Green, eco-friendly and sustainable alternative in dyeing cotton fabric using aqueous extract Mucuna slonaei F dye: effects of metal salts pre-mordanting on color strength and fastness properties Jamiu Mosebolatan Jabar a, * , Tolulope Esther Adedayo b , Yisau Adelaja Odusote c a Textile and Polymer Research Laboratory, Chemistry Department, The Federal University of Technology, P.M.B. 704, Akure, Nigeria b Biochemistry Department, The Federal University of Technology, P.M.B 704, Akure, Nigeria c Condensed Matter and Statistical Physics, Department of Physics, Federal University of Technology, P.M.B., Akure 704, Nigeria ARTICLE INFO Keywords: Color parameters Fastness properties Flavonoids Natural dye Pre-mordanting ABSTRACT Natural dye extracted from Mucuna slonaei F leaves (MSL) was used as green, sustainable and eco-friendly alternative in coloring cotton fabric with and without sodium chloride (NaCl), ferrous sulfate (FeSO 4 ⋅7H 2 O) and alum (KAl(SO 4 ) 2 ⋅12H 2 O) as mordants. Effects of these mordants on color parameters (exhaustion (%), lightness (L*), color axes (a* and b*), hue angle (h o ), color strength (K/S) and fastness properties evaluated) of MSL dyed cotton fabric were investigated. Flavonoids were identified as main chromophoric constituents in extracted MSL dye by UV–visible and Fourier transform infrared (FTIR) spectrophotometry techniques. Satis- factory color parameters in unmordanted MSL dyed fabric indicated that cotton fabric has a moderate affinity for the extracted dye. Metal pre-mordanting enhanced dye exhaustion by 4.85, 13.10 and 10% in Sodium chloride (Na þ ), ferrous sulfate (Fe 2þ ) and alum (Al 3þ ) dyed cotton fabrics respectively. Unmordanted MSL dyed fabric has lighter shade, higher L* and lower K/S value than metal salt pre-mordanted fabrics. The value of a* greater than b* and h o < 45  confirmed attractive colors of unmordanted and metal pre-mordanted MSL dyed cotton fabrics closer to red than yellow. Na þ and Fe 2þ pre-mordanted MSL dyed cotton fabrics have better fastness properties than their unmordanted and Al 3þ pre-mordanted counterparts. 1. Introduction Natural dyes are colorants obtained from nature. They can be clas- sified into three categories, namely; plant, animal and mineral dyes [1,2]. The plant based natural dyes are extractable from different parts of plant, such as bark, flower, seed, root, leaf, stem and fruit. Some researchers that have extracted dyes from plant are Jabar et al. [3] who extracted natural dye from the bark of Bridelia ferruginea B., Singhee and Samanta [4], extracted natural dye from flower's petal of Butea monosperma; and Hong [5] extracted dye from Coffee arabica L. seeds. Other researchers are Bukhari et al. [6] who extracted dye from Juglans regia L bark; Yusuf et al. [7] extracted dye from root of Rubia cordifolia; Jabar and Abayomi [8] extracted dye from Cocos nucifera L coir fibre; Uddin [9]; extracted dye from leaf of Mangifera indica L tree; and Yusuf et al. [10] extracted dye from leaves of Lawsonia inermis. Discovery of man-made (synthetic) dyes in nineteen century brought set back to natural dye industry due to some qualities of synthetic dyes; such as good fastness properties and uniformity of hue. However, man- made dyes are laboratory synthetic products from petrochemical as precursor [11]. Instability in price, non renewable, non biodegradable, toxic, mutagenic, carcinogenic effects etc are some of demerits of pe- troleum based-synthetic dyes. Environmental awareness has revived the use of natural dyes in textile and other chemical and allied industries [12]. Plant is the major source of natural dye. It is interesting to note that the most attractive, economical and sustainable natural dye yielding plant part is leaf, because it is abundant, readily reproducible and obtainable with no detrimental effect on the plant [13]. The techniques used for extracting dye from leaves and other natural sources are aqueous, organic solvent and soxhlet extraction method [3]. Others are microwave, gamma, plasma, ultraviolet and ultrasonic radiation method [14–16]. Among these methods, an aqueous extraction remains simplest, cheapest and most eco-friendly method of extraction, because equipment used is inexpensive, non cumbersome and water used as extracting sol- vent is abundant and non toxic [13]. Therefore, good quality and low cost * Corresponding author. E-mail address: jmjabar@futa.edu.ng (J.M. Jabar). Contents lists available at ScienceDirect Current Research in Green and Sustainable Chemistry journal homepage: www.elsevier.com/journals/ current-research-in-green-and-sustainable-chemistry/2666-0865 https://doi.org/10.1016/j.crgsc.2021.100151 Received 6 May 2021; Received in revised form 25 June 2021; Accepted 3 July 2021 Available online 6 July 2021 2666-0865/© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/). Current Research in Green and Sustainable Chemistry 4 (2021) 100151