Publications by authors named "Yuxiong Huang"

31 Publications

Molecular-Level Insights on the Facet-Dependent Degradation of Perfluorooctanoic Acid.

ACS Appl Mater Interfaces 2021 Sep 26;13(35):41584-41592. Epub 2021 Aug 26.

Tsinghua-Berkeley Shenzhen Institute, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.

Perfluorooctanoic acid (PFOA) has raised significant health concerns due to its high ecotoxicological risks and difficulties in removal by conventional water treatment process. Previous studies have demonstrated that photocatalytic techniques exhibit great potential in PFOA removal. However, the underlying mechanism of the degradation process has not been fully understood, particularly the contribution of the facet effects of catalysts. In this study, a combination of experiments and first-principles calculations were conducted to shed light on the facet-dependence of the interfacial interactions and oxidation during the PFOA degradation process. We proved that the interfacial interaction was essential in initiating the hole-dominated degradation process, and the {110} facet of hexagonal InO features the strongest interaction with PFOA. The overall defluorination rate was mainly controlled by the hole-dominated oxidation processes under UV irradiation, which were further attributed to the electronic structures and reaction site distributions of different InO surfaces. This study provides molecular-level insights on the facet-dependent PFOA catalytic degradation process, which can guide the rational design of photocatalysts to achieve superior decontamination efficiency.
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http://dx.doi.org/10.1021/acsami.1c10136DOI Listing
September 2021

Ecotoxicological effects of DBPs on freshwater phytoplankton communities in co-culture systems.

J Hazard Mater 2021 Jul 17;421:126679. Epub 2021 Jul 17.

State Key Laboratory of Urban Water Resource and Environment of Harbin Institute of Technology, Shenzhen 518055, PR China. Electronic address:

Intensive disinfection of wastewater during the COVID-19 pandemic might elevate the generation of toxic disinfection byproducts (DBPs), which has triggered global concerns about their ecological risks to natural aquatic ecosystems. In this study, the toxicity of 17 DBPs typically present in wastewater effluents on three representative microalgae, including Scenedesmus sp. (Chlorophyta), Microcystis aeruginosa (Cyanophyta), and Cyclotella sp. (Bacillariophyta) was investigated. The sensitivities of the three microalgae to DBPs varied greatly from species to species, indicating that DBPs may change the structure of phytoplankton communities. Later, co-cultures of these phytoplankton groups as a proxy of ecological freshwater scenario were conducted to explore the impacts of DBPs on phytoplankton community succession. M. aeruginosa became surprisingly dominant in co-cultures, representing over 50% after dosing with monochloroacetic acid (MCAA, 0.1-10 mg/L). The highest proportion of M. aeruginosa was 70.3% when exposed to 2 mg/L MCAA. Although Scenedesmus sp. dominated in monochloroacetonitrile (MCAN) exposure, M. aeruginosa accounted for no less than 30% even at 40 mg/L MCAN. In this study, DBPs disrupted the original inter-algal relationship in favor of M. aeruginosa, suggesting that DBPs may contribute to the outbreak of cyanobacterial blooms in aquatic ecosystems.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126679DOI Listing
July 2021

Magnesium Oxide Nanomaterial, an Alternative for Commercial Copper Bactericides: Field-Scale Tomato Bacterial Spot Disease Management and Total and Bioavailable Metal Accumulation in Soil.

Environ Sci Technol 2021 Jul 22. Epub 2021 Jul 22.

Plant Pathology Department, North Florida Research and Education Center, University of Florida, Quincy, Florida 32351, United States.

Copper (Cu) is the most extensively used bactericide worldwide in many agricultural production systems. However, intensive application of Cu bactericide have increased the selection pressure toward Cu-tolerant pathogens, including , the causal agent of tomato bacterial spot. However, alternatives for Cu bactericides are limited and have many drawbacks including plant damage and inconsistent effectiveness under field conditions. Also, potential ecological risk on nontarget organisms exposed to field runoff containing Cu is high. However, due to lack of alternatives for Cu, it is still widely used in tomato and other crops around the world in both conventional and organic production systems. In this study, a Cu-tolerant strain GEV485, which can tolerate eight tested commercial Cu bactericides, was used in all the field trials to evaluate the efficacy of MgO nanomaterial. Four field experiments were conducted to evaluate the impact of intensive application of MgO nanomaterial on tomato bacterial spot disease severity, and one field experiment was conducted to study the impact of soil accumulation of total and bioavailable Cu, Mg, Mn, and Zn. In the first two field experiments, twice-weekly applications of 200 μg/mL MgO significantly reduced disease severity by 29-38% less in comparison to a conventional Cu bactericide Kocide 3000 and 19-30% less in comparison to the water control applied at the same frequency ( = 0.05). The disease severity on MgO twice-weekly was 12-32% less than Kocide 3000 + Mancozeb treatment. Single weekly applications of MgO had 13-19% higher disease severity than twice weekly application of MgO. In the second set of two field trials, twice-weekly applications of MgO at 1000 μg/mL significantly reduced disease severity by 32-40% in comparison to water control applied at the same frequency ( = 0.05). There was no negative yield impact in any of the trials. The third field experiment demonstrated that application of MgO did not result in significant accumulation of total and bioavailable Mg, Mn, Cu, or Zn in the root-associated soil and in soil farther away from the production bed compared to the water control. However, Cu bactericide contributed to significantly higher Mn, Cu, and Zn accumulation in the soil compared to water control ( = 0.05). This study demonstrates that MgO nanomaterial could be an alternative for Cu bactericide and have potential in reducing risks associated with development of tolerant strains and for reducing Cu load in the environment.
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http://dx.doi.org/10.1021/acs.est.1c00804DOI Listing
July 2021

Combined toxicity of nano-TiO and Cd to Scenedesmus obliquus: Effects at different concentration ratios.

J Hazard Mater 2021 09 9;418:126354. Epub 2021 Jun 9.

Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.

