Nanjing UniversityJiangsu

Nanjing, China

Nanjing UniversityJiangsu

Nanjing, China
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Guan D.-X.,Nanjing UniversityJiangsu | Zheng J.-L.,Nanjing UniversityJiangsu | Luo J.,Nanjing UniversityJiangsu | Zhang H.,Lancaster University | And 3 more authors.
Journal of Hazardous Materials | Year: 2017

Desorption/adsorption of bisphenols (BPs) in soils affects their mobility and availability. However, the kinetics of these processes have not been well studied, due to the lack of appropriate means of measurement. Diffusive gradients in thin-films (DGT) technique can assess kinetic processes in soils and have recently been developed for measuring three BPs (BPA, BPB and BPF). DGT was deployed for 2.5 h to 20 d in five soils with different soil properties. Non-linear increase in mass accumulation by DGT with time indicated poor resupply of BPs from soil solid to solution phase. By fitting the data with DIFS (DGT-induced fluxes in soils) model, values for the labile partition coefficient (Kdl), response time (tc) and rates of exchange (k1 and k-1) of BPs between soil solid and solution phases were obtained. The derived values of Kdl showed that most of the BPs in the soil could participate in labile exchange. Average response times of 1–2 h implied that the supply of BPs to DGT was limited by their desorption rate. Soils with more binding sites (higher DOM, CEC and Fe oxides) could resupply BPs more quickly, highlighting the danger of just considering partition effects. © 2017 Elsevier B.V.


Jiang W.,Shandong University | Wang Q.,Shandong University | Qu X.,Nanjing UniversityJiangsu | Wang L.,Shandong University | And 3 more authors.
Science of the Total Environment | Year: 2017

The direct contact between multi-walled carbon nanotubes (MWCNTs) and cell membranes causes membrane disruption, potentially leading to cytotoxicity. However, the role of electrostatic forces and MWCNT properties is still open to debate. In this study, the influences of charge and MWCNT surface defects on membrane disruption were investigated by microscopy and a quartz crystal microbalance with dissipation monitoring (QCM-D). Positively/negatively charged giant unilamellar vesicles (GUVs) and supported lipid bilayers (SLBs) were made as model cell membranes. Negatively charged MWCNTs disrupted the GUVs containing positively charged lipids, which confirmed the electrostatically mediated interaction. However, the mass loss was detected from the negatively charged SLBs after MWCNT exposure, which suggests the extraction of phospholipids. The defect degree of MWCNTs correlated with their adhesion amount on the membranes. Both the oxygenated functional groups and unoxidized dangling carbon bonds were active sites for MWCNT-membrane interactions. The MWCNTs were observed to be engulfed inside the GUVs. The results clearly demonstrate that phospholipid extraction by MWCNTs could occur in electrostatically repulsive conditions, and MWCNT defects were active binding sites whether or not they were oxygenated. Our findings should be helpful in the design and safe applications of carbon nanomaterials. © 2016


Li H.,Nanjing UniversityJiangsu | Dong X.,University of Florida | da Silva E.B.,University of Florida | de Oliveira L.M.,University of Florida | And 3 more authors.
Chemosphere | Year: 2017

Biochar produced by thermal decomposition of biomass under oxygen-limited conditions has received increasing attention as a cost-effective sorbent to treat metal-contaminated waters. However, there is a lack of information on the roles of different sorption mechanisms for different metals and recent development of biochar modification to enhance metal sorption capacity, which is critical for biochar field application. This review summarizes the characteristics of biochar (e.g., surface area, porosity, pH, surface charge, functional groups, and mineral components) and main mechanisms governing sorption of As, Cr, Cd, Pb, and Hg by biochar. Biochar properties vary considerably with feedstock material and pyrolysis temperature, with high temperature producing biochars with higher surface area, porosity, pH, and mineral contents, but less functional groups. Different mechanisms dominate sorption of As (complexation and electrostatic interactions), Cr (electrostatic interactions, reduction, and complexation), Cd and Pb (complexation, cation exchange, and precipitation), and Hg (complexation and reduction). Besides sorption mechanisms, recent advance in modifying biochar by loading with minerals, reductants, organic functional groups, and nanoparticles, and activation with alkali solution to enhance metal sorption capacity is discussed. Future research needs for field application of biochar include competitive sorption mechanisms of co-existing metals, biochar reuse, and cost reduction of biochar production. © 2017


Qu X.,Nanjing UniversityJiangsu | Fu H.,Nanjing UniversityJiangsu | Mao J.,Old Dominion University | Ran Y.,CAS Guangzhou Institute of Geochemistry | And 2 more authors.
Carbon | Year: 2016

