Yongkang Lv

Catalytic oxidation of NO over MnO2 with different crystal structures

α-, β-, γ- and δ-MnO2 catalysts were prepared by a hydrothermal method and their catalytic properties for NO oxidation were evaluated. There were dramatic differences in the activities among the MnO2 catalysts with different crystal structures. The γ-MnO2 catalyst exhibited the best activity among the four catalysts and gave rise to 91% NO conversion at 250 °C. Moreover, 50% of NO conversion was achieved by γ-MnO2 even at 160 °C. To investigate the factors influencing the catalytic activity, the catalysts were then characterized by X-ray diffraction, N2 adsorption, scanning electron microscopy, Fourier transform infrared spectrometry, Raman spectrometry, temperature-programmed reduction by H2 and X-ray photoelectron spectroscopy. On the basis of the characterization results, the tunnel structure and surface chemisorbed oxygen of γ-MnO2 were proposed to be the main factors that contributed to the excellent performance in NO oxidation. In addition, the four catalysts showed stable catalytic activity. Over γ-MnO2, H2O had a reversible inhibiting effect on catalytic activity, while the conversion of NO could not recover after removing SO2. In the presence of H2O and SO2, H2O was able to slow the progression of catalyst deactivation resulting from SO2.

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.

Isolation and characterization of a heterotrophic nitrifier from coke plant wastewater

This study investigated some factors affecting ammonium removal and nitrite accumulation by Alcaligenes faecalis C16, which was isolated from the activated sludge of a coking wastewater treatment plant. Nitrite was produced from ammonium only in the presence of citrate, acetate, meat extract, peptone or ethanol. The highest amount of nitrite was found with citrate as carbon source. A. faecalis C16 could not use glucose, fructose, sucrose and methanol. Under the optimum conditions of initial pH 6.0, C/N 14, 30 °C and 120 rpm, a maximum nitrite accumulation of 28.29 mg/L NO(2)(-)-N was achieved when the organism grew with citrate in four days. Nitrite accumulation increased with the increase of NH(4)(+)-N. Furthermore, A. faecalis C16 was shown to have phenol-degrading capacity during ammonium removal. Metabolism of phenol resulted in acidification of the media, which is not favorable for nitrification, whereas many other carbon sources made the medium more alkaline. However, no inhibitory effect by phenol was observed when phenol and acetate were used as mixed carbon source at different phenol/sodium acetate (P/S) ratios and their pH values were all controlled above 9.2 or P/S ratios below 5:5. These results suggested that A. faecalis C16 has some potential application in industrial wastewater treatment systems.

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.

Acetylene from the Co-pyrolysis of Biomass and Waste Tires or Coal in the H2/Ar Plasma

Abstract Acetylene from carbon-containing materials via plasma pyrolysis is not only simple but also environmental friendly. In this article, the acetylene produced from co-pyrolyzing biomass with waste tire or coal under the conditions of H2/Ar DC arc plasma jet was investigated. The experimental results showed that the co-pyrolysis of mixture with biomass and waste tire or coal can improve largely the acetylene relative volume fraction (RVF) in gaseous products and the corresponding yield of acetylene. The change trends for the acetylene yield of plasma pyrolysis from mixture with raw sample properties were the same as relevant RVF. But the yield change trend with feeding rate is different from its RVF. The effects of the feeding rate of raw materials and the electric current of plasmatron on acetylene formation are also discussed.

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.

Treatment of cotton printing and dyeing wastewater by supercritical water oxidation

AbstractThe cotton printing and dyeing wastewater obtained from a printing and dyeing mill was treated by supercritical water oxidation (SCWO) in a continuous-flow reactor. The experiments were operated between 400 and 600°C, 25 MPa was selected as a suitable pressure, hydrogen peroxide (H2O2) was used as an oxygen source, and excess oxygen varied from 0 to 300%. The studies indicate that the total organic carbon (TOC) degradation efficiency is over 99.7% when the temperature increases to 600°C at 300% excess oxygen. The influence of oxidants on TOC conversion is obvious at a lower temperature and then evidently weakens with temperature. The ammonia nitrogen (NH3–N) removal by the SCWO reaction from the dyeing wastewater was also discussed. The result shows that a high temperature and the right amount of oxidizing agent are required to achieve a good effect on removing NH3–N. A salt separator was applied for the separation of salts contained in the wastewater and to prevent the reactor block. The desalina...

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 .