Hongsen Zhang

High U(VI) adsorption capacity by mesoporous Mg(OH)2 deriving from MgO hydrolysis

Hierarchical mesoporous–macroporous MgO (HMMM) is successfully synthesized by using a facile calcination method. Mesoporous Mg(OH)2 produced from HMMM hydrolysis in uranium solution was used to remove U(VI) from aqueous solutions. TEM confirms that mesoporous Mg(OH)2 partly retains interconnected porous structure of HMMM. Influence of U(VI) concentrations, adsorbent dosage, solution pH, salt concentration, contact time and temperatures on the adsorption properties were studied. The results indicate that mesoporous Mg(OH)2 exhibits excellent adsorption properties, particularly at high uranium concentration. The maximum adsorption capability of U(VI) is 3111 mg g−1 and the highest uranium removal efficiency is 99% at an initial uranium concentration of 500 mg L−1. We also demonstrate that HMMM hydrolysis process greatly improves adsorption capability of U(VI). The isotherm evaluations reveal that the Freundlich model attains a better fit to the experimental equilibrium data than the Langmuir model. The results of adsorption kinetics and adsorption mechanism for U(VI) indicate that chemical adsorption is the rate-limiting step. Furthermore, mesoporous Mg(OH)2 can be regenerated by using 1 M Na2CO3, which is reused with 9.3% loss of activity. Therefore, the mesoporous Mg(OH)2 is a potential absorbent in wastewater treatment because of its high uptake capability of U(VI).

The growth and assembly of the multidimensional hierarchical Ni3S2 for aqueous asymmetric supercapacitors

Mushroom-like Ni3S2 consisting of a thin film on nanorod arrays have been successfully synthesized via a dissolution-precipitation route, which was carried out through a hydrothermal process using the Ni foam in thioacetamide alcohol solution without the introduction of other Ni sources. The thin film played a key role in exhibiting an excellent electrochemistry performance of the mushroom-like Ni3S2 electrode. As a pseudocapacitor material, the as-obtained mushroom-like Ni3S2 electrode showed a significant specific capacitance (1190.4 F g−1 at 8 A g−1). Moreover, an asymmetric supercapacitor, with the mushroom-like Ni3S2 as the positive electrode material and activated carbon powder (AC) as the negative electrode material, exhibited a high energy density (60.3 W h kg−1) at an average power density of 3600 W kg−1 based on the mass of the active material.

Fabrication of ZIF-8@SiO2 Micro/Nano Hierarchical Superhydrophobic Surface on AZ31 Magnesium Alloy with Impressive Corrosion Resistance and Abrasion Resistance

Superhydrophobic coatings are highly promising for protecting material surfaces and for wide applications. In this study, superhydrophobic composites, comprising a rhombic-dodecahedral zeolitic imidazolate framework (ZIF-8@SiO2), have been manufactured onto AZ31 magnesium alloy via chemical etching and dip-coating methods to enhance stability and corrosion resistance. Herein, we report on a simple strategy to modify hydrophobic hexadecyltrimethoxysilan (HDTMS) on ZIF-8@SiO2 to significantly improve the property of repelling water. We show that various liquids can be stable on its surface and maintain a contact angle higher than 150°. The morphologies and chemical composition were characterized by means of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FI-IR). In addition, the anticorrosion and antiattrition properties of the film were assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization and HT, respectively. Such a coating shows promising potential as a material for large-scale fabrication.

Hierarchically structured layered-double-hydroxides derived by ZIF-67 for uranium recovery from simulated seawater

Under the background of increasing and sustainable development of nuclear industry, it is significant to develop materials with high adsorption capacity and high selectivity of uranium as adsorbents. In this work, novel Mg-Co layered-double-hydroxide (LDH) with hierarchical structure was synthesized successfully via self-sacrifice template by ZIF-67. X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller surface area measurement (BET) and X-ray photoelectron spectroscopy (XPS) characterization were conducted, which confirmed the specifically hollow structured material possesses high surface area and abundant mesopores that makes uranium ions diffuse into it more easily. In typical batch adsorption experiments, varieties of parameters were investigated in details. In addition, adsorption of trace concentration of uranium (ppb level) in simulated seawater was also studied. The results showed as-prepared Mg-Co LDHs are promising adsorbents for extraction of uranium from simulated seawater.