The continuous release of manufactured nanomaterials (MNMs) to environments raised concerns on their combined toxicological risks with co-existing contaminants, since MNMs might severely alter the environmental behavior and fate of the contaminants. In this study, the combined toxicity of nano-sized titanium dioxide (nTiO) and cadmium (Cd) to the green alga Scenedesmus obliquus and the underlying physicochemical mechanisms were investigated for the first time at different concentration ratios of Cd to nTiO to closely mimic the realistic environment scenarios where the concentration ratios of nTiO to other contaminants are constantly changing. Our results suggested that under the co-exposure to different concentration ratios of Cd to nTiO, the co-exposure contaminants exhibited three different combined toxicity modes (antagonistic, partially additive, and synergistic). Specifically, antagonistic combined toxicity was observed under co-exposure to a low concentration ratio of nTiO to Cd as the absorption by nTiO decreased the bioavailability of Cd. However, the partially additive and synergistic combined toxicity occurred when the proportion of nTiO in the co-exposure system was relatively high, which would mechanically and/or oxidatively damage the alga cell structures. Even worse, as a carrier of Cd, nTiO enhanced the amount of Cd entering cells, which significantly enhanced the toxicity of Cd to algae. Overall, we demonstrated that concentration ratios of nTiO to Cd play an important role in determining the combined toxicity mode, which would provide a novel reference to environmental and health risk assessment of co-exposure to conventional pollutants and MNMs.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126354DOI Listing
September 2021

Shifting entrepreneurial landscape and development performance of water startups in emerging water markets.

PLoS One 2021 4;16(2):e0246282. Epub 2021 Feb 4.

Tsinghua-Berkeley Shenzhen Institute, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.

Emerging technologies have driven the rise of many water-related startups and created new opportunities in water markets. The global water crisis could be mitigated by applying innovative technologies, sound water management decisions, and successful business models, and it is essential to better understand the status and future trends of emerging water markets. This study aims to discover shifts in the entrepreneurial landscape and evaluate water startups' development performance for the sustainable development of emerging water markets. We collected and analyzed data including the founding date, service area, service provided, details of funding raised, revenues, and consumer responses on 132 water startups founded between 2008 and 2018 in California, USA. Our results indicated that municipal area dominated the emerging water startup market compared to agricultural and industrial areas, and that many of the services provided shifted from conventional technologies to digital technologies. Though digital water startups' current revenues were relatively low, digital techniques applied in the water industry exhibited the good potential to promote public health and water saving. The development trends and performance of water startups enlighten the technological and commercial revolutions in the emerging water market, and provide guidelines for the decision-making in relevant stakeholders in the scientific, governmental, and industrial communities.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0246282PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7861426PMC
July 2021

TiO nanoparticles enhanced bioaccumulation and toxic performance of PAHs via trophic transfer.

J Hazard Mater 2021 04 15;407:124834. Epub 2020 Dec 15.

Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China.

Engineering nanoparticles (NPs) could act as accumulator and carrier of co-contaminants, affecting their fate and toxicity in environments. However, the effects of NPs on the bioaccumulation and trophic transfer of co-contaminants through the food chain and the ensuing effects on higher predators are unclear. In the present study, we investigated the effects of titanium dioxide nanoparticles (nTiO) on the trophic transfer of phenanthrene (Phe) from prey Artemia salina to predator Scophthalmus maximus. We also evaluated the ensuing toxic performance of Phe in S. maximus after been transferred from A. salina in the presence and absence of nTiO. The presence of nTiO significantly (p < 0.05) increased Phe accumulation in A. salina with higher bioconcentration factor (BCF) up to 90.9 than that of 38.6 in Phe exposure along. After trophic transfer, nTiO (1 mg/L) also promoted the bioaccumulation of Phe (1 μg/L) in predator S. maximus from 4.17 mg/kg to 7.85 mg/kg (dry weight). However, nTiO did not enhance the trophic transfer of Phe from A. salina to S. maximus since the biological magnification factor (BMF) decreased from 0.13 to 0.08. Nevertheless, the nTiO-enhanced bioaccumulation of Phe did enhance Phe toxicity performance in predator S. maximus after trophic transfer, showing significant (p < 0.05) growth inhibition and changes of nutrient status in the predator, compared to those of the control. Further physio-biochemical investigations suggested that oxidative stress and inhibition of digestive functions might explain the growth inhibition in treatment with nTiO + Phe. This study demonstrates the first evidence that NP-enhanced bioaccumulation and toxic performance of co-existing pollutants across trophic transfer, which poses potential risks to marine ecosystems, and ultimately human health by seafood consumption.
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http://dx.doi.org/10.1016/j.jhazmat.2020.124834DOI Listing
April 2021

Comparation of the phytotoxicity between chemically and green synthesized silver nanoparticles.

Sci Total Environ 2021 Jan 8;752:142264. Epub 2020 Sep 8.

State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, China. Electronic address:

Green synthesis of silver nanoparticles (Ag NPs) by using plants extracts has provided an eco-friendly alternation for industry and agriculture application. Here, we prepared Ag NPs by using the cucumber leaves and rice husk extracts, and further assessed the antimicrobial activity and phytotoxicity of green synthesized Ag NPs (g-Ag NPs) comparing with chemically synthesized Ag NPs (chem-Ag NPs). The chem-Ag NPs had strong antibacterial activity on the growth of Escherichia coli, while g-Ag NPs by rice husks (gr-Ag NPs) exhibited long-term antibacterial effects. In terms of phytotoxicity, the chem-Ag NPs induced over-generation of ROS and activated plant antioxidant defense systems, thus resulting in the upregulation of MDA and Zn contents and downregulation of antioxidant capacity, carotenoid, globulin and Mo contents. However, g-Ag NPs significantly promoted cucumber photosynthesis by increasing chlorophyll contents. Besides, the green synthesized Ag NPs by cucumber extracts (gc-Ag NPs) increased protein contents and gr-Ag NPs stimulated the upregulation of Mn and the downregulation of Al, which were all positive effects. Overall, compared with chem-Ag NPs, g-Ag NPs exhibited long-tern antimicrobial properties and attenuated toxicity to plants, which could be used as potential nanopesticide or nanoscale growth regulator in agriculture.
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http://dx.doi.org/10.1016/j.scitotenv.2020.142264DOI Listing
January 2021

Remediation of heavy metal contamination of sediments and soils using ligand-coated dense nanoparticles.

PLoS One 2020 30;15(9):e0239137. Epub 2020 Sep 30.

Bren School of Environmental Science and Management, University of California at Santa Barbara, CA, United States of America.

