Degradation Of Methylene Blue In Water By Combined Sonolysis And Fentons Reaction

摘要

The degradation of methylene blue, a cationic dye, upon exposure to ultrasound at 24 kHz using a direct immersion ultrasonic probe was investigated. The rate of decolorization for a 5 mg/L aqueous dye solution at 20C and 200W/L power density followed pseudo first-order kinetics with a rate constant of 0.014 min~(-1). This was increased by a factor of 3.4 when small amounts of ferrous ion (Fe(II), 1 mg/L) were added. At an initial dye concentration of 50 mg/L, 92% decolorization and 60% chemical oxygen demand (COD) reduction was achieved after 360 min sonication. The rate enhancement was attributed to the reaction of Fe(ll) with sonochemically-generated hydrogen peroxide (H_2O_2) via the classical Fenton's reaction, thereby degrading nonvolatile toxic compounds such as methylene blue.