Publications by authors named "Dongye Zhao"

119 Publications

Evaluation of three common alkaline agents for immobilization of multi-metals in a field-contaminated acidic soil.

Environ Sci Pollut Res Int 2021 Jun 24. Epub 2021 Jun 24.

School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.

We investigated three common alkaline agents (NaOH, CaO, and Mg(OH)) for immobilization of four heavy metals (Pb, Zn, Cu, and Cd) in a field-contaminated soil and elucidated the underpinning principles. NaOH caused the highest pH spike in the soil, while CaO and Mg(OH) served as a longer-lasting source of OH. Amending the soil with CaO or Mg(OH) at ≥0.1 mol as OH (kg·soil) for 24 h was able to immobilize all four metals, while NaOH failed. NaOH leached up to 3 times more organic carbon than CaO and Mg(OH), resulting in elevated leachability of the metals. Column elution tests showed that amendments by CaO and Mg(OH) lowered the leachable Pb, Zn, Cu, and Cd by 52-54%, 71-75%, 69-73%, and 68%, respectively, after 1440 pore volumes of elution. Sequential extraction revealed that the soil amendments converted the exchangeable fraction of the metals to the much less available forms. XRD and FTIR analyses indicated that formation of metal oxide precipitates and complexation with soil organic matter were responsible for the metals immobilization. Taken together the chemical cost, technical effectiveness, and environmental impact, CaO is the most suitable alkaline agent for remediation of soil contaminated with heavy metals.
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http://dx.doi.org/10.1007/s11356-021-14670-3DOI Listing
June 2021

A 'Concentrate-&-Destroy' technology for enhanced removal and destruction of per- and polyfluoroalkyl substances in municipal landfill leachate.

Sci Total Environ 2021 May 29;791:148124. Epub 2021 May 29.

CTI and Associates, Inc., 28001 Cabot Dr #250, Novi, MI 48377, USA.

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in landfill leachate due to their widespread applications in various industrial and consumer products. Yet, there has been no cost-effective technology available for treating PFAS in leachate because of the intrinsic persistency of PFAS and the high matrix strength of landfill leachate. We tested a two-step 'Concentrate-&-Destroy' technology for treating over 14 PFAS from a model landfill leachate through bench- and pilot-scale experiments. The technology was based on an adsorptive photocatalyst (Fe/[email protected]), which was able to selectively adsorb PFAS despite the strong matrix effect of the leachate. Moreover, the pre-concentrated PFAS on Fe/[email protected] were effectively degraded under UV, which also regenerates the material. The presence of 0.5 M HO during the photocatalytic degradation enhanced the solid-phase destruction of the PFAS. Fresh Fe/[email protected] at a dosage of 10 g/L removed >95% of 13 PFAS from the leachate, 86% after first regeneration, and 74% when reused three times. Fe/[email protected] was less effective for PFBA and PFPeA partially due to the transformation of precursors and/or longer-chain homologues into these short-chain PFAS. Pilot-scale tests preliminarily confirmed the bench-scale results. Despite the strong interference from additional suspended solids, Fe/[email protected] removed >92% of 18 PFAS in 8 h under the field conditions, and when the PFAS-laden solids were subjected to the UV-HO system, ~84% of 16 PFAS in the solid phase were degraded. The 'Concentrate-&-Destroy' strategy appears promising for more cost-effective removal and degradation of PFAS in landfill leachate or PFAS-laden high-strength wastewaters.
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http://dx.doi.org/10.1016/j.scitotenv.2021.148124DOI Listing
May 2021

Microwave-enhanced reductive immobilization of high concentrations of chromium in a field soil using iron polysulfide.

J Hazard Mater 2021 Jun 3;418:126293. Epub 2021 Jun 3.

School of Environment and Energy, Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Resource Recycling, South China University of Technology, Guangzhou 510006, China; School of Metallurgy and Environment, Central South University, Changsha 410083, China.

High concentrations of Cr(VI) are often detected in contaminated soil. Yet, cost-effective remediation technologies have been lacking. In this study, we prepared a type of FeS based on commercial FeSO.7HO and CaS and tested a microwave-assisted technology based on FeS for reductive immobilization of high concentrations of Cr(VI) in a field contaminated soil. The as-prepared FeS particles appeared as a honeycomb-like and highly porous structure. The microwave-assisted FeS reduction process was able to rapidly reduce the TCLP-based reachability of Cr(VI) from 391.8 to 2.6 mg·L. The dosage of FeS, S/Fe molar ratio, initial moisture content, microwave power, and irradiation time can all affect the treatment effectiveness. After 500 days curing under atmospheric conditions, the TCLP-leached concentration of Cr remained below the regulatory limit of 5 mg·L, while other treatments failed to meet the goal. S or S served as the primary electron donors, whereas Fe facilitated the microwave absorption and the formation of the stable final product of FeCrO. S and Fe are mostly precipitated in soil. The microwave-assisted FeS reduction was shown to be an effective approach to rapidly reduce the leachability of Cr(VI) in contaminated soil, especially in heavily contaminated soil.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126293DOI Listing
June 2021

A novel ball-milled aluminum-carbon composite for enhanced adsorption and degradation of hexabromocyclododecane.

Chemosphere 2021 Sep 8;279:130520. Epub 2021 Apr 8.

Department of Civil and Environmental Engineering, 238 Harbert Engineering Center, Auburn University, Auburn, AL, 36849, USA. Electronic address:

Hexabromocyclododecane (HBCD) is one of the priority persistent organic pollutants (POPs), yet a cost-effective technology has been lacking for the removal and degradation of HBCD. Zero-valent aluminum (ZVAl) is an excellent electron donor. However, the inert and hydrophilic surface oxide layer impedes the release of the electrons from the core metallic Al, resulting in poor reactivity towards HBCD. In this research, a new type of modified mZVAl particles ([email protected]) were prepared through ball milling mZVAl in the presence of activated carbon (AC) and NaCl, and tested for adsorption and reductive degradation of HBCD in water. [email protected] was characterized with a metallic Al core with newly created reactive surface coated with a thin layer of crushed carbon nanoparticles. [email protected] was able to rapidly (within 1 h) adsorb HBCD (C = 2 mg L) and thus effectively enriched HBCD on the carbon surface of [email protected] The pre-enriched HBCD was subsequently degraded by the electrons from the core Al, and ∼63.44% of the pre-sorbed HBCD was completely debrominated after 62 h of the contact. A notable time lag (∼12 h) from the onset of the adsorption to the debromination was observed, signifying the importance of the solid-phase mass transfer from the initially adsorbed AC particles to the reactive Al-AC interface. Overall, [email protected] synergizes the adsorptive properties of AC and the high reactivity of metallic Al, and enables a novel two-step adsorption and reductive degradation process for treating HBCD or likely other POPs.
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http://dx.doi.org/10.1016/j.chemosphere.2021.130520DOI Listing
September 2021

Compositional evolution of nanoscale zero valent iron and 2,4-dichlorophenol during dechlorination by attapulgite supported Fe/Ni nanoparticles.

