The Combination of Amorphous Manganese Oxide and Hollow Fiber with Enhanced Activity and Stable Reusability as Heterogeneous Catalyst for Dye Oxidation

Abstract

Powdered or granular manganese oxide has been used as a catalyst to promote the oxidation of dye in the presence of H2O2. However, the facile separation of manganese oxide from the treated water is still an open question. In order to accomplish a facile recovery, a simple two-step process, hydrolysis and oxidation–reduction, was adopted to immobilize in-situ generated amorphous manganese oxide on polymer fiber in this work. Due to the synergistic effect of manganese oxide and polymer matrix, along with the swelling response of fiber to water stimulus, the obtained catalyst was found to have higher catalytic activity for dye oxidation than single manganese oxide or fiber. When 0.072 g of catalyst and 0.05 mL of H2O2 were added in 10 mL of aqueous solution of cation blue with the concentration of 20 mg/L, the catalyst could be repeatedly used up to 10 cycles without any significant loss in its catalytic activity. The time that was needed for removing 90% of cation blue from its solution was less than 6 min during each cycle, and the removal efficiency of cation blue obtained at 10 min was up to 95%. The catalyst could accelerate the transformation of H2O2 into oxidative species such as HO∙, HOO∙, O2∙− and 1O2 in the presence of H2O, and the strong oxidizability of the oxidative species resulted in the rapid removal of cation blue.