A novel approach for textile cleaning based on supercritical CO2 and Pickering emulsions

A novel green method for textile cleaning, based on supercritical carbon dioxide (scCO2) as solvent and an aqueous suspension as co-solvent, is proposed. The co-solvent (which is a calcium oxide suspension in water) is not mixed with the solvent but is impregnating first the textile. The wet textile is then exposed to scCO2 atmosphere. Calcium hydroxide reacts with carbon dioxide to give calcium carbonate. These particles, which have been deposited on and/or impregnated the soiled textile, stabilize locally carbon dioxide-in-water (C/W, Pickering) emulsions. The soil, depending on its nature (hydrophobic/hydrophilic), is distributed preferably in the favoured phase of the emulsion, and is removed either via a rapid depressurisation or due to solubility. The proposed method has been successfully applied on dyed and non-dyed, cotton and silk textiles that were soiled with soils of different nature. Four different dyes were used. In all cases the extent of soil removal was between 53 and 97%. Characterization of the soiled and cleaned textiles was performed by means of weight loss (soil removal efficiency), colour measurements, optical microscopy, thermogravimetry and tensile testing. The mechanism of the cleaning process was also explored. For this purpose, various experiments were performed including comparative experiments with scCO2, scCO2 + water or isopropanol as co-solvent and scCO2 + SiO2 particles. A mechanism is proposed and its supporting facts are discussed. Our results show that the proposed process can be used for cleaning different textiles soiled with various types of soils such as particulate soils, hydrophilic or hydrophobic, liquid, or solid. It is shown that this cleaning does not affect the existent dyes. Among the advantages of the method is the discontinuous character of the process and the non-requirement of very high pressures, thus minimizing CO2 and energy consumption.

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► Novel, surfactant free, process for textile cleaning, based on supercritical fluid technology and Pickering emulsions.
► Process applied both in polar and non polar soils.
► Successful results for silk and cotton textiles dyed with various natural organic dyes.