Effects of experimental parameters on Hg⁰ removal over magnetic AgI-BiOI/CoFe₂O₄ photocatalysts using wet process

A novel magnetic AgI-BiOI/CoFe₂O₄ hybrid composites were prepared via a solvothermal and subsequent coprecipitation method, and utilized to remove Hg⁰ from coal-fired flue gas under fluorescent light irradiation. The experimental parameters and main products presented in solution after reaction were investigated in detail. The experimental results showed that the AgI-BiOI/CoFe₂O₄ composites showing a poor thermal stability would transform into other compounds when the calcinated temperature was above 400℃. With the increases of photocatalyst dosage, reaction solution pH, temperature of reaction solution in reactor and O₂ concentration, the Hg⁰ removal efficiencies were first increased and then unchanged or decreased. The presences of inorganic anions such as CO₃^2- and SO₄^2- in solution exhibited some inhibitory effects on Hg⁰ removal. Furthermore, the presence of SO₂ had a dramatic inhibition on Hg⁰ removal, while the inhibitory effect of NO on Hg⁰ removal was relatively small. SO₄^2-, NO₃^- and Hg²⁺ species were the final oxidation products of SO₂, NO and Hg⁰ by reactive species.