Colorimetric study of natural dye from Beta vulgaris peels and pomace on cellulosic substrate

Abstract

Synthetic dyes are associated with carcinogenic, toxic, and allergic effects on humans and our environment. Natural dyes have attracted attention globally because of their non-hazardous nature. Beta vulgaris (Beetroot) plant wastes such as peels and pomaces are an unexploited resource. The present study involved solvent extraction of natural dye from B. vulgaris peels and pomace, and its application on cellulosic fabrics alongside natural mordants (alum and tannic acid) in comparison to metallic mordants (potassium dichromate, ferrous sulfate, and copper sulfate) to improve the colour fastness of the cotton substrate and establish colour strength equivalence (ceq) relating to synthetic Reactive Orange HER. In mordanting, the three methods (pre- mordanting, simultaneous, and post-mordanting) were employed. Response surface methodology and central composite design were used to optimize extraction and dyeing conditions, namely temperature, M:L ratio, time, and pH. The optimized extraction conditions were M:L ratio of 1:20 and time of 11 hours. This resulted in a moderate (40%) yield of natural dye from the plant, proving to be better than conventional methods. Optimized dyeing resulted in temperature 55′C, time 75 minutes, and pH 6. The CIE L*, a*, b*, C*, and h◦ values were studied by standard methods. The dyed fabrics exhibited very good to excellent colour fastness test (light, washing, rubbing, and perspiration fastness) in the range of 4–5 in gray scale. These findings reveal that B. vulgaris peels and pomace can be potential alternatives to synthetic dyes in the colouration of cotton fabrics