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In this study, an activated peroxide system was established for low-temperature bleaching of cotton by incorporating N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC), hydrogen peroxide (H2O2) and sodium bicarbonate (NaHCO3) into an aqueous solution. The bleaching performance was modelled by response surface methodology based on a central composite rotatable design of experiment, in which concentration of TBCC ([TBCC]), concentration of NaHCO3 ([NaHCO 3]), temperature (T) and time (t) were four independent variables, and the degree of whiteness (DoW) of bleached cotton was measured as the response variable. For each individual bleaching experiment, TBCC and H2O2 were used in a molar ratio of 1:1.1 and NaHCO3 in a molar amount greater than that of H2O2 for the purpose of driving reactions to completion. A reduced quadratic model (RQM) was constructed using regression analysis with backward elimination, which was used to conduct a practical low-temperature bleaching process for cotton. In comparison to the typical conventional peroxide system, the TBCC-activated peroxide system based on the RQM predication provided cotton with an equivalent DoW and slightly inferior water absorbency, resulted in no apparent damage to cotton fibers, but worked under much milder conditions. This study provides useful insights into scaling up the TBCC-activated peroxide system for low-temperature bleaching of cotton.

A screening experiment was designed to investigate the possible factors affecting the performance of activated peroxide systems (APSs) on bleaching of cotton fabric. The design of experiment comprised thirteen factors such as type of bleach activator (BA), concentration of bleach activator ([BA]), molar ratio of hydrogen peroxide to bleach activator ([H2O2]:[BA]), type of peroxide stabilizer (PS), concentration of peroxide stabilizer ([PS]), type of wetting agent (WA), concentration of wetting agent ([WA]), pH value of bleach bath (pH), bleaching temperature (T), bleaching time (t), liquor-to-goods ratio, cotton substrate (C), and water quality (W). The bleaching performance of APSs was accessed by measuring the degree of whiteness of bleached cotton fabric which was defined as the response factor for statistical analysis. The screening analysis revealed that C was the most significant factor affecting the performance of APSs on bleaching of cotton fabric, followed by T, BA, [BA], pH, PS, and [H2O2]:[BA]. Additionally, two-factor interactions were found as well between C and T, T and pH, C and BA, C and [BA], T and [BA], W and [PS], C and PS, and pH and [H2O2]:[BA]. These significant main effects and two-factor interactions were interpreted in details for a better understanding of the performance of APSs on bleaching of cotton fabric. The findings of this study are valuable for further establishment and optimization of APSs for low-temperature bleaching of cotton fabric.