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Dive into the research topics where Dongqiang Zhu is active.

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Featured researches published by Dongqiang Zhu.


Journal of Colloid and Interface Science | 2010

Amino-functionalized Fe3O4@SiO2 core–shell magnetic nanomaterial as a novel adsorbent for aqueous heavy metals removal

Jiahong Wang; Shourong Zheng; Yun Shao; Jingliang Liu; Zhaoyi Xu; Dongqiang Zhu

A novel amino-functionalized Fe(3)O(4)@SiO(2) magnetic nanomaterial with a core-shell structure was developed, aiming to remove heavy metal ions from aqueous media. The structural, surface, and magnetic characteristics of the nanosized adsorbent were investigated by elemental analysis, FTIR, N(2) adsorption-desorption, transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, and zeta-potential measurement. The amino-functionalized Fe(3)O(4)@SiO(2) nanoadsorbent exhibited high adsorption affinity for aqueous Cu(II), Pb(II), and Cd(II) ions, resulting from complexation of the metal ions by surface amino groups. Moreover, the adsorption affinity for heavy metal ions was not much impacted by the presence of a cosolute of humic acid (10.6mg/L) or alkali/earth metal ions (Na(+), K(+), Mg(2+)) (0.025-0.30mmol/L). The metal-loaded Fe(3)O(4)@SiO(2)-NH(2) nanoparticles could be recovered readily from aqueous solution by magnetic separation and regenerated easily by acid treatment. Findings of the present work highlight the potential for using amino-functionalized Fe(3)O(4)@SiO(2) magnetic nanoparticles as an effective and recyclable adsorbent for the removal of heavy metal ions in water and wastewater treatment.


Langmuir | 2009

Adsorption of Sulfonamide Antibiotics to Multiwalled Carbon Nanotubes

Liangliang Ji; Wei Chen; Shourong Zheng; Zhaoyi Xu; Dongqiang Zhu

The presence of sulfonamide antibiotics in aquatic environments has been recognized as an issue warranting consideration. In this study, we evaluated multiwalled carbon nanotubes (MWNT) as a potential effective adsorbent for removal of two sulfonamide antibiotics, sulfapyridine and sulfamethoxazole, from aqueous solutions. Nonporous, functionality-free graphite was included as a comparative adsorbent. Despite the very low hydrophobicity, the two sulfonamides adsorbed strongly to MWNT and graphite, a fact attributed to pi-pi electron coupling with the graphene surface of the adsorbent. For both sulfonamide antibiotics, similar patterns of pH-dependent adsorption were observed between MWNT and graphite, implying the predominance of graphene structures for the adsorption to MWNT. Moreover, the observed pH effects on adsorption indicate that the protonated neutral form of sulfonamide adsorbs much more strongly than the deprotonated anionic counterpart does. The effects of ionic strength (NaCl and CaCl2) and the presence of a dissolved soil humic acid on adsorption of the two antibiotics to MWNT and graphite were also assessed. Ring current-induced 1H NMR upfield chemical shifts further verified face-to-face complex formation between neutral sulfamethoxazole and model pi-electron donor compounds (naphthalene, phenanthrene, and pyrene) in solution.


Environmental Science & Technology | 2010

Adsorption of Pharmaceutical Antibiotics on Template-Synthesized Ordered Micro- and Mesoporous Carbons