Black carbon (BC) has drawn wide interest due to its important role in the global carbon budget and pollutant sequestration. Its soluble carbonaceous component, dissolved BC, is the key for understanding many geological and environmental processes of BC. In this study, we show that dissolved BC can be readily released in water under stirring from bulk BC produced by the slow pyrolysis of biomass. The chemical and structural properties of bulk, colloidal, and dissolved BC were thoroughly examined using elemental analysis and a variety of spectroscopic techniques. Compared with bulk BC, dissolved BC contained 30-40% more oxygen and more polar functional groups, but lower aromaticity and less condensed aromatic clusters. It is concluded that dissolved BC consists primarily of small aromatic clusters substituted by carboxylic groups, and by phenolic groups to a less extent. Dissolved BC represents an important source for soil and aquatic natural organic matter. The structure of dissolved BC was compared with some well-characterized humic substances. Results obtained from this work would shed new light on the mobility, liability, and reactivity of BC, as well as its impact on the global carbon budget and contaminant transport. © 2015 Elsevier Ltd.


Wei C.,Nanjing UniversityJiangsu | Xu Y.,Nanjing UniversityJiangsu | Ma Y.,Nanjing UniversityJiangsu
International Journal of Simulation: Systems, Science and Technology | Year: 2016

In order to study the influence of the impact of powder gas with high temperature and high pressure on the composite material barrel, a three-dimensional thermal-mechanical analysis was conducted based on finite element analysis model. Regarding the fiber reinforced composite material barrel with metal liner as the research object, the finite element model of the barrel was established by using the nonlinear method. This paper firstly explored the influence of temperature-dependent material properties on the temperature field distribution of the barrel by the thermal load. Then, the stress field distribution was calculated by the non-coupled thermal-elastic theory. Finally, the stress field of the barrel was calculated by the coupled thermal-elastic theory. The effect of material nonlinearity on the temperature field distribution and the distribution law of stress under different load conditions was obtained. The results show that the thermal-mechanical impact loads can cause large transient stress, which clearly influences the strength of the metal liner properties. The paper provides a theoretical basis for the study of the damage of composite material barrel under thermal-mechanical loading. © 2016, UK Simulation Society. All rights reserved.


Fu Y.,Missouri University of Science and Technology | Liu G.,Beihang University | Papadimitriou S.,Rutgers University | Xiong H.,Rutgers University | And 2 more authors.
Decision Support Systems | Year: 2016

In online shopping, product returns are very common. Liberal return policies have been widely used to attract shoppers. However, returns often increase expense and inconvenience for all parties involved: customers, retailers, and manufacturers. Despite the large fraction of purchases that are returned, there are few systematic studies to explain the underlying forces that drive return requests, and to assess the return propensity at the level of individual purchases (i.e., a particular customer purchasing a particular product), rather than in aggregate. To this end, in this paper, we provide a systematic framework for personalized predictions of return propensity. These predictions can help retailers enhance inventory management, improve customer relationships, and reduce return fraud and abuse. Specifically, we treat product returns as a result of inconsistency arising during a commercial transaction. We decompose this inconsistency into two components, one for the buying phase (e.g., product does not match description) and another for the shipping phase (e.g., product damaged during shipping). Along these lines, we introduce a generalized return propensity latent model (RPLM). We further propose a complete framework, called fused return propensity latent model (FRPLM), to jointly model the correlation among user profiles, product features, and return propensity. We present comprehensive experimental results with real-world data to demonstrate the effectiveness of the proposed method for assessing return propensity. © 2016 Elsevier B.V.


Rui Q.-Q.,Nanjing University of Technology | Zhou Y.,Nanjing University of Technology | Fang Y.,Nanjing University of Technology | Yao C.,Nanjing University of Technology | Yao C.,Nanjing UniversityJiangsu
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2016

Two new rhodamine B-based fluorescent probes PyRbS and PyRbO containing pyrene moiety were designed and synthesized. Both of the probes showed colorimetric and fluorometric sensing abilities for Hg2+ with high selectivity over other metal ions. The binding analysis using Job's plot suggested 1:1 stoichiometry for the complexes formed for Hg2+. Compared with PyRbO, the PyRbS showed higher selectivity and sensitivity due to the thiophilic property of Hg2+ ion. The PyRbS exhibited the linear fluorescence quenching to Hg2+ in the range of 0.3 to 4.8 μM (λex = 365 nm) and 0.3 to 5.4 μM (λex = 515 nm), and the detection limit was 0.72 μM. Moreover, ratiometric changes of PyRbS with Hg2+ in absorption spectrum were observed, which could not be obtained in the combination of PyRbO with Hg2+. In addition, the methyl thiazolyl tetrazolium (MTT) assay demonstrated that RbPyS had low cytotoxicity and was successfully used to monitor intracellular Hg2+ levels in living cells. © 2016 Elsevier B.V. All rights reserved.


