Publications by authors named "Mingce Long"

38 Publications

Systematic evaluation of activated carbon-FeO composites for removing and degrading emerging organic pollutants.

Environ Res 2021 07 5;198:111187. Epub 2021 May 5.

Civil and Environmental Engineering Faculty, Technion, Haifa, 32000, Israel. Electronic address:

In this study, a comparative activity assessment of several activated carbon (AC) and AC-FeO composites was performed to evaluate their efficiency and versatility as Fenton-like catalysts. Although many studies have demonstrated the advantages of AC-based materials as Fenton-like catalysts, most have been developed using only one oxidant and/or one pollutant. Here, untreated (AC) and acid-treated AC (AC) iron-oxide composites were synthesized, characterized, and compared in terms of activity to bare AC using several oxidants and pollutants, the activation efficiency of hydrogen peroxide (HO) and ammonium persulfate ((NH)SO), and the subsequent oxidation extent and kinetics of bisphenol-A, atrazine, and carbamazepine by the AC-based materials were studied in depth. The persulfate-based systems showed considerably higher pollutant removal in the presence of the catalysts, despite lower persulfate decomposition rates: atrazine and carbamazepine were partially degraded, mainly through a radical-dependent pathway; the highest removal of atrazine was achieved with the AC-iron composite, whereas carbamazepine was best removed by the AC-iron composite. In contrast, bisphenol A was completely mineralized, probably via a non-radical pathway, in the presence of all AC-based composites, even at very low persulfate concentrations. Furthermore, bisphenol A removal remained high for several consecutive cycles, with the most efficient removal and stability observed in the presence of AC. These findings reveal the high complexity of AC-based systems, with multiple binding sites and degradation pathways unique to each combination of pollutants, catalysts, and oxidants. In general, the composition of the waste stream governs the applicability of these materials. Thus, the structure-function correlations and degradation mechanisms revealed here are crucial for improving sorbent-catalyst design and accelerating the implementation of low-cost remediation and in situ regeneration technologies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.envres.2021.111187DOI Listing
July 2021

Quantification of photocatalytically-generated hydrogen peroxide in the presence of organic electron donors: Interference and reliability considerations.

Chemosphere 2021 Sep 12;279:130556. Epub 2021 Apr 12.

School of Environmental Science and Engineering, Key Laboratory for Thin Film and Microfabrication of the Ministry of Education, Shanghai Jiao Tong University, Shanghai, 200240, China. Electronic address:

Photocatalytic HO production is an innovative on-site HO synthesis method to treat organic pollutants through Fenton-like reactions, avoiding the need and potential liability of HO storage and transportation. Accurate quantification of HO is crucial to explore the mechanism of photocatalytic HO production and optimize reaction parameters. In this work, three common HO quantification methods (i.e., titration with potassium permanganate (KMnO), and colorimetry with ammonium metavanadate (NHVO) or N,N-diethylp-phenylenediamine-horseradish peroxidase (DPD-POD)) were compared and their susceptibility to interference by seven types of representative organics were considered. Interference mechanisms were explored based on the electron-donating (E) and electron-accepting (E) ability of the present organics. The accuracy of the KMnO titration method is greatly compromised by aromatic compounds even at 0.1 mM due to the increased KMnO consumption by direct oxidation. The presence of p-benzoquinone that directly reacts with NHVO and DPD compromises these colorimetric methods, especially DPD-POD colorimetry at concentrations as low as 0.1 mM. The DPD-POD method should also be scrutinized in the presence of phenols due to significant disturbance by oxidation byproducts (e.g. hydroquinone inducing immediate color disappearance). A flowchart was generated to provide guidelines for selecting an appropriate HO quantification method for different water matrices treated by Fenton-like reactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2021.130556DOI Listing
September 2021

Solid peroxides in Fenton-like reactions at near neutral pHs: Superior performance of MgO on the accelerated reduction of ferric species.

Chemosphere 2021 May 16;270:128639. Epub 2020 Oct 16.

School of Environmental Science and Engineering, Key Laboratory of Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China. Electronic address:

Fenton-like reactions at near neutral pHs are limited by the slow reduction of ferric species. Enhancing generation of from solid peroxides is a promising strategy to accelerate the rate-limiting step. Herein, the HO release and Fenton-like reactions of four solid peroxides, MgO, CaO, ZnO and urea hydrogen peroxide (UHP), were investigated. Results indicated that UHP can release HO instantly and show a similar behavior as HO in the Fenton-like reactions. MgO released HO quickly in phosphate buffered solutions, which was comparable to CaO but faster than ZnO. Metal peroxides induced higher initial phenol degradation rates than UHP and HO when the same theoretic HO dosages and Fe(III)-EDTA were used. MgO displayed a superior performance for phenol degradation at pH 5, resulting in more than 93% phenol reduction at 1.5 h. According to kinetic analyses, the generation rate of in the MgO system was 18 and 3.4 times higher than those in ZnO and CaO systems, respectively. The addition of MgO significantly promoted HO based Fenton-like reactions by increasing production of , and the mixture of MgO and HO had an improved utilization efficiency of active oxygen than the MgO system. The findings suggested the critical roles of metal peroxides in favoring Fenton-like reactions and inspired strategies to simultaneously accelerate Fenton-like reactions and improve utilization efficiency of active oxygen.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2020.128639DOI Listing
May 2021

Efficient SO Removal and Highly Synergistic HO Production Based on a Novel Dual-Function Photoelectrocatalytic System.

Environ Sci Technol 2020 09 24;54(18):11515-11525. Epub 2020 Aug 24.

School of Environmental Science and Engineering, Shanghai Jiao Tong University, No. 800, Dongchuan Rd, Shanghai 200240, PR China.

