Review on Natural Dyes for Textiles from Wastes

Abstract

Agriculture and food processing industries generate a large amount of organic waste that still contains colouring pigments. Their sustainable use in dyeing textiles will expectedly solve the problem of their disposal. Some studies involving the use of agro and industrial waste have been documented in this chapter to provide a guideline for further research. Information on some selected wastes that have been used in dyeing of textiles by several authors have been listed, their composition and production details highlighted and their use is explained systematically. The documented studies have been placed in the form of case studies to highlight the different approaches of the authors for explaining the effectiveness of such wastes as a source for textile colourants. As reported in some studies, the extracted dye from the waste doubled up as a mordant itself. Most studies also indicate good dyeability with appreciable fastness with respect to the textiles dyed with such wastes. Some wastes have also reportedly rendered antibacterial and sun/light protective properties to the dyed fabric. Case study 1 Objective of the study : Dyeing of wool, silk, acrylic and cationized cotton and polyamid fibres with aqueous-extract of grape pomace [58]. Baaka et al. [58] have explored the use of a by-product, pomace, abundantly available at relatively inexpensive costs, to dye natural fibres like cotton, wool and silk; and synthetic fibres like polyamide and acrylic using sulphate salts of alum and ferrous as mordants. Since cotton and acrylic are associated with poor affinity to dyes, they were subjected to additional pre-cationization process prior to mordanting for improving dyeability. Surface colour strength of the dyed fabric was found to improve with use of metallic mordants, and good fastness properties to rubbing (4–5), wash (4–5) and light (4) were obtained. Authors have concluded remarkable improvements in the UPF of the fabric dyed with grape pomace in the presence and absence of metallic mordants ( Table 1 ). of plant is the more anthocyanin permitting into plant out 20% and (f) 3% (common salt). Through the results of the FTIR and AAS studies, the postulated the possible corresponding reaction mechanism resulting in the formation of large complexes between the mordant, fibre and the dye. The FTIR studies have indicated the presence of aluminium in dyed cotton khadi fabric, thereby confirming the formation of a complex between the cotton fibre, aluminium sulphate mordant and dye from pomegranate rinds together with the presence of some zinc and sulphur. The dyed cotton khadi fabric shows medium to good level of ultraviolet protection as the UPF rating increases from 5 for the control untreated sample, to 15–20 for the cotton dyed with pomegranate rinds. Mirjalili et al. [16] have used soxhlet extract of walnut shells to dye polyamide fabrics using 3% (owf) of different mordants (potassium aluminium sulphate, cupric sulphate, and ferric sulphate) by simultaneous mordanting and dyeing process. They have reported considerable increased in dye absorption leading to higher 𝐾 / 𝑆 values in case of mordanted samples compared with unmordanted ones, with ferric sulphate giving the highest colour strength. Use of mordant also imparted higher antibacterial activity and here again ferric sulphate was more effective against S. aureus than other mordants; while cupric sulphate was better against E. coli . An increase in the dye concentration resulted in a tangible effect on antibacterial activity of dyed fabrics indicating that increased presence of phenolic and naphthoquinone compounds in the higher concentration of the dye extract is responsible for the improved antimicrobial activity. Use of metallic mordants also improved the wash durability of antimicrobial finish.