Bromate removal driven by far-UVC activated formate: Performance and mechanisms

With the expansion of marine aquaculture, the use of various oxidative processes in seawater systems rich in bromide ions has led to the production of bromate as a harmful byproduct. This study investigated the UV 222 /HCOO − for efficient bromate removal in marine aquaculture water. The UV 222 /HCOO − demonstrated 81 % bromate removal at a UV dose of 3180 mJ cm −2 , significantly outperforming UV 254 /HCOO − . This is attributed to the higher molar absorption coefficients of bromate (ε 222 = 395 M −1 cm −1 ) and HCOO − (ε 222 = 14 M −1 cm −1 ) at 222 nm compared to 254 nm. Carbon dioxide radical (CO 2 • − ) was the primary reactive species in bromate reduction, with hydroxyl radical ( • OH) also contributing to the process. Density functional theory (DFT) was used to verify the reduction mechanism of bromate, and the deduction of transition states and electron transfer processes confirmed the rationality of the mechanism. Optimal bromate reduction efficiency was achieved with an initial HCOO − concentration of 0.1 mM. The reaction rate is inversely proportional to the pH value. Perhaps the distribution of HCOO − forms has altered the reduction reaction rate. Bicarbonate, nitrate, and nitrite anions inhibit the reaction, unlike chloride and sulfate. Dissolved oxygen has no significant effect and better than traditional methods. In practical applications, UV 222 /HCOO − highlights efficient reduction, while in actual water systems rich in TOC and inorganic anions, UV 222 /C 2 O 4 2− exhibits stable performance, which may become an alternative solution to UV 222 /HCOO −