J Hazard Mater 2021 06 26;412:125246. Epub 2021 Jan 26.

Patent Examination Cooperation Hubei Center of the Patent Office, CNIPA, Wuhan 430081, China.

Transformation of chloro-organic compounds by nFe(0) has been studied extensively, but limited study exists on the transformation and fate of nFe(0) during the dechlorination of chloro-organics even though such knowledge is important in predicting its surface chemistry, particularly, toxicity in the environment. In this study, the nFe(0) core became hollowed, collapsed and gradually corroded into poorly crystallized ferrihydrite (FeO(OH)) at the pristine reaction time, which later gave rise to lath-like lepidocrocite (γ-FeOOH), acicular goethite (α-FeOOH) and cubic magnetite (FeO) by the end of the reaction time (120 min). Also, dechlorination of 2,4-DCP into 2-CP, 4-CP and phenol was achieved within 120 min. The rapid dechlorination of 2,4-DCP and transformation of nFe(0) could not be achieved significantly without doping Ni on nFe(0) and supporting on attapulgite. The schematic representation of the transformation and compositional evolution of nFe(0) in A-nFe/Ni was proposed. These findings are critical in understanding the compositional evolution and the fate of nFe(0) upon reaction with chloro-organics and can provide guidance for more efficient uses of the nFe(0) reactivity towards the target contaminants in groundwater remediation.
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http://dx.doi.org/10.1016/j.jhazmat.2021.125246DOI Listing
June 2021

Iron(II) sulfate crystals assisted mechanochemical modification of microscale zero-valent aluminum (mZVAl) for oxidative degradation of phenol in water.

Chemosphere 2021 Jul 27;274:129767. Epub 2021 Jan 27.

Department of Civil and Environmental Engineering, 238 Harbert Engineering Center, Auburn University, Auburn, AL, 36849, USA. Electronic address:

Microscale zero-valent aluminum (mZVAl) is prone to surface passivation due to formation of the surface Al-(hydr)oxide layer, resulting in short reactive life. To overcome this critical drawback, we developed a mechanochemical ball milling approach to modify and activate commercially available mZVAl assisted by the fragile FeSO·7HO crystals. SEM-EDS and XPS analyses indicated that the particle surface of the mechanochemically modified mZVAl (Fe-mZVAl) was not only fractured with newly formed fresh reactive surfaces, but also attached with a rough layer of Fe-oxides that were uniformly distributed on mZVAl. While pristine mZVAl failed to degrade any phenol, Fe-mZVAl was able to rapidly degrade 88.8% within 90 min (initial phenol = 20 mg/L, pH = 2.50, dosage = 3 g/L) under normal oxic conditions, with a pseudo first-order rate constant of 0.040 min and about 70.0% of phenol mineralized in 8 h. Moreover, Fe-mZVAl also showed prolonged reactive life, and no significant reactivity drop was evident after six cycles of consecutive runs for phenol degradation. The much enhanced reactivity and reactive longevity of Fe-mZVAl are attributed to the critical roles of the surface Fe-oxides, including 1) protecting the newly exposed reactive Al from being oxidized by side reactions, 2) serving as an electron mediator facilitating the electron transfer from the core Al reservoir to the exterior surface, and 3) acting as an Fe source and a heterogeneous catalyst to enable the Fenton (-like) reactions. This study provides a novel and practical approach for preparing Fe-oxides modified mZVAl with enhanced and long-lasting reactivity.
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http://dx.doi.org/10.1016/j.chemosphere.2021.129767DOI Listing
July 2021

Simultaneous immobilization of multi-metals in a field contaminated acidic soil using carboxymethyl-cellulose-bridged nano-chlorapatite and calcium oxide.

J Hazard Mater 2021 04 8;407:124786. Epub 2020 Dec 8.

School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China.

We prepared and tested carboxymethyl-cellulose-bridged nano-chlorapatite (CMC-CAP) for simultaneous immobilization of Pb, Zn, Cu, and Cd in a field-contaminated acidic soil. Amending the field-contaminated soil using 0.5 wt.% CMC-CAP and 0.1 wt.% CaO was most effective in immobilizing the four metals, which decreased the leachabilities by 98.2%, 98.3%, 96.3%, and 96.2% for Pb, Zn, Cu, and Cd, respectively, after 1 day of treatment. The acid-leached metals fluctuated in the first 60 days, and then approached to steady state after 180 days, where the acid-leachable concentrations all met the regulation levels, and the immobilization was further consolidated when further aged for 365 days. Column elution tests showed that the soil amendment lowered the peak metal concentrations by > 92.5%, and the total eluted masses by >71.9%. Sequential extraction revealed that the soil amendment converted the exchangeable fractions to the much less available Fe-Mn oxides bound and residual forms, and thus, lowered the risk levels to "low risk" for all the metals. The immobilization of the metals was facilitated through formation of stable metal (chloro)phosphates, surface complexation, and/or ion exchange reactions. Combined CMC-CAP and CaO may serve as an effective formulation for simultaneous and long-term immobilization of multiple heavy metals in acidic soil.
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http://dx.doi.org/10.1016/j.jhazmat.2020.124786DOI Listing
April 2021

Biological aqua crust mitigates metal(loid) pollution and the underlying immobilization mechanisms.

Water Res 2021 Feb 8;190:116736. Epub 2020 Dec 8.