Sediment and soil contamination with toxic heavy metals, including cadmium (Cd2+) and lead (Pb2+), represents a major long-term remediation challenge. Resuspension of contaminated sediments into the water column, or the uptake of toxic metals from top soil, can lead to exposure of aquatic or terrestrial organisms, followed by bioconcentration, bioaccumulation and biomagnification, which may pose a threat to public health. We have developed a novel nanoscale engineered material, namely ligand-coated dense nanoparticles (Ligand DNPs), which contain a dense WO3 nanoparticle core and a shell functionalized with a metal-binding organic ligand (EDTA), to effectively sequester heavy metal ions deeper into the soil and sediments. We demonstrate that one application of Ligand DNPs can remove from 60% to almost 80% of the Cd and Pb in two different soil matrices, driving these metal ions deeper into the sediment or soil column via gravity, and making them less bioavailable. Ligand DNPs can provide a relatively fast, convenient, and efficient in-situ approach for the remediation of sediments and soils contaminated with heavy metals.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0239137PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7526897PMC
November 2020

TiO Nanoparticles in the Marine Environment: Enhancing Bioconcentration, While Limiting Biotransformation of Arsenic in the Mussel .

Environ Sci Technol 2020 10 9;54(19):12254-12261. Epub 2020 Sep 9.

Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, P. R. China.

The increasing use of nanoscale TiO particles (nTiO) and their subsequent leakage into aquatic environments poses a threat to the ecosystem. One major concern is that nTiO may alter the environmental behaviors of arsenic (As) and disrupt the equilibrium of As accumulation and speciation in organisms. In this study, we investigated the effects of nTiO on the bioaccumulation and biotransformation of As(V) in the mussel . Exposure to nTiO significantly increased As accumulation in mussels. Our As speciation analysis demonstrated that nTiO treatment increased the proportion of inorganic As and reduced that of organic As, displaying inhibitory effects on the methylation and detoxification of inorganic As in mussels. Analysis of enzyme systems related to As metabolism in mussels demonstrated that nTiO might limit the methylation of inorganic As by suppressing the GST activity and GSH content. The strong adsorption capacity and weak desorption rate of As by nTiO, which could result in the disruption of As distribution and decrease of the amount of As involved in biotransformation, might serve as another mechanism to the limition on As methylation in mussels. Moreover, exposure to nTiO disturbed the osmotic adjustment system in mussels by reducing arsenobetaine and Na-K-ATPase activity, resulting in enhanced toxicity of As after coexposure. The findings indicate, for the first time, that nTiO can block the transformation and detoxification of As in mussels, which would increase the risk of As to marine animals and even humans via the food chain, and may disrupt the biogeochemical cycle of As in natural environments.
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http://dx.doi.org/10.1021/acs.est.0c01620DOI Listing
October 2020

Multi-technique approach to study the stability of silver nanoparticles at predicted environmental concentrations in wastewater.

Water Res 2019 Dec 9;166:115072. Epub 2019 Sep 9.

Bren School of Environmental Science and Management, University of California, Santa Barbara, CA, 93106, USA; UC Center for Environmental Implications of Nanotechnology, University of California, Santa Barbara, CA, 93106, USA. Electronic address:

The concentration of silver nanoparticles (nano-Ag) in aqueous media influences the kinetics of ion release; hence, the transformation and stability of nano-Ag are also influenced. The stability, dissolution and further transformation of nano-Ag in aqueous media at predicted environmental concentrations (PECs) ≤ μg/L may differ from that reported at higher concentrations. Analytical techniques characterizing nanoparticles (NPs) at μg/L have advantages and limitations, including an inherent bias based on theoretical and analytical considerations, as well as the matrix effects. In this work, we applied nanoparticle tracking analysis (NTA), single particle ICP-MS (sp-ICP-MS), and localized surface plasmon resonance (LSPR) analysis to study the stability and dissolution of nano-Ag with different nominal sizes (20, 40, 80 and 100 nm) at PECs in synthetic wastewater (SWW). The influence of the main wastewater constituents, such as organic matter, Cl, S, PO and NH, on the stability and dissolution of nano-Ag (40 nm) at PECs was also determined. Diagrams of the predominant species of silver exposed to major ligands were generated using MINTEQ. After 5 h in SWW, 20 nm nano-Ag dissolved 19.27% and 40 nm nano-Ag dissolved 14.8%. Aggregates of Ag particles were clearly noted for 80 and 100 nm nano-Ag after 5 h of exposure to SWW. Aggregates size also ranged very similar for both techniques, NTA and sp-ICP-MS, 29-211 nm and 38-241 for NTA and 48-210 and 50-220 nm, for sp-ICP-MS, respectively. Monodispersed size distribution (22-85 nm) and low dissolution (up to 5.1%) of nano-Ag at PECs were observed in presence of organic matter (5-800 μg/L) and PO (9.5-47.5 mg/L), while precipitation and higher dissolution (up to 74.9%) were observed in media containing either Cl (0.07-10.64 g/L), S (0.32-32.1 mg/L) or NH (36-90 mg/L), respectively. Speciation diagrams predict the formation of AgS and AgCl, and soluble species such as AgCl, AgNH and Ag(NH) when Ag at PECs in wastewater. The NTA and sp-ICP-MS were suitable techniques for sizing nano-Ag in wastewater at PECs at experimented nominal sizes. sp-ICP-MS was also useful to quantify the coexistence of Ag and nano-Ag. The LSPR analysis served to determine the relative persistence of original nano-Ag at PECs in the wastewater during the first 5 h after spiking.
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http://dx.doi.org/10.1016/j.watres.2019.115072DOI Listing
December 2019

Alleviative Effects of C on the Trophic Transfer of Cadmium along the Food Chain in Aquatic Environment.

Environ Sci Technol 2019 Jul 5;53(14):8381-8388. Epub 2019 Jul 5.

Graduate School at Shenzhen , Tsinghua University , Shenzhen 518055 , P.R. China.

C could enhance the accumulation of pollutants in organisms, but their effects on higher trophic levels remain unknown. In the present study, the transfer of C from to zebrafish () and its effects on Cd transfer were investigated. The results showed that C could be transferred from to zebrafish through dietary exposure and accumulate mainly in the intestines, but biomagnification was not observed. The presence of C promoted accumulation of Cd in . However, it decreased Cd burden in the higher trophic level (zebrafish), displaying an alleviative effect on the trophic transfer of Cd along the food chain. To explore the underlying mechanisms, the release of Cd from in digestive fluids and changes in zebrafish digestive physiology were further investigated. The results showed that C did not inhibit Cd release from , but stimulated the digestive tracts of zebrafish to excrete Cd earlier and in a greater amount, which consequently lowered assimilation efficiency of Cd in zebrafish. Overall, the present study showed the trophic transfer of C in the aquatic food chain and revealed the effects of C on trophic transfer of Cd along the food chain in aquatic environment.
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http://dx.doi.org/10.1021/acs.est.9b01636DOI Listing
July 2019

Incidence and persistence of silver nanoparticles throughout the wastewater treatment process.

