Metal-activated bisulfite
systems have been widely used to treat recalcitrant wastewater. However,
due to the disadvantages of their narrow effective pH range and difficulty
in recovering metal ions, homogeneous systems are severely limited
in practical applications. To overcome these problems, Fe/Mn bimetallic
catalysts with different molar ratios were prepared using a simple
sol–gel method to activate bisulfite. Influential factors,
such as catalyst and system types, catalyst dosage, bisulfite concentration,
pH value, and bisulfite addition modes, were investigated. The new
system exhibited a wide effective pH range and high degradation efficiency,
and it was found that the dissolved oxygen content played an important
role in the activation system. The radical quenching test showed that
a superoxide radical (O
2
•–
), instead of a hydroxyl radical (HO
•
) or a sulfate radical (SO
4
•–
), was the main oxide species
for the degradation of rhodamine B (RhB).