Role of major constituents of coconut fibres on absorption of ionic dyes

Effort was made to understand the role of major constituents of coconut fibres i.e., lignin, hemicelluloses and cellulose, on its absorption of different ionic dyes. Composition and functional groups of raw coconut fibre were changed by progressive removal of lignin, and hemicelluloses. Differently treated fibres were analyzed through FTIR, TGA, composition analysis and were dyed with anionic (acid, reactive) and cationic (basic) dyes separately. Absorption performance was assessed by surface and core colour uptake. Progressive removal of lignin resulted in reduction of uptake of anionic (acid and reactive) dyes, while increase in uptake of cationic (basic) dye. Treatment causing removal of hemicelluloses improved uptake of basic dye due to structural swelling. Increase in α-cellulose (29.9%), favours uptake of reactive dye to a higher extent. Loss of lignin occurred in case of both delignification and hemicelluloses removal treatments to the extent of 6.3% and 11.9% respectively, consequently uptake of acid dyes reduced. It may be concluded that treatment causing higher removal of hemicelluloses are beneficial and loss of lignin is disadvantageous for absorption of dyes.