Preparation of magnetic calcium silicate hydrate for the efficient removal of uranium from aqueous systems

To obtain an adsorbent for uranium with superb adsorption capacity, a rapid adsorption rate and quick magnetic separation, magnetic calcium silicate hydrate (MCSH) is fabricated through in situ growth of calcium silicate hydrate (CSH) onto the surface of the magnetic silica microspheres via a sonochemical method. The chemical components, and structural and morphological properties of MCSH are characterized by FTIR, XRD, TG, VSM, SEM, TEM and N2 adsorption–desorption methods. The results show that MCSH with a mesoporous structure is constructed by an agglomeration of CSH nanosheets. The BET specific surface area and saturation magnetization of MCSH are determined to be 196 m2 g−1 and 15.4 emu g−1, respectively. Based on the synthetic MSCH, adsorption isotherms, thermodynamics and kinetics are investigated. The adsorption mechanism fits the Langmuir isotherm model with a maximum adsorption capacity of 2500 mg g−1 at 298 K. The calculated thermodynamic parameters demonstrate that the adsorption process, which is in accordance with a pseudo-second-order model, is spontaneous and endothermic. MCSH exhibits a quick and highly efficient adsorption behavior, and more than 80% of uranium (1000 mg L−1) is adsorbed in the first 10 min. The superb adsorption capacity and rapid adsorption rate are likely attributed to the ultrahigh specific surface area and facile exchanges of uranium ions and calcium ions of CSH ultrathin nanosheets. These results demonstrate that MSCH is an excellent adsorbent for uranium removal from aqueous systems.

Interfacial growth of a metal–organic framework (UiO-66) on functionalized graphene oxide (GO) as a suitable seawater adsorbent for extraction of uranium(VI)

Extraction of radioactive uranium (U(VI)) from seawater has recently received extensive attention in the nuclear energy field. In this study, to acquire more void space of an MOF as active points for improving adsorption capacity, GO–COOH/UiO-66 composites were designed via coordination of the carboxyl groups of GO with zirconium ion of UiO-66; this was included as a part of the rapid and effective two-step method. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to determine the effectiveness of the synthesis of GO–COOH/UiO-66 composites. The GO–COOH/UiO-66 composites were investigated for adsorption of U(VI) from an aqueous solution and artificial seawater. The results showed that the GO–COOH/UiO-66 composites had a high adsorption capacity at a suitable seawater pH with a high removal rate of U(VI) at the ppb and ppm levels. The adsorption process closely fitted the Langmuir isotherm model and pseudo-second-order rate equation. Based on the FTIR spectroscopy, the change in pH before and after the adsorption of U(VI), and X-ray photoelectron spectroscopy (XPS), a possible sorption mechanism of U(VI) onto GO–COOH/UiO-66 composites was revealed. In addition, the adsorbent showed good chemical stability under the operating conditions for the adsorption–desorption of U(VI) from an aqueous solution, which indicated a promising potential for applications in the extraction of U(VI) in seawater.

Synthesis of exfoliated titanium dioxide nanosheets/nickel–aluminum layered double hydroxide as a novel electrode for supercapacitors

A facile composite of titanium dioxide nanosheets/nickel–aluminum layered double hydroxide (TiO2/Ni–Al LDH) is fabricated successfully as the electrode material for supercapacitors. The results of scanning electron microscopy and transmission electron microscopy reveal that Ni–Al LDH platelets homogeneously grow onto the surfaces of the TiO2, keeping the neighboring sheets separate. The composite exhibits higher specific capacitance (744.5 F g−1 at a current of 10 mA cm−2) than Ni–Al LDH (519.5 F g−1 at a current of 10 mA cm−2) and 70.7% retained specific capacitance after 4000 cycles in three-electrode system. The unique structure is beneficial for electrode materials because of its sufficient utilization of laminates and high efficiency of transmission for both electrolyte ions and electrons.