Water Res 2019 Jun 20;156:188-198. Epub 2019 Mar 20.

Bren School of Environmental Science and Management, University of California, Santa Barbara, CA, 93106, USA; Center for Environmental Implications of Nanotechnology, University of California, Santa Barbara, CA 93106, USA. Electronic address:

While the predicted or observed concentrations of Ag NPs in wastewater treatment plants (WWTPs) have ranged from μg/L to ng/L, there is still uncertainty with regards to the realistic concentration range of Ag NPs in WWTPs. In addition, the persistence, removal, and size of Ag NPs throughout WWTP process is also not well investigated, particularly in real operating conditions. In this study, the incidence and persistence of Ag NPs in the wastewater process were studied by using single particle inductively coupled plasma mass spectrometry (sp-ICP-MS). The incidence of Ag NPs was determined in samples collected at the influent and effluent of the conventional process, as well as reclaimed and backwash waters of the ultrafiltration (UF) system in a WWTP (Santa Barbara, CA), showing a concentration of 13.5, 3.2, 0.5 and 9.8 ng/L, respectively, with relative standard deviations (RSDs) < 5%. Total Ag concentration (Ag NP and Ag) ranged from 40 to 70 ng/L, in line with lower predicted values. Most of the Ag NPs detected were below 100 nm, with a few above 100 nm in the conventional effluent. Biological and physical processes in the secondary treatment removed 76.3% of the colloidal Ag fraction, while with the tertiary treatment (UF) the WWTP achieved a removal of 96.3% of the colloidal fraction. Persistence of Ag NPs in various water matrixes, including a synthetic wastewater (SWW), was determined by spiking 300 ng/L of Ag NPs (40 nm) and monitoring the concentrations and size change for 15 days. The persistence of Ag NPs in suspension was Influent > Effluent > Reclaimed > SWW. Partial dissolution of NPs in all waters was observed from time 0 h. Although the current concentrations in the outlet flows from WWTP (effluent and reclaimed waters) were low, the presence of small and stable Ag NPs may raise ecotoxicological concerns via bioaccumulation.
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http://dx.doi.org/10.1016/j.watres.2019.03.031DOI Listing
June 2019

Successive removal of Pb and Congo red by magnetic phosphate nanocomposites from aqueous solution.

Sci Total Environ 2019 Mar 20;658:1139-1149. Epub 2018 Dec 20.

Shenzhen Environmental Science and New Energy Technology Engineering Laboratory, Tsinghua-Berkeley Shenzhen Institute, Shenzhen 518055, China; Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106, USA.

The successive removal of Pb and Congo red (CR) from aqueous solution by three magnetic phosphate nanocomposites ([email protected](PO)(OH), [email protected](PO), and [email protected](PO)(OH), denominated FSP, FBP, and FSBP, respectively) was systematically investigated in comparison with FeO (denominated F) nanoparticle. FSP, FSBP, F, and FBP exhibited a high removal capacity of 351, 272, 76, and 23 mg/g for Pb, respectively. These materials could be reclaimed by magnetic separation and then used for successive CR remediation, showing a high CR removal capacity of 224, 163, 126, and 61 mg/g, respectively. The isothermal and kinetic behavior fitted well with the Langmuir model and pseudo-second-order model, respectively. The successive removal mechanism by these magnetic phosphates was proposed to be the ion exchange between Pb and Sr in the lattice and then the loaded Pb could contact with anionic dye CR to form precipitation on the surface of materials, inhibiting the leaching of Pb ions from the reclaimed materials back into water. In addition, these materials showed good reusability and practical application. This study demonstrated the potential of these low cost phosphate nanocomposites as promising materials for successive removal of Pb and CR from water.
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http://dx.doi.org/10.1016/j.scitotenv.2018.12.291DOI Listing
March 2019

C60 Fullerols Enhance Copper Toxicity and Alter the Leaf Metabolite and Protein Profile in Cucumber.

Environ Sci Technol 2019 02 4;53(4):2171-2180. Epub 2019 Feb 4.

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

Abiotic and biotic stress induce the production of reactive oxygen species (ROS), which limit crop production. Little is known about ROS reduction through the application of exogenous scavengers. In this study, C60 fullerol, a free radical scavenger, was foliar applied to three-week-old cucumber plants (1 or 2 mg/plant) before exposure to copper ions (5 mg/plant). Results showed that C60 fullerols augmented Cu toxicity by increasing the influx of Cu ions into cells (170% and 511%, respectively, for 1 and 2 mg of C60 fullerols/plant). We further use metabolomics and proteomics to investigate the mechanism of plant response to C60 fullerols. Metabolomics revealed that C60 fullerols up-regulated antioxidant metabolites including 3-hydroxyflavone, 1,2,4-benzenetriol, and methyl trans-cinnamate, among others, while it down-regulated cell membrane metabolites (linolenic and palmitoleic acid). Proteomics analysis revealed that C60 fullerols up-regulated chloroplast proteins involved in water photolysis (PSII protein), light-harvesting (CAB), ATP production (ATP synthase), pigment fixation (Mg-PPIX), and electron transport ( Cyt b6f). Chlorophyll fluorescence measurement showed that C60 fullerols significantly accelerated the electron transport rate in leaves (13.3% and 9.4%, respectively, for 1 and 2 mg C60 fullerols/plant). The global view of the metabolic pathway network suggests that C60 fullerols accelerated electron transport rate, which induced ROS overproduction in chloroplast thylakoids. Plant activated antioxidant and defense pathways to protect the cell from ROS damaging. The revealed benefit (enhance electron transport) and risk (alter membrane composition) suggest a cautious use of C60 fullerols for agricultural application.
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http://dx.doi.org/10.1021/acs.est.8b06758DOI Listing
February 2019

Competitive removal of Pb and malachite green from water by magnetic phosphate nanocomposites.

