Efficient degradation of orange II by ZnMn2O4 in a novel photo-chemical catalysis system

A ZnMn2O4 catalyst has been synthesized via a sucrose-aided combustion method and characterized by various analytical techniques. It is composed of numerous nanoparticles (15-110 nm) assembled into a porous structure with a specific surface area (SSA) of 19.1 m(2).g(-1). Its catalytic activity has been investigated for the degradation of orange II dye using three different systems, i.e., the photocatalysis system with visible light, the chemocatalysis system with bisulfite, and the photochemical catalysis system with both visible light and bisulfite. The last system exhibits the maximum degradation efficiency of 90%, much higher than the photocatalysis system (15%) and the chemocatalysis system (67%). The recycling experiments indicate that the ZnMn2O4 catalyst has high stability and reusability and is thus a green and eximious catalyst. Furthermore, the potential degradation mechanisms applicable to the three systems are discussed with relevant theoretical analysis and scavenging experiments for radicals. The active species such as Mn(III), O-2(center dot-), h(+), e(aq)(-), SO4 center dot- and HO center dot are proposed to be responsible for the excellent degradation results in the photo-chemical catalysis system with the ZnMn2O4 catalyst.