Latest ArticlesDue to the relatively sluggish charge carrier separation in metal sulfides, the photocatalytic activity of them is still far lower than expected. Herein, sulfur vacancies and in-plane SnS2/SnO2 heterojunction were successfully introduced into the SnS2 nanosheets through high energy ball-milling. These defective structures were studied by the electron paramagnetic resonance, Raman spectra, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope analyses. The sulfur vacancies and in-plane heterojunctions strongly accelerate the separation of photoexcited electron-hole pairs, as confirmed by the photoluminescence emission spectra and time-resolved photoluminescence decay spectra. The introduction of sulfur vacancies and in-plane heterojunction in SnS2 nanosheets results in roughly six times higher photodegrading rate for methyl orange and four times higher photocatalytic reduction rate of Cr6+ than those of pure SnS2 nanosheets.
An innovative method for the ultrasensitive detection of mercury by solution anode glow discharge atomic emission spectroscopy (SAGD-AES) coupled with hydride generation (HG) was first investigated. In this method, the mercury vapor generated by the HG was transmitted to the SAGD through the miniature hollow tungsten tube for excitation and detected by a miniaturized spectrograph. A thorough parametric evaluation of the HG and SAGD system was performed, including the type and concentration of carrier acid, He flow rate, concentrations of NaBH4, discharge current and discharge gap. Under optimal operating conditions, the detection limit for Hg2+ achieved 0.03 μg/L, with a relative standard deviation of 1.1% at the Hg2+ concentration of 5 μg/L. Moreover, the correlation coefficient of the calibration curve was 0.9996 in the range between 0.1 and 10 μg/L. The accuracy and practicability of HG-SAGD-AES were verified by measuring GBW09101b (human hair), GBW10029 (fish), soil and rice samples. The results showed good agreement with the certified values and values from direct mercury analyzer (DMA).
Macroporous 3D carbon doped with nitrogen confined Mo catalyst (MoOx@CN) had been prepared by a facile one-step pyrolysis technique using silica as a template and was employed for oxidative desulfurization (ODS) of dibenzothiophene (DBT) in model fuel with H2O2 as oxidant. The effect of different operating conditions (i.e., reaction temperature and time, catalyst dosage, H2O2/DBT (O/S) molar ratio) were also systematic investigated. Under the optimal reaction condition, MoOx@CN catalyst exhibited highly excellent ODS performance toward DBT, the highest sulfur removal efficiency can be up to 99.9% and sulfur content was wiped out from 800 ppm to 10 ppm. Due to the robust 3D structure promoting rapid transfer, in addition to the increased number of active sites induced by the Mo vacancies, the catalyst, prepared using chitosan and ammonium heptamolybdate in a mass ratio of 1:0.5, displayed rapid kinetics and low activation energy in the oxidation of dibenzothiophene. Moreover, it exhibited excellent recyclability after five cycles without any obvious decrease in catalytic activity for the oxidative desulfurization reaction.
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.
This study demonstrated that as-synthesized nano Fe/Cu bimetals could achieve significant enhancement in the degradation of diclofenac (DCF), as compared to much slow removal of DCF by Cu(Ⅱ) or zero valent iron nanoparticles (nZVI), respectively. Further observations on the evolution of O2 activation process by nano Fe/Cu bimetals was conducted stretching to the preparation phase (started by nZVI/Cu2+). Interesting breakpoints were observed with obvious sudden increase in the DCF degradation efficiency and decrease in solution pH, as the original nZVI just consumed up to Fe(Ⅱ) and Cu(Ⅱ) appeared again. It suggested that the four-electrons reaction of O2 and Cu-deposited nZVI would occur to generate water prior to the breakpoints, while Cu(0) and Fe(Ⅱ) would play most important role in activation of O2 afterwards. Through the electron spin resonance (ESR) analysis and quenching experiments, ·OH was identified as the responsible reactive species. Further time-dependent quantifications in the cases of Cu(0)/Fe(Ⅱ) systems were carried out. It was found that the ·OH accumulation was positively and linearly correlated with nCu dose, Fe(Ⅱ) consumption, and Fe(Ⅱ) dose, respectively. Since either Cu(0) or Fe(Ⅱ) would be inefficient in activating oxygen to produce ·OH, a stage-evolution mechanism of O2 activated by nano Fe/Cu bimetals was proposed involving: (a) Rapid consumption of Fe(0) and release of Fe(Ⅱ) based on the Cu-Fe galvanic corrosion, (b) adsorption and transformation of O2 to O22- at the nCu surface, and (c) Fe(Ⅱ)-catalyzed activation of the adsorbed O22- to ·OH.
