[Show abstract][Hide abstract] ABSTRACT: Abstract The effect of the water matrix components of a secondary effluent of a urban wastewater treatment plant on the photocatalytic activity of Ag/AgCl @ chiral TiO2 nanofibers and the undergoing reaction mechanisms were investigated. These effects were evaluated through the water components-induced changes on the net rate of hydroxyl radical (OH) generation and modeled using a relative rate technique. Dissolved organic matter DOM (k = −2.8 × 108 M−1 s−1) scavenged reactive oxygen species, Cl− (k = −5.3 × 108 M−1 s−1) accelerated the transformation from Ag to AgCl (which is not photocatalytically active under visible-light irradiation), while Ca2+ at concentrations higher than 50 mM (k = −1.3 × 109 M−1 s−1) induced aggregation of Ag/AgCl and thus all of them revealed inhibitory effects. In contrast, NO3− (k = 6.9 × 108 M−1 s−1) and CO32− (k = 3.7 × 108 M−1 s−1) improved the photocatalytic activity of Ag/AgCl slightly by improving the rate of HO generation. Other ubiquitous secondary effluent components including SO42− (k = 3.9 × 105 M−1 s−1), NH3+ (k = 3.5 × 105 M−1 s−1) and Na+ (k = 2.6 × 104 M−1 s−1) had negligible effects. 90% of 17-α-ethynylestradiol (EE2) spiked in the secondary effluent was removed within 12 min, while the structure and size of Ag/AgCl @ chiral TiO2 nanofibers remained stable. This work may be helpful not only to uncover the photocatalytic mechanism of Ag/AgCl based photocatalyst but also to elucidate the transformation and transportation of Ag and AgCl in natural water.
[Show abstract][Hide abstract] ABSTRACT: The unsaturated fatty acid (linoleic acid) sustained-release microspheres were prepared with linoleic acid (LA) using alginate–chitosan microcapsule technology. These LA sustained-release microspheres had a high encapsulation efficiency (up to 62%) tested by high performance liquid chromatography with a photo diode array. The dry microspheres were characterized by a scanning electron microscope, X-ray diffraction measurement, dynamic thermogravimetric analysis and Fourier transform infrared spectral analysis. The results of characterization showed that the microspheres had good thermal stability (decomposition temperature of 236 °C), stable and temperature independent release properties (release time of more than 40 d). Compared to direct dosing of LA, LA sustained-released microspheres could inhibit Microcystis aeruginosa growth to the non-growth state. The results of this study suggested that the LA sustained-release microspheres may be a potential candidate for algal inhibition.
[Show abstract][Hide abstract] ABSTRACT: The presence of nanoparticles (NPs) in natural aquatic environment is a potential risk to aquatic and human life. Periphyton, ubiquitous in aquatic environment, has been used to remove pollutants from aquatic systems. Understanding the interaction between NPs and periphyton will help to better predict the behavior and fate of NPs in aquatic media. This study was aimed to investigate the CuO NP biosorption mechanism by periphyton at acidic, neutral, and alkaline pH and with varying natural organic matter (NOM) concentrations. The rate of adsorption and removal of CuO NPs was decreased with increase in initial pH and NOM concentration. The zeta potential study suggests that the biosorption of CuO NPs by periphyton was related to electrostatic force of attraction. The particle size distribution of CuO NPs in solution with different NOM concentrations played an important role in CuO NP removal. The well fit between pseudo-first-order kinetics and adsorption process indicated that physical sorption appears to be the dominating process. These results show that periphyton can be employed for an environmentally benign and effective solution for NP removal.
Environmental Science and Pollution Research 12/2014; · 2.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Graphene/ZnWO4 (G–ZnWO4) nanorod composite photocatalysts were prepared by a simple one-step method. Namely, the reduction of graphene oxide and the growth of ZnWO4 nanorod occurred simultaneously in one single process. An enhancement in the photocatalytic activities were observed in G–ZnWO4 composites compared with pure ZnWO4 under UV light irradiation.
Materials Research Bulletin 09/2014; 57:41–46. · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ag@AgCl–BiOCl nanocomposites were prepared by an in-situ ultraviolet (UV) reduction method. BiOCl in the composites exhibits morphology of square-like 2D nanoplates. The results indicated that there was an optimum irradiation time (30 min) for obtaining the highest photocatalytic activity.
