Comparison of the effect of metal mordants and bio-mordants on the colorimetric and antibacterial properties of natural dyes on cotton fabric

The main objective of this study was to evaluate the effect of bio-mordants versus metal mordants in terms of colour measurement, colour fastness, and antibacterial properties of a natural dye extract (Hibiscus sabdariffa L.) on the cotton fabric. Accordingly, some bio-mordants including tannic acid, pine cone, lemon peel, and sodium alginate, as well as some metal mordants such as iron(II) sulphate, copper sulphate, zinc sulphate, and aluminium potassium sulphate were investigated based on three conventional mordanting procedures (pre-, meta- and after-mordanting). The method appropriate for H. sabdariffa dyeing on the cotton fabric, according to the colour fastness factor, was found to be the after-mordanting method. The bio-mordants used in this study, the same as metal salts, increased the colour fastness on the dyed cotton fabrics and produced excellent light fastness (rating of 5 to 6), wash fastness (rating of 4 to 5), and dry/wet rub fastness (rating of 4 to 5). The higher antibacterial activities (> 90% bacterial reduction) against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa were observed when tannic acid, pine cone, and lemon peel were applied to the dyed cotton fabric. The use of bio-mordants in the natural dyeing of the cotton fabric could be, therefore, recommended due to the biocompatibility and non-toxicity of natural mordants, along with excellent colour fastness and appropriate antibacterial properties.