Metal–organic frameworks (MOFs) and MOF‐derived materials have recently attracted considerable interest as alternatives to noble‐metal electrocatalysts. Herein, the rational design and synthesis of a ...new class of Co@N‐C materials (C‐MOF‐C2‐T) from a pair of enantiotopic chiral 3D MOFs by pyrolysis at temperature T is reported. The newly developed C‐MOF‐C2‐900 with a unique 3D hierarchical rodlike structure, consisting of homogeneously distributed cobalt nanoparticles encapsulated by partially graphitized N‐doped carbon rings along the rod length, exhibits higher electrocatalytic activities for oxygen reduction and oxygen evolution reactions (ORR and OER) than that of commercial Pt/C and RuO2, respectively. Primary Zn–air batteries based on C‐MOF‐900 for the oxygen reduction reaction (ORR) operated at a discharge potential of 1.30 V with a specific capacity of 741 mA h gZn–1 under 10 mA cm–2. Rechargeable Zn–air batteries based on C‐MOF‐C2‐900 as an ORR and OER bifunctional catalyst exhibit initial charge and discharge potentials at 1.81 and 1.28 V (2 mA cm–2), along with an excellent cycling stability with no increase in polarization even after 120 h – outperform their counterparts based on noble‐metal‐based air electrodes. The resultant rechargeable Zn–air batteries are used to efficiently power electrochemical water‐splitting systems, demonstrating promising potential as integrated green energy systems for practical applications.
A Co@N‐C material, derived from new chiral metal–organic frameworks, exhibits excellent bifunctional electrocatalytic activities toward both oxygen reduction and oxygen evolution reactions, along with a remarkable performance for primary/rechargeable Zn–air batteries (powering water‐splitting systems), outperforming their counterparts based on Pt/C and Pt/C + RuO2, respectively.
Display omitted
•PM, SO2, CO reduced significantly, NO2 was less clear, and O3 increased significantly.•Excess health risks (ER) based on WHO guideline are two times than those from CAAQS ...guideline.•PM10 rather than PM2.5 contributed the most to ER.•~15%, ~85% and ~95% people in YRD, FWP and JJJ were exposed to polluted air (HAQI > 100) in 2018.•Population-normalized HAQI significantly added the inequality of people exposure to polluted air.
Air pollution events occurred frequently in China, and tremendous efforts were devoted to the reduction of air pollution in recent years. Here, analysis of ambient monitoring data of six criteria air pollutants from 367 Chinese cities during 2015–2018, showed that PM2.5, PM10, SO2 and CO were reduced significantly by 22.1%, 13.5%, 46.4% and 21.5%, respectively, NO2 reduction was less significant (6.3%) while O3 level instead increased over China (13.7%). Spatial distribution, seasonal, monthly and diurnal variations of the air pollutants during 2018, implicated of effective control measures, were discussed in details, especially for the five key densely populated regions of Jing-Jin-Ji (JJJ), Fen Wei Plains (FWP), Yangtze River Delta (YRD), Sichuan Basin (SCB) and Pearl River Delta (PRD). Moreover, excess health risks (ERs) of the six pollutants were estimated for 2018, and such risks was two times higher if the World Health Organization (WHO) air quality guideline rather than Chinese guideline was adopted. PM10 rather than PM2.5 was the dominant contributor to ERs, and the case with both PM2.5 and PM10 exceeding threshold values occupied ~1/3 of total days, yet contributed ~2/3 of total ERs. For 2018, the health-risk based air quality index (HAQI) was further calculated by combining health risks from multiple pollutants, and it was found that high HAQI mostly distributed in North China Plain (NCP). ~15%, ~85% and ~95% people in YRD, FWP and JJJ were exposed to polluted air (HAQI > 100), and population-normalized HAQI further added the inequality, JJJ and a small region of SCB had much higher HAQI (>280). Investigations on HAQI with socioeconomic factors show that total population, population density and built-up area presented an inverted U-shape, suggesting existence of Environmental Kuznets Curve (EKC), while a positive relationship was found between HAQI and share of secondary industry. Multiple regression analysis suggested that built-up area was the most prominent factor to HAQI, followed by the gross domestic product (GDP). The findings here demonstrate in great details the current characteristics of air pollution and its associated health risks in China, therefore providing important implications for effective air pollution control strategies in near future for different regions of China.