[Show abstract][Hide abstract] ABSTRACT: This study investigated the kinetics of phenol and 4-chlorophenol (4-CP) biodegradation by a cold-adapted bacteria, Pseudomonas putida LY1, isolated from Songhua River sediment. The results showed that P. putida LY1 cannot grow on 4-CP as a sole carbon source. P. putida LY1 had the potential to cometabolic biodegrade phenol and 4-CP in a wide range of temperature (varying from 5 to 35 °C) with the optimal temperature around 25 °C. Mixture of phenol and 4-CP were completely removed at two 4-CP concentrations (15 and 40 mg/L) over a wide range of phenol (20-400 mg/L) concentrations, whereby the ratio of 4-CP/biomass (S 2/X) was lower than 0.03. The kinetic models of cometabolic biodegradation of phenol and 4-CP were proposed, considering the growth and nongrowth substrate inhibition. These models successfully simulate the processes of cometabolic degradation of phenol and 4-CP.
Environmental science and pollution research international. 08/2014;
[Show abstract][Hide abstract] ABSTRACT: Ag nanoparticles loaded TiO2 nanoplate array which grew on activated carbon fiber (ACF) was prepared for the first time. Results showed that the Ag nanoparticles deposited uniformly on the titania nanoplate array, which grew nearly perpendicularly on the activated carbon fiber. The obtained samples showed high photocatalytic activity for phenol degradation under both UV and visible light.
[Show abstract][Hide abstract] ABSTRACT: A novel bio-reactive capping barrier composed of polysulfone/granular activated carbon (PS/GAC) hybrid membranes immobilized with microorganism was developed for the remediation of nitrobenzene in sediments. The SEM observation demonstrated that all the membranes had a dense top layer and a porous sublayer, this structure can block the transfer of nitrobenzene from sediment to the water and enhance nitrobenzene degradation. Adsorption behaviors of nitrobenzene on membranes showed that the membrane impregnated with GAC had better performance than the pure PS membrane. The values of Kads increased from 4.64 (without GAC) to 6.19 (1:2 GAC). 20mg/L nitrobenzene can be completely degraded by Pseudomonas putida immobilized on membranes. The biodegradation rate of activated carbon-filled membrane system was little higher than that of pure PS membrane system. For remediation experiments, only about 21.7, 28.3 and 43.9% of nitrobenzene in the sediment was removed by the end of the experiments for PS/GAC membrane, sand-alone and sand amended with activated carbon capping systems, respectively. While for PS/GAC+microorganisms capping system, more than 70% of nitrobenzene loss was observed. This demonstrated that nitrobenzene can be effectively removed from contaminated sediments by microbial degradation in the bio-reactive capping system.
Journal of Hazardous Materials 07/2014; 276:415–421. · 4.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The presence of ZnO NPs in waste streams can negatively affect the efficiency of biological nutrient removal from wastewater. However, details of the toxic effects of ZnO NPs on microbial activities of wastewater biofilms have not yet been reported. In this study, the temporal and spatial inhibitory effects of ZnO NPs on the O2 respiration activities of aerobic wastewater biofilms were investigated using an O2 microelectrode. The resulting time-course microelectrode measurements demonstrated that ZnO NPs inhibited O2 respiration within 2h. The spatial distributions of net specific O2 respiration were determined in biofilms with and without treatment of 5 or 50mg/L ZnO NPs. The results showed that 50mg/L of nano-ZnO inhibited the microbial activities only in the outer layer (∼200μm) of the biofilms, and bacteria present in the deeper parts of the biofilms became even more active. Scanning electron microscopy (SEM) analysis showed that the ZnO NPs were adsorbed onto the biofilm, but these NPs had no adverse effects on the cell membrane integrity of the biofilms. It was found that the inhibition of O2 respiration induced by higher concentrations of ZnO NPs (50mg/L) was mainly due to the release of zinc ions by dissolution of the ZnO NPs.
Journal of hazardous materials. 04/2014; 276C:164-170.
[Show abstract][Hide abstract] ABSTRACT: Graphene–carbon nanotubes (CNTs)–TiO2 composites were successfully synthesized by a one-pot solvothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and diffuse reflectance UV–vis spectra. The photocatalytic activity of as-prepared composite photocatalysts was tested by degradation of dye methylene blue (MB) and photoreduction of Cr(VI) in aqueous solution under UV light irradiation. The experiment results showed that the composites exhibited enhanced photocatalytic performance compared to binary one (i.e. graphene–TiO2) and pristine TiO2. The effect of CNTs content on the photocatalytic activity was also studied. It showed that the photocatalytic performance of the graphene–CNTs–TiO2 hybrids was dependent on the proportion of CNTs in the composite. The mass ratio of CNTs:TiO2 = 5% was proved to be the optimal ratio. The apparent rate constants k for MB degradation and Cr(VI) reduction were 2.2 and 1.9 times as graphene–TiO2 composite, respectively. The enhanced activity can be ascribed to the addition of CNTs, which can be severed as charge transmitting paths thus decrease the recombination rate of photoinduced electron–hole pairs. This mechanism for the enhanced photoactivity was further confirmed by measuring the hydroxyl radical and transient photocurrent.
