Latest ArticlesHere we report a facile defect-engineering strategy on the support to optimize the metal-support interaction and enhance the metal's electrocatalytic hydrodechlorination performance in converting 2, 4-dichlorophenol (2, 4-DCP) to phenol. The specific activity of the Pd nanoparticles (Pd NPs) on defective polymer carbon nitride (Pd/PCN-x) reaches 0.09 min-1 m-2Pd, which is 1.5 times that of the Pd NPs supported on the perfect PCN (Pd/PCN-0). The combined experimental and theoretical results demonstrate that the strong adsorption of phenol on Pd/PCN-0 passivates the active sites, limiting the dechlorination progress. The PCN-x containing -C≡N defects can effectively mediate the spatial configuration and electronic structure of Pd NPs, and promote the preferential adsorption of 2, 4-DCP rather than phenol, resulting in an enhanced dechlorination efficiency.
Heavy metal complexes with high mobility are widely distributed in wastewater from modern industries, which are more stable and refractory than free heavy metal ions. Their removals from wastewater draw increasing attentions and various technologies have been developed, among which advanced oxidation processes (AOPs) are more effectively and promising. Progresses on five representative types of AOPs, including Fenton (like) oxidation, electrochemical oxidation, photocatalytic oxidation, ozonation and discharge plasma oxidation for heavy metal complexes degradation are summarized in this review. Their rationales, advantages, applications, challenges and prospects are introduced independently. Combi-nations among these AOPs, such as electrochemical Fenton oxidation and photoelectrocatalytic oxidation, are also comprehensively highlighted. Future efforts should be made to reduce acid requirement and scale up for practical applications of AOPs for heavy metal complex degradation efficiently and cost-effectively.
Developing an effective and mechanically durable biomimetic membrane for the separation of highly emulsified aqueous oil is significant but challenging owing to its low water flux and serious membrane fouling. In this work, a biomimetic membrane with superhydrophobicity and superoleophilicity was rationally developed via co-electrospinning of polysulfonamide/polyacrylonitrile (PSA/PAN) emulsion solution, followed by decorating of α-Fe2O3 nanowire onto the membrane surface to create membrane roughness, and grafting of 1H, 1H, 2H, 2H-perfluorododecyltrichlorosilane (FTCS) to lower membrane surface free energy. Benefiting from the nanowire-wrapped rough membrane structure and the low surface free energy FTCS, the resultant membrane showed superhydrophobicity with a high water contact angle (WCA) of 156°, superoleophilicity with a low oil contact angle (OCA) of 0°, which can separate the highly emulsified aqueous oil with an ultrahigh permeation flux over 7000 L m-2 h-1 and high separation efficiency of about 99%. Significantly, the biomimetic membrane also displayed robust stability for long-term separation owing to its advantage of antifouling property, showing great potential applications in large-scale aqueous oil treatment.
The porous g-C3N4 (PCN) nanosheets are successfully synthesized and further modified with nano-sized Ag by a simple wet-chemical process. Interestingly, the Ag-modified porous g-C3N4 (Ag-PCN) nanosheets exhibit competitive fluorescence detection performance of chloride ion (Cl-) in aqueous solution. Under the optimized conditions, the concentration of Cl- could be quantitative analyzed with the Ag-PCN in a wide detection range from 0.5 mmol/L to 0.1 mol/L, with a low detection limitation of 0.06 mmol/L. It is confirmed that the fluorescence of PCN could be effectively decayed by the photoinduced charge transfer via the adsorbed Cl- for trapping holes, mainly by means of the time-resolved fluorescence and surface photovoltage spectra. The porous structure and modified Ag promote the adsorption of Cl- on resulting Ag-PCN, leading to excellent fluorescence detection for Cl-. This work provides a feasible route to develop a fluorescence detection of Cl- with g-C3N4 nanosheets in environment water.
This study evaluated the removal of multiple pollutants, i.e., polybrominated diphenyl ethers (PBDEs), novel halogenated flame retardants (HFRs), sulfonamide antibiotics (SAs), and heavy metals (HMs), by a full-scale reversed A2/O process in a sewage treatment plant (STP) in Guangzhou, China. The reversed A2/O process demonstrated high removal efficiencies (REs) for total PBDEs (60.5%±4.3%), novel HFRs (98.4%±2.8%) and HMs (70.1%±1.2%), and a relatively low RE for SAs (25.0%±2.3%). BDE 209, the dominant PBDE congener, showed a high residual concentration (13.41±5.18 ng/L) in the suspended particulate matter (SPM) of treated effluents. Some novel HFRs, dechlorane plus (DP) and decabromodiphenyl ethane (DBDPE), were detected in the SPM of the raw sewage (7.50±4.14 ng/L and 11.52±11.65 ng/L, respectively). The removal of SAs was mainly through biodegradation in the activated sludge bioreactors(ASBs).Of the HMs, Mn and Ni exhibited the lowest REs (47.5%±2.2% and 35.0%±2.6%, respectively), while Cr and Cu showed the highest removal (REs > 80%). In terms of treatment units in the reversed A2/O process, ASBs showed the highest RE (27.8%) for the multiple pollutants. The information can aid in our understanding of removal properties of STPs on various pollutants and evaluating the ecological/health risks of STPs as point pollutant sources.
