Electrocatalytic hydrodechlorination on Pd, utilizing the H + of H 2 O as hydrogen sources, represents a promising technology to detoxify the chlorinated organic pollutants (COPs) in water bodies. However, Pd alone affords limited activity due to its low efficacy in H 2 O disassociation and the poor mass diffusion of COPs that are commonly of low concentrations in the environment. Herein, we demonstrate that arming Pd with OH − vacancy-bearing NiAl-layered double hydroxide nanosheets (Pd/ Ni x Al 100−x -LDH-OH v ) can significantly improve its performance, benefiting from the enhanced H 2 O disassociation at OH v and the facilitated C−Cl cleavage on the supported Pd nanoparticles. Al 3+ is also indispensable because it promotes the formation and regeneration of OH v , but an overload will reduce the number of accessible OH v and weaken its function. Pd/Ni 67 Al 33 -LDH-OH v with the optimal Ni/Al ratio delivers a peak specific activity of 0.53 min −1 m −2 and mass activity of 6.54 min −1 g −1 Pd in treating 50.0 mg L −1 2,4-dichlorophenol (2,4-DCP, a probe COP) at −0.25 V versus RHE, outperforming most of the reported catalysts. To address the mass diffusion issue, Pd/Ni 67 Al 33 -LDH-OH v is integrated into a customized continuous-flow membrane cell. When fed a dilute wastewater (20.4 mg L −1 ), the system affords a 2,4-DCP removal rate of 3.75 g 2,4-DCP g catalyst −1 h −1 and faradaic current efficiency of 42.6%, which is 3.2 and 4.0 times that obtained in a traditional batch reaction system, respectively.
In order to study the temporal and spatial distribution characteristics of atmospheric pollutants in cities (districts and counties) in the Chengdu–Chongqing Twin-city Economic Circle (CCEC) and to provide a theoretical basis for atmospheric pollution prevention and control, this paper combined Ambient Air Quality Standards (AAQS) and WHO Global Air Quality Guidelines (GAQG) to evaluate atmospheric pollution and used spatial correlation to determine key pollution areas. The results showed that the distribution of atmospheric pollutants in CCEC presents a certain law, which was consistent with the air pollution transmission channels. Except for particulate matter with an aerodynamic diameter equal to or less than 2.5 μm (PM2.5) and ozone (O3), other pollutants reached Grade II of AAQS in 2020, among which particulate matter with an aerodynamic diameter equal to or less than 10 μm (PM10), PM2.5, sulfur dioxide (SO2), nitrogen dioxide (NO2) and carbon monoxide (CO) have improved. Compared with the air quality guidelines given in the GAQG, PM10, PM2.5, NO2 and O3 have certain effects on human health. The spatial aggregation of PM10 and PM2.5 decreased year by year, while the spatial aggregation of O3 increased with the change in time, and the distribution of NO2 pollution had no obvious aggregation. Comprehensive analysis showed that the pollution problems of particulate matter, NO2 and O3 in CCEC need to be further controlled.
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