Jinlong Zou

Magnetically separable porous graphitic carbon with large surface area as excellent adsorbents for metal ions and dye

Magnetic porous graphitic carbon (MPGC) materials were fabricated through a facile “Solution-Solid” route and their application as excellent adsorbents for metal ions and dye were also demonstrated. In the preparation, glucose, nickel nitrate and TEOS were selected as carbon resource, catalyst precursor and porogent, respectively. In the first step, the solution contained glucose, Ni2+ and TEOS was treated at low temperature to impel polymerization of glucose, coordination of Ni2+ with glucose unit and hydrolysis of TEOS simultaneous, leading to the formation of precursor (Solution process). After heating the precursors under N2 atmosphere, the Ni-SiO2/carbon composites were formed (Solid process). Followed soaking with NaOH to remove SiO2 porogent, the corresponding MPGC materials with magnetic nickel particles embedded in the graphitic carbon framework were obtained. The obtained MPGC materials show good chemical stability due to their high graphitic degree. It is noteworthy that they have exceptionally large surface areas up to 918 m2 g−1. The adsorption performance of MPGC are evaluated by using metal ions (Cd2+, Cu2+, Ag+, Au3+) and dye (Rhodamine B, RhB) in aqueous solutions as the target. The results indicate that MPGC materials exhibit excellent adsorption capacities for metal ions (7.79 mg g−1 for copper for example), which are superior to those of activated carbons and carbon nanotubes. In addition, the materials have also exhibited good ability for adsorption of dye molecular. Notably, MPGC materials could be easily removed for reuse by an external magnet, facilitating separation and reuse of those materials as adsorbents. The adsorption kinetics for these metal ions and dye on MPGC-based adsorbents were well fitted to a pseudo-second order model.

Black TiO 2 nanobelts/g-C 3 N 4 nanosheets Laminated Heterojunctions with Efficient Visible-Light-Driven Photocatalytic Performance

Black TiO2 nanobelts/g-C3N4 nanosheets laminated heterojunctions (b-TiO2/g-C3N4) as visible-light-driven photocatalysts are fabricated through a simple hydrothermal-calcination process and an in-situ solid-state chemical reduction approach, followed by the mild thermal treatment (350 °C) in argon atmosphere. The prepared samples are evidently investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption, and UV-visible diffuse reflectance spectroscopy, respectively. The results show that special laminated heterojunctions are formed between black TiO2 nanobelts and g-C3N4 nanosheets, which favor the separation of photogenerated electron-hole pairs. Furthermore, the presence of Ti3+ and g-C3N4 greatly enhance the absorption of visible light. The resultant b-TiO2/g-C3N4 materials exhibit higher photocatalytic activity than that of g-C3N4, TiO2, b-TiO2 and TiO2/g-C3N4 for degradation of methyl orange (95%) and hydrogen evolution (555.8 μmol h−1 g−1) under visible light irradiation. The apparent reaction rate constant (k) of b-TiO2/g-C3N4 is ~9 times higher than that of pristine TiO2. Therefore, the high-efficient laminated heterojunction composites will have potential applications in fields of environment and energy.

Carbothermal synthesis of ordered mesoporous carbon-supported nano zero-valent iron with enhanced stability and activity for hexavalent chromium reduction

Composites of nano zero-valent iron (nZVI) and ordered mesoporous carbon (OMC) are prepared by using simultaneous carbothermal reduction methods. The reactivity and stability of nZVI are expected to be enhanced by embedding it in the ordered pore channels. The structure characteristics of nZVI/OMC and the removal pathway for hexavalent chromium (Cr(VI)) by nZVI/OMC are investigated. Results show that nZVI/OMC with a surface area of 715.16 m(2) g(-1) is obtained at 900 °C. nZVI with particle sizes of 20-30 nm is uniformly embedded in the OMC skeleton. The stability of nZVI is enhanced by surrounding it with a broad carbon layer and a little γ-Fe is derived from the passivation of α-Fe. Detection of ferric state (Fe 2p3/2, around 711.2eV) species confirms that part of the nZVI on the outer surface is inevitably oxidized by O2, even when unused. The removal efficiency of Cr(VI) (50 mg L(-1)) by nZVI/OMC is near 99% within 10 min through reduction (dominant mechanism) and adsorption. nZVI/OMC has the advantage in removal efficiency and reusability in comparison to nZVI/C, OMC and nZVI. This study suggests that nZVI/OMC has the potential for remediation of heavy metal pollution in water.

