Semistable Emulsion System Based on Spent Cooking Oil for Pilot-Scale Reactive Dyeing with Minimal Discharges

A new reactive dyeing system is designed based on controllable emulsion stability for minimal discharge of pollutants and adaptability to all types of reactive dyes. Conventional aqueous reactive dyeing is considered highly polluted due to discharge of large quantities of hydrolyzed dyes and salts. Though alternative dyeing technologies have been developed to reduce pollutant emission, their applications have been limited due to the release of toxic organic solvents, low dye fixation, or undesirable levelness. In the new emulsion system, the majority of water serves as the solvent to dissolve reactive dyes and then forms a W/O emulsion that serves as the dye-bath. The movement speed of aqueous droplets with dissolved dyes from dyeing medium to cotton and the concentration of dyes in the internal phase are adjusted by the emulsion stability and overall water content for high levelness and dye fixation. Compared to a conventional aqueous system, the semistable emulsion system reduces discharge of dyes by 96% and needs zero addition of salts and dispersants for the same depth of shade. Oil could be completely removed from dyed fabrics via treatments of low costs for reuses. The success in pilot-scale dyeing with the emulsion system demonstrates its industrial feasibility.