Liangliang Ji; Fengling Liu; Zhaoyi Xu; Shourong Zheng; Dongqiang Zhu

The presence of pharmaceutical antibiotics in aquatic environments poses potential human health and ecological risks. We synthesized ordered micro- and mesoporous carbons, and further conducted batch experiments to systematically examine their adsorption properties toward three antibiotics, sulfamethoxazole, tetracycline, and tylosin, in aqueous solution. In comparison, nonporous graphite, single-walled carbon nanotubes, and two commercial microporous activated carbons were included as additional adsorbents. Adsorption of low-sized sulfamethoxazole was stronger on the activated carbons than on other carbonaceous adsorbents resulting from the pore-filling effect; in contrast, due to the size-exclusion effect adsorption of bulky tetracycline and tylosin was much lower on the activated carbons, especially for the more microporous one, than on the synthesized carbons. After normalizing for adsorbent surface area, adsorption of tetracycline and tylosin on the synthesized carbons was similar to that on nonporous graphite, reflecting complete accessibility of the adsorbent surface area in adsorption. Additionally, compared with other porous adsorbents the synthesized carbons showed faster adsorption kinetics of tetracycline and tylosin, which was attributed to their regular-shaped, open and interconnected three-dimensional pore structure. The findings indicate that template-synthesized micro- and mesoporous carbons are promising adsorbents for the removal of antibiotics, particularly, the bulky and flexible-structured compounds, from aqueous solution.


Environmental Science & Technology | 2011

Adsorption of Tetracycline and Sulfamethoxazole on Crop Residue-Derived Ashes: Implication for the Relative Importance of Black Carbon to Soil Sorption

Liangliang Ji; Yuqiu Wan; Shourong Zheng; Dongqiang Zhu

The main objective of this study was to investigate the key factors and mechanisms of antibiotic adsorption on crop residue-derived black carbon, as well as the relative importance of black carbon to the overall sorption to soil. Batch sorption experiments were performed for two reference antibiotics (sulfamethoxazole and tetracycline) on wheat- and maize-residue-derived black carbon. After removal of the mineral fraction from the raw black carbon by acidification, tetracycline exhibited less enhanced adsorption than sulfamethoxazole, implying stronger complexation of tetracycline on the mineral components. The antibiotic adsorption on the demineralized black carbon was very strong (The measured K(d) was in the order of 10(3)-10(5) L/kg). The adsorbent surface area-normalized adsorption of sulfamethoxazole was higher on the demineralized black carbon than on nonporous graphite due to the micropore-filling effect. The opposite trend observed for bulky tetracycline was attributed to the size-exclusion effect. Owing to the strong surface complexation and/or cation exchange reaction, sorption of tetracycline to Na(+)-exchanged montmorillonite, soil humic acids, and bulk soil was remarkably stronger than sulfamethoxazole. It was estimated that the contribution of black carbon to the overall sorption to bulk soil was important for sulfamethoxazole, but negligible for tetracycline.


Environmental Science & Technology | 2010

Adsorption of monoaromatic compounds and pharmaceutical antibiotics on carbon nanotubes activated by KOH etching.

Liangliang Ji; Yun Shao; Zhaoyi Xu; Shourong Zheng; Dongqiang Zhu

The relatively low surface area and micropore volume of carbon nanotubes limit their potential application as effective adsorbents for hydrophobic organic contaminants. In this study, KOH dry etching was explored to prepare activated single-walled carbon nanotubes (SWNT) and multiwalled carbon nanotubes (MWNT) for adsorption of model monoaromatic compounds (phenol and nitrobenzene) and pharmaceutical antibiotics (sulfamethoxazole, tetracycline, and tylosin) in aqueous solutions. With activation, the specific surface area was increased from 410.7 m(2)/g to 652.8 m(2)/g for SWNT and from 157.3 m(2)/g to 422.6 m(2)/g for MWNT, and substantial pore volumes were created for the activated samples. Consistently, adsorption of the test solutes was enhanced 2-3 times on SWNT and 3-8 times on MWNT. Moreover, the activated carbon nanotubes showed improved adsorption reversibility for the selected monoaromatics, as compared with the pristine counterparts, which was attributed to the more interconnected pore structure and less pore deformation of the activated adsorbents. This is the first study on the adsorption/desorption of aqueous organic contaminants by KOH-activated carbon nanotubes. The findings indicate that KOH etching is a useful activation method to improve the adsorption affinity and adsorption reversibility of organic contaminants on carbon nanotubes.


