ACS ES&T engineering最新文献

Novel alkali metal-doped graphite carbon nitride (CN) catalysts (CN–M, where M = K, Na, or Li) with triune active sites (alkali metal atoms, cyano groups, and N vacancies) prepared by one-step pyrolysis to enhance the catalytic ozonation performance of pristine CN. The structural analysis of CN–M and the significant enhancement adsorption of ozone performance are demonstrated by density functional theory calculations and experiment tests. The insertion of alkali atoms can shorten the distance between the layers, forming an electronic bridge and accelerating the transfer of electrons. Cyano groups serve as strong electron-withdrawing groups that effectively modulate the electronic structure of the CN surface. N vacancies ulteriorly optimize the charge distribution on the surface of the material and promote ozone adsorption. The prepared CN–Na, CN–K, and CN–Li catalysts exhibit excellent atrazine (ATZ) degradation efficiencies of 99.6%, 97.0%, and 94.0%, respectively, that greatly exceed that of CN (62.8%) and single ozone oxidation (54.8%). The toxicity results of the ATZ intermediates show a significant toxicity reduction in ATZ after the heterogeneous catalytic ozonation process. This study provides insights into the synergistic interactions of alkali metal atoms, cyano groups, and N vacancies, which will help to guide and design triune active site CN-based catalysts for enhanced ozone activation.

There is an urgent need to develop effective methods for converting nitrous oxide (N₂O) into nonharmful N₂ because N₂O is a potent greenhouse gas, and its increasing concentration in the atmosphere is a major concern for global warming. In this study, we developed a two-step N₂O capture and reduction system, employing CaO-incorporated zeolites (Ca-zeolites) as N₂O adsorbents and Pd nanoparticles on La-containing Al₂O₃ (Pd/La/Al₂O₃) as catalysts for N₂O reduction. This process is suitable for continuous operation over a temperature swing of 50–150 °C. The N₂O capture capacity and subsequent reduction ability were preserved for at least 15 h (10 cycles). Notably, this system can operate at low temperatures (below 150 °C) using a simple temperature-swing process in the presence of O₂.

Producing volatile fatty acids (VFAs) in anaerobic digestion (AD) is of strong interest because of VFAs’ potential values in biomanufacturing. Despite some success of VFA production via pretreatment, in situ inhibition of methanogens for VFA accumulation has yet to be explored. Herein, a system consisting of hydrogen peroxide (H₂O₂) production, application of H₂O₂ for inhibiting methanogens in AD, and VFA separation was investigated. A polytetrafluoroethylene-based electrospinning electrode was synthesized and capable of generating ∼4.2 g L^–1 H₂O₂. When the generated H₂O₂ was applied to the AD, methanogens were inhibited, and VFA accumulation occurred. With the addition of 80 mg L^–1 H₂O₂, an average VFA concentration of 10.6 g COD L^–1 was obtained. The long-term H₂O₂ inhibition effect on methanogenesis was examined for nearly 100 days. A 2.3- to 3.3-fold increase in malondialdehyde levels, which indicated increased cell damage, along with a significant decrease in methane production and an increase in VFA concentration, might suggest that H₂O₂ could potentially inhibit methanogens while allowing acidogenic bacteria to remain functional. The accumulated VFAs were separated and then recovered using an electrodialysis unit, with a maximum VFA concentration of 26.7 g COD L^–1. The results of this study will encourage further exploration of the proposed system for VFA production by addressing several challenges, including a better understanding of the inhibition mechanism and a further increase in VFA yields.