Water Res 2019 03 28;150:442-451. Epub 2018 Nov 28.

College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao, 266109, China.

The competitive removal of Pb and malachite green (MG) from water by three magnetic phosphate nanocomposites (FeO/Ba(PO), FeO/Sr(PO)(OH), and FeO/SrBa(PO)(OH), namely "FBP", "FSP", and "FSBP", respectively) was systematically investigated compared with FeO ("F") nanoparticle. Temperature and adsorbent dosage for competitive removal were optimized to be 20 °C and 0.05 g in 50 mL. The kinetic and isothermal adsorption results were fitted well with the pseudo-second-order model and Langmuir model, respectively. In the competitive removal process, FSP showed a high affinity to Pb (202.8 mg/g) while FBP possessed high selectivity for MG (175.4 mg/g), and FSBP was effective at simultaneous removal of Pb and MG, with a capacity of 143.7 and 90.9 mg/g, respectively. The magnetic contents in nanocomposites allow magnetic separation of materials from the water after treatment. We proposed that the simultaneous removal mechanism by FSBP was due to ion exchange between Pb and Sr in the lattice and then the formation of hydrogen bonds between PO outside the material's surface and positively charged hydrogen in MG. This study indicates the potential of these phosphate nanocomposites to be used as effective materials for selective or simultaneous removal of Pb and MG from water.
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http://dx.doi.org/10.1016/j.watres.2018.11.057DOI Listing
March 2019

Antioxidant response of cucumber (Cucumis sativus) exposed to nano copper pesticide: Quantitative determination via LC-MS/MS.

Food Chem 2019 Jan 17;270:47-52. Epub 2018 Jul 17.

Bren School of Environmental Science and Management, University of California at Santa Barbara, CA 93106, USA; University of California, Center for Environmental Implications of Nanotechnology, Santa Barbara, CA 93106, USA. Electronic address:

Targeted metabolomics aims to provide a new approach to investigate metabolites and gather both qualitative and quantitative information. We describe a protocol for extraction and analysis of plant metabolites, specifically 13 secondary metabolites (antioxidants) using liquid chromatography coupled to triple quadrupole mass spectrometry (LC-MS/MS), with high linearity (R2 > 0.99) and reproducibility (0.23-6.23 R%) with low limits of detection (>0.001 ng/mL) and quantification (>0.2 ng/mL). The protocol was applied to study the antioxidant response of cucumber plants exposed to nanocopper pesticide. Dose-dependent changes in antioxidant concentrations were found, and 10 antioxidants were significantly consumed to scavenge reactive oxygen species, protecting plants from damage. Levels of three antioxidants were up-regulated, as a response to the depletion of the other antioxidants, signaling activation of the defense system. We demonstrated that the reported LC-MS/MS method provides a quantitative analysis of antioxidants in plant tissues, for example to investigate interactions between plants and nanomaterials.
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http://dx.doi.org/10.1016/j.foodchem.2018.07.069DOI Listing
January 2019

Metabolomics Reveals the Molecular Mechanisms of Copper Induced Cucumber Leaf ( Cucumis sativus) Senescence.

Environ Sci Technol 2018 06 1;52(12):7092-7100. Epub 2018 Jun 1.

Bren School of Environmental Science & Management , University of California , Santa Barbara , California 93106-5131 , United States.

Excess copper may disturb plant photosynthesis and induce leaf senescence. The underlying toxicity mechanism is not well understood. Here, 3-week-old cucumber plants were foliar exposed to different copper concentrations (10, 100, and 500 mg/L) for a final dose of 0.21, 2.1, and 10 mg/plant, using CuSO as the Cu ion source for 7 days, three times per day. Metabolomics quantified 149 primary and 79 secondary metabolites. A number of intermediates of the tricarboxylic acid (TCA) cycle were significantly down-regulated 1.4-2.4 fold, indicating a perturbed carbohydrate metabolism. Ascorbate and aldarate metabolism and shikimate-phenylpropanoid biosynthesis (antioxidant and defense related pathways) were perturbed by excess copper. These metabolic responses occur even at the lowest copper dose considered although no phenotype changes were observed at this dose. High copper dose resulted in a 2-fold increase in phytol, a degradation product of chlorophyll. Polyphenol metabolomics revealed that some flavonoids were down-regulated, while the nonflavonoid 4-hydroxycinnamic acid and trans-2-hydroxycinnamic acid were significantly up-regulated 4- and 26-fold compared to the control. This study enhances current understanding of copper toxicity to plants and demonstrates that metabolomics profiling provides a more comprehensive view of plant responses to stressors, which can be applied to other plant species and contaminants.
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http://dx.doi.org/10.1021/acs.est.8b00742DOI Listing
June 2018

Simultaneous molybdate (Mo(VI)) recovery and hazardous ions immobilization via nanoscale zerovalent iron.

J Hazard Mater 2018 Feb 18;344:698-706. Epub 2017 Oct 18.

College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China. Electronic address:

Nanoscale zerovalent iron (nZVI) shows great promise in valuable metal recovery from wastewater due to its high removal capacity. However, nZVI-based processes mainly focus on the sequestration step, ignoring the desorption step, which is crucial for recovery. In this study, a novel method for simultaneous Mo(VI) recovery and hazardous metal ions immobilization by nZVI was developed and the reaction mechanism was further investigated. Results shown that removal capacity of nZVI was significantly influenced by surface charge and the number of active adsorption sites. X-ray photoelectron spectroscopy analysis demonstrated that Mo(VI) reduction occurred in the inner Fe(0) core. K-edge X-ray Absorption Near Edge Structure analysis further confirmed that 5.4% and 18.0% of Mo(VI) are reduced to Mo(IV) at pH 6 and 9, respectively, suggesting that high pH favors for Mo(VI) reduction and H is responsible for the hollow-out structure at pH 6. Through adjusting the pH of wastewater from 3 to 12, over 80% of adsorbed Mo(VI) could be recovered while other metal ions remained immobilized and limited influence with common ions/anions. Overall, the proposed mechanism was significant to the research of metal reduction and competition for proton of nZVI, and the developed method had great prospects in valuable anions recovery.
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http://dx.doi.org/10.1016/j.jhazmat.2017.10.036DOI Listing
February 2018

Interactions, Transformations, and Bioavailability of Nano-Copper Exposed to Root Exudates.

