Desalination 230 (2008) 62–69 Ecofriendly ultrasonic natural dyeing of cotton fabric with enzyme pretreatments Padma S. Vankar*, Rakhi Shanker Facility for Ecological and Analytical Testing, Indian Institute of Technology, Kanpur, India Tel. +91 (512) 259-7844; Fax: +91 (512) 259-7436; email: psv@iitk.ac.in Received 3 March 2006; Accepted 8 November 2007 Abstract Ecofriendly ultrasonic textile dyeing with natural dyes such as Acacia catechu and Tectona grandis show better and faster dye uptake after enzyme pretreatment on cotton fabric, and results of dyeing are better than metal mordanted fabric. It is observed that there is marked improvement in wash-fastness and light-fastness. The role of enzyme pretreatment is primarily for better absorbency, adherence and dyeability of these dyes on cotton fabric, thereby completely replacing metal mordants with enzyme for adherence of natural dyes on cotton. Scanning electron microscopy show surface characteristics at different stages of dyeing. The effect of sonication on the dyeing is compared with conventional heating. The study also shows enhancement in CIELab values. Keywords: Enzyme pretreatment; Protease, α-amylase; Lipase and diasterase; Metal mordants; Cotton fabric; Tectona and catechu dyes, Sonicator 1. Introduction Enzymes are gaining an increasing role in textile wet processing [1,2] due to their proven flexibility, reliability, and concerns about safety, energy and water conservation, and environ- mental responsibility. Unlike chemicals, enzymes are very specific with their actions as each type can only affect one chemical bond and they achieve their specific effects in a cost-effective *Corresponding author. manner, although they are more expensive up front than many chemicals. They are most effi- cient under normal, mild conditions of 30–35°C, pH 4–8, and normal pressures. Different enzymes are commonly used in various stages of textile processing [3–8], which include amylase for desizing the cotton, cellulase for finishing process, and catalase for post- bleaching. In the last ten years, the textile indus- try has become one of the main field of industrial applications of enzymes. From traditional desiz- 0011-9164/08/$– See front matter © 2008 Published by Elsevier B.V. doi:10.1016/j.desal.2007.11.016