High-Efficiency Simultaneous Oxidation of Organoarsenic and Immobilization of Arsenic in Fenton Enhanced Plasma System

Roxarsone (ROX), an organoarsenic compound serving as a common feeding additive, is heavily utilized in the agricultural field and brings about the potential risks of toxic inorganic arsenic contamination in the ambient environment. In this study, the applicability of glow discharge plasma (GDP) for simultaneous oxidation of organoarsenic and immobilization of arsenic is unprecedentedly evaluated. The results show that ROX can be effectively oxidized to inorganic arsenic, and this performance is evidently dependent on energy input. Adding Fe­(II) can significantly enhance the oxidation of ROX mainly because of the additional production of ^•OH via Fenton reaction in GDP, accompanied by which the generated arsenic can be simultaneously immobilized in one process. The immobilization of arsenic can be favorably obtained at pH 4.0–6.0 and Fe­(II) concentration ranging from 500 to 1000 μM. On the basis of the mineral compositions and analysis (XRD/FTIR/XPS) of precipitate, a mechanism can be proposed that the oxidation of Fe­(II) by H₂O₂ generated in situ in GDP significantly accelerates ROX transformation to the ionic As­(V), which can immediately precipitate with Fe­(III) ions or be adsorbed on the ferric oxyhydroxides, forming amorphous ferric arsenate-bearing ferric oxyhydroxides. As such, the present study offer a new recipe for rapid decontamination of organoarsenic pollutants, in which the hypertoxic species can be effectively removed from the wastewater

Synergetic Transformations of Multiple Pollutants Driven by Cr(VI)–Sulfite Reactions

Reduction of Cr­(VI) is often deemed necessary to detoxify chromium contaminants; however, few investigations utilized this reaction for the purpose of treating other industrial wastewaters. Here a widely used Cr­(VI)–sulfite reaction system was upgraded to simultaneously transform multiple pollutants, namely, the reduction of Cr­(VI) and oxidation of sulfite and other organic/inorganic pollutants in an acidic solution. As­(III) was selected as a probe pollutant to examine the oxidation capacity of a Cr­(VI)–sulfite system. Both ^•OH and SO₄^•– were considered as the primary oxidants for As­(III) oxidation, based on the results of electron spin resonance, fluorescence spectroscopy, and specific radicals quenching. As­(III)-scavenging, oxidative radicals greatly accelerated Cr­(VI) reduction and simultaneously consumed less sulfite. In comparison with a Cr­(VI)–H₂O₂ system with 50 μM Cr­(VI), Cr­(VI), the sulfite system had excellent performance for both As­(III) oxidation and Cr­(VI) reduction at pH 3.5. Moreover, in this escalated process, less sulfite was required to reduce Cr­(VI) than the traditional Cr­(VI) reduction by sulfite process. This effectively improves the environmental compatibility of this Cr­(VI) detoxification process, alleviating the potential for SO₂ release and sulfate ion production in water. Generally, this study provides an excellent example of a “waste control by waste” strategy for the detoxification of multiple industrial pollutants

Monodispersed Hollow SO₃H‑Functionalized Carbon/Silica as Efficient Solid Acid Catalyst for Esterification of Oleic Acid

SO₃H-functionalized monodispersed hollow carbon/silica spheres (HS/C-SO₃H) with primary mesopores were prepared with polystyrene as a template and <i>p</i>-toluenesulfonic acid (TsOH) as a carbon precursor and −SO₃H source simultaneously. The physical and chemical properties of HS/C-SO₃H were characterized by N₂ adsorption, TEM, SEM, XPS, XRD, Raman spectrum, NH₃-TPD, element analysis and acid–base titration techniques. As a solid acid catalyst, HS/C-SO₃H shows excellent performance in the esterification of oleic acid with methanol, which is a crucial reaction in biodiesel production. The well-defined hollow architecture and enhanced active sites accessibility of HS/C-SO₃H guarantee the highest catalytic performance compared with the catalysts prepared by activation of TsOH deposited on the ordered mesoporous silicas SBA-15 and MCM-41. At the optimized conditions, high conversion (96.9%) was achieved and no distinct activity drop was observed after 5 recycles. This synthesis strategy will provide a highly effective solid acid catalyst for green chemical processes

Remedying Defects in Carbon Nitride To Improve both Photooxidation and H₂ Generation Efficiencies

The outstanding visible light response of carbon nitride has aroused intense expectations regarding its photocatalysis, but it is impeded by the inevitable defects. Here, we report on a facile melamine-based defect-remedying strategy and resultant carbon nitride high-performance photocatalysts (R-C₃N₄). Melamine with amino groups and a triazine structure was selected as a “little patch” to passivate and remedy various defects inside carbon nitride. Such a remedying effect has been comprehensively proven by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) analyses, and the ninhydrin test. In addition, their effects on photocatalysis were also individually confirmed by chemical methods, including cyano reduction reactions and deamination reactions. Furthermore, melamine remediation can result in g-C₃N₄/mpg-C₃N₄ junctions, which also favors electron transfer and charge separation during the photocatalytic reaction. In order to explore its broader applications, R-C₃N₄ was used as a photocatalyst for the photooxidation reaction of 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate (1,4-DHP) and simultaneous H₂ evolution. The conversion rates of 1,4-DHP and H₂ production catalyzed by R-C₃N₄ were enhanced 2 and 6.5 times, respectively. This rational design is beneficial for the conversion of 1,4-DHP during the preparation of bioactive compounds and clean hydrogen production at the same time