Sustainable pilot scale reactive dyeing based on silicone oil for improving dye fixation and reducing discharges

The textile dyeing industry has been under the increasing pressure from liberalized economic regime and environmental protection. To alleviate the pressure, nonaqueous dyeing technology has been extensively investigated for improving dye fixation and reducing effluent discharge. In this investigation, a pilot scale dyeing of cotton with high temperature reactive dye Procion Red in silicone oil nonaqueous dyeing system was studied. When the amount of dye is the same, the color depth of dyed cotton fiber and the fixation of dye in the silicone non-aqueous dyeing system are higher than that of the traditional water based dyeing system. When the K/S value of dyed sample is same, silicone and water based dyeing system required initial dye is 2.0% and 4.9% on weight of fiber, respectively. Compared with the traditional water based dyeing, the water consumption and wastewater treatment are only 20% of the traditional water based dyeing system. The higher fixation of reactive dyes not only saves water consumption, but also reduces the consumption of dyes, alkalis and other chemicals by 41%. Moreover, the loss of the silicone nonaqueous medium is controlled within 2%. The hydrolytic reaction energy gap of reactive dye with density functional theory was investigated in silicone nonaqueous medium and traditional water based dyeing system. It was found that the hydrolytic reaction energy of the Procion Red H-E3B in an alkaline environment is much lower than that in a pure aqueous environment. The higher hydrolytic reaction energy of reactive dye in the silicone nonaqueous medium dyeing system proves that why reactive dye can keep a long reactivity during the dyeing. The success of the pilot-scale silicone nonaqueous medium dyeing system shows that this dyeing technology will change the current conventional water dyeing in terms of the huge amount of water consumption and the serious issue of wastewater pollution.