An Ultrasound-Fenton Process for the Degradation of 2,4,6-Trinitrotoluene.

2,4,6-Trinitrotoluene (TNT), one of the main compounds in ammunition wastewater, is harmful to the environment. In this study, the treatment efficiency of 2,4,6-TNT by different treatment processes, including ferrous ion (Fe2+), hydrogen peroxide (H2O2), Fenton, ultrasound (US) irradiation, US + Fe2+, US + H2O2 and US-Fenton process, was compared. The results showed that US-Fenton was the most effective among all methods studied. The effects of initial pH, reaction time and H2O2 to Fe2+ molar ratio were investigated. The results showed that the removal of TNT, TOC and COD was maximum at an initial pH of 3.0 and H2O2 to Fe2+ molar ratio of 10:1. TNT, TOC and COD removal was fast in the first 30 min, reaching 83%, 57% and 50%, then increased gradually to 99%, 67% and 87% until 300 min, respectively. Semi-batch mode operation increased the removal of TNT and TOC by approximately 5% and 10% at 60 min, respectively. The average carbon oxidation number (ACON) was increased from -1.7 at 30 min to a steady-state value of 0.4, indicating the mineralization of TNT. Based on GC-MS analysis, 1,3,5-trinitrobenzene, 2,4,6-trinitrobenzene acid, 3,5-dinitrobenznamine and 3,5-dinitro-p-toluidine were the major byproducts from the US-Fenton process. The TNT degradation pathway was proposed, which involved methyl group oxidation, decarboxylation, aromatic ring cleavage and hydrolysis.

Enhanced carriers separation in novel in-plane amorphous carbon/g-C3N4 nanosheets for photocatalytic environment remediation.

Although carbon-based materials/g-C3N4 heterostructure with an up-down structure in space can inhibit the recombination of charge carriers, the electron transfer is still suppressed by the interlayer van der Waals force. Herein, amorphous carbon is successfully introduced into the g-C3N4 nanosheet (CNS) by a self-conversion process to form an in-plane heterostructure of amorphous carbon/g-C3N4 (CNSC1). Kelvin probe atomic force microscopy (KPFM) and density functional theory (DFT) confirm that g-C3N4 and amorphous carbon are in the same plane, which can generate the surface electric field of CNSC1, providing a driving force for the transfer of electrons from g-C3N4 to amorphous carbon. Meanwhile, the sp2-hybridized π conjugation bond of amorphous carbon can rapidly capture and store photogenerated electrons, inhibiting charge carrier recombination and thus generating more electrons to facilitate the yield of hydroxyl radicals. The photocatalytic activity of CNSC1 for the degradation of tetracycline and rhodamine B is 2.7 times and 4.8 times higher than that of CNS, respectively, due to the efficient interface charge separation. This work is expected to provide a new idea for the combination of carbon materials and g-C3N4.

Highly efficient heterostructured stannic disulfide/stannic anhydride hybrids: Synthesis, morphology, and photocatalytic reduction of chromium (VI) under visible light.

Highly efficient heterostructured stannic disulfide/stannic anhydride (SnS2/SnO2) hybrids with different morphologies were fabricated via a two-step hydrothermal method. The composition and morphology of the obtained products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (DRS). The SEM images showed that core-shell structured SnS2/SnO2 nanotubes and hierarchical SnS2 flowers decorated with SnO2 particles were fabricated under different synthetic conditions. The DRS results of the hybrids showed that the absorption edges were gradually redshifted with increasing SnS2 content. In the photocatalytic reduction of chromium (VI) under visible light, the SnS2/SnO2 hybrid prepared with thioacetamide addition of 0.60 g exhibited the best photocatalytic activity, which was approximately 6.8 times higher than that of pure SnS2. This increase in the reduction performance might be ascribed to the strengthened absorption of visible light, the rapid interfacial charge transfer and the promoted charge separation efficiency. Photocurrent- response measurements, electrochemical impedance spectroscopy, and photoluminescence emission tests confirmed the faster charge transfer and efficient charge separation over the heterostructured SnS2/SnO2 hybrids. Lastly, a photocatalytic reduction mechanism for chromium (VI) over SnS2/SnO2 hybrids was proposed.