An alternative way has been proposed for the PVC-containing medical wastes valorization by co-hydrothermal carbonization (HTC) with lignocellulosic biomass. The organic-Cl in PVC can be converted to ...the inorganic-Cl via hydrolysis, defunctionalization, recondensation, and aromatization in the HTC process. Followed by the washing process with the condensed water, the inorganic-Cl with high water-solubility could be removed from the solid products (i.e. hydrochar). Lignin as a biomass component can significantly improve the dechlorination efficiency of PVC in the HTC process. Here, the dechlorination performance of lignocellulosic components is given as the following order: lignin > cellulose > hemicellulose. In addition, lignin can adjust the particle sizes of solid products by inhibiting the agglomeration in the order of lignin > hemicellulose > cellulose. In the pilot-scale HTC process, the addition of woodchips improves the dechlorination efficiency of hospital wastes (HW). The hydrochar particles with low-chlorine content and higher heating value could be used as a clean coal-alternative fuel.
Display omitted
•An alternative method has been proposed for converting PVC wastes to energy.•Dechlorination efficiency was enhanced by co-HTC with lignocellulosic biomass.•Organic chlorine was transformed into the inorganic chlorine via the HTC process.•The dechlorination performance of lignocellulose was given: lignin > cellulose > hemicellulose.•Lignin can adjust the particle sizes of hydrochars by inhibiting the agglomeration.
Excess mortality (ΔMort) in China due to exposure to ambient fine particulate matter with aerodynamic diameter ≤2.5 μm (PM2.5) was determined using an ensemble prediction of annual average PM2.5 in ...2013 by the community multiscale air quality (CMAQ) model with four emission inventories and observation data fusing. Estimated ΔMort values due to adult ischemic heart disease, cerebrovascular disease, chronic obstructive pulmonary disease, and lung cancer are 0.30, 0.73, 0.14, and 0.13 million in 2013, respectively, leading to a total ΔMort of 1.3 million. Source-oriented CMAQ modeling determined that industrial and residential sources were the two leading sources of ΔMort, contributing to 0.40 (30.5%) and 0.28 (21.7%) million deaths, respectively. Additionally, secondary ammonium ion from agriculture, secondary organic aerosol, and aerosols from power generation were responsible for 0.16, 0.14, and 0.13 million deaths, respectively. A 30% ΔMort reduction in China requires an average of 50% reduction of PM2.5 throughout the country and a reduction by 62%, 50%, and 38% for the Beijing–Tianjin–Hebei, Jiangsu–Zhejiang–Shanghai, and Pearl River Delta regions, respectively. Reducing PM2.5 to the CAAQS grade II standard of 35 μg m–3 would only lead to a small reduction in mortality, and a more stringent standard of <15 μg m–3 would be needed for more remarkable reduction of ΔMort.
Abstract
Severe events of wintertime particulate air pollution in Beijing (winter haze) are associated with high relative humidity (RH) and fast production of particulate sulfate from the oxidation ...of sulfur dioxide (SO
2
) emitted by coal combustion. There has been considerable debate regarding the mechanism for SO
2
oxidation. Here we show evidence from field observations of a haze event that rapid oxidation of SO
2
by nitrogen dioxide (NO
2
) and nitrous acid (HONO) takes place, the latter producing nitrous oxide (N
2
O). Sulfate shifts to larger particle sizes during the event, indicative of fog/cloud processing. Fog and cloud readily form under winter haze conditions, leading to high liquid water contents with high pH (>5.5) from elevated ammonia. Such conditions enable fast aqueous-phase oxidation of SO
2
by NO
2
, producing HONO which can in turn oxidize SO
2
to yield N
2
O.This mechanism could provide an explanation for sulfate formation under some winter haze conditions.
Advanced removal of phosphate by low-cost adsorbents from municipal wastewater or industrial effluents is an effective and economic way to prevent the occurrence of eutrophication. Here, we proposed ...a novel method to immobilize hydrous zirconium oxide nanoparticle within quaternary-aminated wheat straw, and obtained an inexpensive, eco-friendly nanocomposite Ws–N–Zr. The biomass-based Ws–N–Zr exhibited higher preference toward phosphate than commercial anion exchanger IRA-900 when competing sulfate ions coexisted at relatively high levels. Such excellent performance of Ws–N–Zr resulted from its specific hybrid structure, the quaternary ammonium groups bonded on the host favor the preconcentration of phosphate ions inside the wheat straw based on Donnan effect, and the encapsulated HZO nanoparticle exhibits preferable sequestration of phosphate ions through specific interaction, as further demonstrated by FTIR and X-ray photoelectron spectroscopy. Cycle adsorption and regeneration experiments demonstrated that Ws–N–Zr could be employed for repeated use without significant capacity loss, when the binary NaOH–NaCl solution was employed as the regenerant. The influence of solution pH and contact time was also examined. The results suggested that Ws–N–Zr has a great potential in efficient removal of phosphate in contaminated waters.