The direct conversion of SO to SO is rather difficult for flue gas desulfurization due to its inert dynamic with high reaction activation energy, and the absorption by wet limestone-gypsum also needs the forced oxidation of O to oxidize sulfite to sulfate, which is necessary for additional aeration. Here, we propose a method to remove SO with highly synergistic HO production based on a novel dual-function photoelectrocatalytic (PEC) system in which the jointed spontaneous reaction of desulfurization and HO production was integrated instead of nonspontaneous reaction of O to HO. SO was absorbed by alkali liquor then oxidized quickly into SO by a nanorod α-FeO photoanode, which possessed high alkali corrosion resistance and electron transport properties. HO was produced simultaneously in the cathode chamber on a gas diffusion electrode and was remarkably boosted by the conversion reaction of SO to SO in the anode chamber in which the released chemical energy was effectively used to increase HO. The photocurrent density increased by 40% up to 1.2 mA·cm, and the HO evolution rate achieved 58.8 μmol·L·h·cm with the synergistic treatment of SO, which is about five times than that without SO. This proposed PEC cell system offers a cost-effective and environmental-benign approach for dual purpose of flue gas desulfurization and simultaneous high-valued HO production.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.0c00886DOI Listing
September 2020

2D N-Doped Porous Carbon Derived from Polydopamine-Coated Graphitic Carbon Nitride for Efficient Nonradical Activation of Peroxymonosulfate.

Environ Sci Technol 2020 07 17;54(13):8473-8481. Epub 2020 Jun 17.

School of Environmental Science and Engineering, Key Laboratory for Thin Film and Microfabrication of the Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.

Nitrogen-doped carbon materials attract broad interest as catalysts for peroxymonosulfate (PMS) activation toward an efficient, nonradical advanced oxidation process. However, synthesis of N-rich carbocatalysts is challenging because of the thermal instability of desirable nitrogenous species (pyrrolic, pyridinic, and graphitic N). Furthermore, the relative importance of different nitrogenous configurations (and associated activation mechanisms) are unclear. Herein, we report a "coating-pyrolysis" method to synthesize porous 2D N-rich nanocarbon materials (PCN-) derived from dopamine and g-CN in different weight proportions. PCN-0.5 calcined at 800 °C had the highest surface area (759 m/g) and unprecedentedly high N content (18.5 at%), and displayed the highest efficiency for 4-chlorophenol (4-CP) degradation via PMS activation. A positive correlation was observed between 4-CP oxidation rates and the total pyridinic and pyrrolic N content. These N dopants serve as Lewis basic sites to facilitate 4-CP adsorption on the PCN surface and subsequent electron-transfer from 4-CP to PMS, mediated by surface-bound complexes (PMS-PCN-0.5). The main degradation products were chlorinated oligomers (mostly dimeric biphenolic compounds), which adsorbed to and deteriorated the carbocatalyst. Overall, this study offers new insights for rational design of nitrogen-enriched carbocatalysts, and advances mechanistic understanding of the critical role of N species during nonradical PMS activation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.0c03207DOI Listing
July 2020

The role of soil organic matters and minerals on hydrogen peroxide decomposition in the soil.

Chemosphere 2020 Jun 12;249:126146. Epub 2020 Feb 12.

School of Environmental Science and Engineering, Key Laboratory of Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, Shanghai, 200240, China. Electronic address:

Application of HO in in-situ chemical oxidation (ISCO) for soil remediation has been limited by its rapid decomposition. However, effect of main factors involving in this phenomenon are not well understood. In this contribution, HO decomposition in the six types of natural soils was investigated by kinetic analyses and soil characterizations. The grassland soil (GS) and red soil (RS) have the highest HO decomposition rates (respective 0.048 and 0.069 min), while the paddy soil (PS) shows the lowest one (0.004 min). The decomposition mainly takes place on the surface adsorption sites of soil particles. PS has the highest content of SOM, which can block the active adsorption sites for HO decomposition. The effects of dissolved organic matter (DOM) and biological debris in the soil are minor. Iron and manganese containing minerals are significantly influential on HO decomposition, and the soil with a higher content of clay can induce faster HO decomposition. The immobilized goethite (GM) and birnessite (BM) on montmorillonite were synthesized to simulate soil minerals. Results show HO decomposition rates in BM is even faster than GM when the former dosage is two orders of magnitude lower than that of the latter. This indicates the crucial role of manganese minerals although their contents are generally much lower than that of iron in the soils. This study advanced the understanding of HO decomposition in the soil and bring insights for HO based ISCO technology in soil remediation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2020.126146DOI Listing
June 2020

Nitrogen doped carbon quantum dots and GO modified WO nanosheets combination as an effective visible photo catalyst.

J Hazard Mater 2020 01 23;382:121087. Epub 2019 Aug 23.

School of Environmental Science and Engineering Shanghai Jiao Tong University, Shanghai 200240, China.

Nitrogen doped carbon quantum dots (NCQDs) based highly efficient ternary photocatalyst are fabricated by modifying surface of GO incorporated WO nano-sheets. XRD confirmed the formation of monoclinicWO nano-sheets. All the characteristic peaks of WO, GO and NCQDs are obvious in XRD patterns of WO/GO/NCQDs ternary photocatalysts confirming successful fabrication of the photocatalysts. SEM images showed that WO host matrix is distorted after incorporation of GO and NCQDs owing to lower interfacial tension. The surface of WO nano-sheets is modified with morphological defects making more active sites available. UV-vis spectra exhibited extended visible light absorption and remarkable reduction of WO band gap energy. The photoluminescence spectra confirmed the efficient charge separation in NCQDs modified ternary photocatalyst. The synthesized composites were applied for the photocatalytic degradation of harmful organic dye i.e. methyl orange (MO). The ternary composites represented the excellent photocatalytic activity as compared to binary and pure WO photocatalysts. This enhanced photocatalytic activity is attributed to the availability of active sites, extended light absorption in visible region and enhanced charge separation efficiency.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jhazmat.2019.121087DOI Listing
January 2020

Sunlight-Mediated Lead and Chromium Release from Commercial Lead Chromate Pigments in Aqueous Phase.

