We synthesized a series of carbon‐supported atomic metal‐N‐C catalysts (M‐SACs: M=Mn, Fe, Co, Ni, Cu) with similar structural and physicochemical properties to uncover their catalytic activity trends ...and mechanisms. The peroxymonosulfate (PMS) catalytic activity trends are Fe‐SAC>Co‐SAC>Mn‐SAC>Ni‐SAC>Cu‐SAC, and Fe‐SAC displays the best single‐site kinetic value (1.65×105 min−1 mol−1) compared to the other metal‐N‐C species. First‐principles calculations indicate that the most reasonable reaction pathway for 1O2 production is PMS→OH*→O*→1O2; M‐SACs that exhibit moderate and near‐average Gibbs free energies in each reaction step have a better catalytic activity, which is the key for the outstanding performance of Fe‐SACs. This study gives the atomic‐scale understanding of fundamental catalytic trends and mechanisms of PMS‐assisted reactive oxygen species production via M‐SACs, thus providing guidance for developing M‐SACs for catalytic organic pollutant degradation.
A series of carbon‐supported atomic metal‐N‐C catalysts with similar structural and physicochemical properties were synthesized to uncover the activity trends and mechanisms in peroxymonosulfate‐assisted reactive oxygen species production. Fe‐SAC displays the best single‐site kinetic value (1.65×105 min−1 mol−1), and the PMS→OH*→O*→1O2 is the most reasonable 1O2 reaction pathway.
H2O2 is a versatile and environmentally friendly chemical involved in water treatment, such as advanced oxidation processes. Anthraquinone oxidation is widely used for large‐scale production of H2O2, ...which requires significant energy input and periodic replacement of the carrier molecule. H2O2 production should be customized considering the specific usage scenario. Electrochemical synthesis of H2O2 can be adopted as alternatives to traditional method, which avoids concentration, transportation, and storage processes. Herein, we identified Bi2WO6:Mo as a low‐cost and high‐selectivity choice from a series of Bi‐based oxides for H2O2 generation via two‐electron water oxidation reaction. It can continuously provide H2O2 for in situ degradation of persistent pollutants in aqueous solution. Clean energy from H2 can also be produced at the cathode. This kind of water splitting producing sustainable resources of H2O2 and H2 is an advance in environmental treatment and energy science.
H2O2 is synthesized by direct electrochemical oxidation of water on the surface of Bi2WO6:Mo anode, which provides a straightforward route to H2O2 for onsite needs such as advanced oxidation processes. Combined with the superior H2 evolution efficiency at the cathode, this electrolytic cell enables sustainable resources produced at both electrodes.
The electro-Fenton (EF) process is regarded as an efficient and promising sewage disposal technique for sustainable water environment protection. However, current developments in EF are largely ...restricted by cathode electrocatalysts. Herein, a supramolecular self-assembly strategy is adopted for synthetization, based on melamine–cyanuric acid (MCA) supramolecular aggregates integrated with carbon fixation using 5-aminosalicylic acid and zinc acetylacetonate hydrate. The prepared carbon materials characterize an ordered lamellar microstructure, high specific surface area (595 m2 g−1), broad mesoporous distribution (4~33 nm) and high N doping (19.62%). Such features result from the intrinsic superiority of hydrogen-bonded MCA supramolecular aggregates via the specific molecular assembly process. Accordingly, noteworthy activity and selectivity of H2O2 production (~190.0 mg L−1 with 2 h) are achieved. Excellent mineralization is declared for optimized carbon material in several organic pollutants, namely, basic fuchsin, chloramphenicol, phenol and several mixed triphenylmethane-type dyestuffs, with total organic carbon removal of 87.5%, 74.8%, 55.7% and 54.2% within 8 h, respectively. This work offers a valuable insight into facilitating the application of supramolecular-derived carbon materials for extensive EF degradation.
Graphitic carbon nitride(C3N4)/carbon nanotubes (CNTs) composite photocatalyst was synthesised by a facile and simple method. The resulting graphitic C3N4/CNTs composite was characterised by X-ray ...powder diffraction, scanning electron microscopy and ultraviolet–visible diffuse reflectance spectroscopy techniques. The results showed that the CNTs modified by polyvinylpyrrolidone could provide a large amount of space and support for the surface area of graphitic C3N4 so that the redox reaction was faster. Therefore, the photocatalytic properties of graphitic C3N4/CNTs composite could be greatly improved. Meanwhile, compared to the pure graphitic C3N4, the surface-modified graphitic C3N4/CNTs composite showed stronger photocatalytic activity in degradation of rhodamine B under visible-light irradiation, especially the graphitic C3N4/CNTs (0.03 wt.%). In addition, the results also showed that the photocatalytic properties of the optimised nanocomposites were not decreased obviously.
