Decolourisation and detoxifying of Remazol Red dye and its mixture using Fenton's reagent

A systematic approach was followed to optimise pH, temperature and the doses of FeSO₄ and H₂O₂ for Feton's reagent (FR) to decolourize and detoxify the solutions containing of Remazol Red 120 (RR) dye and its mixture with Remazol Brillant Blue (RB) and Remazol Yellow 84 (RY) reactive dyes. The acute toxicity of each dye composition was measured using D. magna. Optimum pH for RR singly used and for the dye mixture was found 3.5 while optimum temperature was determined 50°C, 40°C and 30°C for 100 mg/l of RR, 200 mg/l of RR and the dye mixture, respectively. More than 98% of colour and 92% of COD removal were obtained for the dye solutions. For obtaining high colour and COD removal H₂O₂ concentration had to be increased 3 times when RR concentration was doubled whereas FeSO₄ was to be increased 2.5 times for the dye mixture. The results obtained indicate that FR can be assurely used for complete toxicity removal and obtaining high colour and COD efficiency with no toxic effluent on D. magna for the dye solutions studied. Acute toxicity test with H₂O₂ was useful to evaluate the complete oxidation resulting in practically no residual H₂O₂ (<3 mg/l) in the solution.