Sustainable dyeing and functionalization of jute fabric with a Chinese sumac gall-derived gallotannin using eco-friendly mordanting agents

Natural fiber-made apparel dyed with natural dyes is drawing consumer attention because of the possible toxic and health hazards associated with fabric dyed with synthetic dyes. However, many textile products dyed with natural dyes available in the market could pose a health risk because of the use of toxic heavy metals as a dye-complexing agent. In this work, jute fabrics were dyed and multi-functionalized with gallotannin (GT), using ferrous sulfate (FeSO₄), calcium chloride (CaCl₂), and aluminum chloride (AlCl₃) as a non-toxic mordanting agent. The shades produced and other physicochemical properties of the GT-dyed jute fabrics were compared with the jute fabric treated with GT using copper sulfate (CuSO₄), a common mordanting agent. It was found that the GT with various mordanting agents produced navy blue and brown shades with tonal changes along with quite good colorfastness to washing. The concentration of GT and mordanting agents, types of mordanting agents, and the treatment pH affected the shade produced and physicochemical properties of the treated fabrics. The surface resistivity was reduced from 235 × 10¹⁰ Ω/sq for the control to 6.7 × 10¹⁰  Ω/sq for the AlCl₃ mordanting agent, slightly higher than the surface resistivity exhibited by the CuSO₄ mordant. The fabric treated with GT using FeSO₄ and CaCl₂ mordanting agents showed excellent antioxidant activity, even at the lowest GT dosage applied. Similarly, FeSO₄ and CaCl₂ also showed excellent UV radiation absorption capability. The developed treatment can be used in the textile industry to make cellulosic textiles multifunctional without using any toxic dyes and chemicals.