In this paper, a novel mesoporous silica gel evenly doped by Prussian blue nanoparticles (PBMSG) was successfully synthesized by using N, N-dimethylamide as template with a large Barrett-Emmett-Teller (BET) surface area of 505 m2/g and an average pore size of 2.9 nm. The static adsorption experiments showed that the equilibration time of PBMSG for Cs+ was about 30 min. The adsorption isotherm of PBMSG for Cs+ accorded with Langmuir model and the theoretical maximum adsorption capacity was 80.0±2.9 mg/g. When the initial concentration of Cs+ was 1.00 mg/L, the adsorption partition coefficient Kd could reach 3.5×104 mL/g After adsorption, Cs+ could be eluted by dilute hydrochloric acid (pH 2) with an efficiency of 89.8%, while no K+, Fe3+, Fe2+ was eluted. PBMSG exhibited good selectivity toward Cs+ and Rb+. In the presence of high concentration of K+, the selective adsorption of PBMSG could change the mass ratio of K+, Rb+ and Cs+ from 96.63:0.83:1.00–1.12:0.73:1.00. The separation of Cs+ and Rb+ from K+ with similar concentration (100 mg/g) was realized by column experiment. This indicated that PBMSG was suitable for rapid recovery of low concentration of rubidium and cesium from complex matrixes, such as wastewater and salt lake brine, etc.
Electrochemical detection is an efficient method for the detection of Bisphenol A (BPA). Herein, a sensitive photo-electrochemical sensor based on two-dimensional (2D) TiO2 (001) nanosheets was fabricated and then used for BPA electrochemical detection. Upon light irradiation, the 2D TiO2 (001) nanosheets electrode provided a lower detection limit of BPA detection compared with an ambient electrochemical determination. The low detection limit is ~5.37 nmol/L (S/N=3). Furthermore, profiting from the photoelectric characteristics, the 2D TiO2 (001) nanosheets electrode exhibits a nice regeneration property. After 45 min of light irradiation, the electrochemical signal was regenerated from 14.7% to 82.9% of the original signal at the 6th cycle. This is attributed to the non-selective ·OH mediation produced by the 2D TiO2 (001) nanosheets mineralizing anodic polymeric products and resuming surface reactive sites. This investigation indicates that photo-assistance is an efficient method to improve the electrochemical sensor for detecting BPA in water environments.
There is a growing need to eliminate antibiotic resistance genes (ARGs) in the environment and mitigate widespread antibiotic resistance. Graphitic carbon nitride (g-C3N4) was successfully synthesized via facile thermal polymerization approach and its potential for adsorption treatment of ARGs in water was examined. Batch adsorption experimental results revealed that g-C3N4 powders had robust adsorption activity for the gene ampC and ermB. Adsorption kinetics and isotherms were systematically investigated to explain the adsorption mechanism. The apparent adsorption equilibrium could be reached within 180 min. The adsorption process effectively removed ARGs (ampC and ermB) from water with 3.2 log and 4.2 log reductions, respectively. In addition, experimental data were analyzed by several models and simulated well with Langmuir isotherm and pseudo-second-order model. It indicated that adsorption process might be dominated by the chemical rate-limiting step. Moreover, the effects of temperature and pH on the removal of ARGs were conducted and the isoelectric point (IEP) was obtained. Finally, we have demonstrated that the g-C3N4 is a novel adsorbent and can be used as column packing to remove ARGs by filtration.
A magnetic mesoporous expanded perlite-based (EPd-APTES@Fe3O4) composite was designed and synthesized as a novel adsorbent for enrichment of rare earth ions in aqueous solution. Effect of various factors including the pH of solution, contact time and adsorbent dosage on the adsorption behaviors of yttrium(Ⅲ) by the EPd-APTES@Fe3O4 nano-material composites from aqueous solution was investigated. The maximum adsorption capacity of the as-prepared materials for yttrium(Ⅲ) ions was 383.2 mg/g. Among the various isotherm models, the Freundlich isotherm model could well described for the adsorption of the rare earth ions at pH 5.5 and 298.15 K. The kinetic analysis indicated that the adsorption process followed the pseudo-second order kinetics model, and the rate-determining step might be chemical adsorption. Thermodynamic parameters declared that the adsorption process was endothermic. In addition, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and the quantum chemical calculation indicated that the yttrium(Ⅲ) ions were captured on the EPd-APTES@Fe3O4 surface mainly by coordination with functional group of -NH2. More importantly, the adsorption-desorption studies indicated that the EPd-APTES@Fe3O4 nano-material composites had a high stability and good recyclability.
In recent years, oil spills caused by human activities have occurred frequently, and the resultant oil pollution has received extensive attention worldwide. In this paper, a total of 50 water samples were collected from the northeastern part of the South China Sea, and total petroleum hydrocarbons (TPHs) and n-alkane content in the samples were analyzed by gas chromatography-flame ionization detector (GC-FID) technology. The petroleum hydrocarbon characteristic indices, such as carbon predominance index (CPI) and terrigenous/aquatic ratio (TAR), were calculated to trace the source of petroleum hydrocarbons. The measured value of TPHs ranged from 121.31–603.02 μg/L. For surface waters, the TPHs in the northern coastal waters and the central waters were higher than that in the far shore. For vertical waters, the TPHs sharply decreased at first, and then increased slowly and finally reached a steady state. The n-alkanes in the water samples were concentrated in C10-C38, and they were mainly from terrestrial higher plant. The waters in the near shore, mid-layer and deep sea showed a strong reducing terrestrial characteristic, while the surface waters in the open sea showed an obvious oxidizing endogenous characteristic.
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