Waterless beam dyeing in supercritical CO2: Establishment of a clean and efficient color matching system

A green approach for dyeing cotton fabrics using synthesized reactive disperse dyes and their mixtures under supercritical CO2 medium

Dyeing natural fabrics using supercritical carbon dioxide is challenging, especially without essential color hues. This work demonstrated that two newly developed reactive disperse dyes with distinct colors and shades were generated, one of which featured from the anthraquinone family and the other yellow, containing a pyrazole moiety. These new dyes and their combinations were used to dye cotton fabric using supercritical carbon dioxide and the highest K/S values were achieved at 8.73 for the mixture of (blue dye: yellow dye 80:20), however the lowest K/S was observed at 7.71 for (blue dye: yellow dye 20:80). The new dyes' chemical compositions were identified using elemental and spectroscopic analyses. The effectiveness of these dyes and their mixtures for cotton dyeing was discussed. The dyed samples were tested for color fastness, and the results indicated that they had excellent color retention and were highly durable in washing. The increasing patterns in both dyeing rate and build-up curves show good compatibility. Furthermore, desirable shades of green can be achieved by mixing blue and yellow dyes at various ratios in supercritical CO2. The compatibility test involves calculating color difference index values for dyed cotton fabrics by utilizing various ratios of a binary mixture of dyes. Furthermore, the dyes under study and dyed samples displayed superior antibacterial properties against gram-positive and gram-negative bacteria compared to certain antibiotics used as a control. These results aligned with the quality and eco-friendly standards required by the industry without the use of water.

Supercritical fluid technology as a sustainable alternative method for textile dyeing: An approach on waste, energy, and CO2 emission reduction

The clothing industry is considered one of the most polluting industries on the planet due to the high consumption of water, energy, chemicals/dyes, and high generation of solid waste and effluents. Faced with environmental concerns, the textile ennoblement sector is the most critical of the textile production chain, especially the traditional dyeing processes. As an alternative to current problems, dyeing with supercritical CO2 (scCO2) has been presented as a clean and efficient process for a sustainable textile future. Supercritical fluid dyeing (SFD) has shown a growing interest due to its significant impact on environmental preservation and social, economic, and financial gains. The main SFD benefits include economy and reuse of non-adsorbed dyes; reduction of process time and energy expenditure; capture of atmospheric CO2 (greenhouse gas); use and recycling of CO2 in SFD; generation of carbon credits; water-free process; effluent-free process; reduction of CO2 emission and auxiliary chemicals. Despite being still a non-scalable and evolving technology, SFD is the future of dyeing. This review presented a comprehensive overview of the environmental impacts caused by traditional processes and confronted the advantages of SFD. The SFD technique was introduced, along with its latest advances and future perspectives. Financial and environmental gains were also discussed.

A Dissolution Kinetic Study of Disperse Dye in Supercritical Carbon Dioxide to Design an Efficient Supercritical Dyeing Process

The dissolution behavior of dye in supercritical carbon dioxide influences the overall mass transfer that controls a supercritical dyeing process. Increasing the dissolution rate of the dye leads to shortening of the dyeing process time and can improve the efficiency of the process. Controlling the properties of the carbon dioxide flow is a good method to improve the dissolution rate of dyes. In this study, a dissolution kinetic model was designed by quantitatively analyzing and formulating the dissolution phenomenon of dyes using an in situ UV/Vis spectrometer. Through this model, the dissolution rate was compared by varying the geometric shape of the column containing the dye and the flow rate of carbon dioxide. Moreover, the correlation equation between the Reynolds number and Sherwood number was obtained through mass transfer coefficients derived under various conditions. In order to verify the utility of this equation, it was applied to a scaled-up device and the precise result could be predicted. This study can be useful in the design of dyeing processes and make-up equipment.