School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275, China; Guangdong Laboratory for Lingnan Modern Agriculture, College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China. Electronic address:

Biocrust-mediated in situ bioremediation could be an alternative strategy to mitigate metal(loid) pollution in aquatic habitats. To better understand the roles of biocrusts in regulating the fate of metal(loid)s, we examined the morphology, composition and structure of biological aqua crusts (BAC) developed in the mine drainage of a representative Pb/Zn tailing pond, and tested their effectiveness for immobilizing typical metal(loid)s. Unlike terrestrial biocrusts, BAC results from an assembly of compounds produced by the strong microbial activity and mineral compounds present in the aquatic environment. The BAC exhibited a unique flexible, spongy and porous structure with a specific surface area of 12-22 m g, and was able to effectively concentrate various metal(loid)s (e.g. Cd, 0.26-0.60 g kg; Pb, 0.52-0.66 g kg; As, 10.4-24.3 g kg). The concentrations of metal(loid)s (e.g. Cd and As) in the BAC were even three to seven times higher than those in the source tailings, and more than 98% of immobilized metal(loid)s were present as the highly stable non-EDTA-exchangeable fraction. Adsorption on the well distributed micro-particles of the clay minerals (e.g. kaolinite) and the organic matters (2.0-2.7 wt.%) were found to be the major mechanisms for BAC to bind metal cations, whereas adsorption and coprecipitation on Fe/Mn oxide (e.g. FeOOH), was proposed to be the dominant pathway for accumulating metal(loid)s, especially As. The decrease in aqueous concentrations of the metal(loid)s along the drainage could be attributed in part to the scavenging effects of the BAC. These findings therefore provide new insights into the possible and efficient strategy for metal(loid) removal from water bodies, and highlighted the important role of BAC as a nature-based solution to benefit the bioremediation of mining area.
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http://dx.doi.org/10.1016/j.watres.2020.116736DOI Listing
February 2021

Enhanced removal of zinc and cadmium from water using carboxymethyl cellulose-bridged chlorapatite nanoparticles.

Chemosphere 2021 Jan 19;263:128038. Epub 2020 Aug 19.

School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou, 510006, China.

Zinc (Zn) and cadmium (Cd) in water pose serious threats to human health and the environment. In search for a more effective treatment technology, we prepared a type of carboxymethyl cellulose (CMC) bridged chlorapatite (CMC-CAP) nanoparticles and tested the material for removal of Zn and Cd from water. CMC macromolecules were attached to CAP by bidentate bridging and hydrogen bonding, preserving the high adsorption capacity of CAP nanoparticles while allowing for easy gravity-separation of the nanoparticles. CMC-CAP showed rapid adsorption kinetics and 22.8% and 11.2% higher equilibrium uptake for Zn and Cd, respectively, than pristine CAP. An extended dual-mode isotherm model, which takes into account both sorption and chemical precipitation, provided the best fits to the sorption isotherms, giving a maximum Langmuir sorption capacity of 141.1 mg g for Zn and 150.2 mg g for Cd by CMC-CAP. Na at up to 5 mM showed modest effects on the uptake of the heavy metals, while 2-5 mM of Ca exerted notable inhibitive effects. Dissolved organic matter (up to 5 mg L as TOC) inhibited the Zn uptake by 16.5% but enhanced the Cd removal by 8.6%. Material characterizations and surface binding analyses revealed that ion exchange, surface precipitation, and surface complexation were the removal mechanisms for the heavy metals. This study demonstrates stabilizer bridging may serve as a convenient strategy to facilitate water treatment uses of nanoparticles.
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http://dx.doi.org/10.1016/j.chemosphere.2020.128038DOI Listing
January 2021

A concentrate-and-destroy technique for degradation of perfluorooctanoic acid in water using a new adsorptive photocatalyst.

Water Res 2020 Oct 22;185:116219. Epub 2020 Jul 22.

Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849, United States. Electronic address:

Per- and polyfluoroalkyl substances (PFAS) have emerged as a major concern in aquatic systems worldwide due to their widespread applications and health concerns. Perfluorooctanoic acid (PFOA) is one of the most-detected PFAS. Yet, a cost-effective technology has been lacking for the degradation of PFAS due to their resistance to conventional treatment processes. To address this challenge, we prepared a novel adsorptive photocatalyst, referred to Fe/[email protected], based on low-cost commercial activated carbon (AC) and TiO. The composite material exhibited synergistic adsorption and photocatalytic activity and enabled a novel "concentrate-&-destroy" strategy for rapid and complete degradation of PFOA in water. Fe/[email protected] was able to adsorb PFOA within a few minutes, thereby effectively concentrating the target contaminant on the photoactive sites. Subsequently, Fe/[email protected] was able to degrade >90% of PFOA that was preconcentrated on the solid in 4 h under UV irradiation (254 nm, 21 mW cm), of which 62% was completely mineralized to F. The efficient photodegradation also regenerated Fe/[email protected], eliminating the need for expensive chemical regenerants, and after six cycles of adsorption/photodegradation, the material showed no significant drop in adsorption capacity or photocatalytic activity. Simulations based on the density functional theory (DFT) revealed that Fe/[email protected] adsorbs PFOA in the side-on parallel mode, facilitating the subsequent photocatalytic degradation of PFOA. According to the DFT analysis, scavenger tests, and analysis of degradation intermediates, PFOA decomposition is initiated by direct hole oxidation, which activates the molecule and leads to a series of decarboxylation, C-F bond cleavage, and chain shortening reactions. The innovative "concentrate-&-destroy" strategy may significantly advance conventional adsorption or photochemical treatment of PFAS-contaminated water and holds the potential to degrade PFOA, and potentially other PFAS, more cost-effectively.
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http://dx.doi.org/10.1016/j.watres.2020.116219DOI Listing
October 2020

Immobilization of perrhenate using synthetic pyrite particles: Effectiveness and remobilization potential.

Sci Total Environ 2020 Jul 4;725:138423. Epub 2020 Apr 4.

Institute of Environmental Science, Taiyuan University of Science and Technology, Taiyuan, Shanxi 030024, China.