Environmental Toxicology and Chemistry | 2010

Adsorption of tetracycline on single-walled and multi-walled carbon nanotubes as affected by aqueous solution chemistry.

Liangliang Ji; Wei Chen; Jun Bi; Shourong Zheng; Zhaoyi Xu; Dongqiang Zhu; Pedro J. J. Alvarez

Carbon nanotubes have shown great potential as effective adsorbents for hydrophobic organic contaminants in water treatment. The present study investigated the influence of aqueous solution chemistry on the adsorption of tetracycline to carbon nanotubes. Specifically, the effects of ionic strength (NaCl and CaCl(2) ) and presence of Cu(2+) ion (7.5 mg/L) or dissolved soil or coal humic acids (50 mg/L) on adsorption of tetracycline to single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT), and nonporous pure graphite as a model of the graphite surface were systematically estimated. The presence of humic acids suppressed tetracycline adsorption on graphite and MWNT prominently, with stronger effects observed on graphite, but only slightly affected tetracycline adsorption on SWNT. The relatively large humic acid components could not readily access the small interstitial spaces of SWNT and thus were less competitive with tetracycline adsorption. The presence of Cu(2+) ion increased tetracycline adsorption to both SWNT and MWNT through the mechanism of cation bridging, with much larger effects observed on MWNT. This was probably because when compared with the Cu(2+) ions complexed on the surface of SWNT, those on the surface of MWNT having larger mesoporous interstices were more accessible to the relatively bulky tetracycline molecule. Increasing the ionic strength from 10 mM to 100 mM decreased tetracycline adsorption on both SWNT and MWNT, which was attributed to electronic shielding of the negatively charged surface sites. These results show that aqueous solution chemistry is important to tetracycline adsorption on carbon nanotubes.


Environmental Science & Technology | 2013

Graphene Oxide-Facilitated Reduction of Nitrobenzene in Sulfide-Containing Aqueous Solutions

Heyun Fu; Dongqiang Zhu

The main objective of this study was to test the possibility that graphene-based nanomaterials can mediate environmentally relevant abiotic redox reactions of organic contaminants. We investigated the effect of graphene oxide (GO) on the reduction of nitrobenzene by Na2S in aqueous solutions. With the presence of GO (typically 5 mg/L), the observed pseudofirst-order rate constant (kobs) for the reduction of nitrobenzene was raised by nearly 2 orders of magnitude (from 7.83 × 10(-5) h(-1) to 7.77 × 10(-3) h(-1)), strongly suggesting reaction mediation by GO. As reflected by the combined spectroscopic analyses, GO was reduced in the beginning of the reaction, and hence the reduced GO (RGO) mediated the reduction of nitrobenzene. It was proposed that the zigzag edges of RGO acted as the catalytic active sites, while the basal plane of RGO served as the conductor for the electron transfer during the catalytic process. Furthermore, changing the pH (5.9-9.1) and the presence of dissolved humic acid (10 mg TOC/L) were found to greatly influence the catalytic activity of RGO. The results imply that graphene-based nanomaterials may effectively mediate the reductive transformation of nitroaromatic compounds and can contribute to the natural attenuation and remediation of these chemicals.


Environmental Science & Technology | 2014

Microbial Extracellular Polymeric Substances Reduce Ag+ to Silver Nanoparticles and Antagonize Bactericidal Activity