Environ Sci Technol 2019 05 23;53(9):4931-4939. Epub 2019 Apr 23.

State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment , Nanjing University , Jiangsu 210023 , China.

Lead chromate pigments are included in a group of the most widely used pigments, which account for 3% of worldwide lead consumption. This study reports the photoactivity of commercial lead chromate pigment (i.e., chrome yellow) under simulated sunlight. It underwent photodissolution in the presence of organic acid and dissolved organic matter in the aqueous phase, releasing Pb(II) and Cr(III). Pb(II) was released more readily than Cr(III) which mainly formed hydroxides and oxides. The photodissolution can be activated by light with a wavelength <514 nm. The reaction is mediated by the reduction of Cr(VI) in the pigment by self-generated electrons. The kinetics were mainly affected by the electron-hole separation efficiency which can be enhanced by electron donors. The reaction rate decreases with increasing solution pH as the photodissolution process consumes protons. The photodissolution of the chrome yellow pigment was further confirmed in a river water sample under natural sunlight, with 11.28% of lead and 2.56% of chromium released in 7 h. This study highlights the importance of considering photochemical processes in risk assessments and regulations of commercial semiconductor pigments, which are currently based on their solubility.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.8b06839DOI Listing
May 2019

Selenium and nitrogen co-doped carbon quantum dots as a fluorescent probe for perfluorooctanoic acid.

Mikrochim Acta 2019 04 10;186(5):278. Epub 2019 Apr 10.

School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China.

Highly fluorescent carbon quantum dots co-doped with selenium and nitrogen  (SeN-CQDs) were fabricated via a one-pot hydrothermal route using selenomethionine as the sole precursor. The SeN-CQDs aggregates have sizes between 30 and 45 nm and display blue fluorescence with a quantum yield of 8% at excitation/emission wavelengths of 350/445 nm. The fluorescence is pH dependent and decreases under acidic conditions. The doping of the CQDs with selenium and nitrogen was proven by X-ray photoelectron spectroscopy (XPS). Fluorescence is selectively quenched by perfluorooctanoic acid (PFOA), and this is accompanied by a decreased fluorescence lifetime. Quenching is not due to aggregation in view of the unaltered sizes of nanoparticles as revealed by TEM and DLS analyses. UV-vis absorption titration suggested the formation of an excited state complex between SeN-CQDs and PFOA, and quenching originates from the internal electron transfer in the excited state complex. The method was used to detect PFOA quantitatively in the linear range of 10-70 μM with a 1.8 μM detection limit. The nanoprobe has a high selectivity for PFOA over potentially interfering molecules. The practicability of the method was ascertained by accurate detection of PFOA in real samples by the standard addition method. The method may be further improved by tuning the interaction between PFOA and SeN-CQDs through optimizing the doping and the surface composition of the SeN-CQDs. Graphical abstract Schematic presentation of a fluorometric method for perfluorooctanoic acid detection by using a selenium and nitrogen co-doped carbon quantum dots as the fluorescent probe.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00604-019-3400-2DOI Listing
April 2019

CaO based Fenton-like reaction at neutral pH: Accelerated reduction of ferric species and production of superoxide radicals.

Water Res 2018 11 5;145:731-740. Epub 2018 Sep 5.

School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Key Laboratory for Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, Shanghai, 200240, China. Electronic address:

One challenge in HO based Fenton-like reaction is to break through the limitation of slow reduction of ferric species (Fe). Present work describes a dramatic acceleration of Fenton-like reaction at neutral pH by using calcium peroxide (CaO) as a source of hydrogen peroxide (HO) and EDTA as a chelating agent of ferric ions. In an optimized condition, phenol degradation in the HO system displayed an initial latent time of 60 min, while phenol can be degraded immediately and removed completely in 30 min in the CaO system. Visual MINTEQ analyses indicated Fe-EDTA was the active species in the reaction. The contribution of O in CaO system was excluded by the poor selectivity in phenol conversion and the comparable O-TEMP EPR signals in both CaO and HO systems. Kinetic analyses using chloroform as the probe of O suggested the high production rate of O, which is four orders of magnitude higher than that in HO system. The mechanism of the accelerated CaO based Fenton-like reactions was featured by that two electrons coming from CaO can be utilized to promote reduction of Fe: an inner sphere electron transfer takes place to reduce Fe-EDTA and produce O, and subsequently O provides an electron to reduce another Fe-EDTA. The revealed intrinsic reducibility in CaO based Fenton-like reaction represents a new strategy to break through the well-known rate limiting step of Fe reduction in Fenton-like reaction and facilitate the removal of organic pollutants at neutral pHs, and also indicates a promising source of O for diverse applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.watres.2018.09.020DOI Listing
November 2018

Novel Composite Electrodes for Selective Removal of Sulfate by the Capacitive Deionization Process.

Environ Sci Technol 2018 08 6;52(16):9486-9494. Epub 2018 Aug 6.

Department of Civil and Environmental Engineering , Rice University , MS 519, 6100 Main Street , Houston 77005 , United States.

