Colour stripping of reactive‐dyed cotton by ozone treatment

Abstract

Trials have been carried out to investigate the efficiency of ozone treatment in the colour stripping of reactivedyed cotton fabrics. The trials were performed on a specially designed apparatus to inject ozone gas into the liquor passing through a perforated beam with fabric rolls on it, just like a beam dyeing machine with ozone venturi injection. Conventional reductive colour stripping was applied as the control treatment, and ozone treatment was applied for three different application times (15, 30, and 45 min). Trials were performed with seven selected reactive dyes having various chromophores and reactive groups. The results indicate that 45 min ozone treatment yielded the best colour stripping results among the three application times. Furthermore, the colour stripping percentages of the 45 min ozone treatment were higher for four of the tested dyes, the same for one of the tested dyes, and lower for two of the tested dyes compared with the control treatment, which consisted of conventional reductive colour stripping. Colour stripping of 90% and above was achieved for all samples of the 45 min ozone treatment. The chemical oxygen demand values of the colour stripping baths were compared: the average value of the 45 min ozone application baths was 105 mg l À1 , and it was 1993 mg l À1 for the conventional reductive treatment baths. Consequently, a reduction in chemical oxygen demand of almost 94% was achieved by ozone treatment compared with conventional reductive treatment. The strength values of the fabrics after the respective treatments were similar, with a difference of only 3%.

Use of Ozone in the Textile Industry

“…The longest ozonation time gives the best color stripping result. COD value of effluent from ozonation is less than that of conventional reductive treatment [47].…”

Application of Ozone Treatment for the Decolorization of the Reactive-Dyed Fabrics in a Pilot-Scale Process—Optimization through Response Surface Methodology

“…Three different pH values (3,5,7) were used for color removal. The pH of solutions was adjusted using different concentrations of phosphoric acid and/or caustic soda (laboratory grade).…”

“…Application of ozone in several domains of textile finishing has been reported. These include reduction clearing of polyester dyed with disperse dyes [5], discharge printing of reactive-dyed cotton fabrics [6], color stripping of reactive dyes from cotton textiles [7], and bleaching of raw cotton textiles [8]. The industrial application of ozone has been limited to denim and garment washing only, and its application to other areas can be a scope of study [9].…”

Ozone utilisation for discharge printing of reactive dyed cotton

“…Successful decolorisation of reactive dyes by ozone treatment has been reported in the literature [17,[20][21][22][23]. Furthermore, Eren et al [24] reported a successful study on colour discharge of reactive dyed cotton by ozone. From this, it was suggested that discharge printing should be performed by ozone if colour discharge of the reactive dyed cotton fabric can be achieved through selected patterns.…”