Zhongshan Chen

Layered double hydroxide intercalated with aromatic acid anions for the efficient capture of aniline from aqueous solution.

Aniline is toxic and hard to be degraded, and thereby causes the environmental pollution seriously. Herein, a practical and green hydrothermal method was applied to fabricate terephthalic acid and pyromellitic acid intercalated layered double hydroxides (LDH) (named as TAL and PAL) for aniline efficient removal. The sorption of aniline on LDH-based materials were investigated at different experimental conditions, and the results indicated that aniline sorption on LDH, TAL and PAL were strongly dependent on pH and independent of ionic strength. The maximum sorption capacities of aniline on TAL and PAL at pH 5.0 and 293K were 90.4 and 130.0mg/g, respectively, which were significantly higher than that of aniline on LDH (52.6mg/g). Based on the BET, FTIR and XPS analysis, the higher sorption capacities of TAL and PAL were mainly due to high surface area and basal spacing as well as the abundant functional groups (e.g. -COO-). The interactions of aniline with TAL and PAL were mainly dominated by hydrogen bonds and electrostatic interactions. Such a facile synthesis method, efficient removal performance and superior reusability indicated that the aromatic acid modified LDH materials had potential application for efficient treatment of organic pollutants in environmental pollution cleanup.

Graphene oxides for simultaneous highly efficient removal of trace level radionuclides from aqueous solutions

Graphene oxides (GOs) were synthesized via modified Hummers method, and were applied as adsorbents to remove radionuclides from large volumes of aqueous solutions. The single and competitive sorption of four radionuclides (i.e., U(VI), 152+154Eu(III), 85+89Sr(II) and 134Cs(I)) on the GOs from aqueous solutions were investigated as a function of pH, ionic strength and radionuclide initial concentrations using batch technique. The results showed that the GOs had much higher sorption capacity than many other contemporary materials, for the preconcentration of radionuclides from large volumes of aqueous solutions. The sorption of radionuclides on GOs obeyed the Langmuir model, and was mainly attributed to surface complexation via the coordination of radionuclides with the oxygen-containing functional groups on GO surfaces. The competitive sorption results indicated that the selectivity sorption capacities were U(VI)>Eu(III)>Sr(II)>Cs(I). The GOs are suitable materials for the efficient removal and preconcentration of radionuclides from aqueous solutions in nuclear waste management and environmental pollution cleanup.

One-pot synthesis of graphene oxide and Ni-Al layered double hydroxides nanocomposites for the efficient removal of U(VI) from wastewater

Graphene oxide and Ni-Al layered double hydroxides (GO@LDH) nanocomposites were synthesized via a one-pot hydrothermal process, and characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy in detail. The exploration of U(VI) sorption on GO@LDH surface was performed as a function of ionic strength, solution pH, contact time, U(VI) initial concentrations and temperature. Results of Langmuir isotherms showed that the sorption capacity of GO@LDH (160 mg/g) was much higher than those of LDH (69 mg/g) and GO (92 mg/g). The formed surface complexes between surface oxygen-containing functional groups of GO@LDH and U(VI) turned out to be the interaction mechanism of U(VI) with GO@LDH. According to the thermodynamic studies results, the sorption interaction was actually a spontaneous and endothermic chemical process. The sorption isotherms were better fitted with the Langmuir model compared with other models, which suggested the interaction was mainly dominated by monolayer coverage. The GO@LDH nanocomposites provide potential applications as adsorbents in the enrichment of radionuclides from wastewater in nuclear waste management and environmental remediation.

The role of graphene oxide and graphene oxide-based nanomaterials in the removal of pharmaceuticals from aqueous media: a review

In this review paper, the ill effects of pharmaceuticals (PhAs) on the environment and their adsorption on graphene oxide (GO) and graphene oxide-based (GO-based) nanomaterials have been summarised and discussed. The adsorption of prominent PhAs discussed herein includes beta-blockers (atenolol and propranolol), antibiotics (tetracycline, ciprofloxacin and sulfamethoxazole), pharmaceutically active compounds (carbamazepine) and analgesics such as diclofenac. The adsorption of PhAs strictly depends upon the experimental conditions such as pH, adsorbent and adsorbate concentrations, temperature, ionic strength, etc. To understand the adsorption mechanism and feasibility of the adsorption process, the adsorption isotherms, thermodynamics and kinetic studies were also considered. Except for some cases, GO and its derivatives show excellent adsorption capacities for PhAs, which is crucial for their applications in the environmental pollution cleanup.