Environ Sci Technol 2017 Sep 21;51(17):9774-9783. Epub 2017 Aug 21.

Bren School of Environmental Science and Management, University of California at Santa Barbara , Santa Barbara, California 93106, United States.

Due to the potential for interactions between crop plants and engineered nanomaterials (ENMs), there is increasing interest in understanding the bioavailability and effects of ENMs released into soil systems. Here, we investigate the influence of root exudates on the fate of ENMs from a thermodynamic perspective. Nano isothermal titration calorimetry was applied to determine thermodynamic parameters for the interaction between nanocopper (nCu) and synthetic root exudate (SRE) and its components (including sugars, organic acids, amino acids, and phenolic acids), as well as Cu and SRE. The measured binding constant (K = 5.645 × 10 M) indicated strong interactions between nCu particles and SRE, as well as with individual organic acids. The interaction between Cu and SRE was stronger (K = 7.181 × 10 M) but varies for the individual SRE components. nCu dissolution in the presence of SRE was the predominant interaction. In addition, SRE resulted in a complex transformation of nCu, where Cu, Cu, and Cu were formed via oxidation and reduction. Plant-nCu exposure experiments indicate that the binding of SRE with nCu and dissolved Cu ions can significantly decrease Cu uptake and bioaccumulation in plants. nITC provides a fundamental thermodynamic understanding of interactions between nCu and plant root exudates, providing an important tool for understanding plant NP-interactions.
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http://dx.doi.org/10.1021/acs.est.7b02523DOI Listing
September 2017

Metabolomics Reveals Cu(OH) Nanopesticide-Activated Anti-oxidative Pathways and Decreased Beneficial Antioxidants in Spinach Leaves.

Environ Sci Technol 2017 Sep 9;51(17):10184-10194. Epub 2017 Aug 9.

Bren School of Environmental Science & Management and ‡Center for Environmental Implications of Nanotechnology, University of California , Santa Barbara, California 93106, United States.

While the use of nanopesticides in modern agriculture continues to increase, their effects on crop plants are still poorly understood. Here, 4 week old spinach plants grown in an artificial medium were exposed via foliar spray to Cu(OH) nanopesticide (0.18 and 18 mg/plant) or Cu ions (0.15 and 15 mg/plant) for 7 days. A gas chromatography-time-of-flight-mass spectrometry metabolomics approach was applied to assess metabolic alterations induced by Cu(OH) nanopesticide in spinach leaves. Exposure to Cu(OH) nanopesticide and copper ions induced alterations in the metabolite profiles of spinach leaves. Compared to the control, exposure to 18 mg of Cu(OH) nanopesticide induced significant reduction (29-85%) in antioxidant or defense-associated metabolites including ascorbic acid, α-tocopherol, threonic acid, β-sitosterol, 4-hydroxybutyric acid, ferulic acid, and total phenolics. The metabolic pathway for ascorbate and aldarate was disturbed in all exposed spinach plants (nanopesticide and Cu). Cu is responsible for the reduction in antioxidants and perturbation of the ascorbate and aldarate metabolism. However, nitrogen metabolism perturbation was nanopesticide-specific. Spinach biomass and photosynthetic pigments were not altered, indicating that metabolomics can be a rapid and sensitive tool for the detection og earlier nanopesticide effects. Consumption of antioxidants during the antioxidant defense process resulted in reduction of the nutritional value of exposed spinach.
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http://dx.doi.org/10.1021/acs.est.7b02163DOI Listing
September 2017

Comparative Metabolic Response between Cucumber ( Cucumis sativus) and Corn ( Zea mays) to a Cu(OH) Nanopesticide.

J Agric Food Chem 2018 Jul 17;66(26):6628-6636. Epub 2017 May 17.

Bren School of Environmental Science & Management , University of California , Santa Barbara , California 93106-5131 , United States.

Due to their unique properties, copper-based nanopesticides are emerging in the market. Thus, understanding their effect on crop plants is very important. Metabolomics can capture a snapshot of cellular metabolic responses to a stressor. We selected maize and cucumber as model plants for exposure to different doses of Cu(OH) nanopesticide. GC-TOF-MS-based metabolomics was employed to determine the metabolic responses of these two species. Results revealed significant differences in metabolite profile changes between maize and cucumber. Furthermore, the Cu(OH) nanopesticide induced metabolic reprogramming in both species, but in different manners. In maize, several intermediate metabolites of the glycolysis pathway and tricarboxylic acid cycle (TCA) were up-regulated, indicating the energy metabolism was activated. In addition, the levels of aromatic compounds (4-hydroxycinnamic acid and 1,2,4-benzenetriol) and their precursors (phenylalanine, tyrosine) were enhanced, indicating the activation of shikimate-phenylpropanoid biosynthesis in maize leaves, which is an antioxidant defense-related pathway. In cucumber, arginine and proline metabolic pathways were the most significantly altered pathway. Both species exhibited altered levels of fatty acids and polysaccharides, suggesting the cell membrane and cell wall composition may change in response to Cu(OH) nanopesticide. Thus, metabolomics helps to deeply understand the differential response of these plants to the same nanopesticide stressor.
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http://dx.doi.org/10.1021/acs.jafc.7b01306DOI Listing
July 2018

Metabolomics to Detect Response of Lettuce (Lactuca sativa) to Cu(OH)2 Nanopesticides: Oxidative Stress Response and Detoxification Mechanisms.

Environ Sci Technol 2016 09 17;50(17):9697-707. Epub 2016 Aug 17.

Bren School of Environmental Science & Management, University of California , Santa Barbara, California 93106-5131, United States.

