Abstract
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► We realise extraction and isolation of betanin from reddish purple fruits of Opuntia ficus-indica. ► We investigate the deability of modified acrylic fabrics with betanin dye. ► The dyeing conditions and the overall fastness properties were investigated. ► Cobalt was the best mordant for the improvement of colour strength and light fastness.
Mature red fruits of Opuntia ficus-indica contain two soluble pigment, betanin and indicaxanthin. The optimal conditions for dye extraction were to mix 50g of juice from cactus pears with 100mL of acidified water as solvent for dye extraction. Two main dyes were purified from the pigment extract by chromatography and identified by UV–vis, HPLC and LC–MS techniques as indicaxanthin (15mg per 100g) and betanin (280mg per 100g). The effect of dye bath pH, salt concentration, dyeing time and temperature was studied. The optimal conditions for dyeing modified acrylic fabrics with betanin dye were carried out at 50°C for 45min at pH 5. Un-mordanted samples have good properties of water and washing fastness. Mordant CoSO4 was found to give good light fastness (rating 5).