A strategically designed porous magnetic N-doped Fe/Fe3C@C matrix and its highly efficient uranium(VI) remediation

With the growing development of the nuclear industry and the peaceful utilization of nuclear energy, the safe treatment and disposal of high-level wastes in nuclear waste management is still a major challenge. Overcoming this issue requires developing highly efficient materials for capturing U(VI) from nuclear wastewater. Herein, magnetic porous microcubes with a graphitic shell and highly dispersed active cores (Fe/Fe3C nanoparticles) are rationally designed and fabricated by simply annealing preformed polydopamine (PDA) coated Prussian blue (PB) microcubes. To assess the sorption properties, sequestration of U(VI) on N-doped metal/metal carbide nanoparticles encapsulated in a carbon matrix (N-doped Fe/Fe3C@C) was systematically investigated using batch experiments. The sorption performance revealed that the N-doped Fe/Fe3C@C samples exhibited highly efficient removal efficiency for U(VI), and the sample prepared at 800 °C (N-doped Fe/Fe3C@C-800) was the best among the series with a maximum sorption capacity of 203 mg g−1. The U(VI) adsorption and reduction by N-doped Fe/Fe3C@C-800 were affected significantly by solution pH and concentrations of bicarbonate and calcium. The main reaction mechanism involved U(VI) reduction into insoluble U(IV) species by Fe0/Fe(II) and trapping the guest U(IV) in the porous carbon matrix, which synergistically promoted U(VI) removal from solution to N-doped Fe/Fe3C@C-800. This study demonstrated the simple synthesis of magnetic N-doped Fe/Fe3C@C derived from metal–organic frameworks and their potential application in U(VI)-contaminated wastewater remediation. Introduction to the international collaboration In 2003, Prof. X. K. Wang and Prof. B. Grambow started their collaboration in nuclear waste management and the environmental behavior of long-lived radionuclides such as the removal of radionuclides from aqueous solutions, the microstructures and species of radionuclides at the molecular level. They have published many papers in international journals such as Environmental Science & Technology and Geochimica et Cosmochimica Acta.

Surface Modification of Graphene Oxides by Plasma Techniques and Their Application for Environmental Pollution Cleanup.

Graphene oxides (GOs) have come under intense multidisciplinary study because of their unique physicochemical properties and possible applications. The large amount of oxygen-containing functional groups on GOs leads to a high sorption capacity for the removal of various kinds of organic and inorganic pollutants from aqueous solutions in environmental pollution cleanup. However, the lack of selectivity results in difficulty in the selective removal of target pollutants from aqueous solutions in the presence of other coexisting pollutants. Herein, the surface grafting of GOs with special oxygen-containing functional groups using low-temperature plasma techniques and the application of the surface-modified GOs for the efficient removal of organic and inorganic pollutants in environmental pollution are reviewed. This paper gives an account of our research on the application of GO-based nanomaterials in environmental pollution cleanup, including: (1) the synthesis and surface grafting of functional groups on GOs, summarizing various types of low-temperature plasma techniques for the synthesis of graphene/GOs; and (2) the application of graphene/GOs and their composites for the efficient removal of organic and inorganic pollutants from aqueous solutions, including the interaction mechanism according to recently published results.

Complexation of radionuclide 152+154 Eu(III) with alumina-bound fulvic acid studied by batch and time-resolved laser fluorescence spectroscopy