There has been an increasing influx of nanopesticides into agriculture in recent years. Understanding the interaction between nanopesticides and edible plants is crucial in evaluating the potential impact of nanotechnology on the environment and agriculture. Here we exposed lettuce plants to Cu(OH)2 nanopesticides (1050-2100 mg/L) through foliar spray for one month. Inductively coupled plasma-mass spectrometry (ICP-MS) results indicate that 97-99% (1353-2501 mg/kg) of copper was sequestered in the leaves and only a small percentage (1-3%) (17.5-56.9 mg/kg) was translocated to root tissues through phloem loading. Gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS) based metabolomics combined with partial least squares-discriminant analysis (PLS-DA) multivariate analysis revealed that Cu(OH)2 nanopesticides altered metabolite levels of lettuce leaves. Tricarboxylic (TCA) cycle and a number of amino acid-related biological pathways were disturbed. Some antioxidant levels (cis-caffeic acid, chlorogenic acid, 3,4-dihydroxycinnamic acid, dehydroascorbic acid) were significantly decreased compared to the control, indicating that oxidative stress and a defense response occurred. Nicotianamine, a copper chelator, increased by 12-27 fold compared to the control, which may represent a detoxification mechanism. The up-regulation of polyamines (spermidine and putrescine) and potassium may mitigate oxidative stress and enhance tolerance. The data presented here provide a molecular-scale perspective on the response of plants to copper nanopesticides.
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http://dx.doi.org/10.1021/acs.est.6b02763DOI Listing
September 2016

Simultaneous removal of PAHs and metal contaminants from water using magnetic nanoparticle adsorbents.

Sci Total Environ 2016 Nov 19;571:1029-36. Epub 2016 Jul 19.

Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106, USA. Electronic address:

Many industrial wastewaters are contaminated with both heavy metal ions and organic compounds, posing a major threat to public health and the environment. In this study, magnetic nanoparticle adsorbents, namely Mag-PCMA-T, which contain a maghemite core and a silica mesoporous layer that permanently confines surfactant micelles within the mesopores, were synthesized to achieve simultaneous removal of polycyclic aromatic hydrocarbons (PAHs) (1mg/L) and metal contaminants (1mg/L). The individual removal efficiency of Cd(2+) and acenaphthene using Mag-PCMA-T was evaluated under a range of initial ion concentrations and adsorbent dosages, as well as the competitive adsorption with Cd(2+) and acenaphthene simultaneously present. The isotherms and kinetics of Cd(2+) and acenaphthene sorption onto Mag-PCMA-T were determined. Mag-PCMA-T removed >85% of the acenaphthene in <30min, with relatively high sorption capacity (up to 1060mg/kg). Mag-PCMA-T also exhibited high sorption capacity for Cd(2+) (up to 2250mg/kg). The simultaneous sorption performance was stable across a wide pH range (4-9) as well as in the presence of competitive metal ions (Ca(2+) and Mg(2+)) or natural organic matters. The Mag-PCMA-T can be regenerated and reused, providing a sustainable, fast, convenient, and efficient approach for water treatment.
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http://dx.doi.org/10.1016/j.scitotenv.2016.07.093DOI Listing
November 2016

Direct Synthesis of Novel and Reactive Sulfide-modified Nano Iron through Nanoparticle Seeding for Improved Cadmium-Contaminated Water Treatment.

Sci Rep 2016 04 20;6:24358. Epub 2016 Apr 20.

State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China.

Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) is of great technical and scientific interest because of its promising application in groundwater remediation, although its synthesis is still a challenge. We develop a new nanoparticle seeding method to obtain a novel and reactive nanohybrid, which contains an Fe(0) core covered by a highly sulfidized layer under high extent of sulfidation. Syntheses monitoring experiments show that seeding accelerates the reduction rate from Fe(2+) to Fe(0) by 19%. X-ray adsorption near edge structure (XANES) spectroscopy and extended X-ray absorption fine structure analyses demonstrate the hexahedral Fe-Fe bond (2.45 and 2.83 Å) formation through breaking down of the 1.99 Å Fe-O bond both in crystalline and amorphous iron oxide. The XANES analysis also shows 24.2% (wt%) of FeS with bond length of 2.4 Å in final nanohybrid. Both X-ray diffraction and Mössbauer analyses further confirm that increased nanoparticle seeding results in formation of more Fe(0) crystals. Nano-SiO2 seeding brings down the size of single Fe(0) grain from 32.4 nm to 18.7 nm, enhances final Fe(0) content from 5.9% to 55.6%, and increases magnetization from 4.7 to 65.5 emu/g. The synthesized nanohybrid has high cadmium removal capacity and holds promising prospects for treatment of metal-contaminated water.
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http://dx.doi.org/10.1038/srep24358DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4837343PMC
April 2016

H NMR and GC-MS based metabolomics reveal nano-Cu altered cucumber (Cucumis sativus) fruit nutritional supply.

Plant Physiol Biochem 2017 Jan 10;110:138-146. Epub 2016 Feb 10.

Bren School of Environmental Science & Management, University of California, Santa Barbara, CA 93106-5131, United States; University of California, Center for Environmental Implications of Nanotechnology, Santa Barbara, CA United States. Electronic address:

It is imperative to study the interaction of nanoparticles residuals with crop plants in agricultural soils, due to the increased application of nanotechnology in agriculture. So far, a few studies have focused on the impact of nanoparticles on fruit quality and nutritional supply. In this work, a thorough and comprehensive analysis of metabolite changes of cucumber fruits from plants under nano-Cu stress was possible through the use of both H NMR and GC-MS. The results of supervised partial least-squares discriminant analysis from both platforms showed that cucumber fruit extracts samples were clearly grouped based on the nano-Cu level in soil. This indicates that the fruit metabolite profile was influenced by exposure to nano-Cu. GC-MS data showed concentrations of some sugars, organic acids, amino acids, and fatty acids were increased or decreased by nano-Cu. Several metabolites, such as methylnicotinamide (MNA), trigonelline, imidazole, quinolinate were only detected and quantified by H NMR. Our results showed that combining the two platforms provided a comprehensive understanding about the metabolites (nutrient supply) changes in cucumber fruits impacted by exposure to nano-Cu.
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http://dx.doi.org/10.1016/j.plaphy.2016.02.010DOI Listing
January 2017

(1)H NMR and GC-MS Based Metabolomics Reveal Defense and Detoxification Mechanism of Cucumber Plant under Nano-Cu Stress.

Environ Sci Technol 2016 Feb 26;50(4):2000-10. Epub 2016 Jan 26.

Bren School of Environmental Science and Management, University of California , Santa Barbara, California 93106-5131, United States.

