Latest ArticlesH2O2 has been widely applied in the fields of chemical synthesis, medical sterilization, pollutant removal, etc., due to its strong oxidizing property and the avoidable secondary pollution. Despite of the enhanced performance for H2O2 generation over g-C3N4 semiconductors through promoting the separation of photo-generated charge carriers, the effect of migration orientation of charge carriers is still ambiguous. For this emotion, surface modification of g-C3N4 was employed to adjust the migration orientation of charge carriers, in order to investigate systematically its effect on the performance of H2O2 generation. It was found that ultrathin g-C3N4 (UCN) modified by boron nitride (BN), as an effective hole-attract agent, demonstrated a significantly enhanced performance. Particularly, for the optimum UCN/BN-40% catalyst, 4.0-fold higher yield of H2O2 was obtained in comparison with the pristine UCN. As comparison, UCN modified by carbon dust demonstrated a completely opposite tendency. The remarkably improved performance over UCN/BN was ascribed to the fact that more photo-generated electrons were remained inside of triazine structure of g-C3N4, leading to the formation of larger amount of 1, 4-endoxide. It is anticipated that our work could provide new insights for the design of photocatalyst with significantly improved performance for H2O2 generation.
The existence of many anions in wastewater reduces the removal efficiency of phosphate by adsorbents under realistic conditions. Facing this challenge, the study reports on an insistent and stable composite adsorbent of molybdate complexes Fe-(MoOx) embedded in a macroporous anion exchange resin (D-201). [Fe(MoOx)]-D-201 shows 93.7% adsorption capacity (28.3 mg/g) for phosphate even when the molar concentration of coexisting ions is 5 times higher than phosphate. The capacity of adsorbent is maintained more than 84.2% after five regeneration cycles to remove phosphate in the wastewater containing coexisting ions. The ability of highly selective removal of phosphate is maintained during the regeneration cycles explained by the change of the binding of molybdate clusters with phosphate, which is due to the different structures of molybdate clusters depending on various pH. In general, this work puts forward a new idea for the development of phosphorus removal adsorbents for the treatment of wastewater containing coexisting ions.
Hydrogen peroxide (H2O2) disproportionation, iron precipitation, and narrow pH range are the drawbacks of traditional Fenton process. To surmount these barriers, we proposed a ferric ion (Fe3+)-ascorbic acid (AA) complex catalyzed calcium peroxide (CaO2) Fenton-like system to remove organic dyes in water. This collaborative Fe3+/AA/CaO2 system presented an obvious improvement in the methyl orange (MO) decolorization, and also effectively eliminated other dyes. Response surface method was employed to optimize the running parameters for this coupling process. Under the optimized arguments (2.76 mmol/L Fe3+, 0.68 mmol/L AA, and 4 mmol/L CaO2), the MO removal achieved 98.90% after 15 min at pH 6.50, which was close to the computed outcome of 99.30%. Furthermore, this Fenton-like system could perform well in a wide range of pH (3-11), and enhance the H2O2 decomposition and Fe ions recycle. The scavenger experiment result indicated that hydroxyl radical, superoxide anion free radical, and singlet oxygen were acted on the dye elimination. Moreover, electron spin resonance analysis corroborated that the existences of these active species in the Fe3+/AA/CaO2 system. This study could advance the development of Fenton-like technique in organic effluent disposal.
With the ever-growing demand of clean water for the healthy world, water purification has become an urgent global issue. Singlet oxygen (1O2) as unique non-radical derivative of oxygen, possessing unoccupied π* orbital and exhibiting high selectivity towards electron-rich organic pollutants. Nevertheless, most of the approaches suffer from low-efficiency or biotoxicity, which severely restrict their potential applications. Therefore, in this work, we propose a general strategy via photoelectrocatalytic for selectively reducing oxygen to 1O2 with designed carbon bridged carbon nitride (CBCN). This work highlights the important role of synergistic photo-electro-catalytic effect for selectively generating the 1O2 via oxygen reduction pathway, which can be a promising way especially for degrading electron-rich pollutants.
A hydrophobic carbon dots (Glc-OCDs) derived from octadecylamine and glucose were successfully synthesized for the first time and then grafted onto the porous silica surface by the "Nano-on-Micro" strategy, which was served as a new stationary phase (Sil-Glc-OCDs) for reversed-phase liquid chromatography. The structure of this stationary phase was carefully verified by laser scanning confocal microscope, Fourier transform infrared spectrometry, elemental analysis, contact angle measurement, etc. Several analytes including seven polycyclic aromatic hydrocarbons, eight alkylbenzenes, eight phenols and seven sulfonamides can be well separated on this stationary phase. Better separation performance for certain analytes over commercial C18 column was obtained. Interestingly, this stationary phase exhibited excellent chromatographic selectivity in the separation of the isomers of tert‑butylbenzene, sec‑butylbenzene, isobutylbenzene and n-butylbenzene. In addition, this new Sil-Glc-OCDs column was also applied for detection of calycosin-7-glucoside, ononin, calycosin, formononetin, genistein and isorhamnetin in the extract of Radix Astragali, which were found that the concentration was 0.15 g/L, 0.088 g/L, 0.14 g/L, 0.086 g/L, 0.18 g/L and 0.29 g/L, respectively. We believe that this CDs-grafted silica materials are promising for chromatographic separation.