To contribute to the understanding of Eu(III) interaction preperties on hydrous alumina particles in the absence and presence of fulvic acid (FA), the complexation properties of Eu(III) with hydrous alumina, FA and FA-alumina hybrids are studied by batch and time-resolved laser fluorescence spectroscopy (TRLFS) techniques. The continuous increase in the fluorescence lifetime of Eu-alumina and Eu-FA with increasing pH indicates that the complexation is accompanied by decreasing number of hydration water in the first coordination sphere of Eu(III). Eu(III) is adsorbed onto alumina particles as outer-sphere surface complexes of ≡(Al−O)−Eu· (OH)· 7H2O and ≡(Al−O)−Eu· 6H2O at low pH values, and as inner-sphere surface complexes as ≡(Al−O)2−Eu+· 4H2O at high pH. In FA solution, Eu(III) forms complexes with FA as (COO)2Eu+(H2O)x and the hydration water number in the first coordination sphere decreases with pH increasing. The formation of ≡COO−Eu−(O−Al≡)· 4H2O is observed on FA-alumina hybrids, suggesting the formation of strong inner-sphere surface complexes in the presence of FA. The surface complexes are also characterized by their emission spectra [the ratio of emission intensities of 5D0→7F1 (λ=594 nm) and 5D0→7F2 (λ=619 nm) transitions] and their fluorescence lifetime. The findings is important to understand the contribution of FA in the complexation properties of Eu(III) on FA-alumina hybrids that the clarification of the environmental behavior of humic substances is necessary to understand fully the behavior of Eu(III), or its analogue trivalent lanthanide and actinide ions in natural environment.

Synthesis of ordered mesoporous carbonaceous materials and their highly efficient capture of uranium from solutions

An extremely effortless method was applied for successful synthesis of mesoporous carbonaceous materials (MCMs) using well-ordered mesoporous silica as template. Various characterizations (scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman, X-ray photoelectron spectroscopy (XPS), Brunner-Emmet-Teller (BET) and Zeta potential) confirmed that MCMs had large surface area, uniform pore size distribution, and abundant oxygen-containing functional groups. The batch techniques were employed to study U(VI) adsorption on MCMs under a wide range of experiment conditions. The adsorption kinetics of U(VI) onto MCMs were well-fitted by pseudo-second-order kinetic model, indicating a chemisorption process. The excellent adsorption capacity of MCMs calculated from the Langmuir model was 293.95 mg g−1 at pH 4.0. The FT-IR and XPS analyses further evidenced that the binding of U(VI) onto MCMs was ascribed to the plentiful adsorption sites (–OH and –COOH groups) in the internal mesoporous structure, which could efficiently trap guest U(VI) ions. The results presented herein revealed that MCMs were ideal adsorbents in the efficient elimination of uranium or other lanthanides/actinides from aqueous solutions, which would play an important role in environmental pollution management application.

Microstructures and speciation of radionuclides in natural environment studied by advanced spectroscopy and theoretical calculation

The environmental behavior of radionuclides is mainly dependent on their speciation and microstructures at solid particles. The speciation and microstructures of radionuclides at molecular level can be achieved from advanced spectroscopy techniques and theoretical calculations. In this perspective, we give a brief introduction of the advanced X-ray absorption fine structure (XAFS) technique and theoretical calculation in the analysis of the speciation and microstructures of radionuclides in the natural environment, which is crucial to evaluate the physicochemical behavior of radionuclides in the environment.

Rational design of carbonaceous nanofiber/Ni-Al layered double hydroxide nanocomposites for high-efficiency removal of heavy metals from aqueous solutions

Heavy metal pollution of water sources has raised global environmental sustainability concerns, calling for the development of high-performance materials for effective pollution treatment. Herein, we report a facile approach to synthesize carbonaceous nanofiber/NiAl layered double hydroxide (CNF/LDH) nanocomposites for high-efficiency elimination of heavy metals from aqueous solutions. The CNF/LDH nanocomposites were characterized by three-dimensional architectures formed by the gradual self-assembly of flower-like LDH on CNF. The nanocomposites exhibited excellent hydrophilicity and high structural stability in aqueous solutions, guaranteeing the high availability of active sites in these environments. High-efficiency elimination of heavy metal ions by the CNF/LDH nanocomposites was demonstrated by the high uptake capacities of Cu(II) (219.6 mg/g) and Cr(VI) (341.2 mg/g). The sorption isotherms coincided with the Freundlich model, most likely because of the presence of heterogeneous binding sites. The dominant interaction mechanisms consisted of surface complexation and electrostatic interaction, as verified by a combination of X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy analyses and density functional theory calculations. The results presented herein confirm the importance of CNF/LDH nanocomposites as emerging and promising materials for the efficient removal of heavy metal ions and other environmental pollutants.