In this study, the kinetics of photocatalytic removal of imidacloprid, a systemic chloronicotinoid insecticide, from water using two advanced oxidation systems (ZnO(normal)/H 2 O 2 /artificial sunlight and ZnO(nano)/H 2 O 2 /artificial sunlight) were investigated. Moreover, the effects of pH, insecticide concentration, catalyst concentration, catalyst particle size, and water type on the photocatalytic removal of imidacloprid were evaluated. Furthermore, total mineralization of imidacloprid under these advanced oxidation systems was evaluated by monitoring the decreases in dissolved organic carbon (DOC) concentrations and formation rate of inorganic ions (Cl À and NO 2 À ) with irradiation time using total organic carbon (TOC) analysis and ion chromatography to confirm the complete detoxification of imidacloprid in water. The degradation rate of imidacloprid was faster under the ZnO(nano)/H 2 O 2 /artificial sunlight system than the ZnO(normal)/artificial sunlight system in both pure and river water. The photocatalytic degradation of imidacloprid under both advanced oxidation systems was affected by pH, catalyst concentration, imidacloprid concentration, and water type. Almost complete mineralization of imidacloprid was only achieved in the ZnO(nano)/H 2 O 2 /artificial sunlight oxidation system. The photogeneration rate of hydroxyl radicals was higher under the ZnO(nano)/H 2 O 2 /artificial sunlight system than the ZnO(normal)/H 2 O 2 /artificial sunlight system.Advanced oxidation processes, particularly those using nanosized zinc oxide, can be regarded as an effective photocatalytic method for imidacloprid removal from water.

Airborne infectious diseases such as the new Coronavirus 2019 (COVID-19) pose serious threat to human health. Indoor air pollution is a problem of global environmental concern as well. Singlet oxygen ( 1 O 2 ) is a reactive oxygen species that plays important role in bacteria/virus inactivation and pollutant degradation. In this study, we found that commercially available filters typically deployed in air purifier and air conditioning units, when impregnated with Rose Bengal (RB) as a 1 O 2 sensitizer, can be used for heterogeneous gas-phase generation of 1 O 2 . It was confirmed that irradiation of the RB filter under oxygen gas stream produced 1 O 2 , which was measured using furfuryl alcohol trapping method followed by HPLC analysis. It was also observed that the amount of 1 O 2 generated increases as the light intensity increased. Similarly, the sensitizer loading also positively influenced the 1 O 2 generation. The heterogeneous gas-phase generation of 1 O 2 can find potential applications in air purifier and air conditioning units for the purpose of bacteria/virus inactivation and/or pollutant degradation thereby improving indoor air quality.

Chromophoric-dissolved organic matter (CDOM) acts as the precursor to singlet oxygen ( 1 O 2 ) in natural waters, while water acts as the main scavenger. In this study, we showed that 1 O 2 in coastal seawater can be successfully predicted from CDOM parameters. The 1 O 2 steady-state concentration [ 1 O 2 ] ss and photoformation rate (R 1 O 2 ) varied by a factor of 6 across 13 sampling stations in the Seto Inland Sea, Japan, ranging from 1.2 to 8.2 × 10 −14 M and 3.32 to 22.7 × 10 −9 M s −1 , respectively. Investigation of CDOM optical properties revealed that CDOM abundance measured as the absorption coefficient at 300 nm (a 300 ) had the strongest correlation (r = 0.96, p < 0.001) with [ 1 O 2 ] ss , while parameters indicative of CDOM quality (e.g., spectral slope) did not influence [ 1 O 2 ] ss . A linear relationship between [ 1 O 2 ] ss and a 300 , normalized to a sunlight intensity of 0.91 kW/m 2 , was derived as [ 1 O 2 ] ss (10 −14 M) = 2.12(a 300 ) + 0.48. This was then used to predict [ 1 O 2 ] ss using a 300 values from a subsequent, independent sampling exercise conducted 2 years after the first sampling. There was a good agreement (r = 0.93, p < 0.001) between the predicted values and the experimentally determined values based on a 95% prediction interval plot. Kinetic estimations using [ 1 O 2 ] ss suggest that 1 O 2 mediates the degradation of tetrabromobisphenol A in surface seawater (t 1/2 = 0.63 days) while also contributing to the indirect photolysis of methyl mercury. The findings from this study suggest that large-scale modeling of 1 O 2 generation in surface seawater from CDOM parameters is possible with useful environmental significance for determining the fate of pollutants.