Because copper nanoparticles are being increasingly used in agriculture as pesticides, it is important to assess their potential implications for agriculture. Concerns have been raised about the bioaccumulation of nano-Cu and their toxicity to crop plants. Here, the response of cucumber plants in hydroponic culture at early development stages to two concentrations of nano-Cu (10 and 20 mg/L) was evaluated by proton nuclear magnetic resonance spectroscopy ((1)H NMR) and gas chromatography-mass spectrometry (GC-MS) based metabolomics. Changes in mineral nutrient metabolism induced by nano-Cu were determined by inductively coupled plasma-mass spectrometry (ICP-MS). Results showed that nano-Cu at both concentrations interferes with the uptake of a number of micro- and macro-nutrients, such as Na, P, S, Mo, Zn, and Fe. Metabolomics data revealed that nano-Cu at both levels triggered significant metabolic changes in cucumber leaves and root exudates. The root exudate metabolic changes revealed an active defense mechanism against nano-Cu stress: up-regulation of amino acids to sequester/exclude Cu/nano-Cu; down-regulation of citric acid to reduce the mobilization of Cu ions; ascorbic acid up-regulation to combat reactive oxygen species; and up-regulation of phenolic compounds to improve antioxidant system. Thus, we demonstrate that nontargeted (1)H NMR and GC-MS based metabolomics can successfully identify physiological responses induced by nanoparticles. Root exudates metabolomics revealed important detoxification mechanisms.
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http://dx.doi.org/10.1021/acs.est.5b05011DOI Listing
February 2016

Heteroaggregation of nanoparticles with biocolloids and geocolloids.

Adv Colloid Interface Sci 2015 Dec 22;226(Pt A):24-36. Epub 2015 Jul 22.

Bren School of Environmental Science and Management, University of California, Santa Barbara, CA, 93106, USA. Electronic address:

The application of nanoparticles has raised concern over the safety of these materials to human health and the ecosystem. After release into an aquatic environment, nanoparticles are likely to experience heteroaggregation with biocolloids, geocolloids, natural organic matter (NOM) and other types of nanoparticles. Heteroaggregation is of vital importance for determining the fate and transport of nanoparticles in aqueous phase and sediments. In this article, we review the typical cases of heteroaggregation between nanoparticles and biocolloids and/or geocolloids, mechanisms, modeling, and important indicators used to determine heteroaggregation in aqueous phase. The major mechanisms of heteroaggregation include electric force, bridging, hydrogen bonding, and chemical bonding. The modeling of heteroaggregation typically considers DLVO, X-DLVO, and fractal dimension. The major indicators for studying heteroaggregation of nanoparticles include surface charge measurements, size measurements, observation of morphology of particles and aggregates, and heteroaggregation rate determination. In the end, we summarize the research challenges and perspective for the heteroaggregation of nanoparticles, such as the determination of αhetero values and heteroaggregation rates; more accurate analytical methods instead of DLS for heteroaggregation measurements; sensitive analytical techniques to measure low concentrations of nanoparticles in heteroaggregation systems; appropriate characterization of NOM at the molecular level to understand the structures and fractionation of NOM; effects of different types, concentrations, and fractions of NOM on the heteroaggregation of nanoparticles; the quantitative adsorption and desorption of NOM onto the surface of nanoparticles and heteroaggregates; and a better understanding of the fundamental mechanisms and modeling of heteroaggregation in natural water which is a complex system containing NOM, nanoparticles, biocolloids and geocolloids.
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http://dx.doi.org/10.1016/j.cis.2015.07.002DOI Listing
December 2015

EDTA functionalized magnetic nanoparticle sorbents for cadmium and lead contaminated water treatment.

Water Res 2015 Sep 10;80:159-68. Epub 2015 May 10.

Bren School of Environmental Science and Management, University of California at Santa Barbara, CA 93106, USA. Electronic address:

Cadmium (Cd(2+)) and lead (Pb(2+)) are toxic to human beings and other organisms, and the U.S. Environmental Protection Agency (EPA) has classified both as probable human carcinogens. In this study, a regenerable magnetic ligand particle (Mag-Ligand) which includes a metal-binding organic ligand (EDTA) attached to an iron oxide nanoparticle was developed for rapid removal of Cd(2+) and Pb(2+) as well as other metals from contaminated water. Mag-Ligand showed fast removal ability for both Cd(2+) (<2 h) and Pb(2+) (<15 min) with relatively high sorption capacity (79.4 and 100.2 mg/g for Cd(2+) and Pb(2+), respectively). The removal performance of Mag-Ligand was high across a wide pH range (3-10) as well as in the presence of competitive metal ions (Ca(2+) and Mg(2+)). In addition, Mag-Ligands can be easily regenerated (washed by 1% HCl) and reused several cycles with high sorption capacity. This study indicated that Mag-Ligand is a reusable sorbent for rapid, convenient, and efficient removal of Cd(2+) and Pb(2+) from contaminated aquatic systems.
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http://dx.doi.org/10.1016/j.watres.2015.05.011DOI Listing
September 2015

Magnetic sulfide-modified nanoscale zerovalent iron (S-nZVI) for dissolved metal ion removal.

Water Res 2015 May 12;74:47-57. Epub 2015 Feb 12.

State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China; Key Laboratory of Yangtze Water Environment for Ministry of Education, Tongji University, Shanghai 200092, China. Electronic address:

Sulfide-modified nanoscale zerovalent iron (S-nZVI) is attracting a lot of attention due to its ease of production and high reactivity with organic pollutants. However, its structure is still poorly understood and its potential application in heavy metal remediation has not been explored. Herein, the structure of S-nZVI and its cadmium (Cd) removal performance under different aqueous conditions were carefully investigated. Transmission electron microscopy (TEM) with an energy-dispersive X-ray spectroscopy (EDS) analysis suggested that sulfur was incorporated into the zerovalent iron core. Scanning electron microscopy (SEM) with EDS analysis demonstrated that sulfur was also homogeneously distributed within the nanoparticles. When the concentration of Na2S2O4 was increased during synthesis, a flake-like structure (FeSx) increased significantly. S-nZVI had an optimal Cd removal capacity of 85 mg/g, which was >100% higher than for pristine nZVI. Even at pH 5, over 95% removal efficiency was observed, indicating sulfide compounds played a crucial role in metal ion removal and particle chemical stability. Oxygen impaired the structure of S-nZVI but enhanced Cd removal capacity to about 120 mg/g. Particle aging had no negative effect on removal capacity of S-nZVI, and Cd-containing mixtures remained stable in a two months experiment. S-nZVI can efficiently sequester dissolved metal ions from different contaminated water matrices.
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http://dx.doi.org/10.1016/j.watres.2015.02.004DOI Listing
May 2015
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