Applied Catalysis A General 03/2014; 473:83–89. · 3.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A series of mesoporous BiOBr–activated carbon (AC) composite photocatalysts with different content of AC were synthesized by an in situ loading solvothermal method. The obtained samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area and UV/vis diffuse reflectance spectrum (DRS). Results showed that the composite samples exhibit higher BET values and stronger adsorption ability for organic pollutants. Moreover, the existence of AC influenced the size of BiOBr deposited on ACs. High photocatalytic activity was observed for the degradation of the heteropolyaromatic dye methylene blue (MB) under both UV and visible light irradiation. Additionally, the results indicated that there was an optimum AC amount of 80% for obtaining the highest photocatalytic activity.
Composites Part B Engineering 03/2014; 59:96–100. · 2.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose
Sediments are significant methane (CH4) sources of the atmosphere. However, the mechanisms of CH4 generation remain unclear in sediments of shallow urban lakes. The aims of this investigation were to study the characterization of environmental parameters, CH4 generation, and methanogen populations in Wulongtan Lake, China, which is affected solely by nonpoint pollution.
Materials and methods
The concentrations of CH4 in the atmosphere and of vertical sediment profiles and the methane flux at the air–water interface were monitored in the summer of 2012. Environmental parameters in the water column and in the vertical sediment profiles were assayed. The activities of cellulose, saccharase, polyphenol oxidase, and urease enzyme and 16S rRNA gene copy numbers of Archaea (ARC), Methanobacteriales (MBT), Methanococcales (MCC), Methanomicrobiales (MMB), Methanosarcinales (MSL), Methanosarcinaceae (MSC), and Methanosaetaceae (MST) were determined in the vertical sediment profiles. The abundance of methyl–coenzyme A reductase (ME) gene was also determined to evaluate the total activities of methanogens.
Results and discussion
High CH4 concentrations were detected in the atmosphere above the lake, and the mean CH4 flux at the air–water interface was 6.21 mM m−2 h−1. Dissolved oxygen decreased with an increase of water depth. Eh values and CH4 contents increased, but total nitrogen, water content, and total organic carbon (TOC) decreased with an increase of sediment depth. Cellulose, saccharase, polyphenol oxidase, and urease activities were detected in all sedimentary layers. The copy number of 16S rRNA gene (wet weight) for Archaea reached the highest value in the surface sediment. Copy numbers of ME were higher at 12–33 cm than at 0–6 cm. In general, abundances of MMB, MBT, and MSL were higher than that of MCC in the same sedimentary layer. 16S rRNA gene copy numbers of MST decreased with increasing depth, while MSC was higher at 18–27 cm than that at other sections. These indicate that hydrogenotrophic, aceticlastic, and methylotrophic pathways coexisted in these sediments. Principal component analysis revealed that in the sediments, the level of CH4 was closely related with several parameters including saccharase, urease, ME, and MBT, while TOC content was related to CEL, MST, ARC, water content, and Eh.
High CH4 release potential was detected in this shallow urban lake and can be ascribed to the anaerobic aquatic environment, bacterial enzyme activities, and methanogens. The orders MMB, MBT, and MSL were dominant in sediments for CH4 production. The presence of orders or families of methanogens might be determined by the types of available substrates in lake sediments.
Journal of Soils and Sediments 02/2014; · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Flume experiments were conducted to investigate the distribution and composition of extracellular polymeric substances (EPS) in biofilms and the detachment mechanism of biofilms grown under different flow velocity conditions. The results of biofilm growth kinetics showed that the growth trends were coincident with the logistic growth model. The growth kinetics parameters reached their maximum under intermediate velocity (IV) condition. Biofilms exhibited different profiles of EPS composition and distribution, depending on the flow conditions in which the biofilms were grown. The amounts of total polysaccharide and total protein in the thin biofilm (high velocity condition 2 - HV2) were both generally greater than those in the thick biofilm (IV). As compared to the heterogeneous distribution of EPS in the thick biofilms (IV), the EPS in the thin biofilms (HV2) exhibited more homogeneous distribution, and the bound EPS in the thin biofilms (HV2) were much greater than those in the thick biofilms (IV). From the detachment tests, an inverse relationship was observed between the proportion of detached biomass and the value of flow velocity during growth. Biofilms grown under higher velocities showed stronger cohesion than those grown under lower velocities. Therefore, water velocity during biofilm growth conditioned the distribution and composition of EPS, as well as its detachment characteristics under higher shear stress.
