TOC values of water measured after sonophotocatalysis were not satisfactory because of PP degradation. Therefore, it is suggested to include TOC evaluation in each case study where different supports for TiO2 nanoparticles are used since these nanoparticles may guarantee the dye removal from solution but the stability of support could be problematic causing even more serious environmental impact.

Application of cellulose acetate for controlled release of thymol

Cellulose acetate (CA) was investigated as a carrier towards development of material with controlled release of thymol as a natural substance with strong antibacterial properties using high pressure techniques. Effect of thymol content on CA was confirmed by SEM, FTIR and DSC methods. Kinetic of thymol release from CA was tested using simulated gastric and intestinal fluids (hydrochloric acid and phosphate buffer saline). Results were correlated with Korsmeyer-Peppas and Weibull model. Depending on the thymol content and chemical nature of the release medium, the time of thymol release varied from one to three days indicating CA as a promising carrier of thymol with potential uses from medicine to agriculture. The impregnated CA showed antibacterial activity against 23 tested bacterial strains including methicillin-resistant Staphylococcus aureus (MRSA) which is particularly important bearing in mind that this strain causes fatal infections in humans and animals.

Floating Photocatalyst Based on Poly(ε-caprolactone) Foam and TiO2 Nanoparticles for Removal of Textile Dyes

This study discusses a novel approach for fabrication of floating photocatalyst which can be efficiently exploited for photodegradation of dyes in aqueous solutions. A fabrication of the floating photocatalyst consisted of two steps: transformation of the poly(ε-caprolactone) beads (PCLb) into poly(ε-caprolactone) foam (PCLf) with porous structure in supercritical carbon-dioxide and subsequent loading of PCLf with TiO2 nanoparticles (NPs). Morphological characterization of the PCLf before and after TiO2 NPs loading was carried out by FESEM. The presence of titanium on the surface and inside the PCLf was detected by EDX. Photocatalytical activity of the floating photocatalyst was investigated in aqueous solution of textile dyes C.I. Acid Orange 7 (AO7) and C.I. Basic Yellow 28 (BY28) which were exposed to lamp that simulates the sun light. In addition to sustainable floatability for a long period of time, developed floating photocatalyst exhibited high rate of photodegradation since the complete discoloration of AO7 and BY28 solutions and photocatalysts alone occurred after 300 and 180 min of illumination, respectively. Its photocatalytic activity was preserved after three repeated photodegradation cycles with unchanged chemical structure that was confirmed by FTIR analysis.

In situ synthesis of Cu/Cu 2 O nanoparticles on the TEMPO oxidized cotton fabrics

In situ synthesis of Cu/Cu2O nanoparticles on the cotton fabric discussed in this study relies on adsorption of Cu2+-ions by carboxylate groups generated through the TEMPO-mediated oxidation of cellulose and their subsequent reduction by sodium borohydride. In order to establish the influence of aldehyde and carboxylate groups on the nanoparticles formation, the duration of TEMPO-mediated oxidation was varied. Chemical changes induced by TEMPO-mediated oxidation were evaluated by titrimetric determination of the amounts of aldehyde and carboxylic groups in cotton and FTIR spectroscopy. The presence of Cu/Cu2O nanoparticles on the cotton fabric was confirmed by FE-SEM, AAS and XRD analyses. Antimicrobial activity of synthesized nanoparticles was tested against Gram-negative bacteria E. coli, Gram-positive bacteria S. aureus and fungi C. albicans. The extension of TEMPO oxidation time led to an increase of carboxylate group content and consequently, formation of larger amounts of Cu/Cu2O nanoparticles. All fabricated textile nanocomposites provided excellent antibacterial and acceptable antifungal activity. They also ensured a controlled release of Cu2+-ions in physiological solution which is an imperative for infection prevention.

Antibacterial activity of Cu-based nanoparticles synthesized on the cotton fabrics modified with polycarboxylic acids

The fabrication of antimicrobial textile nanocomposite by in situ synthesis of Cu-based nanoparticles on cotton fabrics modified with different polycarboxylic acids was discussed in this study. In order to evaluate the influence of carboxyl group content on Cu2+-ions adsorption, their subsequent reduction with sodium borohydride and formation of Cu-based nanoparticles, cotton fabrics were modified with succinic, citric and 1,2,3,4-butanetetracarboxylic acids. It was shown that the larger the number of carboxyl groups in applied acid, the larger the content of free carboxyl groups on the fibers and consequently, the larger the Cu2+-ions uptake and total amounts of Cu-based nanoparticles. On the basis of the XPS and XRD measurements, it was suggested that synthesized nanoparticles were mixture of Cu2O and CuO. Fabricated nanocomposites provided maximum reduction of Gram-negative bacterium E. coli and Gram-positive bacterium S. aureus and controlled release of Cu2+-ions in physiological saline solution which are necessary prerequisites for infection prevention.