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Metal smelting processes are important sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The present work aims to clarify the formation characteristics of PCDD/Fs by heterogeneous mechanisms on fly ash from typical multiple secondary aluminum (SAl), secondary lead (SPb) smelting, and iron ore sintering (SNT) sources in China. The formation characteristics of PCDD/Fs on fly ash were studied in the temperature range 250–450 °C for 10–150 min. Substantial thermochemical formation of PCDD/Fs on SAl and SNT ash was observed. The maximum increase of PCDD/F concentrations under 350 °C for 30 min was 604 times greater than the initial concentration in SAl ash. The concentration of PCDD/Fs was 77 times greater than that of SNT fly ash under 350 °C for 30 min. However, the maximum increase of PCDD/F concentrations was less than 8 times that in raw SPb ash under 350 °C. Contents of total organic carbon (TOC), Cu, Al, Zn and Cl, which are widely recognized as important elements for promoting PCDD/F formation, were obviously higher in SAl and SNT ash than in SPb ash. This may explain the greater observed formation times of PCDD/Fs on SAl and SNT ash than that on SPb ash. It was found that several congeners tended to form at higher temperatures than those for SAl ash. Activation energy calculation according to the Arrhenius equations could explain the dominant formation of those congeners at much higher temperatures on SAl ash. [ABSTRACT FROM AUTHOR]

Abstract In this study, nitrobenzene (NB) as typical refractory organic pollutants was effectively degraded by a new green approach, which was achieved by the chemical effect of natural organic matters (NOMs) under solar illumination as a potential natural degradation process. 4-hydroxycoumarin (4HC), which is natural compound and can be extracted from many plants, was found as an efficient photosensitizer to promote the photoreduction of NB to 4-aminophenol under the solar illumination. The reaction products were definitely identified by LC-MS/MS and 1H NMR. The response spectrum of 4HC excited state (4H-chromene-2,4-diol radical, S 1) as key intermediate was also obtained by transient absorption spectroscopy (TAS) measurements, which showed that the decay time of S 1 was around 250 ps. Then, the measurements of electron paramagnetic resonance (EPR) confirmed the existence of OH. As a result, the reaction mechanism between 4HC and NB was proposed. In addition, the influence parameters such as light sources, gas surroundings, solvents, pH values were investigated to further reveal the reaction process. Graphical abstract The degradation pathway of refractory nitrobenzene in water through the natural 4-hydroxycoumarin under solar illumination. Image 1 Highlights • A new natural organic matter could be activated as reducing agent under illumination. • 4-hydroxycoumarin as natural compound was found to be an efficient photosensitizer. • The refractory nitrobenzene was degraded to 4-aminophenol by 4HC as green process. • 4HC excited state (4H-chromene-2,4-diol radical) as key intermediate was confirmed. • Reaction pathway between 4HC and NB was completely proposed by product analysis. [ABSTRACT FROM AUTHOR]

A novel CuO-CeO 2 -Co 3 O 4 nanocatalyst loaded on Al 2 O 3 ceramic composite membrane (CCM-S) was synthesized through spraying-calcination method, which can be beneficial to the engineering application of scattered granular catalyst. BET and FESEM-EDX testing revealed that CCM-S possessed a porous character with high BET surface area of 22.4 m 2 /g and flat modified surface with extremely fine particle aggregation. The CCM-S calcined above 500 °C presented excellent anti-dissolution effect due to the formation of crystals. XPS indicated that the composite nanocatalyst possessed the variable valence states, which were conducive to exert the catalytic effect of Fenton-like reaction. Subsequently, the effects of experimental parameters including fabricate method, calcination temperature, H 2 O 2 dosage, initial pH value, and CCM-S amount were further investigated considering the removal efficiency of Ni(II)-complex and COD after decomplexation and precipitation (pH = 10.5) treatment within 90 min. Under the optimal reaction condition, the residual Ni(II)-complex and Cu(II)-complex concentration from actual wastewater was all lower than 0.18 mg/L and 0.27 mg/L, respectively; meanwhile, the removal efficiency of COD was all higher than 50% in the mixed electroless plating effluent. Besides, the CCM-S could still maintain high catalytic activity after a six-cycle test, and the removal efficiency was slightly declined from 99.82% to 88.11%. These outcomes indicated that CCM-S/H 2 O 2 system was provided with a potential applicability on treatment of real chelated metal wastewater., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)