Low Water and Energy Saving Process for Cotton Pretreatment

Abstract

Cotton fabric was alkaline scoured with sodium hydroxide and bioscoured with acid or alkaline pectinases. In addition, the scoured fabrics were bleached with hydrogen peroxide (HP) or peracetic acid (PAA). The cotton fabric was treated simultaneously with pectinases and PAA in a one-bath process. The CIE whiteness, water absorbency, weight loss, tenacity at maximum load, and dyeability with a reactive dye were evaluated on differently pretreated samples. The remaining scouring and bleaching baths were analyzed for ecological parameters including pH, total organic carbon (TOC), chemical oxygen demand (COD), and biological oxygen demand (BOD5). The quantity of water and energy used for different processes was estimated. The water absorbency of all scoured fabrics was satisfactory. The degree of whiteness of all bleached fabrics was improved. The highest degrees of whiteness were from HP bleached samples. Less whiteness was achieved in PAA bleached samples. The whiteness was greater in the alkaline scoured fabrics relative to the enzymatic scoured fabrics. One-bath processes produced whiteness values comparable to alkaline scouring and bleaching with PAA. Neither of the processes had little effect on the tenacity at maximum load. All samples were evenly dyed with reactive dye. There was a remarkable color difference between samples that were alkaline or enzymatically scoured before dyeing and between differently bleached samples. On the other hand, there was no noticeable color difference between samples that were scoured and bleached in two-bath or one-bath processes before dyeing. In comparison to conventional pretreatment, less energy and water is used in enzymatic and/or PAA treatments since they proceed at 60°C and at a pH between 6 and 8. Therefore, neutralization is unnecessary. The remaining baths are biodegradable. During the one-bath scouring/bleaching process, the consumption of water and energy was even lower and the production time was shorter.