A novel degradation system, combined with photon-efficient thin-film photocatalysis, conventional bulk-phase photocatalysis and photocarrier-efficient electrocatalysis (TBPE), was developed on a ...vertically ordered one-dimensional (1D) TiO
2 nanotube (TNT)/Ti electrode for the purification of organics. The TBPE system possessed excellent optical, electrochemical, photoelectrochemical and photoelectrocatalytic properties as well as a high mass-transfer coefficient and interfacial activity. The combined degradation of methyl orange (MO) was optimized by varying the rotation angular velocity, applied bias and substrate concentration, and a photoelectrochemical synergetic effect of 62.2% was observed under the optimized conditions for TBPE compared to the individual electrocatalytic (EC) and photocatalytic (PC) systems. To explore the mechanisms, the combined thin-film degradation system of photon-efficient thin-film photocatalysis with photocarrier-efficient electrocatalysis (TPE), and the combined bulk-phase degradation system of conventional bulk-phase photocatalysis with photocarrier-efficient electrocatalysis (BPE), were comparatively estimated. A dramatic increase of 29.4–74.4% was observed in the MO removal efficiency via the thin-film TPE system compared to the bulk-phase BPE system. The results indicated that in the proposed TBPE system on the 1D TNT electrode, the predominant degradation occurred via the TPE system due to its excellent UV utilization efficiency and resultant interfacial photoactivity.
In previous study, non-thermal plasma system with addition of O2 gas was proven to accelerate the decolorization process of dye solution, resulting in faster treatment of the synthetic wastewater. ...The present study deals with the influence of variation of O2 gas admixing to the Ar plasma discharge to examine the decolorization of methylene blue solution underwater through measurement of absorbance value of the plasma-treated solution by UV/VIS measurement. From the experiments it was found that the best result of methylene blue solution decomposition was obtained from the application of Ar 0.3 lpm with the admixing of O2 gas 0.3 lpm in an underwater plasma system generated at 1.56 kV. Modelling the decomposition process of methylene blue by using Ar+O2 plasma with variation of O2 flow rate, it was found that the system was confirmed to follow the first order kinetics equation. From this study it could be said that the plasma-based oxidation process is promising for the application in the decomposition of textile wastewater to support sustainable industry with environmentally friendly orientation.
The natural attenuation of polyaromatic hydrocarbons (PAHs) in the vadose zone of a naturally revegetated former industrial sludge basin (0.45 ha) was examined. This was accomplished by comparing the ...concentration of 16 PAH contaminants present in sludge collected below the root zone of plants with contaminants present at 3 shallower depths within the root zone. Chemical analysis of 240 samples from 60 cores showed the average concentration of total and individual PAHs in the 0-30 cm, 30-60 cm, and bottom of the root zone strata were approximately 10, 20, and 50%, respectively, of the 16, 800 ppm average total PAH concentration in deep non-rooted sludge. Statistically significant differences in average PAH concentrations were observed between each strata studied and the non-rooted sludge except for the concentrations of acenaphthene and chrysene present at the bottom of the root zone in comparison to sludge values. The rooting depth of the vegetation growing in the basin was dependent on both vegetation type and plant age. Average rooting depths for trees, forbs (herbaceous non-grasses), and grasses were 90, 60, and 50 cm, respectively. The deepest root systems observed (100-120 cm) were associated with the oldest (12-14 year-old) mulberry trees. Examination of root systems and PAH concentrations at numerous locations and depths within the basin indicated that plant roots and their microbially active rhizospheres fostered PAH disappearance; including water insoluble, low volatility compounds, i.e. benzo(a)pyrene and benzo(ghi)perylene. The reduced concentration of PAHs in the upper strata of this revegetated former sludge basin indicated that natural attenuation had occurred. This observation supports the concept that through appropriate planting and management practices (phytoremediation) it will be possible to accelerate, maximize, and sustain natural processes, whereby even the most recalcitrant PAH contaminants (i.e. benzo(a)pyrene) can be remediated over time.
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