Preparation of the g-C<sub>3</sub>N<sub>4</sub>/BiOI fluorescent film for integrated oxidation and enrichment based detection of elemental mercury

<p indent="0mm">Coal-fired flue gas is one of the major sources for atmospheric mercury emissions. Developing convenient and high-precision methods for volatile and long-range migratory elemental mercury (Hg⁰) detection is essential for air quality improvement. To address the challenges of complex procedures and low accuracy in mercury detection in coal-fired flue gas, a g-C₃N₄/BiOI composite fluorescent film (CN/BiOI) is successfully synthesized via an ultrasonic-assisted method for integrated oxidation and enrichment-based detection of Hg⁰. The CN/BiOI film efficiently suppressed the recombination of photogenerated electron-hole pairs, achieving an oxidation and enrichment efficiency of 98.2% for Hg⁰. Furthermore, fluorescence analysis was combined with machine learning techniques to achieve high-precision detection of Hg⁰ concentrations. Machine learning models were employed to establish the relationship between the fluorescence color of the CN/BiOI film and Hg⁰ concentrations, with both Linear and support vector regression (SVR) models demonstrating excellent fitting accuracy (<italic>R</italic>²&gt;0.9), indicating a strong linear correlation. In summary, the CN/BiOI composite material provides a new strategy for real-time mercury monitoring in flue gas, promoting the pollution control system evaluation efficiency.