Zastosowanie odczynnika Fentona modyfikowanego nanożelazem do rozkładu barwników azowych (AR27 i RB5) w roztworach wodnych

Effectiveness of two azo dyes decomposition (Acid Red 27 - AR27 and Reactive Black 5 - RB5) with the Fenton reagent modified with nanoiron (H₂O₂/nFe^o) was studied in aqueous solutions at a concentration of 100 mg/L. For each dye, the most favorable process parameters were determined to obtain visual discoloration of tested solutions (AR27: pH=3, H₂O₂=40 mg/L, nFe^o=60 mg/L, t=15 min; RB5: pH=3, H₂O₂=50 mg/L, nFe^o=20 mg/L, t=15 min). Under these conditions, the decrease in COD values for AR27 and RB5 was 82.6% and 86.5, respectively and in toxicity (Microtox test) - 100% and 92.7%, respectively. For comparative purposes, classic Fenton reagent (H₂O₂/Fe²⁺) was also used for the dye decomposition. For AR27, the visual discoloration of the aqueous solution was obtained within 15 min at pH=3.5, H₂O₂=60 mg/L, [Fe2+]/[H₂O₂]=0.3 and for RB5 - within 15 min at pH=3.5, H₂O₂=40 mg/L, [Fe2+]/[H₂O₂]=0.75. The decrease in COD values for AR27 and RB5 was 71.5% and 71.8%, respectively and in toxicity - 100% and 84.4%, respectively. Both oxidation methods applied, beside visual discoloration of the aqueous solutions, allowed for the COD reduction to the level of 21-49 mgO₂/L. According to the toxicity classification for water samples, all the highly toxic samples of dye solutions tested (toxicity >75%) could be considered non-toxic (toxicity <25%) after the Fenton reagent application.