•A novel and Ecofriendly method for photocatalitic color stripping of fiber was developed.•Fixed Reactive Red X-3B dye on cotton was efficiently decolorized by nano-TiO2/UV.•A process was recommended for photocatalitic stripping of Fixed X-3B dye on cotton.•The photocatalitic stripping was further investigated by ATR-FTIR, XPS and SEM.A novel, green and Ecofriendly method for photocatalitic stripping of fixed Reactive Red X-3B dye on cotton substrate was developed at the first time by employing a nano-TiO2/UV system in a self-built photoreactor. The effects of photocatalitic stripping parameters such as the initial pH value of working solution, temperature and stripping duration, on color stripping efficiency and fabric tensile strength were investigated. Moreover, the photocatalitic stripping of the fixed reactive dye on cotton substrate in the nano-TiO2/UV system was further explored by Attenuated total reflection-Fourier transform infrared spectrometry (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). The results show that the fixed Reactive Red X-3B dye on cotton could be photocatalitically stripped or decolorized efficiently by employing the nano-TiO2/UV system with a dipped stripping manner in which the substrate was immersed into working solution. The tested stripping parameters of temperature and treatment duration presented notably positive effects on the color stripping efficiency, while an inappropriate control of all the parameters could result in a deterioration of the tensile strength of the substrate. Furthermore, a heterogeneous photocatalitic color stripping mechanism was also supposed for the fixed Reactive dye molecules on cotton substrate in nano-TiO2/UV system with the dipped stripping manner.Download high-res image (224KB)Download full-size image

•Basic information for dye fixation was explored on cotton with phase-transfer catalyst.•Significant improvement of dye fixation efficiency and color strength was achieved.•The catalytic fixation reaction was characterized and confirmed by FT-IR, XPS, SEM.•Dye fixation could be effectively facilitated by phase transfer catalyst of FC-134.A clean fixation of disperse reactive dye on cotton was investigated by employing a heterogeneous and phase transfer catalytical reaction with a phase transfer agent in a liquid-supercritical-solid triphase system, as an environmentally friendly alternative to conventional and heavy pollutional wet-chemical process. The catalytic fixation reaction was characterized by color intensity, fixation efficiency and Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). The results show that the dye fixation through a nucleophilic addition at a solid cellulosic polymer substrate phase could be effectively facilitated as the transportation of the anion of OH− or CO32− by the phase transfer catalyst of FC-134 from a liquid phase to supercritical phase and then onto the solid substrate in a self-built reactor. A heterogeneous and triphase transfer catalytic reaction mechanism was also supposed for the dye fixation at the solid substrate in supercritical carbon dioxide fluid with the presence of a base.

A novel method was developed for the dyeing of cotton fabric with a vinylsulfone reactive disperse dye in supercritical carbon dioxide by carrying out dye adsorption (or uptake) and a catalytic fixation reaction with a phase transfer catalyst—Triethylene diamine (TEDA) in separated baths, respectively. The results show that the dye adsorption or uptake in supercritical carbon dioxide dyeing bath significantly depended on system temperature and pressure, as well as an appropriate experiment time; significant improvements of dye fixation efficiency and color strength on wet and dry cotton fabrics after a Soxhlet extraction were achieved by employing the catalyst of TEDA under various conditions. The fastness data indicate that acceptable rub and staining fastness rated at 4–5 was obtained for the dyed cotton samples involving a catalytic fixation step, except that a fading fastness should be further improved.Graphical abstractHighlights► A novel dyeing method was developed for cotton fabric with a reactive disperse dye. ► The dyeing was carried out with dye adsorption and fixation in separated baths. ► The dye adsorption depended on temperature, pressure and favorable experiment time. ► Significant improvement of dye fixation efficiency and color strength was achieved. ► Satisfactory color fastness data were obtained on fabrics except a fading fastness.

The level dyeing of fabrics in supercritical carbon dioxide was investigated by employing an improved beam (a perforated pipe on which the knitted or woven fabric/warp is wound around). The effects of system temperature, pressure, dyeing time, a time ratio of fluid circulation to static dyeing (Rtime), different fabric layers wrapped around the beam, and the species and chemical structures of dyestuffs on leveling properties and color strength of polyester and cotton fabrics were observed. The results show that the leveling properties and color strength of fabrics were improved on the new beam, as well as with a favorably increased system temperature, pressure, dyeing time, and a time ratio of fluid circulation to static dyeing; while the leveling property and color strength decreased with fabric layers on the beam under an identical condition. Highly leveling results were obtained on polyester and cotton fabrics with disperse and reactive disperse dyes involving different chemical structures.Graphical abstract.Research highlights► The leveling property and color strength of fabrics were improved on the new beam. ► The leveling property and color strength of fabrics were also improved with favorable parameters. ► The leveling property and color strength of fabrics were affected by fabric layers. ► Highly leveling results were obtained on fabrics with different species of dyes.

The treatment of wool in supercritical carbon dioxide fluid is an environmentally friendly and advantageous solution for cleaner production of wool textiles with water free and energy preserving, as well as avoiding a large amount of effluent discharge and serious environment pollution in conventional wet chemical processes. In the present work, some basic supports for the applications of supercritical carbon dioxide fluid in the cleaner production of wool were developed at different system pressures. The effects of treatment pressures on the crystal and chemical structures, macrochain conformations, thermal property and surface morphology of wool were investigated by employing Wide-angle X-ray diffraction (WAXD), Fourier transform infrared spectrometry (FT-IR), thermogravimetric (TG)/differential thermogravimetric analysis (DTG) and scanning electron microscopy (SEM). The WAXD analysis indicates that an improvement of crystallization both in α-helix and β-sheet structures was obtained for wool treated at different pressures in supercritical CO2 fluid, although the improvement tendency was decreased with pressures. Moreover, a re-crystallization and a swelling of crystals in wool fiber were also occurred during the supercritical treatment. FT-IR analysis shows that more powerful interactions of hydrogen bonds between the macromolecular chains of wool were formed during the supercritical treatment, accompanying with a significant transformation of α-helix to β-sheet structure and an oxidation or acidic hydrolysis of disulfide bonds in wool scales. The TG-DTG analysis shows that an enhanced thermal stability of wool was obtained after a treatment in supercritical CO2 fluid. Moreover, a notable etching effect or dilapidation on the scales of wool was observed in SEM analysis with a decrease in scale height, thickness and coating density on fiber.Graphical abstractDownload full-size imageHighlights► Supercritical CO2 treatment is a favorable solution for cleaner production of wool. ► Various effects of treatment pressure on wool in supercritical CO2 were investigated. ► Variations of supramolecular structures and interactions of chains were observed. ► Thermal property of wool was enhanced after a treatment in supercritical CO2. ► An etching effect or even damage on wool was observed at a high pressure treatment.