Optimization of salt free dyeing of cotton using hot and cold reactive dyes

Abstract

Dyeing of cotton with reactive dye requires very high concentration of salt. These salts improve exhaustionby reduction of the repletion forces between the anionic dye and hydroxyl functional groups of cotton. The salt is released after dyeing process and increases salinity in drain water stream which affect human health and biodiversity in water bodies. To eliminate salt consumption and enhance chicken feather waste utilization, the research aims at using an eco-friendly approach of salt free dyeing of cotton with two types of reactive dyes (cold and hot brand). The aim of the study was to determine the effect of pre-treating the cotton fabric with extracted keratin hydrolysate without the usage of salt on dye exhaustion, to optimize the dyeing parameters, compare dye exhaustion values of hot and cold reactive dyeing and to analyse the effects of dyeing parameters on colourfastness properties of pre-treated cotton fabric dyed with hot and cold reactive dyes. Keratin hydrolysate was extracted from chicken feather waste. Cotton fabric weighing 126.2 g/m 2 , 22.8 warps and 13 wefts per centimetre was used. Central composite experimental design was used to optimize temperature and time in hot and cold reactive dyeing. Dye exhaustion at maximum wavelength were evaluated using spectrophotometer before and after dyeing pre-treated cotton fabric. The experimental data was used to predict optimum dye exhaustion and optimum dyeing parameters. The models for dye exhaustion in hot and cold brand reactive dyeing yielded P value of less than 0.05 and coefficient of determination (R 2 ) of 0.9595 and 0.9444 respectively. The model established optimum dye exhaustion of 52.9 % in hot and 48.3 % in cold reactive dyeing. The study established optimum dyeing temperature of 69.7 0 C and time of 75 minutes in hot brand dyeing and 34.4 0 C and 45 minutes in cold brand dyeing. The cotton fabric showed acceptable dye exhaustion in hot and cold reactive dyes in the absence of salt. The untreated sample dyed in absence of salt exhibited low exhaustion values of 21.4 % and 28.7 % for cold and hot dye brands. This is lower when compared with the exhaustion values of treated cotton fabrics. Therefore, the treated cotton fabric dyed in the two types of reactive dyes exhibited high exhaustion values than the control sample dyed in the presence of salt . The research further established that dyed keratin treated cotton samples exhibited better wash fastness and rubbing fastness. While this research has led to the utilization of chicken feather waste and reduction of salt usage in reactive dyeing, more research should be carried out to assess the environmental impact of the effluent which is generated from the salt free reactive dyeing of treated cotton fabrics.