Sulfate hydrolysis and high-pressure homogenization were combined to reduce the size of microcrystalline cellulose to the nanoscale. The obtained needle-shaped nanocrystals showed a relative uniform ...size with length of 90±50nm and width of 10±4nm. Rheology and phase transition of the nanocrystal colloids were studied. The flowability and modulus of the colloids showed a strong relationship with frequency, temperature, and concentration of the nanocrystals. Nanocrystals self-assembled into a liquid crystal phase in colloids and even in the dried film. Structure and morphology of the ordered liquid crystalline phase were characterized by scanning electron microscope and polarized optical microscope. It was found that cellulose nanocrystals were self-aligned layer by layer, which was responsible for the color of the dried film and also allowed an ordered layered microporous foam from the freeze-dried nanocrystalline colloids.
Secondary organic aerosol (SOA) produced by atmospheric oxidation of primary emitted precursors is a major contributor to fine particulate matter (PM
) air pollution worldwide. Observations during ...winter haze pollution episodes in urban China show that most of this SOA originates from fossil-fuel combustion but the chemical mechanisms involved are unclear. Here we report field observations in a Beijing winter haze event that reveal fast aqueous-phase conversion of fossil-fuel primary organic aerosol (POA) to SOA at high relative humidity. Analyses of aerosol mass spectra and elemental ratios indicate that ring-breaking oxidation of POA aromatic species, leading to functionalization as carbonyls and carboxylic acids, may serve as the dominant mechanism for this SOA formation. A POA origin for SOA could explain why SOA has been decreasing over the 2013-2018 period in response to POA emission controls even as emissions of volatile organic compounds (VOCs) have remained flat.
•A novel BiOCl/BiOCOOH heterojunction photocatalyst was prepared for the first time.•The composites exhibited significantly enhanced activity for RhB degradation.•The heterojunctions promote the ...photo-generated carriers separation and transmission.
A simple solvothermal method was reported to prepare a novel BiOCl/BiOCOOH heterojunction photocatalyst. The as prepared composite photocatalysts exhibited significantly enhanced photocatalytic activity for RhB degradation under simulated sunlight. The composite photocatalysts even exhibited much higher activity than that of P25. The effect of the BiOCl amount on the activity of the composites was also investigated. Results showed that apparent rate constant of the optimal sample was 3, 7.7 and 35.9 times as high as that of P25, BiOCl and BiOCOOH, respectively. The composites would be promising material for the removal of contaminants in water.
With outbreak of the novel coronavirus disease (COVID-19), immediate prevention and control actions were imposed in China. Here, we conducted a timely investigation on the changes of air quality, ...associated health burden and economic loss during the COVID-19 pandemic (January 1 to May 2, 2020). We found an overall improvement of air quality by analyzing data from 31 provincial cities, due to varying degrees of NO2, PM2.5, PM10 and CO reductions outweighing the significant O3 increase. Such improvement corresponds to a total avoided premature mortality of 9410 (7273–11,144) in the 31 cities by comparing the health burdens between 2019 and 2020. NO2 reduction was the largest contributor (55%) to this health benefit, far exceeding PM2.5 (10.9%) and PM10 (23.9%). O3 instead was the only negative factor among six pollutants. The period with the largest daily avoided deaths was rather not the period with strict lockdown but that during February 25 to March 31, due to largest reduction of NO2 and smallest increase of O3. Southwest, Central and East China were regions with relatively high daily avoided deaths, while for some cities in Northeast China, the air pollution was even worse, therefore could cause more deaths than 2019. Correspondingly, the avoided health economic loss attributable to air quality improvement was 19.4 (15.0–23.0) billion. Its distribution was generally similar to results of health burden, except that due to regional differences in willingness to pay to reduce risks of premature deaths, East China became the region with largest daily avoided economic loss. Our results here quantitatively assess the effects of short-term control measures on changes of air quality as well as its associated health and economic burden, and such information is beneficial to future air pollution control.
Display omitted
•Overall air quality improvement during COVID-19 pandemic was observed in China.•Avoided premature deaths were 9410 (7273–11,144) in 31 provincial capitals.•Avoided economic loss was 19.4 (15.0–23.0) billion RMB in 31 provincial capitals.•NO2 reduction was the largest contributor, much higher than those of PM2.5 and PM10•Northeast China had serious air pollution-related deaths even during strict lockdown period.
PDF
