Development of efficient and economic Bi2O3/BN/Co3O4 composite photocatalyst: Degradation mechanism, pathway and toxicity study of norfloxacin.

The production of cheap, efficient, and stable photocatalysts for degrading antibiotic contaminants remains challenging. Herein, Bi2O3/boron nitride (BN)/Co3O4 ternary composites were synthesized using the impregnation method. The morphological characteristics, structural features, and photochemical properties of the prepared photocatalysts were investigated via X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and ultraviolet-visible (Vis) diffuse reflectance spectrum techniques. BN was used as a charge transfer bridge in the ternary composites, which afforded a heterojunction between the two semiconductors. The formation of the heterojunction substantially enhanced the charge separation and improved the photocatalyst performance. The degradation activity of the Bi2O3/BN/Co3O4 ternary composites against norfloxacin (NOR) under Vis light irradiation was investigated. The degradation rate of NOR using 5-wt% Bi2O3/BN/Co3O4 reached 98% in 180 min, indicating excellent photocatalytic performance. The ternary composites also exhibited high photostability with a degradation efficiency of 88.4% after five cycles. Hydroxyl radicals (•OH), superoxide radicals (•O2-), and holes (h+) played a synergistic role in the photocatalytic reaction, where h+ and •O2- were more important than •OH. Consequently, seven intermediates and major photocatalytic degradation pathways were identified. Toxicity experiments showed that the toxicity of the degradation solution to Chlorella pyrenoidosa decreased. Finally, the ecotoxicity of NOR and its intermediates were analyzed using the Toxicity Estimation Software Tool, with most intermediates exhibiting low toxicity.

Investigation on Distribution and Risk Assessment of Volatile Organic Compounds in Surface Water, Sediment, and Soil in a Chemical Industrial Park and Adjacent Area.

The occurrences, distributions, and risks of 55 target volatile organic compounds (VOCs) in water, sediment, sludge, and soil samples taken from a chemical industrial park and the adjacent area were investigated in this study. The Σ55-VOCs concentrations in the water, sediment, sludge, and soil samples were 1.22-5449.21 µg L-1, ND-52.20 ng g-1, 21.53 ng g-1, and ND-11.58 ng g-1, respectively. The main products in this park are medicines, pesticides, and novel materials. As for the species of VOCs, aromatic hydrocarbons were the dominant VOCs in the soil samples, whereas halogenated aliphatic hydrocarbons were the dominant VOCs in the water samples. The VOCs concentrations in water samples collected at different locations varied by 1-3 orders of magnitude, and the average concentration in river water inside the park was obviously higher than that in river water outside the park. However, the risk quotients for most of the VOCs indicated a low risk to the relevant, sensitive aquatic organisms in the river water. The average VOCs concentration in soil from the park was slightly higher than that from the adjacent area. This result showed that the chemical industrial park had a limited impact on the surrounding soil, while the use of pesticides, incomplete combustion of coal and biomass, and automobile exhaust emissions are all potential sources of the VOCs in the environmental soil. The results of this study could be used to evaluate the effects of VOCs emitted from chemical production and transportation in the park on the surrounding environment.

[Distribution, Sources, and Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Tributary Waters of the Lower Reaches of the Yangtze River, China].

The lower reaches of the Yangtze River are a typical gathering place of chemical industrial parks in China. Polycyclic aromatic hydrocarbons (PAHs) emitted in the production process of chemical enterprises enter the tributary water body through atmospheric deposition and surface runoff, and finally merge into the Yangtze River. In this study, the distribution characteristics, source analysis, and ecological risk assessment of PAHs in a series of typical water samples collected in the tributary waters of the Yangtze River were studied. PAH monomers in the samples were mainly low-ring. The total concentration of PAHs was in the range of 37.27 to 285.88 ng·L-1 with a mean value of 78.31 ng·L-1, while the monomer concentration of PAHs ranged from 0 to 61.35 ng·L-1. The lowest detection rate was benzo[k] fluoranthene and benzo[a] pyrene at 75%. As a toxic PAH monomer, the concentration of benzo[a] pyrene ranged from 0 to 11.08 ng·L-1. According to "Water Quality Standards for Drinking Water Sources (CJ 3020-1993)" of China, the concentration of benzo[a] pyrene in a water sample (S12) located near Wuxi City exceeded the limit of drinking water standards (10 ng·L-1). Compared with the total concentration of PAHs in rivers in some typical regions of the world, the concentration of PAHs in this study was generally at low to moderate levels. According to the source analysis results of the ratio method and principal component analysis, the concentration of PAHs in water was mainly affected by fossil combustion, automobile exhaust, and chemical emissions. To assess the potential ecosystem risk of PAHs in the investigated area, the risk quotient (RQ) was used. In addition to the DBA monomer, the relative quantities (RQs) (replication) of the remaining monomers were greater than 1, and the RQ (MPCs) values in all the monomers were less than 1, indicating that the ecological risk of water samples was at a medium level. From the perspective of long-term environmental exposure, appropriate control measures should be considered to prevent further pollution. The results can provide reference for PAH risk assessment and pollution control of chemical industrial parks in the lower reaches of the Yangtze River.