Purification and reuse of coloured textile wastewater

Abstract

Wastewater of baths after an exhaust dyeing of cotton knitted fabric with reactive dyestuffs, soaping and rinsing was investigated. It was found that the wastewater of rinsing baths after dyeing in a light shade, which had a small amount of dyes and electrolytes, could be used for dyeing or rinsing after dyeing in a dark shade. The dyes present in the wastewater can be removed by treatment with cross‐linked cationic starch (CCS) with a degree of substitution of about 0,3. In all cases wastewater must be filtered before reuse. Such a wastewater was used for dyeing of cotton knitted fabrics in a dark shade with a laboratory apparatus. It was found that the use of wastewater in the dyeing process was risky because in some cases the colour of coloured products did not satisfy colour standards. Filtered wastewater as well as that treated with CCS were used for rinsing after dyeing of cotton and viscose knitted fabrics in a dark shade with reactive dyestuffs in industrial‐scale experiments. The colour of dyed textiles satisfied colour standards, and the colour fastness to rubbing was good. Spalvotųjų tekstilės nuotekų valymas bei pakartotinis naudojimas Santrauka Ištirta medvilninio trikotažo dažymo, plovimo ir skalavimo po dažymo aktyviais dažais šviesiomis spalvomis nuotekų sudėtis ir jų antrinio panaudojimo galimybės. Nustatyta, kad antriniam panaudojimui tinka sorbentu valytos ir filtruotos arba tik filtruotos nuotekos, kuriose yra nedaug dažų ir elektrolitų. Valyti nuotekas galima pridedant į jas sorbento – 0,25–0,5 g/l tinklinio katijoninio krakmolo, kurio pakeitimo laipsnis (PL) ~0,3. Tamsiomis spalvomis dažyto, naudojant nuotekas dažymo vonioje, trikotažo dažinių spalva ne visada atitinka spalvos etaloną. Panaudojus nuotekas medvilniniam arba viskoziniam trikotažui plauti arba skalauti gaunami spalvos ir atsparumo standartus atitinkantys dažiniai. Šie rezultatai patikrinti gamybinių naujos technologijos bandymų metu. Firstd Published Online: 14 Oct 2010 Reikšminiai žodžiai: tinklinis katijoninis krakmolas, spalvotos tekstilės nuotekos, adsorbcija, antrinis naudojimas.

Keywords

• crosslinking cationic starch
• coloured textile wastewater
• adsorption
• reuse