Application of ozone in cotton bleaching with multiple reuse of a water bath

Abstract

This paper discusses the effect of ozone bleaching on the quality of cotton fabric in terms of whiteness, dye pick-up, copper number and degree of polymerization (DP). The process parameters (pH, ozone dose and treatment time) were optimized, and the best whiteness (60–62) and quality of bleached fabric was obtained at pH 5, 45 min treatment time and room temperature. A strongly acidic environment and longer ozonation time decreased the quality of fabric by producing a higher copper number (0.18) and DP loss (51.5%). Statistical analysis of the experimental data using analysis of variance confirmed that process parameters significantly affected the bleaching efficiency. The process was then applied to bleach 20 different samples of cotton fabric re-using the same water bath, and the whiteness of ozone-bleached samples did not decrease, even after the 20th reuse of the water bath.