Sulfur-driven autotrophic denitrification (SDAD), a process suited for the treatment of nitrogen and sulfur-polluted wastewater without extra supplement of organic carbon, is a promising biological nitrogen removal process. However, the SDAD process was affected by many factors such as various electron donors, organic carbon and exogenous substances (e.g., antibiotics and heavy metal), which prevent further application. Thus, we conducted a detailed review of previous studies on such influence factors and its current application. Besides, a comparative analysis was adopted to recognize the current challenges and future needs for feasible application, so as to ultimately perfect the SDAD process and extend its application scope.
Graphitic carbon nitride (g-C3N4) as a metal-free candidate of photocatalyst has received worldwide attention because of its great potentials in solar light-induced degradation and hydrogen evolution, yet the industrial application is seriously hindered by the small specific surface area and rapid recombination rate of carriers. Herein, we demonstrate that porous g-C3N4 (HCl-CNU-X) can be prepared via the co-polymerization of acidified melamine and a green bubble template (urea). Transmission electron microscopy and nitrogen sorption characterization results show that the prepared HCl-CNU-X possesses an in-plane porous structure and large specific surface area, enabling the exposure of more accessible active sites. As a result, HCl-CNU-X exhibits both enhanced photocatalytic tetracycline hydrochloride degradation and higher hydrogen evolution than bulk g-C3N4. The boosted photocatalytic performance was ascribed to the formation of the porous structure, which dramatically promotes the separation of charge-carriers and facilitates the electron transfer. This work demonstrates that the acidification of nitrogen-rich precursors combined with a bubble-template can develop a new paradigm of highly porous photocatalysts for environmental remediation and water splitting.
The binary Ag3PO4/MIL-125-NH2 (AMN-X) composites were synthesized through ion exchange-solution method, and the ternary Ag/Ag3PO4/MIL-125-NH2 (AAMN-X) Z-scheme heterojunctions were prepared via the photo chemical reduction deposition strategy. The photocatalytic hexavalent chromium (Cr(Ⅵ)) sequestration over AMN-X and AAMN-X were investigated under visible light. AAMN-120 accomplished superior reduction performance due to that Ag nanoparticles (NPs) act as electrons transfer bridge to enhance the separation efficiency of photogenerated e--h+ pairs, in which the reaction rates (k value) were 2.77 and 124.2 fold higher than those of individual MIL-125-NH2 and Ag3PO4, respectively. The influences of different pH values, small organic acids and coexisting ions on the photocatalytic performance of AAMN-120 were also investigated. In addition, the AAMN-120 heterojunction expressed great reusability and stability in cycling experiments. The mechanism of photocatalytic Cr(Ⅵ) was investigated and verified through photoluminescence (PL), electrochemistry, electron spin resonance (ESR), active species capture, and Pt element deposition experiments.
The selective catalytic reduction (SCR) of NOx by NH3 is one of the most mature technologies for NOx treatment. Catalysts are the main factors affecting denitrification efficiency. Zeolites as low-temperature NH3-SCR catalysts have been extensively studied in the past few years. In this work, the mechanism of zeolites for NH3-SCR reaction was reviewed and the denitrification performances of zeolite catalysts prepared by different methods were compared. The effects of sulfur and water poisoning on zeolite catalysts in NH3-SCR reaction were also analyzed. Several ways to address the problems in low-temperature NH3-SCR reaction were discussed. Hopefully, this review could provide a fundamental understanding of SCR reaction on zeolite catalysts and pave the way toward similar studies to realize its commercial applications.
The development of photocatalysts for hydrogen evolution is a promising alternative to industrial hydrogen evolution; however, generation of high active, recyclable, inexpensive heterojunctions are still challenging. Herein, a novel strategy was developed to synthesize non-noble metal co-catalyst/solid solution heterojunctions using metal-organic frameworks (MOFs) as a precursor template. By adjusting the content of MOFs, a series of Cu1.8S/ZnxCd1-xS heterojunctions were obtained, and the Cu1.8S(3.7%)/Zn0.35Cd0.65S sample exhibits a maximum hydrogen evolution rate of 14.27 mmol h-1 g-1 with an apparent quantum yield of 3.7% at 420 nm under visible-light irradiation. Subsequently, the relationship between the heterojunction and photocatalytic activity were investigated by detailed characterizations and density functional theory (DFT) calculations, which reveal that loading Cu1.8S can efficiently extend the light absorption, meanwhile, the electrons can efficiently transfer from Zn0.35Cd0.65S to Cu1.8S, thus resulting more photogenerated electrons participating in surface reactions. This result can be valuable inspirations for the exploitation of advanced materials using rationally designed nanostructures for solar energy conversion.
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