A new circular economy concept is presented for the textile sector to convert unwearable polyester textile waste into valuable chemical feedstock. The idea behind it is to develop a new circular economy concept for the most used material in the textile industry, that is, polyester. Hydrothermal hydrolysis, an environmentally friendly process, has been studied for recovering polyester monomeric units. Under high-temperature and high-pressure conditions complete chemical depolymerization of pure poly(ethylene terephthalate) (PET) to terephthalic acid (TPA) was achieved at high yield. The produced TPA was characterized by potentiometric titrations, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and elemental analysis. A series of experiments were performed on the PET material with different intrinsic viscosities to define the appropriate depolymerization conditions related to the temperature ( T), time ( t) and PET:H₂O ratio, which enables total conversion of the polymer. Maximal conversion (92%) to TPA was defined at 250℃, pressure of 39–40 bar, PET:water ratio of 1:10 and hydrolysis time of 30 min after reaching steady-state conditions in the reactor. The applied depolymerization route resulted in moderate purity of the originated TPA, which was applied successfully in a laboratory-scale two-step re-polymerization to produce PET resins.

The microencapsulation of the cannabidiol and its integration into the tampon can eliminate vaginal inflammation, which at the same time lead to relaxation of the abdominal muscles. The tampon, which contains the active substance cannabidiol (CBD), was developed as an advanced fibrous composite for sanitary application. The active substances were microencapsulated, and, as a carrier, liposomes micro/nano capsules were used. The CBD liposome formulation was analyzed by particle size, polydispersity index, zeta potential, and encapsulation efficiency. Particle size of the CBD liposome liquid formulation was increased by 19%, compared to the liposome liquid formulation and the encapsulation efficiency of CBD in liposome particles, which was 90%. The CBD liposome formulation was applied to cellulose material. The composition of the fibrous composite material was evaluated by Fourier transform infrared spectroscopy, the fiber morphology was analyzed by scanning electron spectroscopy, while the bioactive properties were assessed by antioxidant efficiency, antimicrobial properties, and desorption kinetics. CBD liposome functionalized tampons have both antioxidant and antimicrobial properties. Antimicrobial properties were more pronounced against Gram-positive bacteria. The desorption kinetics of the CBD liposome immobilized on the surface of the composite material was studied using antioxidant activity in the desorption bath. The prepared CBD liposome functionalized tampon additionally shows higher biodegradability compared to references. This high-quality, biodegradable sanitary material based on microencapsulated CBD components as a functional coating provides a platform for many different applications besides medical textiles, also for packaging, pharmaceuticals, paper and wood-based materials, etc.

Since millions of tons of packaging material cannot be recycled in conventional ways, most of it ends up in landfills or even dumped into the natural environment. The researched methods of chemical depolymerization therefore open a new perspective for the recycling of various PET materials, which are especially important for packaging. Food preservative packaging materials made from PET plastics are complex, and their wastes are often contaminated, so there are no sophisticated solutions for them in the recycling industry. After integrating the biopolymer chitosan, which is derived from natural chitin, as an active surface additive in PET materials, we discovered that it not only enriches the packaging material as a microbial inhibitor to reduce the bacteria Staphylococcus aureus and Escherichia coli, thus extending the shelf life of the contained food, but also enables economical chemical recycling by alkaline or neutral hydrolysis, which is an environmentally friendly process. Alkaline hydrolysis at a high temperature and pressure completely depolymerizes chitosan-coated PET packaging materials into pure terephthalic acid and charcoal. The products were characterized by Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and elemental analysis. The resulting reusable material represents raw materials in chemical, plastic, textile, and other industries, in addition to the antimicrobial function and recyclability itself.

This study presents chemical modification of a Rhodamine B (RhB) sensor probe by ethylenediamine (EDA), and investigation of its spectral as well as sensor properties to the various metals. The synthesised N-(Rhodamine-B)-lactam-ethylenediamine (RhB-EDA) fluorescent probe shows interesting optical sensor properties, and high sensitivity and selectivity to Ag⁺ ions among all the tested metal ions (K⁺, Mg²⁺, Cu²⁺, Ni²⁺, Fe²⁺, Pb²⁺, Na⁺, Mn²⁺, Li⁺, Al³⁺, Co²⁺, Hg²⁺, Sr²⁺, Ca²⁺, Ag⁺, Cd²⁺ and Zn²⁺), while the well-known Rhodamine B (RhB) fluorescent probe shows much less sensitivity to Ag⁺ ions, but high sensitivity to Fe²⁺ ions. The novel fluorescent sensor probe RhB-EDA has the capabilities to sense Ag⁺ ions up to µM ranges by using the fluorescence quenching approach. The probe displayed a dynamic response to Ag⁺ in the range of 0.43 × 10⁻³–10⁻⁶ M with a detection limit of 0.1 μM. The sensing system of an RhB-EDA novel fluorescent probe was optimised according to the spectral properties, effect of pH and buffer, photostability, incubation time, sensitivity, and selectivity. Since all the spectral and sensing properties were tested in green aqueous media, although many other similar sensor systems rely on organic solvent solutions, the RhB-EDA sensing probe may be a good candidate for measuring Ag⁺ ions in real-life applications.

The sensitivity of chitosan to environmental conditions and processing conditions can stress its structure and cause degradation of this polymer on various application carriers. The stability of chitosan in a designed textile structure of standard polyester fabric with chitosan was analysed in a multiple washing process with a standard detergent by studying the properties before and after 10 washing cycles. The chitosan was coated on standard and alkali treated polyester fabrics. Washing was performed with an ECE A reference detergent at 60 °C according to the Standard protocol HRN EN ISO 6330 in 10 cycles. The washing stability of chitosan onto polyester fabrics was monitored by a staining test, zeta potential, breaking force, breaking elongation, pilling propensity, touch, whiteness, moisture transport, antimicrobial activity and morphological features. The staining test confirmed the wash stability of chitosan coated on alkali hydrolised polyester fabrics, while the chitosan coated on standard polyester fabric disappeared. Zeta potential proved to be the significant parameter for determining chitosan` stability. The tensile properties of fabric samples were harmonised with other characterisation parameters. Coating of polyester fabric with chitosan increased the elasticity of all samples. The antimicrobial activity of polyester fabrics coated with chitosan against Staphylococcus aureus was reduced by 20% after 10 washing cycles. All the characterisation parameters proved that polyester fabric as a chitosan carrier should be surface modified for designing a stable bioactive textile structure of chitosan and polyester.