Fe2(MoO4)3 as a novel heterogeneous catalyst to activate persulfate for Rhodamine B degradation

Iron molybdate (Fe2(MoO4)3) was used as a novel heterogeneous catalyst to activate persulfate () for rhodamine B (RhB) degradation. Results indicated 10 mg/L RhB can be completely removed under the addition of 4 mM and 0.4 g/L Fe2(MoO4)3 within 240 min. Fe2(MoO4)3 can be repeatedly used for six cycles and showed high stability with Fe leaching amounts less than 2.9% in each run. Possible catalytic mechanism was proposed as follows: RhB degradation intermediate products such as hydroxybenzene, quinone compounds and organic compound radicals acted as electron transfer agents to reduce Fe3+ to Fe2+, which reacted with persulfate to form Fe3+ creating the redox cycling of iron, the RhB and those intermediate products are oxidized directly by the molybdenum peroxo complexes which forming probably with and persulfate, and the synergy between Fe3+ and occurring the catalytic effect on the persulfate. Additionally, the major intermediates of RhB were identified according to GC/MS and the possible degradation pathway was proposed.