Sustainable reactive dyes derived from soil humic acids for high-efficiency cellulose fabric dyeing

The conversion of biomass waste into high-performance textile dyes contributes to both the environment and the green and sustainable development of the textile industry. We proposed a novel strategy for the cleaner transformation of the humic acids (HA) from soils to a low-molecular-weight and water-soluble reactive dye by depolymerization followed by grafting with chlorotriazine and sulfonic acid groups. Comprehensive analyses (FTIR, NMR, and GPC) confirmed the successful synthesis of the final product, the DPHA-Tr-SO₃Na dye. Studies on the dyeing mechanism and properties demonstrated that DPHA-Tr-SO₃Na exhibited characteristics typical of a reactive dye. Under the optimal dyeing conditions (pH 10, 90 °C, 25 g/L NaCl, and 4 % owf dye), DPHA-Tr-SO₃Na displayed acceptable dyeing properties on cotton fabric, comparable to those of commercial synthetic dyes: exhaustion rate (86.1 %), fixation rate (70.0 %), and good color fastnesses (Grade 4–5) to washing, rubbing, and sunlight exposure. Most importantly, cytotoxicity tests confirmed the dye's high safety for textile applications. Besides, this approach offered significant economic and environmental advantages compared to common synthetic reactive dyes, achieving a 55.0 % lower cost and a 23.1 % reduction in carbon emissions. The proposed strategy provides new insights for the cleaner production of sustainable biomass-based dyes.