Application of pistachio hull as an agricultural waste and natural mordant in dyeing of wool yarn

Natural dyeing of wool as pile yarn in hand-made carpet is getting popularity recently due to several advantages of the natural colorants over synthetic dyes. However, a problem in natural dyeing is the low affinity of textile fibers for natural dyes and consequently low exhaustion of the dyebath. To increase the exhaustion of natural dyes on textile fibers, usually a mordanting process using salts of metals such as chromium, aluminum, tin, copper, and iron is considered. Most of the metal mordants contain heavy metals which are toxic and harmful to the environment and humans. It is important to find approaches to promote the natural dyeing of textiles in green ways without the application of harmful chemicals. Finding natural dye sources which are usually considered as waste by-products of other industries and are produced in large quantities is of great importance. Agriculture processing industries generate a large amount of organic waste that still contains coloring pigments. Their sustainable use in dyeing of textiles will expectedly solve the problem of their disposal. In addition, the cost can be lowered by the use of by-products from agriculture and food industry, and wastes from forestry. Pistachio is one of the main agricultural products of Iran. The tannins present in pistachio hulls may impart antibacterial activity to textiles. In this project, wool fiber was dyed with different natural dyes and the extract of pistachio hulls as a major agricultural by-product as a green source of mordant. It is observed that using pistachio hull as a natural mordant resulted in close similar color characteristics compared with alum mordant in wool dyed samples with madder.

کلیدواژه ها:

natural dyeing ، agricultural waste ، weld ، madder ، cochineal ، mordant ، tannin