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 onebath 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 (BOD 5 ). 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.

Biotechnology in Textiles – an Opportunity of Saving Water

“…After the bioscouring the cotton fibres are darker than after alkaline scouring (Preša & Tavčer, 2009;Tavčer, 2008). In further bleaching with hydrogen peroxide, it was established that a better degree of whiteness can be attained on alkaline scoured sample than on the bioscoured one, however, it need to be taken into account that alkaline scoured fibred are very sensitive to oxidative damage during bleaching.…”

“…The degree of whiteness attained in this procedure is lower than the degree of whiteness of the fibres bleached in a classic procedure with hydrogen peroxide. Dyeing with direct and reactive dyes was efficient and equal on fabrics that were differently scoured (Canal et al, 2004;Preša & Tavčer, 2009). Etters (Etters et al, 2001) did not notice any statistically significant difference between the rate of uptake, equilibrium exhaustion, or colour depth on the cotton substrate between the two fabrics that were either alkaline scoured or bioscoured.…”

“…Bleaching with peracetic acid (PAA) is an alternative to bleaching with hydrogen peroxide (Gürsoy & Daioglu, 2000;Križman et al, 2005, Hickman, 2002Prabaharan et al, 2000, Tavčer, 2008Tavčer, 2010). It is a powerful oxidizing agent (redox potential: 1.81 eV) (Preša & Tavčer, 2009) with excellent antimicrobial and bleaching properties. It is efficient at low concentrations, temperatures and in neutral to slightly alkaline medium.…”

Dyeing of Environmentaly Friendly Pretreated Cotton Fabric

“…The consumption of water and energy is the lowest at combined scouring/bleaching treatments. Consequently, at these processes arises the lowest amount of effluents and the produced wastewater is biodegradable (Preša & Tavčer, 2009). …”

“…Bleaching with peracetic acid (PAA) is an alternative to bleaching with hydrogen peroxide (Tavčer, 2010). It is a powerful oxidizing agent (redox potential: 1.81 eV) (Preša & Tavčer, 2009) with excellent antimicrobial and bleaching properties. It is efficient at low concentrations, temperatures and in neutral to slightly alkaline medium.…”