Radioactive pertechnetate (TcO4) has been detected in nuclear waste affected soil and groundwater, posing significant effect on human health and the environment. Yet, cost-effective remediation of Tc-contaminated soil and groundwater remains challenging. To address this critical technology need, we prepared a class of pyrite (FeS) particles for effective immobilization of pertechnetate. Using perrhenate (ReO) as a non-radioactive surrogate of TcO, we tested the immobilization effectiveness of the material through batch kinetic experiments, and evaluated the remobilization potential of immobilized Re under anoxic (sealed from air) and oxic (exposed to air) conditions and in the presence of humic acid (HA), EDTA, nitrate, and a Chinese loess soil. The results showed that more acidic pH gave faster Re(VII) removal due to more abundant electron sources (Fe and S). X-ray diffraction (XRD) and/or X-ray photoelectron spectroscopy (XPS) analyses confirmed formation of ReO/ReS as the major reduction products. The immobilized Re remained highly stable when aged for 360 days under anoxic conditions at different influence factors. Yet, the immobilized Re was vulnerable to oxygen oxidation, and about 78% of Re was remobilized after 40 days of exposure to air regardless of the initial pH (3.5-9.0) due to excessive pyrite oxidation and the associated pH drop (~2). HA at 120 mg/L inhibited Re remobilization under oxic conditions, which lowered the Re remobilization by ~21% after 40 days of oxic aging. The presence of EDTA facilitated dissolution of Fe but inhibited the dissolution of Re under oxic conditions. Nitrate showed negligible effect on Re remobilization. The presence of a Chinese loess soil effectively inhibited Re remobilization under both oxic and anoxic conditions, lowering the leachable Re by ~32% under oxic conditions. The findings may guide engineered application of pyrite particles as a long-lasting reducing material for immobilization pertechnetate or similar redox-active contaminants in soil and water.
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http://dx.doi.org/10.1016/j.scitotenv.2020.138423DOI Listing
July 2020

Editorial: Water and wastewater in a time of crisis.

Authors:
Dongye Zhao

Water Environ Res 2020 May 20;92(5):644-645. Epub 2020 Apr 20.

Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, Alabama.

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http://dx.doi.org/10.1002/wer.1334DOI Listing
May 2020

Learning Cognitive Map Representations for Navigation by Sensory-Motor Integration.

IEEE Trans Cybern 2020 Apr 3. Epub 2020 Apr 3.

How to transform a mixed flow of sensory and motor information into memory state of self-location and to build map representations of the environment are central questions in the navigation research. Studies in neuroscience have shown that place cells in the hippocampus of the rodent brains form dynamic cognitive representations of locations in the environment. We propose a neural-network model called sensory-motor integration network model (SeMINet) to learn cognitive map representations by integrating sensory and motor information while an agent is exploring a virtual environment. This biologically inspired model consists of a deep neural network representing visual features of the environment, a recurrent network of place units encoding spatial information by sensorimotor integration, and a secondary network to decode the locations of the agent from spatial representations. The recurrent connections between the place units sustain an activity bump in the network without the need of sensory inputs, and the asymmetry in the connections propagates the activity bump in the network, forming a dynamic memory state which matches the motion of the agent. A competitive learning process establishes the association between the sensory representations and the memory state of the place units, and is able to correct the cumulative path-integration errors. The simulation results demonstrate that the network forms neural codes that convey location information of the agent independent of its head direction. The decoding network reliably predicts the location even when the movement is subject to noise. The proposed SeMINet thus provides a brain-inspired neural-network model for \nobreak cognitive map updated by both self-motion cues and visual cues.
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http://dx.doi.org/10.1109/TCYB.2020.2977999DOI Listing
April 2020

Enhanced adsorption of perfluorooctanoic acid (PFOA) from water by granular activated carbon supported magnetite nanoparticles.

Sci Total Environ 2020 Jun 5;723:137757. Epub 2020 Mar 5.

School of Architecture and Urban Planning, Suzhou University of Science and Technology, Suzhou 215009, PR China.

A new composite material ([email protected], FeO nanoparticles loaded on a commercial granular activated carbon (GAC)) was prepared through a facile hydrothermal process at controlled Fe:Fe molar ratios in air. [email protected] was thoroughly characterized and tested for adsorption of perfluorooctanoic acid (PFOA) in water. [email protected](2:1), prepared at an Fe:Fe molar ratio of 2:1, showed the best PFOA removal and offered 28.8% higher adsorption capacity than the parent GAC at final pH 4.0. The enhanced adsorption of PFOA was attributed to concurrent hydrophobic, electrostatic and complexation interactions between PFOA, GAC and FeO. GAC in the composite played an important role for PFOA adsorption. The presence of Ca ions (10 mM) at final pH 5.0-10.0 more than doubled the PFOA equilibrium uptake of PFOA by [email protected](2:1) due to the calcium bridging effect between PFOA and the Si-OH or Fe-OH groups in [email protected](2:1), and because of the Ca-modification induced formation of PFOA hemi-micelles on the surface or in the relatively large pores (2.27 nm) of [email protected](2:1). [email protected](2:1) was amenable to efficient regeneration using a mixture of NaOH solution and methanol. [email protected] holds the potential to be used as a simple and low-cost adsorbent for enhanced adsorption of PFOA, especially in waters of high hardness and alkalinity.
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http://dx.doi.org/10.1016/j.scitotenv.2020.137757DOI Listing
June 2020

Screening for the action mechanisms of Fe and Ni in the reduction of Cr(VI) by Fe/Ni nanoparticles.

Sci Total Environ 2020 May 21;715:136822. Epub 2020 Jan 21.

College of Resource and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430081, China; Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, Wuhan University of Science and Technology, Wuhan 430081, China.

Zero-valent iron (ZVI), Fe and H are possible electron donors in the reduction of Cr(VI) by nanoscale ZVI (n-ZVI). However, it is often ambiguous about the roles of these electron donors in the reductive removal of Cr(VI) from groundwater and wastewater. This study investigated the action mechanisms of Fe and Ni in Cr(VI) reduction by Fe/Ni nanoparticles (n-Fe/Ni). Among the three possible reduction mechanisms of ZVI, direct electron transfer from ZVI and its corrosion product, Fe, were confirmed to be responsible for the reduction removal of Cr(VI). H, another product of ZVI corrosion, was found incapable of reducing Cr(VI). In addition, the secondary metal Ni in n-Fe/Ni was found to facilitate the direct electron transfer from ZVI owing to its ability to inhibit the passivation of ZVI and to enhance the production of Fe due to the formation of FeNi galvanic cells. The results of characterizations on n-Fe/Ni before and after the reaction with Cr(VI) demonstrated that Cr(VI) was reduced to Cr(III), which existed as FeCrO precipitates on the surface of n-Fe/Ni, resulting in effective sequestration of Cr(VI). These findings are important for understanding the main mechanisms of bimetallic nanoparticles or nanomaterials for reductive immobilization of Cr(VI), and may guide further ZVI-based technology development for remediation of contaminated water or soil with redox-active contaminants.
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http://dx.doi.org/10.1016/j.scitotenv.2020.136822DOI Listing
May 2020

Efficient removal and long-term sequestration of cadmium from aqueous solution using ferrous sulfide nanoparticles: Performance, mechanisms, and long-term stability.