Capacitive deionization (CDI) can remove ionic contaminants from water. However, concentrations of background ions in water are usually much higher than target contaminants, and existing CDI electrodes have no designed selectivity toward specific contaminants. In this study, we demonstrate a selective CDI process tailored for removal of SO using activated carbon electrodes modified with a thin, quaternary amine functionalized poly(vinyl alcohol) (QPVA) coating containing submicron sized sulfate selective ion exchange resin particles. The resin/QPVA coating exhibited strong selectivity for SO at Cl: SO concentration ratios up to 20:1 by enabling preferential transport of SO through the coating, but had no negative impact on the electrosorption kinetics when the coating thickness was small. The cationic nature of the coating also significantly improved the charge efficiency and consequently the total salt adsorption capacity of the electrode by 42%. The resin/QPVA coated CDI system was stable, showing highly reproducible performance in more than 50 adsorption and desorption cycles. This work suggests that addition of selective ion exchange resins on the surface of a carbon electrode could be a generally applicable approach to achieve selective removal of target ions in a CDI process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.8b01868DOI Listing
August 2018

Quantitative structure-activity relationship for the oxidation of aromatic organic contaminants in water by TAML/HO.

Water Res 2018 09 2;140:354-363. Epub 2018 May 2.

School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China; Key Laboratory for Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200240, China. Electronic address:

Tetra-amido macrocyclic ligand (TAML) activator is a functional analog of peroxidase enzymes, which activates hydrogen peroxide (HO) to form high valence iron-oxo complexes that selectively degrade persistent aromatic organic contaminants (ACs) in water. Here, we develop quantitative structure-activity relationship (QSAR) models based on measured pseudo first-order kinetic rate coefficients (k) of 29 ACs (e.g., phenols and pharmaceuticals) oxidized by TAML/HO at neutral and basic pH values to gain mechanistic insight on the selectivity and pH dependence of TAML/HO systems. These QSAR models infer that electron donating ability (E) is the most important AC characteristic for TAML/HO oxidation, pointing to a rate-limiting single-electron transfer (SET) mechanism. Oxidation rates at pH 7 also depend on AC reactive indices such as f and qH, which respectively represent propensity for electrophilic attack and the most positive net atomic charge on hydrogen atoms. At pH 10, TAML/HO is more reactive towards ACs with a lower hydrogen to carbon atoms ratio (#H:C), suggesting the significance of hydrogen atom abstraction. In addition, lnk of 14 monosubstituted phenols is negatively correlated with Hammett constants (σ) and exhibits similar sensitivity to substituent effects as horseradish peroxidase. Although accurately predicting degradation rates of specific ACs in complex wastewater matrices could be difficult, these QSAR models are statistically robust and help predict both relative degradability and reaction mechanism for TAML/HO-based treatment processes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.watres.2018.04.062DOI Listing
September 2018

Turn-on fluorometric and colorimetric probe for hydrogen peroxide based on the in-situ formation of silver ions from a composite made from N-doped carbon quantum dots and silver nanoparticles.

Mikrochim Acta 2017 12 6;185(1):31. Epub 2017 Dec 6.

School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China.

The authors describe a fluorometric and colorimetric nanoprobe for HO. The detection scheme is based on the in-situ formation of silver(I) ions from a composite consisting of nitrogen-doped carbon quantum dots (N-CQDs) and silver nanoparticles (AgNPs). A drastic change occurs both in fluorescence and color of the solution of the N-CQD/AgNPs composite. The fluorescence of composite (with excitation/emission peaking at 320/384 nm) is enhanced on increasing the concentration of HO due to the oxidation of silver metal in the N-CQD/AgNPs to form Ag(I) ions. The latter undergo strong coordination with the nitrogen atoms of the N-CQDs. In-situ formation of Ag(I) ions further results in a change in color of the solution from pale yellow (with a peak at 408 nm) to colorless. Under optimized conditions, the probe gives a fluorometric and colorimetric response in the 10 to 50 μM HO concentration range with a 4.7 μM limit of detection. The probe is highly selective over several potentially interfering ions and agents. It was successfully applied to the determination of HO in spiked samples without prior treatment. Graphical abstract Graphical presentation for specific detection of HO based on the in-situ formation of Ag(I) ions from a composite consisting of silver nanoparticles and nitrogen-doped carbon quantum dots.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00604-017-2545-0DOI Listing
December 2017

FRET based integrated pyrene-AgNPs system for detection of Hg (II) and pyrene dimer: Applications to environmental analysis.

Spectrochim Acta A Mol Biomol Spectrosc 2018 Jun 7;198:168-176. Epub 2018 Mar 7.

School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China; Key Laboratory for Thin Film and Microfabrication of the Ministry of Education, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China. Electronic address:

The integrated system of pyrene and cetyltrimethyl ammonium bromide (CTAB) capped silver nanoparticles (AgNPs) with a distance (r) of 2.78nm has been developed for the detection of Hg (II) and pyrene dimer. The interaction between pyrene and AgNPs results in the fluorescence quenching of pyrene due to the energy transfer, whose mechanism can be attributed to the Forster Resonance Energy Transfer (FRET) supported by experimental observation and theoretical calculations. The developed probe shows a highly selective and sensitive response towards Hg (II) probably due to the amalgam formation, which results in the fluorescence recovery (90%) of pyrene and color change of solution from yellowish brown to colorless. The addition of Hg (II) may increase the distance between pyrene and AgNPs undergoes the 'FRET OFF' process. This system gives a selective response towards Hg (II) over other competing metal ions. Under the optimal condition, the system offers good linearity between 0.1 and 0.6μgmL with a detection limit of 62ngmL. In addition, the system also provides an effective platform for detection of pyrene in its dimer form even at very low concentrations (10ngmL) on the surface of AgNPs. Therefore, it could be used as effective alternatives for the detection of Hg (II) as well as pyrene simultaneously.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.saa.2018.03.012DOI Listing
June 2018

Levels, sources and probabilistic health risks of polycyclic aromatic hydrocarbons in the agricultural soils from sites neighboring suburban industries in Shanghai.