The effects of different species and concentrations' signal molecules on aerobic activated sludge system were investigated through batch experiments. Results showed that the fastest NH4+-N oxidization rate and the most extracellular polymeric substances (EPS) secretion were obtained by adding 5 nmol/L N-hexanoyl-l-homoserine lactone (C6-HSL) into the aerobic activated sludge. Further study investigated the correlation among N-acyl-homoserine lactones-mediated quorum sensing (AHLs-mediated QS), nutrient removal performances and microbial communities with the long-term addition of 5 nmol/L C6-HSL. It was found that C6-HSL-manipulation could enhance the stability and optimize the decontamination performance of aerobic granular sludge (AGS) system. Microbial compositions considerably shifted with long-term C6-HSL-manipulation. Exogenous C6-HSL-manipulation inhibited quorum quenching-related (QQ-related) activities and enhanced QS-related activities during the stable period. The proposed C6-HSL-manipulation might be a potential technology to inhibit the growth of harmful bacteria in AGS, which could provide a theoretical foundation for the realization of more stable biological wastewater treatments.
It is still a challenge to eliminate efficiently fluoride ion from groundwater, especially to design and synthesis an adsorbent possessing high adsorption capacity, recyclability and wide pH application conditions. Herein we present millimeter-sized sulfate-type zirconium alginate hydrogel beads with 3D network structure (AHB@Zr-SO42−) that exhibited a maximum adsorption capacity of 101.3 mg/g with wide pH applicability (pH 3−9). This material have ~2.5 times higher adsorption capacity than that of pure zirconium alginate hydrogel beads (AHB@Zr) and it was ascribed to ion exchange between SO42− and F− on the surface of AHB@Zr-SO42−, which was verified via ion chromatography measurement coupled with X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectrometer (FTIR Spectrometer) analysis. Density functional theory (DFT) calculations indicated that the ion exchange process between SO42− and F− in AHB@Zr-SO42− was energetically favorable than OH− and F− in AHB@Zr. In addition, 310 bed volumes (BV) of effluent was realized via column adsorption of groundwater containing fluoride on AHB@Zr-SO42− and indicated that it is a promising candidate for mitigating the problem of fluoride-containing groundwater.
Tracking the movement of droplets in digital microfluidics is essential to improve its control stability and obtain dynamic information for its applications such as point-of-care testing, environment monitoring and chemical synthesis. Herein, an intelligent, accurate and fast droplet tracking method based on machine vision is developed for applications of digital microfluidics. To continuously recognize the transparent droplets in real-time and avoid the interferes from background patterns or inhomogeneous illumination, we introduced the correlation filter tracker, enabling online learning of the multi-features of the droplets in Fourier domain. Results show the proposed droplet tracking method could accurately locate the droplets. We also demonstrated the capacity of the proposed method for estimation of the droplet velocity as faster as 20 mm/s, and its application in online monitoring the Griess reaction for both colorimetric assay of nitrite and study of reaction kinetics.
In this work, a very simple dual-readout lateral flow test strip (LFTS) platform was developed for sensitive detection of alkaline phosphatase (ALP) based on a portable device. In this assay, quantum dots (QDs) conjugated with bovine serum albumin (QDs-BSA) were chosen as fluorescence signal labels. In the absence of ALP, MnO2 nanosheets aggregate on the test line and exhibit an obvious brown color, which can be observed by naked eyes to realize semi-qualitative analysis. Meanwhile, fluorescence intensity of QDs-BSA can also be effectively quenched by MnO2 nanosheets due to inner-filter effect. Correspondingly, in the presence of ALP, ALP can catalyze the hydrolysis of ascorbic acid 2-phosphate (AAP) to generate L-ascorbic acid (AA), which can reduce MnO2 into Mn2+, accompanying with the obvious fluorescence recovery of the QDs. By simply monitoring the change of colorimetric and fluorescent signal on the test line, trace amount of ALP can be quantitatively detected. Under the optimal conditions, measurable evaluation of ALP was reached in a linear range from 1 U/L to 20 U/L with a detection limit of 0.7 U/L based on fluorescence signal. Furthermore, this colorimetric/fluorescent dual-readout assay was successfully applied to monitor ALP in human serum samples, showing its great potential as a point of care biosensor for clinical diagnosis.
5-Methylcytosine (5mC) is the most important epigenetic modification in mammals. The active DNA demethylation could be achieved through the ten-eleven translocation (TET) protein-mediated oxidization of 5mC with the generation of 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). It has been known that 5mC, 5hmC and 5fC play critical roles in modulating gene expression. However, unlike the 5mC, 5hmC, and 5fC, the functions of 5caC are still underexplored. Investigation of the functions of 5caC relies on the accurate quantification and localization analysis of 5caC in DNA. In the current study, we developed a method by chemical conversion in conjugation with ligation-based real-time quantitative PCR (qPCR) for the site-specific quantification of 5caC in DNA. This method depends on the selective conversion of 5caC to form dihydrouracil (DHU) by pyridine borane treatment. DHU behaves like thymine and pairs with adenine (DHU-A). Thus, the chemical conversion by pyridine borane leads to the transformation of base paring from 5caC-G to DHU-A, which is utilized to achieve the site-specific detection and quantification of 5caC in DNA. As a proof-of-concept, the developed method was successfully applied in the site-specific quantification of 5caC in synthesized DNA spiked in complex biological samples. The method is rapid, straightforward and cost-effective, and shows promising in promoting the investigation of the functional roles of 5caC in future study.
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