Clean fixation of dye on cotton in supercritical carbon dioxide with a heterogeneous and phase transfer catalytic reaction

•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.

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