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The present paper demonstrates a simple way for revalorization of differently softened cotton and cotton/elastane knitted fabric waste collected from the textile industry. Such waste was used as an adsorbent for Congo Red (CR) dye, whereby up to 96% removal efficiency was reached. The CR adsorption process onto cationic and silicone softened fabrics is in conformity with Langmuir (with maximum adsorption capacity of 12.533 mg/g) and Freundlich isotherms, respectively. Different adsorption of CR onto cationic and silicone softened fabrics is ascribed to the different softeners’ fixation to them, while the adsorption of CR operates in the same manner, via hydrophobic interactions. The adsorption kinetic data follow the pseudo-second-order model, while the equilibrium was reached after 90 min. Additionally, this study proposed a new circular economy solution for the disposal of fabric waste with adsorbed CR generating additional revenues. The volume electrical resistivity measurements confirmed that the knitted fabric wastes with adsorbed CR have 169–737 times lower resistivities (0.008–0.037 GΩ·cm) than before the adsorption. The inversely proportional correlation between fabrics’ adsorption efficiencies and their volume electrical resistivities after CR adsorption was found. Such knitted fabric waste with adsorbed CR could be defined as dissipative materials and could be used for providing antistatic protection.

Bleached cotton yarns were oxidized by potassium periodate and TEMPO-mediated oxidation systems, with different concentrations and treatment time, to obtain aldehyde and carboxyl oxy-cellulose with different oxidation levels. Oxidized celluloses were further treated with sodium chlorite to convert the created aldehyde to carboxyl groups. The oxidation level was evaluated by assessing the amount of introduced aldehyde and carboxyl groups, the changes in surface morphology and incurred degradation. Functional groups were determined by titration methods, while surface morphology by FTIR-ATR and SEM analyses. Degradation was analysed by determining the mechanical properties, degree of polymerization, alkali solubility and whiteness stability of the cotton samples. It has been established that a properly selected oxidation system, with appropriate working conditions, can provide satisfactory results for achieving low, medium and extensively oxidized celluloses, with a defined degradation profile. For a short treatment time, a higher oxidation level could be achieved by potassium periodate and TEMPO-mediated oxidation with sodium bromide, while by using the bromide-free TEMPO system a longer time was necessary to reach the same oxidation level. The type and oxidation level of the obtained oxy-celluloses influenced their mechanical properties, degree of polymerization, alkaline and whiteness stability. Low-level oxidized celluloses are suitable for producing stable, long-lasting materials with high added value, while extensively oxidized ones are more appropriate for developing disposable products.

The influence of different temperature of drying after mercerizing on enzymatic scouring through changes in the surface properties and scouring efficiency were investigated. Mercerized cotton yarns dried at room temperature (20 o C) and 80 o C were scoured with alkaline and acid pectinases. Alkaline scouring was also done for comparing. Surface properties and scouring efficiency were followed through the CIE whiteness degree, CIELAB coordinates, X-ray photoelectron spectroscopy, staining the non-cellulosic components with appropriate dyes, wettability and surface fee energy. Mercerization changes the cotton surface, and removes part of the cuticle components. Drying at 80 o C melted down the residual waxes covering the surface of the fiber, enhancing the alkaline and alkaline pectinase scouring and enabling acid pectinase scouring. While way of scouring has significant influence on the most measured properties, temperature of drying has significant influence on CIE whiteness, CIELAB coordinates a*, b*, L*BB and on x-ray photoelectron spectroscopy value O/C.

Proučavano je bojadisanje pletiva od različitih vrsta pamuka u industrijskim uvjetima rada s bifunkcionalnim reaktivnim bojilima radi ocjenjivanja reproducibilnosti procesa. U kontroli kvalitete praćene su propratne tvari pamuka, alkalini i zemnoalkalni metali u sirovim i iskuhanim pletivima, hidrofilnost, razlikama obojenja uzoraka pletiva bojadisanih u različitim kupeljima određivanjem CIELab koordinata, čistoće elektrolita kao i kvaliteta vode (određivanje tvrdoće, povremene bikarbonatne tvrdoće, alkalnih i zemnoalkalnih metala i iona teških metala). Kod uzoraka crno obojadisana pletiva dobiveni su visoki koeficijenati varijacije vrijednosti za ukupnu razliku boje (dE*), što ukazuje na velike razlike u nijansi, neravnomjernosti obojenja i nereproducibilnosti procesa bojadisanja. Enzimatsko iskuhavanje, kvaliteta sirovog pamuka, kvaliteta vode i elektrolita imaju velik utjecaj na kvalietu obojenja reaktivnim bojilima., Dyeing of knitted fabrics from different grades of cotton in industrial conditions by a single recipe with bi-functional reactive dye has been investigated in order to estimate the efficiency and reproducibility of the process. Quality control in different stages of the process was followed through the content of the non-cellulose components, alkaline and alkaline earth elements in raw and scoured cotton, the hydrophilic properties, and CIELab coordinates, color difference between different batch dyeing, purity of the electrolyte as well as the quality of the water through permanent hardness, temporary bicarbonates hardness, alkaline, earth-alkaline and heavy metal ions. Black dyed fabrics had high variance coefficients of ΔE*, indicating shade variations and unacceptable color levelness and reproducibility. Enzymatic scouring, quality of the raw cotton, water and electrolyte have significant influence on the dyed fabrics.

Micro-Raman and micro-FTIR spectroscopy were used to investigate raw and dyed polyacrylonitril (PAN) fibers with three different linear densities (3, 6 and 9 den), dyed with three cationic dyes (red, blue and yellow) by standard procedure. The Raman and the IR spectra of the raw and dyed fibers as well as the corresponding spectra of pure dyes were analyzed. High quality spectra, both Raman and IR were obtained, requiring no sample preparation. Dyed fibers gave Raman spectra with bands characteristic for both the polymer and the dyes, while the IR spectra consist of predominantly bands due to the fiber polymer. Spectral subtraction procedures were used to separate the Raman spectra of the raw PAN fiber from the corresponding spectrum of dyed fiber and were then compared with the Raman spectra of pure dyes. The recorded Raman spectra of the three different linear densities of dyed fibers did not show variation in band frequencies, but in one dyed (blue) fiber, a regular variation in the band intensities was observed. This effect has been related to the quantity of the dye fixed on the (blue) fiber in three different linear densities. The results were compared with the quantity of the absorbed dye, previously determined for the blue fiber by colorimetric measurements. (doi: 10.5562/cca1888)