Sci Total Environ 2018 Mar 23;616-617:1365-1373. Epub 2017 Oct 23.

School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China; Key Laboratory for Thin Film and Microfabrication of the Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, PR China. Electronic address:

The levels, sources and quantitative probabilistic health risks for polycyclic aromatic hydrocarbons (PAHs) in agricultural soils in the vicinity of power, steel and petrochemical plants in the suburbs of Shanghai are discussed. The total concentration of 16 PAHs in the soils ranges from 223 to 8214ng g. The sources of PAHs were analyzed by both isomeric ratios and a principal component analysis-multiple linear regression method. The results indicate that PAHs mainly originated from the incomplete combustion of coal and oil. The probabilistic risk assessments for both carcinogenic and non-carcinogenic risks posed by PAHs in soils with adult farmers as concerned receptors were quantitatively calculated by Monte Carlo simulation. The estimated total carcinogenic risks (TCR) for the agricultural soils has a 45% possibility of exceeding the acceptable threshold value (10), indicating potential adverse health effects. However, all non-carcinogenic risks are below the threshold value. Oral intake is the dominant exposure pathway, accounting for 77.7% of TCR, while inhalation intake is negligible. The three PAHs with the highest contribution for TCR are BaP (64.35%), DBA (17.56%) and InP (9.06%). Sensitivity analyses indicate that exposure frequency has the greatest impact on the total risk uncertainty, followed by the exposure dose through oral intake and exposure duration. These results indicate that it is essential to manage the health risks of PAH-contaminated agricultural soils in the vicinity of typical industries in megacities.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2017.10.179DOI Listing
March 2018

Selective Degradation of Organic Pollutants Using an Efficient Metal-Free Catalyst Derived from Carbonized Polypyrrole via Peroxymonosulfate Activation.

Environ Sci Technol 2017 Oct 14;51(19):11288-11296. Epub 2017 Sep 14.

Department of Civil and Environmental Engineering, Rice University , Houston, Texas 77005, United States.

Metal-free carbonaceous materials, including nitrogen-doped graphene and carbon nanotubes, are emerging as alternative catalysts for peroxymonosulfate (PMS) activation to avoid drawbacks of conventional transition metal-containing catalysts, such as the leaching of toxic metal ions. However, these novel carbocatalysts face relatively high cost and complex syntheses, and their activation mechanisms have not been well-understood. Herein, we developed a novel nitrogen-doped carbonaceous nanosphere catalyst by carbonization of polypyrrole, which was prepared through a scalable chemical oxidative polymerization. The defective degree of carbon substrate and amount of nitrogen dopants (i.e., graphitic nitrogen) were modulated by the calcination temperature. The product carbonized at 800 °C (CPPy-F-8) exhibited the best catalytic performance for PMS activation, with 97% phenol degradation efficiency in 120 min. The catalytic system was efficient over a wide pH range (2-9), and the reaction of phenol degradation had a relatively low activation energy (18.4 ± 2.7 kJ mol). The nitrogen-doped carbocatalyst activated PMS through a nonradical pathway. A two-step catalytic mechanism was extrapolated: the catalyst transfers electrons to PMS through active nitrogen species and becomes a metastable state of the catalyst (State I); next, organic substrates are oxidized and degraded by serving as electron donors to reduce State I. The catalytic process was selective toward degradation of various aromatic compounds with different substituents, probably depending on the oxidation state of State I and the ionization potential (IP) of the organics; that is, only those organics with an IP value lower than ca. 9.0 eV can be oxidized in the CPPy-F-8/PMS system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.7b03014DOI Listing
October 2017

Sunlight Promotes Fast Release of Hazardous Cadmium from Widely-Used Commercial Cadmium Pigment.

Environ Sci Technol 2017 Jun 30;51(12):6877-6886. Epub 2017 May 30.

School of Urban and Environmental Sciences, Peking University , Beijing 100871, China.

Cadmium pigments are widely used in the polymer and ceramic industry. Their potential environmental risk is under debate, being the major barrier for appropriate regulation. We show that 83.0 ± 0.2% of hazardous cadmium ion (Cd) was released from the commercial cadmium sulfoselenide pigment (i.e., cadmium red) in aqueous suspension within 24 h under simulated sunlit conditions. This photodissolution process also generated sub-20 nm pigment nanoparticles. Cd release is attributed to the reactions between photogenerated holes and the pigment lattices. The photodissolution process can be activated by both ultraviolet and visible light in the solar spectrum. Irradiation under alkaline conditions or in the presence of phosphate and carbonate species resulted in reduced charge carrier energy or the formation of insoluble and photostable cadmium precipitates on pigment surfaces, mitigating photodissolution. Tannic acid inhibited the photodissolution process by light screening and scavenging photogenerated holes. The fast release of Cd from the pigment was further confirmed in river water under natural sunlight, with 38.6 ± 0.1% of the cadmium released within 4 h. Overall, this study underscores the importance to account for photochemical effects to inform risk assessments and regulations of cadmium pigments which are currently based on their low solubility.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.7b00654DOI Listing
June 2017

Monolithic cobalt-doped carbon aerogel for efficient catalytic activation of peroxymonosulfate in water.

J Hazard Mater 2017 Jun 6;332:195-204. Epub 2017 Mar 6.

School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China.