Sci Total Environ 2020 Feb 21;704:135402. Epub 2019 Nov 21.

Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849, United States. Electronic address:

Cadmium (Cd) is one of the most commonly detected toxic heavy metals in the environment. Ferrous sulfide (FeS) nanoparticles were prepared using sodium carboxymethyl cellulose (CMC) as a stabilizer and tested for removal of Cd from aqueous solutions. Effects of CMC concentration, initial Cd concentration, pH, humic acid (HA) and dissolved oxygen were examined. Fully stabilized FeS (100 mg/L) nanoparticles were obtained using 0.01 wt% CMC. Batch kinetic tests showed that the nanoparticles at 100 mg/L as FeS rapidly removed 93% of 1 mg/L Cd within 4 h at pH 7.0, and the kinetic data were well interpreted by a pseudo-second-order rate model with a rate constant of 6.68 g·mg·hr. Sorption isotherm was well simulated by a dual-mode isotherm model with a maximum Langmuir sorption capacity of 497.5 mg/L at pH 7.0. Fourier transform infrared (FTIR) spectroscopy and X-ray powder diffraction (XRD) analyses suggested that chemical precipitation and surface complexation between Cd and FeS were dominant immobilization mechanisms. Increasing pH from 4.0 to 8.0 enhanced Cd removal rate from 73.0% to 98.8%, whereas addition of 3 mg/L HA (as total organic matter) inhibited the removal rate by 2.7% and the presence of molecular oxygen had negligible effect. Increasing NaCl or CaCl from 0 to 10 mM suppressed Cd removal by 10.1% and 27.7%, respectively. The immobilized Cd remained insoluble when aged for 717 days under anoxic or oxic conditions. This study demonstrated that CMC-stabilized FeS nanoparticles can facilitate long-term immobilization of cadmium in contaminated water.
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http://dx.doi.org/10.1016/j.scitotenv.2019.135402DOI Listing
February 2020

Simultaneous control of soil erosion and arsenic leaching at disturbed land using polyacrylamide modified magnetite nanoparticles.

Sci Total Environ 2020 Feb 4;702:134997. Epub 2019 Nov 4.

Department of Chemistry and Biochemistry, Auburn University, Auburn, AL, 36849, USA.

Rapid urbanization and human disturbance of land often results in serious soil erosion and releases of fine sediments and soil-bound toxic metals/metalloids. Yet, technologies for simultaneously controlling soil erosion and metals/metalloids leaching have been lacking. This study developed a new class of polyacrylamide-dispersed magnetite (PAM-MAG) nanoparticles and tested the effectiveness for simultaneous control of soil erosion and arsenic leaching from a model soil. Two parallel box test setups (L × W × H: 91.4 × 30.5 × 7.6 cm) were constructed to test the releases of sediments and soluble pollutants from the surface soil under simulated rainfall conditions (intensity = 11.15 cm/hr). A sandy loam soil from a local quarry mining site was used as the model soil, and arsenate As(V) as a prototype leachable metalloid. A stable dispersion of PAM-MAG was prepared with 0.3 wt% of PAM and 0.1 g/L as Fe of magnetite. The results indicated that treating the soil with 5.985 g/m of PAM-MAG was able to decrease cumulative soil mass loss in the runoff by 90.8% (from 254.50 ± 0.10 g to 23.35 ± 3.19 g), or turbidity of the runoff by 79.9% (from 244.5 ± 27.5 NTU to 49.2 ± 22.5 NTU). Compared to PAM only, the PAM-MAG suspension showed a 30% reduction of viscosity, allowing for easier application and transport of the nanoparticles in soil. Concurrently, the PAM-MAG treatment also immobilized 82.5% of water-leachable arsenate compared to untreated controls. Fourier-transform infrared (FTIR) spectroscopy analyses revealed that arsenate was immobilized by magnetite nanoparticles through inner sphere surface complexation (Fe-O-As). Overall, the PAM-MAG based technology holds the promise for simultaneously controlling soil erosion and metal/metalloid releases from disturbed land.
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http://dx.doi.org/10.1016/j.scitotenv.2019.134997DOI Listing
February 2020

Sorption of dispersed petroleum hydrocarbons by activated charcoals: Effects of oil dispersants.

Environ Pollut 2020 Jan 15;256:113416. Epub 2019 Oct 15.

Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL, 36849, USA. Electronic address:

Marine oil spill often causes contamination of drinking water sources in coastal areas. As the use of oil dispersants has become one of the main practices in remediation of oil spill, the effect of oil dispersants on the treatment effectiveness remains unexplored. Specifically, little is known on the removal of dispersed oil from contaminated water using conventional adsorbents. This study investigated sorption behavior of three prototype activated charcoals (ACs) of different particle sizes (4-12, 12-20 and 100 mesh) for removal of dispersed oil hydrocarbons, and effects of two model oil dispersants (Corexit EC9500A and Corexit EC9527A). The oil content was measured as n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and total petroleum hydrocarbons (TPHs). Characterization results showed that the smallest AC (PAC100) offered the highest BET surface area of 889 m/g and pore volume of 0.95 cm/g (pH = 6.1). Sorption kinetic data revealed that all three ACs can efficiently adsorb Corexit EC9500A and oil dispersed by the two dispersants (DWAO-I and DWAO-II), and the adsorption capacity followed the trend: PAC100 > GAC12 × 20 > GAC4 × 12. Sorption isotherms confirmed PAC100 showed the highest adsorption capacity for dispersed oil in DWAO-I with a Freundlich K value of 10.90 mg/g∙(L/mg) (n = 1.38). Furthermore, the presence of Corexit EC9500A showed two contrasting effects on the oil sorption, i.e., adsolubilization and solubilization depending on the dispersant concentration. Increasing solution pH from 6.0 to 9.0 and salinity from 2 to 8 wt% showed only modest effect on the sorption. The results are useful for effective treatment of dispersed oil in contaminated water and for understanding roles of oil dispersants.
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http://dx.doi.org/10.1016/j.envpol.2019.113416DOI Listing
January 2020

Critical role of oxygen vacancies in heterogeneous Fenton oxidation over ceria-based catalysts.

J Colloid Interface Sci 2020 Jan 21;558:163-172. Epub 2019 Sep 21.

Department of Civil Engineering, Auburn University, Auburn, AL 36849, USA.

