Rui-Peng Ren

Removal of nitrogen by heterotrophic nitrification-aerobic denitrification of a novel metal resistant bacterium Cupriavidus sp. S1.

A novel heterotrophic nitrifying and metal resistant bacterium was isolated and identified as Cupriavidus sp. S1. The utilization of ammonium, nitrate and nitrite as well as the production of N2 proved the heterotrophic nitrification and aerobic denitrification ability of S1. The ammonium, nitrate and nitrite removal efficiencies were 99.68%, 98.03% and 99.81%, with removal rates of 10.43, 8.64 and 8.36mg/L/h, respectively. A multiple regression equation well described the relationship between carbon source utilization, cell growth and nitrification. Keeping the shaking speed at 120rpm was beneficial for denitrification. Moreover, different forms of nitrogen source could be utilize in simultaneous nitrification and denitrification. Additionally, the efficient removal of ammonium occurred at 20.0mg/LZn(2+), or 10.0mg/LNi(2+) or 8.0mg/LCu(2+) or 5.0mg/LCr(6+), 33.35mmol/L sodium pyruvate, C/N 12-28. These findings demonstrate that S1 was effective for nitrogen removal in industrial wastewater containing heavy metal.

A robust, superhydrophobic graphene aerogel as a recyclable sorbent for oils and organic solvents at various temperatures

To address oil spillage and organic contaminant problems, the preparation of efficient sorbent materials is of great importance for global environment and water source protection. Despite extensive studies, sorbents with both high efficiency and recyclability are still desired, particularly with the outstanding sorption performance for different temperature environmental conditions. Herein, we report a robust reduced graphene aerogel (rGA) as an efficient and recyclable sorbent for oils and organic solvents, which shows highly efficient absorption of various oils and organic solvents (up to 19-26 times of its own weight) and excellent recyclability (>5 times) by heat treatment. Moreover, the absorption ability of rGA can be maintained over a wide temperature range of -40°C to 240°C, which can be attributed to the inherent excellent thermal stability of graphene and goodheat dispersal of three dimensional network structure. Based on these excellent properties, the rGA is considered to be an ideal material can be employed for separation and absorption of waste oil and organic contaminants from the water surface at various temperatures.

An adsorption-release-biodegradation system for simultaneous biodegradation of phenol and ammonium in phenol-rich wastewater

The feasibility of simultaneous biodegradation of phenol and ammonium in phenol-rich wastewater was evaluated in a reusable system, which contained macroporous adsorption resin and Alcaligenes faecalis strain WY-01. In the system, up to 6000mg/L phenol could be completely degraded by WY-01; meanwhile, 99.03±3.95% of ammonium was removed from the initial concentration of 384mg/L. This is the first study to show the capability of single strain in simultaneous removal of ammonium and phenol in wastewater containing such high concentrations of phenol. Moreover, the resin was regenerated during the biodegradation process without any additional manipulations, indicating the system was reusable. Furthermore, enzyme assay, gene expression patterns, HPLC-MS and gas chromatography analysis confirmed that phenol biodegradation accompanied with aerobic nitrifier denitrification process. Results imply that the reusable system provides a novel strategy for more efficient biodegradation of phenol and ammonium contained in some particular industrial wastewater.

Effect of temperature, salinity, heavy metals, ammonium concentration, pH and dissolved oxygen on ammonium removal by an aerobic nitrifier

An aerobic nitrifier WY-01, isolated from coking wastewater, was identified as Alcaligenes faecalis by its 16S rRNA gene sequence analysis. It exhibited unusual capability for ammonium removal at initial NH4+–N 400 mg L−1 with low accumulated intermediates, and converted ammonium to N2 under aerobic conditions. Based on nitrogen removal and enzyme assay, two distinct nitrogen removal pathways were proposed in strain WY-01. Additionally, the effect of different factors on ammonium removal by strain WY-01 was investigated. The results show that efficient removal of ammonium occurred at temperatures as low as 10 °C, 60 g L−1 salinity, 8 mmol L−1 Cu2+ or 0.5 mmol L−1 Zn2+ or 1 mmol L−1 of equivalent Cu2+–Zn2+, initial NH4+–N concentration from 50 to 1200 mg L−1 and pH from 5 to 10. The strong adaptability of strain WY-01 makes it a promising candidate for future application in actual wastewater treatment.

Why is metallic Pt the best catalyst for methoxy decomposition

Abstract The decomposition of methoxy on Cu(111), Ag(111), Au(111), Ni(111), Pt(111), Pd(111), and Rh(111) has been studied in detail by the density functional theory calculations. The calculated activation barriers were successfully correlated with the coupling matrix element V ad 2 and the d -band center (ɛ d ) for the group IB metals and group VIII metals, respectively. By comparison of the activation energy barriers of the methoxy decomposition on different metals, it was found that Pt is the best catalyst for methoxy decomposition. The possible reason why the metallic Pt is the best catalyst has been analyzed from both the energetic data and the electronic structure information, that is, methoxy decomposition on Pt(111) has the largest exothermic behavior due to the closest p -band center of the CH 3 O among all metals after the adsorption.