Water Science & Technology 02/2014; 69(4):825-832. · 1.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The presence of ZnO NPs in waste streams can negatively affect the efficiency of biological nutrient removal from wastewater. However, details of the toxic effects of ZnO NPs on microbial activities of wastewater biofilms have not yet been reported. In this study, the temporal and spatial inhibitory effects of ZnO NPs on the O2 respiration activities of aerobic wastewater biofilms were investigated using an O2 microelectrode. The resulting time–course microelectrode measurements demonstrated that ZnO NPs inhibited O2 respiration within 2 h. The spatial distributions of net specific O2 respiration were determined in biofilms with and without treatment of 5 or 50 mg/L ZnO NPs. The results showed that 50 mg/L of nano-ZnO inhibited the microbial activities only in the outer layer (∼200 μm) of the biofilms, and bacteria present in the deeper parts of the biofilms became even more active. Scanning electron microscopy (SEM) analysis showed that the ZnO NPs were adsorbed onto the biofilm, but these NPs had no adverse effects on the cell membrane integrity of the biofilms. It was found that the inhibition of O2 respiration induced by higher concentrations of ZnO NPs (50 mg/L) was mainly due to the release of zinc ions by dissolution of the ZnO NPs.
Journal of Hazardous Materials. 01/2014; 276:164–170.
[Show abstract][Hide abstract] ABSTRACT: Abstract The feasibility of simultaneous production of hydrogen and electricity with simultaneous contaminants removal from “actual” urban wastewater within a dye-sensitized photoelectrochemical cell (DSPC) is demonstrated for the first time. The photoanode in the DSPC was a novel nanostructured plasmonic Ag/AgCl @ chiral TiO2 nanofibers (Ag and AgCl nanoparticles supported on chiral TiO2 nanofibers). The electrolyte in the DSPC was actual wastewater to which an estrogen (17-β-ethynylestradiol, EE2) and a heavy metal (Cu2+) were added. The contaminants in the wastewater rather than I-/I3− (usual electrolyte in conventional DSPCs) acted as electrons bridges for the stabilization of charges in this DSPC. Almost total removal of total organic carbon (TOC), Cu2+, EE2, and 70% removal of total nitrogen (TN) were achieved under visible-light irradiation. A relatively high solar energy conversion efficiency (PCE 3.09%) was recorded and approximately 98% of the electricity was converted to H2 after the consumption of dissolved oxygen (DO), Cu2+ and TN. This performance was attributed to the “symbiotic” relationship between the TiO2 chiral nanofibers and the plasmonic effect of Ag nanoparticles at the photoanode although Ag acting as a recombination site may hinder the generation of electricity. The dye N719 in this study exhibited a temporary sensitization effect, and a more efficient sensitizer is expected to be studied in the future. This study opens up new opportunities for producing renewable energy from wastewater treatment processes including organic and inorganic matter as viable resources.
Applied Catalysis B Environmental 01/2014; · 5.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A solvothermal method was employed to prepare a novel magnetic composite adsorbent composed of graphene, multi-walled carbon nanotubes (MWCNTs) and Fe3O4 nanoparticles. The prepared adsorbents were characterized by X-ray diffraction, scanning electron microscopy and X-ray fluorescence spectrometry and Fourier transform infrared spectroscopy. Fourier transform infrared spectroscopy and the particle size distribution of the samples before and after adsorption was also carried out. The performance of as-prepared composites was investigated by the adsorption of dye methylene blue. Results showed that the maximum adsorption capacity of the samples was up to 65.79 mg g−1, which was almost equal to the sum of magnetic graphene and magnetic MWCNTs. The effect of pH and temperature on the adsorption performance of methylene blue onto the magnetic adsorbents was investigated. The kinetic was well-described by pseudo-second-order and intraparticle diffusion model, while the isotherm obeyed the Langmuir isotherm. Furthermore, the as-prepared composites were found to be regenerative and reusable. The application in the treatment of an artificial dye wastewater and its cost estimation were also discussed. Therefore, the as-prepared magnetic composites can be severed as a potential adsorbent for removal of dye pollutant, owing to its high adsorption performance, magnetic separability and efficient recyclable property.