This study examined the relationship between surface oxygen vacancies (OVs) and ceria-based heterogeneous Fenton catalytic activity. Compared with pure iron oxide and ceria, iron-doped ceria with abundant OVs (FeCeOx) exhibits higher rhodamine B (RhB) degradation efficiency (98%) and has a wider applicable pH range (3.0-9.0). The surface hydroxyl radicals are proved to be the predominant reactive species in the oxidation of RhB. Annealing the FeCeOx in an oxygen atmosphere appears to eliminate the OVs, significantly inhibiting the decomposition of HO and the degradation of target pollutants. As multifunctional active sites, OVs are energetically more favorable for the adsorption of reactants than other sites, due to their high electron density. They not only accelerate the Fe(III)/Fe(II) cycle, they also immediately activate HO, dissolved oxygen or even water molecules to produce oxidative species, which accounts for the ideal degradation of RhB in the heterogeneous Fenton system. This study clarifies the mechanism of the ceria-based heterogeneous Fenton and provides a better understanding of the surface design of heterogeneous Fenton catalysts.
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http://dx.doi.org/10.1016/j.jcis.2019.09.079DOI Listing
January 2020

Immobilization of hexavalent chromium in soil and groundwater using synthetic pyrite particles.

Environ Pollut 2019 Dec 1;255(Pt 1):112992. Epub 2019 Aug 1.

Environmental Engineering Program, Department of Civil Engineering, 238 Harbert Engineering Center, Auburn University, Auburn, AL 36849, USA. Electronic address:

In this study, reactive pyrite (FeS) particles were prepared through a modified hydrothermal method and tested for immobilization of Cr(VI) in contaminated soil and synthetic groundwater. The addition of a NaAc buffer in the synthetic process resulted in pyrite particles of greater specific surface area, more uniform size, and more crystalline structure. The particles can effectively immobilize Cr(VI) in both water and a model Chinese loess soil. Over 99.9% of Cr(VI) was rapidly removed from water at pH 6.0 (Initial Cr(VI) = 25 mg/L, FeS dosage = 0.48 g/L), and the removal remained high (>82%) even at pH 9.5. Both adsorption and reductive precipitation were found operative in the Cr(VI) immobilization, with ∼66% of Cr immobilized due to reduction. Fe(II) ions associated on the FeS surface played a key role in the reduction of Cr(VI) to Cr(III), and S also facilitated the reductive removal of Cr(VI). The presence of humic acid enhanced Cr(VI) removal at pH 4.0, but the effect was negligible at pH 6.0. Batch kinetic tests showed that treating a Cr(VI)-laden soil with 0.48 g/L (as Fe) of FeS decreased the equilibrium water-leachable Cr(VI) by >99.0% at pH 6.0 and by >70.0% at pH 9.0. The distribution coefficient (K) value of the pyrite-amended soil was 1477.8 at pH 6.0, which is 306 times higher than that for the untreated soil. Column elution tests showed that installation of a 3-cm reactive layer of FeS in a soil column was able to capture the leachable Cr(VI) from the soil, and the retardation factor (R) for the 3-cm FeS layer sample was 381 times higher than that for the plain soil. The synthetic pyrite particles may serve as a reactive material for effective removal or immobilization of Cr(VI) in contaminated water or soil.
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http://dx.doi.org/10.1016/j.envpol.2019.112992DOI Listing
December 2019

A new insight into the main mechanism of 2,4-dichlorophenol dechlorination by Fe/Ni nanoparticles.

Sci Total Environ 2019 Dec 19;697:133996. Epub 2019 Aug 19.

College of Resource and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430081, China; Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, Wuhan University of Science and Technology, Wuhan 430081, China.

Three possible dechlorination mechanisms of chloroorganics by nanoscale zero-valent iron (n-ZVI) have been proposed and widely accepted, however, the main mechanism is still controversial and not verified by experimental results. In this study, 2,4-dichlorophenol (2,4-DCP) was selected as the target pollutant and the experiments were carried out for the screening of the main mechanism of 2,4-DCP dechlorination by n-ZVI and Fe/Ni nanoparticles (n-Fe/Ni). The results indicated that >95% of 2,4-DCP could be dechlorinated to phenol by n-Fe/Ni within 120 min, while 2,4-DCP could hardly be dechlorinated by n-ZVI particles. The active hydrogen atom (H*) that transformed from H under the catalysis of Ni was responsible for >90% of 2,4-DCP dechlorination by n-Fe/Ni and <10% of the dechlorination was attributed to the direct electron transfer from ZVI. Fe was not able to dechlorinate 2,4-DCP. Correspondently, Ni in n-Fe/Ni mainly acted as a catalyst, while the acceleration of electron transfer from ZVI by Ni had a positive effect on 2,4-DCP dechlorination. The investigations on the relative importance of these three mechanisms are essential to iron-based remediation technology.
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http://dx.doi.org/10.1016/j.scitotenv.2019.133996DOI Listing
December 2019

Impact of an Extreme Winter Storm Event on the Coagulation/Flocculation Processes in a Prototype Surface Water Treatment Plant: Causes and Mitigating Measures.

Int J Environ Res Public Health 2019 08 6;16(15). Epub 2019 Aug 6.

Environmental Engineering Program, Department of Civil Engineering, 238 Harbert Engineering Center, Auburn University, Auburn, AL 36849, USA.

Climate change has often caused failure in water treatment operations. In this study, we report a real case study at a major surface water treatment plant in Alabama, USA. Following a severe winter storm, the effluent water turbidity surged to >15.00 Nephelometric Turbidity Units (NTU), far exceeding the 0.30 NTU standard. As a result, the plant operation had to be shut down for three days, causing millions of dollars of losses and affecting tens of thousands of people. Systematic jar tests were carried out with sediment samples from 22 upstream locations. The coagulation and settleability of sediment particles were tested under simulated storm weather conditions, i.e., low temperature (7 °C) and in the presence of various types and concentrations of natural organic matter (NOM) that was extracted from the local sediments. Experimental results proved that elevated NOM (6.14 mg·L as Total Organic Carbon, TOC) in raw water was the root cause for the failure of the plant while the low temperature played a minor but significant role. Pre-oxidation with permanganate and/or elevated coagulant dosage were found effective to remove TOC in raw water and to prevent similar treatment failure. Moreover, we recommend that chemical dosages should be adjusted based on the TOC level in raw water, and a reference dosage of 0.29 kg-NaMnO/kg-TOC and 19 kg- polyaluminum chloride (PACl) /kg-TOC would be appropriate to cope with future storm water impacts. To facilitate timely adjustment of the chemical dosages, the real time key water quality parameters should be monitored, such as turbidity, TOC, Ultraviolet (UV) absorbance, pH, and color. The findings can guide other treatment operators to deal with shock changes in the raw water quality resulting from severe weather or other operating conditions.
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http://dx.doi.org/10.3390/ijerph16152808DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6695649PMC
August 2019

Pyrolysis of different biomass pre-impregnated with steel pickling waste liquor to prepare magnetic biochars and their use for the degradation of metronidazole.