As an emerging carbonaceous material, carbon aerogels (CAs) display a great potential in environmental cleanup. In this study, a macroscopic three-dimensional monolithic cobalt-doped carbon aerogel was developed by co-condensation of graphene oxide sheets and resorcinol-formaldehyde resin in the presence of cobalt ions, followed by lyophilization, carbonization and thermal treatment in air. Cobalt ions were introduced as a polymerization catalyst to bridge the organogel framework, and finally cobalt species were retained as both metallic cobalt and CoO, wrapped by graphitized carbon layers. The material obtained after a thermal treatment in air (CoCA-A) possesses larger BET specific surface area and pore volume, better hydrophilicity and lower leaching of cobalt ions than that without the post-treatment (CoCA). Despite of a lower loading of cobalt content and a larger mass transfer resistance than traditional powder catalysts, CoCA-A can efficiently eliminate organic contaminants by activation of peroxymonosulfate with a low activation energy. CoCA-A can float beneath the surface of aqueous solution and can be taken out completely without any changes in morphology. The monolith is promising to be developed into an alternative water purification technology due to the easily separable feature.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jhazmat.2017.03.010DOI Listing
June 2017

Phosphate Changes Effect of Humic Acids on TiO Photocatalysis: From Inhibition to Mitigation of Electron-Hole Recombination.

Environ Sci Technol 2017 01 16;51(1):514-521. Epub 2016 Dec 16.

Civil and Environmental Engineering, Rice University , Houston, Texas 77005, United States.

A major challenge for photocatalytic water purification with TiO is the strong inhibitory effect of natural organic matter (NOM), which can scavenge photogenerated holes and radicals and occlude ROS generation sites upon adsorption. This study shows that phosphate counteracts the inhibitory effect of humic acids (HA) by decreasing HA adsorption and mitigating electron-hole recombination. As a measure of the inhibitory effect of HA, the ratios of first-order reaction rate constants between photocatalytic phenol degradation in the absence versus presence of HA were calculated. This ratio was very high, up to 5.72 at 30 mg/L HA and pH 4.8 without phosphate, but was decreased to 0.76 (5 mg/L HA, pH 8.4) with 2 mM phosphate. The latter ratio indicates a surprising favorable effect of HA on TiO photocatalysis. FTIR analyses suggest that this favorable effect is likely due to a change in the conformation of adsorbed HA, from a multiligand exchange arrangement to a complexation predominantly between COOH groups in HA and the TiO surface in the presence of phosphate. This configuration can reduce hole consumption and facilitate electron transfer to O by the adsorbed HA (indicated by linear sweep voltammetry), which mitigates electron-hole recombination and enhances contaminant degradation. A decrease in HA surface adsorption and hole scavenging (the predominant inhibitory mechanisms of HA) by phosphate (2 mM) was indicated by a 50% decrease in the photocatalytic degradation rate of HA and 80% decrease in the decay rate coefficient of interfacial-related photooxidation in photocurrent transients. These results, which were validated with other compounds (FFA and cimetidine), indicate that anchoring phosphate - or anions that exert similar effects on the TiO surface - might be a feasible strategy to counteract the inhibitory effect of NOM during photocatalytic water treatment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.6b04845DOI Listing
January 2017

Magnetically separable maghemite/montmorillonite composite as an efficient heterogeneous Fenton-like catalyst for phenol degradation.

Environ Sci Pollut Res Int 2017 Jan 31;24(2):1926-1937. Epub 2016 Oct 31.

School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou, 450001, China.

To develop highly efficient and conveniently separable iron containing catalysts is crucial to remove recalcitrant organic pollutants in wastewater through a heterogeneous Fenton-like reaction. A maghemite/montmorillonite composite was synthesized by a coprecipitation and calcination method. The physiochemical properties of catalysts were characterized by XRD, TEM, nitrogen physisorption, thermogravimetric analysis/differential scanning calorimetry (TG/DSC), zeta potential, and magnetite susceptibility measurements. The influence of calcination temperatures and reaction parameters was investigated. The calcined composites retain magnetism because the presence of montmorillonite inhibited the growth of γ-FeO nanoparticles, as well as their phase transition. The catalytic activities for phenol degradation were significantly enhanced by calcinations, which strengthen the interaction between iron oxides and aluminosilicate framework and result in more negatively charged surface. The composite (73 m/g) calcined at 350 °C had the highest catalytic activities, with more than 99 % phenol reduction after only 35 min reaction at pH 3.6. Simultaneously, this catalyst exhibited high stability, low iron leaching, and magnetically separable ability for consecutive usage, making it promising for the removal of recalcitrant organic pollutants in wastewater.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11356-016-7866-8DOI Listing
January 2017

Sulfur Dioxide Capture by Heterogeneous Oxidation on Hydroxylated Manganese Dioxide.

Environ Sci Technol 2016 06 12;50(11):5809-16. Epub 2016 May 12.

School of Environmental Science and Engineering, Shanghai Jiao Tong University , Shanghai 200240, China.

Here we demonstrate that sulfur dioxide (SO2) is efficiently captured via heterogeneous oxidation into sulfate on the surface of hydroxylated manganese dioxide (MnO2). Lab-scale activity tests in a fluidized bed reactor showed that the removal efficiency for a simulated flue gas containing 5000 mg·Nm(-3) SO2 could reach nearly 100% with a GHSV (gas hourly space velocity) of 10000 h(-1). The mechanism was investigated using a combination of experimental characterizations and theoretical calculations. It was found that formation of surface bound sulfate proceeds via association of SO2 with terminal hydroxyls. Both H2O and O2 are essential for the generation of reactive terminal hydroxyls, and the indirect role of O2 in heterogeneous SO2 oxidation at low temperature was also revealed. We propose that the high reactivity of terminal hydroxyls is attributed to the proper surface configuration of MnO2 to adsorb water with degenerate energies for associative and dissociative states, and maintain rapid proton dynamics. Viability analyses suggest that the desulfurization method that is based on such a direct oxidation reaction at the gas/solid interface represents a promising approach for SO2 capture.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.5b05592DOI Listing
June 2016

Inhibitory effect of natural organic matter or other background constituents on photocatalytic advanced oxidation processes: Mechanistic model development and validation.