Kumar K.V.,Queen Mary, University of London | Preuss K.,Queen Mary, University of London | Lu L.,Nanjing UniversityJiangsu | Guo Z.X.,University College London | Titirici M.M.,Queen Mary, University of London
Journal of Physical Chemistry C | Year: 2015

Nitrogen (N) doping is considered an effective design strategy to improve CO2 adsorption in carbon materials. However, experimental quantification of such an effect is riddled with difficulties, due to the practical complexity involved in experiments to control more than one parameter, especially at the nanoscale level. Here, we use molecular simulations to clarify the role of N doping on the CO2 uptake and the CO2/N2 selectivity in representative carbon pore architectures (slit and disordered carbon structures) at 298 K. Our results indicate that N doping shows a marginal improvement on the CO2 uptake, although it can improve the CO2/N2 selectivity. CO2 uptake and CO2/N2 selectivity are predominantly controlled by the pore architecture as well as ultra-micropores; the tendency of linear CO2 molecules to lie flat on the carbon surface favors the CO2 uptake in slit pore architectures rather than disordered carbon pore structures. We also demonstrated through molecular simulations that the N doping effect may be difficult to exemplify experimentally if the material has a disordered pore architecture and complex surface chemistry (such as the presence of other functional groups). © 2015 American Chemical Society.


Chen H.,University of Florida | Gao B.,University of Florida | Yang L.-Y.,Nanjing UniversityJiangsu | Ma L.Q.,University of Florida | Ma L.Q.,Nanjing UniversityJiangsu
Journal of Contaminant Hydrology | Year: 2015

Antibiotic ciprofloxacin (CIP) is immobile in the subsurface but it has been frequently detected in the aquatic system. Therefore it is important to investigate the factors impacting CIP's mobilization in aquifer. Laboratory columns packed with sand were used to test colloid-facilitated CIP transport by 1) using kaolinite or montmorillonite to mobilize presorbed-CIP in a column or 2) co-transporting with CIP by pre-mixing them before transport. The Langmuir model showed that CIP sorption by montmorillonite (23 g kg-1) was 100 times more effective than sand or kaolinite. Even with strong CIP complexation ability to Fe/Al coating on sand surface, montmorillonite promoted CIP transport, but not kaolinite. All presorbed-CIP by sand was mobilized by montmorillonite after 3 pore volumes through co-transporting of CIP with montmorillonite. The majority of CIP was fixed onto the montmorillonite interlayer but still showed inhibition of bacteria growth. Our results suggested that montmorillonite with high CIP sorption ability can act as a carrier to enhance CIP's mobility in aquifer. © 2015, Elsevier B.V. All rights reserved.


Liu X.,Nanjing UniversityJiangsu | Yang G.-M.,Nanjing UniversityJiangsu | Guan D.-X.,Nanjing UniversityJiangsu | Ghosh P.,University of Florida | And 2 more authors.
Environmental Pollution | Year: 2015

The impact of siderophore produced by arsenic-resistant bacterium Pseudomonas PG12 on FeAsO4 dissolution and plant growth were examined. Arsenic-hyperaccumulator Pteris vittata was grown for 7 d in 0.2-strength Fe-free Hoagland solution containing FeAsO4 mineral and PG12-siderophore or fungal-siderophore desferrioxamine B (DFOB). Standard siderophore assays indicated that PG12-siderophore was catecholate-type. PG12-siderophore was more effective in promoting FeAsO4 dissolution, and Fe and As plant uptake than DFOB. Media soluble Fe and As in PG12 treatment were 34.6 and 3.07 μM, 1.6- and 1.4-fold of that in DFOB. Plant Fe content increased from 2.93 to 6.24 g kg-1 in the roots and As content increased from 14.3 to 78.5 mg kg-1 in the fronds. Besides, P. vittata in PG12 treatment showed 2.6-times greater biomass than DFOB. While P. vittata fronds in PG12 treatment were dominated by AsIII, those in DFOB treatment were dominated by AsV (61-77%). This study showed that siderophore-producing arsenic-resistant rhizobacteria may have potential in enhancing phytoremediation of arsenic-contaminated soils.

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