Synthesis of Iron Oxide/Partly Graphitized Carbon Composites as a High-Efficiency and Low-Cost Cathode Catalyst for Microbial Fuel Cells

Waste cornstalks and pomelo skins are used as carbon resources for preparing nanocomposites of iron oxide and partly graphitized carbon (Fe3O4/PGC-CS and Fe3O4/PGC-PS). The results showed that Fe3O4 with a face-centered cubic structure is uniformly dispersed on the skeleton of Fe3O4/GC, and the highest SBET values of Fe3O4/PGC-CS (476.5 m(2) g(-1)) and Fe3O4/PGC-PS (547.7 m(2) g(-1)) are obtained at 1000 °C. The electrical conductivity and density of catalytic active sites are correspondingly improved by the introduction of Fe species. Microbial fuel cells (MFCs) with a mixed composite (Fe3O4/PGC-CS:Fe3O4/PGC-PS = 1:1) cathode (three-dimensional structures) generate the highest power density of 1502 ± 30 mW m(-2), which is 26.01% higher than that of Pt/C (1192 ± 33 mW m(-2)) and only declines by 7.12% after 18 cycles. The Fe3O4/PGC-CS cathode has the highest Coulombic efficiency (24.3 ± 0.7%). The Fe3O4/PGC composites exhibit high oxygen reduction reactivity, low charge transfer resistances, and long-term stability and can be used as a low-cost and high-efficiency catalyst for MFCs.

Bifunctional Ag/Fe/N/C Catalysts for Enhancing Oxygen Reduction via Cathodic Biofilm Inhibition in Microbial Fuel Cells

Limitation of the oxygen reduction reaction (ORR) in single-chamber microbial fuel cells (SC-MFCs) is considered an important hurdle in achieving their practical application. The cathodic catalysts faced with a liquid phase are easily primed with the electrolyte, which provides more surface area for bacterial overgrowth, resulting in the difficulty in transporting protons to active sites. Ag/Fe/N/C composites prepared from Ag and Fe-chelated melamine are used as antibacterial ORR catalysts for SC-MFCs. The structure-activity correlations for Ag/Fe/N/C are investigated by tuning the carbonization temperature (600-900 °C) to clarify how the active-constituents of Ag/Fe and N-species influence the antibacterial and ORR activities. A maximum power density of 1791 mW m(-2) is obtained by Ag/Fe/N/C (630 °C), which is far higher than that of Pt/C (1192 mW m(-2)), only having a decline of 16.14% after 90 days of running. The Fe-bonded N and the cooperation of pyridinic N and pyrrolic N in Ag/Fe/N/C contribute equally to the highly catalytic activity toward ORR. The ·OH or O2(-) species originating from the catalysis of O2 can suppress the biofilm growth on Ag/Fe/N/C cathodes. The synergistic effects between the Ag/Fe heterojunction and N-species substantially contribute to the high power output and Coulombic efficiency of Ag/Fe/N/C catalysts. These new antibacterial ORR catalysts show promise for application in MFCs.

Characteristics and antibacterial activity of Ag-embedded Fe3O4@SiO2 magnetic composite as a reusable water disinfectant

Silver nanoparticles (AgNPs) are one of the most effective disinfectants for eliminating pathogenic microbial contamination from water. The difficult separation of Ag-based disinfectants from water impedes their large-scale application. In this study, Ag-coated Fe3O4@SiO2 magnetic composite material (MCM-Ag) is prepared by a facile route and its antibacterial activity against Escherichia coli (E. coli) is also investigated by analyzing the growth and morphology of cells after treatment. Results show that the fixed AgNPs (10–20 nm) are well dispersed on the surface of MCM-Ag. Some AgNPs are also embedded in the structure of the silica shell to avoid oxidation and release, which enhances the stability of this disinfectant. The antibacterial effect of released Ag+ is distinguished from that of AgNPs by monitoring E. coli growth in presence or absence of O2. MCM-Ag with its ferromagnetic property can be repetitively used 5 times and the possible contamination of disinfectant to environment is avoided. MCM-Ag can damage the functional groups of vital enzymes and proteins of E. coli by released Ag+ and destroy the structure of cell membrane by the generated reactive oxygen species. It is concluded that the easily-separated MCM-Ag is an efficient and environment-friendly antibacterial agent, deserving further application.

3D urchin-like black TiO2−x/carbon nanotube heterostructures as efficient visible-light-driven photocatalysts

3D urchin-like black TiO2−x/CNT heterostructures are successfully fabricated via a facile one-pot solvothermal reaction combined with a subsequent in situ solid-state chemical reduction approach. The as-prepared photocatalysts are characterized in detail via X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The results demonstrate that the obtained black TiO2−x/CNT heterostructures exhibit a 3D urchin-like heterojunction structure, and Ti3+ is doped into the lattice of anatase TiO2. This unique 3D structure with abundant active sites can enhance light scattering capability, and the Ti3+ self-doping defective TiO2 with a narrow bandgap can promote visible-light photocatalytic activity. Therefore, the TiO2−x/CNT heterostructures exhibit unparalleled high visible-light-driven photocatalytic activity and electrochemical properties. The visible-light-driven photocatalytic degradation rate for methylene orange is up to 99.6% and the hydrogen production rate is as high as 242.9 μmol h−1 g−1, which is ascribed to the 3D urchin-like structure offering abundant active sites, the heterostructures resulting in the separation of photogenerated charge carriers, and the Ti3+ self-doping narrowing the bandgap and favoring visible light absorption.