Fuxing Kang; Pedro J. J. Alvarez; Dongqiang Zhu

Whereas the antimicrobial mechanisms of silver have been extensively studied and exploited for numerous applications, little is known about the associated bacterial adaptation and defense mechanisms that could hinder disinfection efficacy or mitigate unintended impacts to microbial ecosystem services associated with silver release to the environment. Here, we demonstrate that extracellular polymeric substances (EPS) produced by bacteria constitute a permeability barrier with reducing constituents that mitigate the antibacterial activity of silver ions (Ag(+)). Specifically, manipulation of EPS in Escherichia coli suspensions (e.g., removal of EPS attached to cells by sonication/centrifugation or addition of EPS at 200 mg L(-1)) demonstrated its critical role in hindering intracellular silver penetration and enhancing cell growth in the presence of Ag(+) (up to 0.19 mg L(-1)). High-resolution transmission electron microscopy (HRTEM) combined with X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectrometry (EDS) analyses showed that Ag(+) was reduced to silver nanoparticles (AgNPs; 10-30 nm in diameter) that were immobilized within the EPS matrix. Fourier transform infrared (FTIR) and (13)C nuclear magnetic resonance (NMR) spectra suggest that Ag(+) reduction to AgNPs by the hemiacetal groups of sugars in EPS contributed to immobilization. Accordingly, the amount and composition of EPS produced have important implications on the bactericidal efficacy and potential environmental impacts of Ag(+).


Journal of Environmental Quality | 2013

Graphene nanosheets and graphite oxide as promising adsorbents for removal of organic contaminants from aqueous solution.

Liangliang Ji; Wei Chen; Zhaoyi Xu; Shourong Zheng; Dongqiang Zhu

Graphenes are an emerging class of carbon nanomaterials whose adsorption properties toward organic compounds have not been well understood. In the present study, graphene nanosheets were prepared by reoxidation and abrupt heating of graphite oxide, which was prepared by sequential chemical oxidation of commercial nonporous graphite powder. Adsorption properties of three aromatic compounds (naphthalene, 2-naphthol, and 1-naphthylamine) and one pharmaceutical compound (tylosin) on graphene nanosheets and graphite oxide were examined to explore the potential of these two adsorbents for the removal of organic contaminants from aqueous solutions. Compared with the literature data of adsorption on carbon nanotubes, adsorption of bulky, flexible tylosin on graphene nanosheets exhibited markedly faster adsorption kinetics, which can be attributed to their opened-up layer structure. Graphene nanosheets and graphite oxide showed similar sequences of adsorption affinity: 1-naphthylamine > 2-naphthol > tylosin > naphthalene (with much larger differences observed on graphite oxide). It was proposed that the strong adsorption of the three aromatic compounds was mainly due to π-π electron donor-acceptor interactions with the graphitic surfaces of adsorbents. Additionally, Lewis acid-base interaction was likely an important factor contributing to the strong adsorption of 1-naphthylamine and tylosin, especially for the O-functionality-abundant graphite oxide. After being normalized on the basis of adsorbent surface area, adsorption affinities of all four tested adsorbates on graphene nanosheets were very close to those on nonporous graphite powder, reflecting complete accessibility of the adsorbent surface area in adsorption.


Environmental Pollution | 2014

Adsorption of sulfonamides to demineralized pine wood biochars prepared under different thermochemical conditions

Mengxing Xie; Wei Chen; Zhaoyi Xu; Shourong Zheng; Dongqiang Zhu

The main objective of this study was to understand the key factors and mechanisms controlling adsorption of sulfonamides to biochars. Batch adsorption experiments were performed for sulfamethoxazole and sulfapyridine to three pine-wood biochars prepared under different thermochemical conditions: pyrolysis at 400 °C (C400) and 500 °C (C500), and pyrolysis at 500 °C followed with hydrogenation (C500-H). For both sulfonamides, the adsorbent surface area-normalized adsorption was stronger to C500 than to C400. This is attributable to the enhanced π-π electron-donor-acceptor interaction with the carbon surface of C500 due to the higher degree of graphitization. Despite the relatively large difference in surface O-functionality content between C500 (12.2%) and C500-H (6.6%), the two biochars exhibited nearly identical adsorbent surface area-normalized adsorption, indicating negligible role of surface O-functionalities in the adsorption to these adsorbents. Effects of solution chemistry conditions (pH, Cu(2+), and dissolved soil humic acid) on adsorption were examined.

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Hui Li

Michigan State University

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