Photodegradation of Malachite Green Catalyzed by Aqueous Iron(III)-Citrate Complex: Roles of Iron(II) and Hydrogen Peroxide

In this paper, photodegradation experiments of toxic dye malachite green (MG) by Fe(III), citric acid and their complexes were carried out, and the effects of citrate concentration, Fe(III) concentration, solution pH, and initial dye concentration on MG photodegradation were explored. It was found that the maximum removal efficiency of 95.9% could be achieved after 2 h for MG solution of 20 mg/L containing both 0.1 mM Fe(III) and 1 mM citrate. The MG photodegradation process fitted well with pseudo-first-order kinetics, and the observed pseudo-first-order reaction rate constant (k) was proportional to citrate concentrations. The photochemically formed Fe(II) and H2O2 showed good correlation with MG photodegradation rate by Fe(III)-citrate complex. The presence of citrate enhanced the photoformation of Fe(II) and H2O2, and the continuous production of hydroxyl radical (center dot OH) played an important role in MG photodegradation.