Water Res 2015 Nov 29;84:362-71. Epub 2015 Jul 29.

Rice University Department of Civil and Environmental Engineering, Houston, TX, USA. Electronic address:

The ability of reactive oxygen species (ROS) to interact with priority pollutants is crucial for efficient water treatment by photocatalytic advanced oxidation processes (AOPs). However, background compounds in water such as natural organic matter (NOM) can significantly hinder targeted reactions and removal efficiency. This inhibition can be complex, interfering with degradation in solution and at the photocatalyst surface as well as hindering illumination efficiency and ROS production. We developed an analytical model to account for various inhibition mechanisms in catalytic AOPs, including competitive adsorption of inhibitors, scavenging of produced ROS at the surface and in solution, and the inner filtering of the excitation illumination, which combine to decrease ROS-mediated degradation. This model was validated with batch experiments using a variety of ROS producing systems (OH-generating TiO2 photocatalyst and H2O2-UV; (1)O2-generating photosensitive functionalized fullerenes and rose bengal) and inhibitory compounds (NOM, tert-butyl alcohol). Competitive adsorption by NOM and ROS scavenging were the most influential inhibitory mechanisms. Overall, this model enables accurate simulation of photocatalytic AOP performance when one or more inhibitory mechanisms are at work in a wide variety of application scenarios, and underscores the need to consider the effects of background constituents on degradation efficiency.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.watres.2015.07.044DOI Listing
November 2015

Enhanced photocatalytic performance of N-nitrosodimethylamine on TiO2 nanotube based on the role of singlet oxygen.

Chemosphere 2015 Feb 4;120:521-6. Epub 2014 Oct 4.

College of Environmental Science and Engineering, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Nankai University, Wei Jin Road 94, Tianjin 300071, China.

N-nitrosodimethylamine (NDMA) photocatalytic degradation performance and mechanism were investigated on the TiO2 nanotube prepared from anatase TiO2 nanopowder in terms of the production of reactive oxygen species including hydroxyl radical, singlet oxygen and superoxide radical. Significantly higher NDMA degradation efficiency was obtained on anatase TiO2 nanotube rather than anatase TiO2 nanopowder. The tubular morphology may be responsible for almost 100% NDMA removal on TiO2 nanotube, presumably due to its confinement effect leading to NDMA molecules within the nanotube being attacked by reactive oxygen species such as hydroxyl radical and singlet oxygen, and initiating reaction inside the nanotube. In particular, the ability of the nanotubular structure of TiO2 nanotube to promote a singlet oxygen oxidation pathway contributes much to the enhanced NDMA degradation efficiency and favors the formation of dimethylamine and NO3(-). Such function originating from nanotube morphology could bring new insights for the photocatalytic degradation of organic pollutants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2014.09.002DOI Listing
February 2015

Advanced nanoarchitectures of silver/silver compound composites for photochemical reactions.

Nanoscale 2014 Jul;6(14):7730-42

School of Environmental Science and Engineering, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China.

Silver/silver compound (SSC) composites have received much attention as a type of potential materials in photochemical reactions due to their high efficiency, facile syntheses and availability of raw materials. This article reviews the state-of-the-art progress on the advanced nanoarchitectures of SSC composites. We begin with a survey on the general synthetic strategies for SSC composites, and then step into relatively detailed methods for size and morphology tunable two-component and more delicate multi-component SSC nanostructures. In addition, the electronic structure-related mechanisms of such materials and the recent studies on their stability are summarized. This review also highlights some perspectives on challenges related to the SSC composites and the possible research in the future.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c3nr06302jDOI Listing
July 2014

Trading oxidation power for efficiency: differential inhibition of photo-generated hydroxyl radicals versus singlet oxygen.

Water Res 2014 Sep 15;60:259-266. Epub 2014 May 15.

Rice University, Department of Civil and Environmental Engineering, United States. Electronic address:

The ability of reactive oxygen species (ROS) to interact with target pollutants is crucial for efficient water treatment using advanced oxidation processes (AOPs), and inhibition by natural organic matter (NOM) can significantly reduce degradation efficiency. We compare OH-based degradation (H2O2-UV) to (1)O2-based degradation (Rose Bengal) of several probe compounds (furfuryl alcohol, ranitidine, cimetidine) interacting in water containing background constituents likely to be found in treatment water such as natural organic matter (NOM) and phosphate, as well as in effluent from a waste-water treatment plant (WWTP). Hydroxyl radicals were much more susceptible to hindrance by all three background matrices (NOM, phosphate and WWTP effluent) tested, while (1)O2 was only slightly inhibited by NOM and not by phosphate or WWTP effluent. A mechanistic model accounting for this inhibition in terms of radical scavenging and inner filter effects was developed, and accurately simulated the results of the NOM interactions. These results underscore the importance of considering the effect of background constituents in the selection of photocatalysts and in the design of AOPs for emerging applications in tertiary treatment of wastewater effluent and disinfection of natural waters.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.watres.2014.05.005DOI Listing
September 2014

Large-scale preparation of nanoporous TiO2 film on titanium substrate with improved photoelectrochemical performance.

Nanoscale Res Lett 2014 24;9(1):190. Epub 2014 Apr 24.

School of Environmental Science and Engineering, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China.

