Decolorisation of Remazol vinyl sulphone reactive dyes by potassium permanganate

Abstract

Three Remazol vinyl sulphone-based reactive dyes were selected to investigate their decolorisation by potassium permanganate, in relation to pH, concentration of potassium permanganate and time. The amount of colour removal was measured by ultraviolet–visual spectrometry and it was found that potassium permanganate only partially degraded the dye solution; this was also proved by the percent removal of chemical oxygen demand and total organic carbon. Decolorisation was observed to increase when the pH of the dye solution was decreased. Up to a pH level of 5, the decolorisation efficiency is very much slower, but as the pH level shifts towards 2 the rate of decolorisation becomes relatively faster, while a further decrease in pH results in a rapid change in decolorisation. The concentration of potassium permanganate also showed significant effects on the decolorisation. Rapid decolorisation was observed within 10 min for all three dyes, but after that time the decolorisation became slower.