Bioresour Technol 2019 Oct 7;289:121613. Epub 2019 Jun 7.

School of Chemistry and Environment, South China Normal University, Guangzhou 510006, China; Guangdong Technology Research Center for Ecological Management and Remediation of Water System, Guangzhou 510006, China. Electronic address:

In this study, Fenton-like catalysts (magnetic biochar) were synthesised by pyrolysis the different biomass pre-impregnated with steel pickling waste liquor. The results of degradation of metronidazole illustrated that the catalytic performance of magnetic biochar was significantly affected by biomass feedstocks. Electron spin resonance (ESR) and radical quenching experiments showed that the hydroxide radicals (OH) were the key reactive oxygen species responsible for the metronidazole removal. Levels of OH varied among different systems consistent with the removal of metronidazole. The activation of HO by carbon-containing components and Fe species (FeO and FeO) in magnetic biochar were confirmed to be less crucial to the degradation of metronidazole. Moreover, the Fe(II) (FeO) in magnetic biochar played the dominating role in degradation of metronidazole, and the Fe(II) content difference caused by biomass feedstocks was responsible for differences in the catalytic performance of different types of magnetic biochar.
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http://dx.doi.org/10.1016/j.biortech.2019.121613DOI Listing
October 2019

Development of an in situ diagnostic system for mapping the deposition distribution on plasma facing components of the HL-2M tokamak.

Rev Sci Instrum 2019 May;90(5):053503

Dalian University of Technology, Dalian, Liaoning 116024, China.

The assessment of material deposition and fuel retention on Plasma Facing Components (PFCs) is of primary importance for the steady-state operations of future fusion devices. In this paper, an in situ diagnostic for mapping the deposition distribution (IMap) on a wide area of PFCs for HL-2M (Huan Liu Qi-2 Modification) is developed. The design, fabrication, integration, and lab test of the IMap have been implemented. This system is built with the laser-induced breakdown spectroscopy technique which is an in situ diagnostic technique to determine the constituents and the depth profile of deposition compositions on PFCs. With a molybdenum reflection mirror inside the chamber and its manipulator, the IMap system can scan from the inner wall across the lower divertor to the outer middle plane. The system can be remotely controlled, and its optical lenses, mirrors, and fibers can be adjusted automatically when scanning over the PFCs. Therefore, the wall properties over a wide area of the vessel can be measured. All elements with the emission lines in the range of 380-850 nm can be analyzed, and the isotope species H and D can also be identified clearly with this diagnostic. Moreover, the depth profiles of the deposited materials can be determined, and the fuel retention on PFCs can be evaluated in situ. This gives a clear picture of the deposition and retention over the wall of HL-2M.
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http://dx.doi.org/10.1063/1.5082630DOI Listing
May 2019

Electrophilicity index as a critical indicator for the biodegradation of the pharmaceuticals in aerobic activated sludge processes.

Water Res 2019 Sep 18;160:10-17. Epub 2019 May 18.

Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha, 410083, China; Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha, 410083, China. Electronic address:

Improving biodegradation of pharmaceuticals during wastewater treatment is critical to control the release of emerging micropollutants to natural waters. In this study, biodegradation of six model pharmaceuticals was investigated at different initial concentrations in two discrete activated sludge systems, and moreover, the correlation was explored between the biodegradation rate and key molecular properties of the contaminants. First, the biodegradation rates of the pharmaceuticals were measured fitting a pseudo first-order kinetic model to the experimental kinetic data. The degradation rate constants (k) were found to negatively correlate to the initial concentration of the chemicals, indicating an inhibitory effect on the microorganisms by the pharmaceuticals. Further examinations of the rate data against the key molecular properties of the pharmaceuticals revealed, for the first time, that the electrophilicity index (ω), a measure of electrophilic power, served as a better indicator of the biodegradability and predictive parameter for the k than the conventional log K (a measure of hydrophobicity) in the two discrete aerobic activated sludge systems. However, the correlation strength (goodness‒of‒fit) between ω and k deteriorated when the reactor turned from aerobic to anoxic and anaerobic conditions, suggesting that electron transfer from pharmaceutical molecules to enzymes was inhibited when dissolved oxygen was deficit or absent. Our results show that ω can potentially serve as a straightforward and robust indicator for predicting the biodegradability of pharmaceutical in conventional activated sludge processes.
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http://dx.doi.org/10.1016/j.watres.2019.05.057DOI Listing
September 2019

Distribution, Source and Risk Assessment of Heavy Metal(oid)s in Water, Sediments, and Corbicula Fluminea of Xijiang River, China.

Int J Environ Res Public Health 2019 05 23;16(10). Epub 2019 May 23.

School of Environmental Science and Engineering, Guangzhou University, Guangzhou 510006, China.

A total of 43 water and sediment samples, and 34 samples were collected in Xijiang River in southern China to determine the spatial distribution and sources of 12 metals/metalloids (V, Co, Cr, Ni, Cu, Mn, Zn, Cd, Pb, As, Sb, and Tl) and to assess the pollution levels and ecological risks of the pollutants. The results showed that the levels of the metals/metalloids (except for Tl) in the river water from almost all of the sampling sites met the Chinese national surface water quality standards. However, the concentrations of the metals/metalloids in the sediments exceeded the background values by a factor of 1.03-56.56 except for V, Co, and Mn, and the contents of Zn, Cd, and Pb in the soft tissue exceeded the limits of the Chinese Category I food Quality Standards. The spatial distribution analysis showed that the concentrations of the contaminants in the lower reaches of Xijiang River were higher than in the upper reaches. The bioaccumulation factor (), biota-sediment accumulation factor (), geo-accumulation index (), and the potential ecological risk index () were obtained to assess the pollution levels and ecological risks. The results indicated that Cu, Cd, and Zn were the most prone to bio-accumulation in the soft tissue, and the lower reaches showed a much higher pollution level and risk than the upper reaches. The metals/metalloids in the sediments posed serious threat on the aquatic ecosystem, of which Cd, As, and Sb are the most risky contaminants. The results of principal component analysis (PCA) indicated Cr, Ni, Cu, Mn, Cd, Pb, and As in the sediments came from relevant industrial activities, and V and Co originated from natural sources, and Sb from mining activities, Zn and Tl came from industrial activities and mining activities.
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http://dx.doi.org/10.3390/ijerph16101823DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6572011PMC
May 2019

Learning joint space-time-frequency features for EEG decoding on small labeled data.