Synthesis of ketoxime-functionalized Fe3O4@C core–shell magnetic microspheres for enhanced uranium(VI) removal

Ketoxime-functionalized carbon coated iron oxide (Fe3O4@C–KO) was synthesized and characterized by transmission electron microscopy, X-ray diffraction, Fourier transformed infrared spectroscopy, and magnetic measurements. The essential factors affecting uranium(VI) adsorption from an aqueous solution of Fe3O4@C–KO, such as initial pH, contact time and temperature, were investigated. The adsorption is highly dependent on solution pH. Analysis of the experimental data using sorption kinetic models, reveal that the process follows a pseudo-second-order kinetic model. In addition, adsorption isotherms and thermodynamics were investigated. The adsorption of uranium(VI) from an aqueous solution onto Fe3O4@C–KO was fitted to Langmuir and Freundlich adsorption isotherms. The adsorption of uranium(VI) is well-described by the Langmuir isotherm. Thermodynamic parameters further show that the sorption is an endothermic and spontaneous process. Fe3O4@C–KO is a powerful and promising sorbent for the efficient removal of uranium(VI) from aqueous solutions.

Rapid and efficient uranium(VI) capture by phytic acid/polyaniline/FeOOH composites

Uranium plays an indispensable role in nuclear energy, but there are limited land resources to meet the ever growing demand; therefore, a need exists to develop efficient materials for capturing uranium from water. Herein, we synthesize a promising adsorbent of phytic acid/polyaniline/FeOOH composites (PA/PANI/FeOOH) by oxidative polymerization. Phytic acid, acting asa gelator and dopant, plays an important role in the formation of polyaniline (PANI). The PA/PANI/FeOOH exhibites high adsorption capacity (qm=555.8mgg-1, T=298K), rapid adsorption rate (within 5min), excellent selectivity and cyclic stability. In addition, the results show that the adsorption isotherm is well fitted to the Langmuir isotherm model, and the adsorption kinetics agree with a pseudo-second order model. XPS analysis indicates that the removal of uranium is mainly attributed to abundant amine and imine groups on the surface of PA/PANI/FeOOH. Importantly, the removal of uranium from low concentrations of simulated seawater is highly efficient with a removal rate exceeding 92%. From our study, superior adsorption capacities, along with a low-cost, environmentally friendly and facile synthesis, reveal PA/PANI/FeOOH asa promising material for uranium capture.

Ni–Mn LDH-decorated 3D Fe-inserted and N-doped carbon framework composites for efficient uranium(VI) removal

Extraction of uranium from seawater is of great interest because of its potential applications in the nuclear energy field. In this study, we prepared 3D Fe-inserted and N-doped carbon nanosheet frameworks by a polymer-blowing process, followed by decoration with nickel–manganese layered double hydroxide (Fe-NCNF-LDH). Employing SEM, FTIR, XPS, XRD, TEM, and BET techniques, we confirmed the existence of 3D structured porous materials with advantageous interconnectivity to provide a highly accessible freeway for uranium(VI) ionic diffusion. We investigated the removal of uranium(VI) from an aqueous solution (ppm level) and simulated seawater (ppb level) by the Fe-NCNF-LDH composites. The results showed that the adsorption process fitted well with a pseudo-second-order model and Langmuir isotherm model. Based on XRD and XPS, before and after the adsorption of uranium(VI), we proposed a possible sorption mechanism (anion exchange, chemical reduction, and surface complexation). In addition, the Fe-NCNF-LDH composites show good adsorption properties after five adsorption–desorption cycles, which augur well for potential application in the field of the adsorption of uranium from seawater.