Fabrication of three-dimensional TiO2 films on Ti substrates is one important strategy to obtain efficient electrodes for energy conversion and environmental applications. In this work, we found that hierarchical porous TiO2 film can be prepared by treating H2O2 pre-oxidized Ti substrate in TiCl3 solution followed by calcinations. The formation process is a combination of the corrosion of Ti substrate and the oxidation hydrolysis of TiCl3. According to the characterizations by scanning electron microscopy (SEM), X-ray diffraction (XRD), and diffuse reflectance spectroscopy (DRS), the anatase phase TiO2 films show porous morphology with the smallest diameter of 20 nm and possess enhanced optical absorption properties. Using the porous film as a working electrode, we found that it displays efficient activity for photoelectrocatalytic decolorization of rhodamine B (RhB) and photocurrent generation, with a photocurrent density as high as 1.2 mA/cm(2). It represents a potential method to fabricate large-area nanoporous TiO2 film on Ti substrate due to the scalability of such chemical oxidation process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1556-276X-9-190DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4002557PMC
May 2014

Magnetically separable core-shell structural γ[email protected]/Al-MCM-41 nanocomposite and its performance in heterogeneous Fenton catalysis.

J Hazard Mater 2014 Jan 13;264:195-202. Epub 2013 Nov 13.

School of Environmental Science and Engineering, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China.

To target the low catalytic activity and the inconvenient separation of copper loading nanocatalysts in heterogeneous Fenton-like reaction, a core-shell structural magnetically separable catalyst, with γ-Fe2O3 nanoparticles as the core layer and the copper and aluminum containing MCM-41 as the shell layer, has been fabricated. The role of aluminum has been discussed by comparing the copper containing mesoporous silica with various Cu contents. Their physiochemical properties have been characterized by XRD, UV-vis, FT-IR, TEM, nitrogen physisorption and magnetite susceptibility measurements. Double content Cu incorporation results in an improved catalytic activity for phenol degradation at the given condition (40°C, initial pH=4), but leads to a declined BET surface area and less ordered mesophase structure. Aluminum incorporation helps to retain the high BET surface area (785.2m(2)/g) and the regular hexagonal mesoporous structure of MCM-41, which make the catalyst possess a lower copper content and even a higher catalytic activity than that with the double copper content in the absence of aluminum. The catalysts can be facilely separated by an external magnetic field for recycle usage.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jhazmat.2013.11.008DOI Listing
January 2014

A facile method for fabricating [email protected] carbon and three-layered nanocomposites.

Nanotechnology 2012 Aug 23;23(32):325602. Epub 2012 Jul 23.

School of Chemistry and Chemical Technology, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China.

Herein, we report a new and facile method for fabricating TiO(2)@mesoporous carbon hybrid materials. Uniform polydopamine (PDA) layers were coated onto the surface of titanate nanotubes (TNTs) and TiO(2) nanorods (TNDs) through the spontaneous adhesion and self-polymerization of dopamine during the dipping process. Core-shell mesoporous carbon nanotubes with TiO(2) nanorods or nanoparticles encapsulated inside (TiO(2)@MC) were then obtained by transforming PDA layers into carbonaceous ones through calcination in nitrogen at 800 °C. The thickness of the mesoporous carbon layers is tens of nanometers and can be controlled by adjusting the coated PDA layers through the self-polymerization reaction time. In addition, three-layered nanocomposites of TiO(2)@[email protected] (MO, metal oxide) can be readily prepared by utilizing PDA layers in [email protected] or [email protected] to adsorb the metal ions, followed by the calcination process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0957-4484/23/32/325602DOI Listing
August 2012

Preparation of hollow porous Cu2O microspheres and photocatalytic activity under visible light irradiation.

Nanoscale Res Lett 2012 Jun 27;7(1):347. Epub 2012 Jun 27.

Key Laboratory for Thin Film and Microfabrication of the Ministry of Education, Research Institute of Micro/Nano Science and Technology, Shanghai Jiao Tong University, Shanghai 200240, China.

Cu2O p-type semiconductor hollow porous microspheres have been prepared by using a simple soft-template method at room temperature. The morphology of as-synthesized samples is hollow spherical structures with the diameter ranging from 200 to 500 nm, and the surfaces of the spheres are rough, porous and with lots of channels and folds. The photocatalytic activity of degradation of methyl orange (MO) under visible light irradiation was investigated by UV-visible spectroscopy. The results show that the hollow porous Cu2O particles were uniform in diameters and have an excellent ability in visible light-induced degradation of MO. Meanwhile, the growth mechanism of the prepared Cu2O was also analyzed. We find that sodium dodecyl sulfate acted the role of soft templates in the synthesis process. The hollow porous structure was not only sensitive to the soft template but also to the amount of reagents.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1556-276X-7-347DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3443013PMC
June 2012

Visible light assisted photocatalytic degradation of methyl orange using Ag/N-TiO₂ photocatalysts.

Water Sci Technol 2012 ;65(6):1027-32

School of Chemical and Environmental Engineering, Hubei University for Nationalities, Enshi, Hubei 445000, China.

For the sake of efficient utilization of sunlight, Ag nanoparticles loaded N-doped TiO₂ photocatalysts (Ag/N-TiO₂) were successfully fabricated via a two-step method to make the best use of the respective advantages of noble metal loading and nonmetal doping. Ag/N-TiO₂ was characterized using XRD, XPS and UV-Vis DRS. Compared to TiO₂, the dramatic enhancement of the visible-light-induced photocatalytic degradation efficiency of Ag/N-TiO₂ obtained for the degradation of methyl orange should be attributed to the synergistic effect of N-doping and Ag-loading, including the good visible light absorption and the effective electron-hole separations. This demonstrates Ag/N-TiO₂ is a promising photocatalytic material for organic pollutant degradation under visible light irradiation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2166/wst.2012.926DOI Listing
May 2012