Gas-phase catalytic hydration of I_(2)O_(5) in the polluted coastal regions:Reaction mechanisms and atmospheric implications

Marine aerosols play an important role in the global aerosol system.In polluted coastal regions,ultra-fine particles have been recognized to be related to iodine-containing species and is more serious due to the impact of atmospheric pollutants.Many previous studies have identified iodine pentoxide(I_(2)O_(5),IP)to be the key species in new particles formation(NPF)in marine regions,but the role of IP in the polluted coastal atmosphere is far to be fully understood.Considering the high humidity and concentrations of pollutants in the polluted coastal regions,the gas-phase hydration of IP catalyzed by sulfuric acid(SA),nitric acid(NA),dimethylamine(DMA),and ammonia(A)have been investigated at DLPNO-CCSD(T)//ωB97 XD/aug-cc-pVTZ+aug-cc-pVTZ-PP with ECP28 MDF(for iodine)level of theory.The results show that the hydration of IP involves a significant energy barrier of 22.33 kcal/mol,while the pollutants SA,NA,DMA,and A all could catalyze the hydration of IP.Especially,with SA and DMA as catalysts,the hydration reactions of IP present extremely low barriers and high rate constants.It is suggested that IP is unstable under the catalysis of SA and DMA to generate iodic acid,which is the key component in NPF in marine regions.Thus,the catalytic hydration of IP is very likely to trigger the formation of iodine-containing particles.Our research provides a clear picture of the catalytic hydration of IP as well as theoretical guidance for NPF in the polluted coastal atmosphere.

Preparation and photocatalytic kinetics of nano-ZnO powders by precipitation stripping process

Ultra-fine zinc oxalate powders were prepared through a precipitation stripping method with bis(2-ethylhexyl)phosphate(HDEHP)diluted by tetrachloride carbon as the extractant,and oxalic acid ethanol aqueous solution as the re-extractant and precipitator.Zinc oxide powders were obtained by decomposing zinc oxalate powders at 450℃.The prepared zinc oxide powders were characterized by transmission electron microscope(TEM),Scanning electron microscope(SEM),Thermogravimetric analysis(TG),X-ray diffraction(XRD)and Fourier transmission infrared(FT-IR)spectrum.The photocatalytic performance of methylene blue by zinc oxide was studied based on the Langmuir model and Photo-Layer model.The results show that some zinc oxide powders were micro-multipore materials with hexagonal crystal.The particle size was around 32 nm.The photocatalytic process was the control step in the chemical reaction.The photo catalytic process followed pseudo-first order kinetics and NOH concentration inside the photo-layer in different reaction condition were calculated according to the Photo-Layer model.