Neural Netw 2019 Jun 11;114:67-77. Epub 2019 Mar 11.

State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016, China; Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang 110016, China. Electronic address:

Brain-computer interfaces (BCIs), which control external equipment using cerebral activity, have received considerable attention recently. Translating brain activities measured by electroencephalography (EEG) into correct control commands is a critical problem in this field. Most existing EEG decoding methods separate feature extraction from classification and thus are not robust across different BCI users. In this paper, we propose to learn subject-specific features jointly with the classification rule. We develop a deep convolutional network (ConvNet) to decode EEG signals end-to-end by stacking time-frequency transformation, spatial filtering, and classification together. Our proposed ConvNet implements a joint space-time-frequency feature extraction scheme for EEG decoding. Morlet wavelet-like kernels used in our network significantly reduce the number of parameters compared with classical convolutional kernels and endow the features learned at the corresponding layer with a clear interpretation, i.e. spectral amplitude. We further utilize subject-to-subject weight transfer, which uses parameters of the networks trained for existing subjects to initialize the network for a new subject, to solve the dilemma between a large number of demanded data for training deep ConvNets and small labeled data collected in BCIs. The proposed approach is evaluated on three public data sets, obtaining superior classification performance compared with the state-of-the-art methods.
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http://dx.doi.org/10.1016/j.neunet.2019.02.009DOI Listing
June 2019

The humic acid influenced the behavior and reactivity of Ni/Fe nanoparticles in the removal of deca-brominated diphenyl ether from aqueous solution.

Environ Sci Pollut Res Int 2019 Apr 12;26(10):10136-10147. Epub 2019 Feb 12.

Department of Science and Environmental Studies, The Education University of Hong Kong, Hong Kong, 00852, China.

The removal of contaminants by iron-based nanomaterials was inevitably affected by the natural organic matter (NOM), which is one of the most abundant material on earth and exists in natural waters. This study was performed to investigate the main influence of humic acid (HA, representing NOM) on the behavior and reactivity of Ni/Fe nanoparticles in the removal of deca-brominated diphenyl ether (BDE209). Generally, the inhibitory effect of HA on the removal of BDE209 by Ni/Fe showed greater significance with an increase of HA concentration. The zeta potential and sedimentation experiments showed that the HA enhanced the dispersion and stabilization of Ni/Fe particles; however, the removal of BDE209 was found to be inhibited. Moreover, the corrosion capacity of the Ni/Fe nanoparticles showed a positive correlation with the effect of HA on the reactivity of Ni/Fe nanoparticles. Meanwhile, typical quinone compounds in HA had an adverse effect on the removal of BDE209. Additionally, the competitive adsorption experiments and characterization illustrated that the adsorption of HA by Ni/Fe nanoparticles was superior to BDE209. Overall, it was proposed that the corrosion of Ni/Fe was reduced as the contact between the nanoparticles and HO was hindered due to the surface of Ni/Fe was occupied by the adsorbed HA, and thus inhibited the reactivity of Ni/Fe nanoparticles in the removal of BDE209.
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http://dx.doi.org/10.1007/s11356-019-04403-yDOI Listing
April 2019

Bromate reduction and reaction-enhanced perchlorate adsorption by FeCl-impregnated granular activated carbon.

Water Res 2019 02 5;149:149-158. Epub 2018 Nov 5.

State Key Laboratory of Pollution Control and Resource Rescue, Tongji University, Shanghai, 200092, PR China.

This work studied simultaneous bromate (BrO) reduction and adsorption of perchlorate (ClO) by FeCl-impregnated granular activated carbon (Fe-GAC) and the mutual co-solute effects. We report that BrO reduction by Fe-GAC was coupled with enhanced adsorption of ClO by the material. The Langmuir maximum adsorption capacity for ClO by Fe-GAC was increased from 0.179 mmol g (without BrO) to 0.256 mmol g in the presence of 0.2 mmol L of BrO (a 43% increase) at pH 6.0. While the activated carbon alone was able simultaneously remove both BrO and ClO, Fe-GAC offered much greater removal efficacy and synergistic effect, likely because the immobilized Fe acted as a catalyst and provided a local acidic environment, both being in favor of accelerated BrO reduction. Mechanistic analyses revealed that BrO removal was through a two-step process: ion exchange with OH and Cl on Fe-GAC, and then Fe-catalyzed reduction of BrO to Br by carbon. The carbon-BrO redox reaction generated more Fe-O and C-O groups on the material surface, which can bind with ClO by surface complexation and electrostatic interactions. To our knowledge, this is the first report that metal modified activated carbon may facilitate synergistic removal of both BrO and ClO, which are common co-solutes in contaminated waters.
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http://dx.doi.org/10.1016/j.watres.2018.11.005DOI Listing
February 2019

An overview of field-scale studies on remediation of soil contaminated with heavy metals and metalloids: Technical progress over the last decade.

Water Res 2018 12 10;147:440-460. Epub 2018 Oct 10.

Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Ultimo, NSW, 2007, Australia.

Soil contamination by heavy metals and metalloids has been a major concern to human health and environmental quality. While many remediation technologies have been tested at the bench scale, there have been only limited reports at the field scale. This paper aimed to provide a comprehensive overview on the field applications of various soil remediation technologies performed over the last decade or so. Under the general categories of physical, chemical, and biological approaches, ten remediation techniques were critically reviewed. The technical feasibility and economic effectiveness were evaluated, and the pros and cons were appraised. In addition, attention was placed to the environmental impacts of the remediation practices and long-term stability of the contaminants, which should be taken into account in the establishment of remediation goals and environmental criteria. Moreover, key knowledge gaps and practical challenges are identified.
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http://dx.doi.org/10.1016/j.watres.2018.10.024DOI Listing
December 2018