The Comparison of Photocatalytic Degradation and Decolorization Processes of Dyeing Effluents

Table 1

The characteristics of the investigated dye effluents.

Effluent from dyeing process of	Dyeing technology	Abbreviation in text	Azo dyes in effluents		Other substances in effluents	pH	COD (mg O2^1)	Max of absorbance (𝜆max) in raw effluents	Comments
			C.I. name	Chemical character
Polyacrylic fibres	Continuous process	WPac	Basic Yellow 28; Basic Red 22; Basic Blue 41; Basic Black	Cationic; Cationic; Cationic; Cationic	Thickener (Prisulon),; Auxiliary agents (Roksol PAN 3K),; Glutaric acids	4.4 ± 0.1	1440	0.262 (340 nm); 0.159 (430 nm); 0.166 (540 nm); 0.199 (610 nm)	Biologically stable^a
			Acid Red 88	Anionic
Leather	Batch process	WLeat	Acid Blue 193	Anionic	<10% of tannery wastes	7.0 ± 0.1	460	0.365 (510 nm); 0.075 (620 nm)	Biologically unstable^c
			Other dyes^b	Anionic
Flax fabric	Batch process	WFlax	Unknown	Anionic	Unknown	6.9 ± 0.1	910	0.965 (350 nm)^d	Biologically stable^a
Cotton fabric	Batch process	WCot	Direct Black 22	Anionic	Unknown	8.2 ± 0.2	8930	40.05 (480 nm)	Biologically stable^a

^aThe biological stability of dyeing effluent was estimated based on changes in their appearance (changes in UV-VIS spectrum, precipitation of sediments) and their digestion during the storage period of 28 days (at 20°C under anaerobic conditions).
^bOnly in trace amounts.
^cEffluents were digested during short-time storage (about few hours) but their absorbance at 𝜆 510 nm did not undergo significant changes.
^dAbsorption band without any clear maximum.