DFT study on the selective oxidation of vinyl chloride on different metal surfaces

Abstract Selective epoxidation of vinyl chloride on Ag(111), Pt(111) and Rh(111) with pre-adsorbed atomic oxygen has been studied by density functional theory (DFT) calculation with the periodic slab model. The reaction energies and activation energies of the epoxidation reaction are determined. Because of the asymmetry of vinyl chloride, three competitive reaction pathways are investigated. The results indicate that the most possible reaction pathway is pathway III. Compared the activation energies of the epoxidation reaction on Ag(111), Pt(111) and Rh(111), it is obvious that the reaction via OMMC(3) on Ag(111) is the most possible process. However, the selectivity to the target product over Ag(111) is the lowest among the three metals. The results also indicate that the formation of chloroacetaldehyde is more favorable than that of chloroepoxide.

A New Anode for Lithium-Ion Batteries Based on Single-Walled Carbon Nanotubes and Graphene: Improved Performance through a Binary Network Design

Carbon nanomaterials, especially graphene and carbon nanotubes, are considered to be favorable alternatives to graphite-based anodes in lithium-ion batteries, owing to their high specific surface area, electrical conductivity, and excellent mechanical flexibility. However, the limited number of storage sites for lithium ions within the sp2 -carbon hexahedrons leads to the low storage capacity. Thus, rational structure design is essential for the preparation of high-performance carbon-based anode materials. Herein, we employed flexible single-walled carbon nanotubes (SWCNTs) with ultrahigh electrical conductivity as a wrapper for 3D graphene foam (GF) by using a facile dip-coating process to form a binary network structure. This structure, which offered high electrical conductivity, enlarged the electrode/electrolyte contact area, shortened the electron-/ion-transport pathways, and allowed for efficient utilization of the active material, which led to improved electrochemical performance. When used as an anode in lithium-ion batteries, the SWCNT-GF electrode delivered a specific capacity of 953 mA h g-1 at a current density of 0.1 A g-1 and a high reversible capacity of 606 mA h g-1 after 1000 cycles, with a capacity retention of 90 % over 1000 cycles at 1 A g-1 and 189 mA h g-1 after 2200 cycles at 5 A g-1 .

Theoretical study on the influence of a secondary metal on the Cu(110) surface in the presence of H2O for methanol decomposition

Density functional theory calculations with the continuum solvation slab model are performed to investigate the effect of metal dopants on the Cu(110) surface in the presence of H2O for the methanol decomposition. The sequential dehydrogenation of methanol (CH3OH → CH3O → CH2O → CHO → CO) is studied in the present work. The results show that the introduction of different metals (Pt, Pd, Ni, Mn) on the H2O/Cu(110) surface notably influence the adsorption configurations and adsorption energies of all adsorbates, and remarkably affect the reaction energies and activation energies of the elementary steps. The Pt, Pd and Ni doped H2O/Cu(110) surfaces are able to promote hydrogen production from methanol decomposition, but Mn doped H2O/Cu(110) surfaces are unfavorable for the reaction. The activity of methanol decomposition decreases as follows: Pd–H2O/Cu(110) > Pt–H2O/Cu(110) > Ni–H2O/Cu(110) > H2O/Cu(110) > Mn–H2O/Cu(110). Finally, the Bronsted–Evans–Polanyi plot for the main methanol dissociation steps on the metal doped and un-doped H2O/Cu(110) surfaces are identified, and a linear relationship between the reaction energies and transition state energies is obtained.

Theoretical investigation of H2S removal on γ-Al2O3 surfaces of different hydroxyl coverage

The sulfurized processes of H2S on dehydrated (100) and (110) as well as partially hydrated (110) surfaces of γ-Al2O3 were investigated using a periodic density functional theory method. The adsorption configurations of possible intermediates and the potential energy profiles of reaction are depicted. Our results show that H2S adsorbs preferentially on the Al site along with the S bond, and the adsorption energies are −32.52 and −114.38 kJ mol−1 on the dehydrated (100) and (110) surfaces, respectively. As the reaction temperature of the desulfurization changes, the (110) surface presents different levels of hydroxyl coverage, which affects the adsorption structures of species and reaction energies of dissociation processes. The bonding strengths of H2S on the partially hydrated (110) surfaces are weaker than on the dehydrated (110) surface. Compared with the 3.0 and 8.9 OH per nm2 surfaces, the H2S has the weakest adsorption energy (−39.85 kJ mol−1) and the highest activation energy (92.06 kJ mol−1) on the 5.9 OH per nm2 surface. On the 8.9 OH per nm2 surface, the activation energy of the second dissociation step (rate-determining step) for H2S dissociation is merely 38.32 kJ mol−1. On these involved surfaces, cleavage processes of the two H–S bonds present facile activation energies, which are facilitative to desulfurization.

Metal catalyzed ethylene epoxidation: A comparative density functional theory study

Ethylene epoxidation on Ag(111), Pt(111), Rh(111) and Mo(100) has been studied by density functional theory (DFT) calculations. The results show that the adsorption energies of possible adsorbed species involved in the ethylene epoxidation increase in the order: Ag<Pt<Rh<Mo, and the activation energies of the formation of epoxide (EtO) and acetaldehyde (Ac) follow the same order. Moreover, it is found that the smallest difference in the activation energies between EtO formation and Ac formation is shown on Ag. These results indicate that the metallic Ag shows the highest between activity and selectivity for ethylene epoxidation among the studied metal surfaces. Perhaps, the stability of OMME intermediate is the crucial factor in controlling the activity and selectivity. And the stronger the binding of OMME, the lower the activity and selectivity are. In addition, the relationships between the reaction enthalpy and activation energy on these four metal surfaces are investigated, and it is found that such a correlation is only applied for OMME(a) → EtO(a) and OMME(a) → Ac(a), while invalid for the case of C 2 H 4 (a) + O(a) → OMME(a).