The uptake behavior of acid dye on silk fabric under laminar flow in a coloration circular pipe

To achieve a highly efficient and cleaner dyeing production, the uptake behavior of acid dye molecules on silk fabric under laminar flow status was explored for the first time by using a C.I. Acid Red 134 dye (AR-134) based on a self-built special fluid dynamics coloration machine in this work. The effects of the coloration liquid Reynolds number and its velocity distribution on the uptake behaviors of the AR-134 dye were investigated and optimized in a circular pipe. Meanwhile, the adsorption kinetics, thermodynamics and diffusion behaviors in silk fiber, etc., of the AR-134 dye under laminar flow were further investigated. The obtained results indicate that more acid dye could be adsorbed on the silk substrate when the coloration liquid Reynolds number was about 1750 in the pipe. Furthermore, the uptake behavior of the AR-134 dye on silk substrate conformed to the quasi-second-order kinetic equation and the Langmuir adsorption model under laminar flow, which indicates that the lower the Reynolds number was, the higher the saturation adsorption value of the AR-134 dye could be achieved. Particularly, when the coloration liquid Reynolds number was about 1750, the largest diffusion coefficient and the shortest half-saturation adsorption duration of the acid dye were obtained on the silk substrate under laminar flow. Additionally, the silk fiber surface morphologies after the dyeing process under laminar flow were efficiently protected by avoiding various damages. The obtained results further clearly indicate that an appropriate control of the coloration liquid flow in laminar flow is not only beneficial to protect substrate well, but also to improve the utilization of dyes, shorten the coloration duration and reduce the discharge of pollutants for performing an efficient, energy conservation and cleaner coloration process.