Hollow silica nanoparticles loaded with industrial dyes for high exhaustion leather dyeing and its sustainability impact

Abstract

Nowadays, it is difficult to maintain acceptable water quality owing to dye pollution caused by rapid industrialization. Coloured dye discharge from the leather dyeing process has numerous anthropogenic effects on water sources. Synthetic leather dyes can be considered environmental pollutants because of their toxicity, and mutagenic and carcinogenic effects. Hence, there is an increasing demand to develop a high-exhaustion dyeing process without influencing leather quality. In this study, high dye exhaustion was attempted using hollow nanoparticle-stabilised industrial dyes, which are the most interesting liquid dyes in the context of sustainable dyeing. A simple method of preparing dye-modified hollow silica nanoparticles for better binding with leather has been reported using silica with hydroxyl and acrylate groups. The optimum condition for maximum dye uptake was obtained at pH 5.5–6, 90 min of drumming and 25–30 °C. Further, the effect of changes in the nanoparticle surface functional groups, particle size and type of tanned leather for dyeing were evaluated. The hollow spheres model with acrylate groups showed good dyeing characteristics with 98% dye uptake by applying the leather matrix. Compared to the conventional dyeing process, the E factor (environmental factor) of the new way of dyeing by hollow nanoparticles was estimated to be lower (at a value of 0.35), indicating minimum emissions and less pollution load. The economic viability of the newer dyeing system was also analysed through a cost-benefit analysis. A high exhaustion (high uptake) dyeing system is a sustainable alternative to conventional dyeing, providing a fundamental and innovative contribution. Thus, nanotechnology offers a technology that can be used as a tangible solution for coloured discharge in leather processing. As per the sustainability goal (goal 6), this new dyeing system was related to the ethical imperative of providing humanity with a minimum standard of living (affordable clean water by minimum dye discharge).