Recovery of silicon from sewage sludge for production of high-purity nano-SiO2

Generation of excess sewage sludge has already caused many environmental problems. A novel investigation for recovery of Si from the carbonized raw sewage sludge (RS) has been conducted in this study. Results show that early rupture (by OH(-)) of Si-O-Si bond in the networks of SiO(4)(4-) tetrahedron is the key step for formation of RS-derived sodium silicate (Na(2)O·(SiO(2))(x)·(H(2)O)(y)). SiO(2) gel is formed through the silica colloidal-particles cohesion, which is partly affected by the bridging role of the hydrated Na(+) (1070.7eV). O1s peaks of the SiO(2) can be decomposed into two components, i.e. Si-O bridging oxygen atoms (532.4 eV) and hydroxyl groups (O-H, 533.0 eV). Intensity of the O-H stretching vibration bands around 3450 cm(-1) (residual Si-OH), which is inversely related to the condensation degree, decreases as sol pH increases. Properties of this high purity RS-SiO(2) enable it to have the potential for numerous technological (environmental and biotechnology) applications. Reutilization of RS for production of SiO(2) may provide an environmental benefits to communities by protecting water, soil and air.

Enhanced methanol oxidation and CO tolerance using oxygen-passivated molybdenum phosphide/carbon supported Pt catalysts

To improve the sluggish kinetics of the methanol oxidation reaction (MOR), one efficient way is to improve the properties of catalyst supports to enhance the activity and durability of Pt-based catalysts. In this study, molybdenum phosphide/porous carbon (MoP/C) composites as Pt-supports and co-catalysts for the MOR are prepared by varying the molar ratio of citric acid (CiA) to glucose (Glu). Pt–MoP/C-2 (CiA : Glu = 2) has far higher electro-catalytic activity (platinum electrochemical surface area and mass activity) and durability for the MOR than commercial Pt/C. Because of the close integration between MoP and carbon and the ligand effect of Mo–P bonds, MoP/C can maintain a commendable stability for facilitating the fast transport of electrons. A fast oxidative removal of CO can reduce the adsorption of poisoning species (CO and CHO) onto the surface active sites of Pt and lead to the regeneration of active sites in Pt–MoP/C. Furthermore, the surface of MoP/C contains abundant absorbed –OH (hydrophilic) and oxygen-containing functional groups originating from the O2 passivation, which promotes the dispersion of deposited Pt and the mass transfer of fuel. This study provides useful information for the design and preparation of a state-of-the-art anodic electro-catalyst support with promising co-catalytic effects for the MOR.

Structure and Properties of Noncrystalline Nano-Al(OH)3 Reclaimed from Carbonized Residual Wastewater Treatment Sludge

Performance of wastewater treatement sludge-carbon (SC) can be evidently improved by removing the inorganic fractions. A novel investigation for recovery of Al from acid leaching of SC and synthesis of nano-Al(OH)(3) has been conducted. Results show that the sodium aluminates with high purity can be obtained by effectively dissolving the inorganic fractions from SC and by further removing the impurities (Fe(3+), Ca(2+), Mg(2+), S(4+), and P(3+)). Highly dispersed Al(OH)(3) with high S(BET) is obtained at pH = 6. The peaks of -CH(2)- vibration and the C1s peaks (binding energies of 284.6 eV) imply that polyethylene glycol 1000 (PEG-1000) is chemically adsorbed on the surface of Al(OH)(3) samples, which is propitious to reduce the hydrogen bonds between water molecules and surface -OH groups to prevent hard agglomeration. The stretching vibration peaks of [AlO(2)](-) and the Na1s peaks confirm that a trace of sodium aluminate (NaAl(OH)(4), Na(+)(H(2)O)(4)[Al(OH)(4)(-)], or the dehydrated monomers) is retained in the prepared Al(OH)(3). The main phase transformation for calcination (≤800 °C) of the SC-derived Al(OH)(3) is from amorphous Al(OH)(3) to amorphous A1(2)O(3). Here we highlight that production of Al(OH)(3) and SC from sludge provides the potential application in significant quantities that can revolutionize the handling of such kinds of harmful waste.