Degradation of azo dyes using low iron concentration of Fenton and Fenton-like system

Optimization of Fenton-biological treatment scheme for the treatment of aqueous dye solutions

“…It was also observed during the study that at pH lower than pH 3, the degradation efficiency decreases; it may be due to scavenging of hydroxyl radical with H + ions as also reported by Neyens and Baeyens [48]. The observed maximum decolorization at pH 3 is in agreement with previous studies [1,29,42,43,49].…”

“…During the optimization studies, it was found that the decolorization increases with increase in H 2 O 2 concentration up to a critical concentration of 100 mg L −1 (2.94 mM) for all three dyes. Further as H 2 O 2 concentrations were increased, a decrease in decolorization of dyes were observed, which may be due to the hydroxyl radical scavenging effect of H 2 O 2 according to equation (1)-(3) [1,3]. According to Hsueh et al [1] degradation rate of organic compounds increases as the H 2 O 2 concentration increases until a critical H 2 O 2 concentration is achieved.…”

“…Further as H 2 O 2 concentrations were increased, a decrease in decolorization of dyes were observed, which may be due to the hydroxyl radical scavenging effect of H 2 O 2 according to equation (1)-(3) [1,3]. According to Hsueh et al [1] degradation rate of organic compounds increases as the H 2 O 2 concentration increases until a critical H 2 O 2 concentration is achieved. However, when a concentration higher than the critical concentration is used, the degradation of organic compounds was decreased as a result of the so-called scavenging effect.…”

“…Many researchers [1,29,42,43,49] have shown that complete color removal is possible at pH 3. During the dose optimization studies the dyes concentration were kept constant at 50 mg L −1 and the pH of the dye solutions (pH 3) and Fe 2+ dose of 20 mg L −1 (0.36 mM) were kept constant.…”

“…Wastewater from textile industry is the major source of color and aromatic amines into the environment [1]. The color from textile industries is mainly due to dyeing process.…”