ALBERT

Description: Developing Pd-lean catalysts for oxygen reduction reaction (ORR) is the key for large-scale application of proton exchange membrane fuel cells (PEMFCs). In the present paper, we have proposed a multiple-descriptor strategy for designing efficient and durable ORR Pd-based alloy catalysts. We demonstrated that an ideal Pd-based bimetallic alloy catalyst for ORR should possess simultaneously negative alloy formation energy, negative surface segregation energy of Pd, and a lower oxygen binding ability than pure Pt. By performing detailed DFT calculations on the thermodynamics, surface chemistry and electronic properties of Pd-M alloys, Pd-V, Pd-Fe, Pd-Zn, Pd-Nb, and Pd-Ta, are identified theoretically to have stable Pd segregated surface and improved ORR activity. Factors affecting these properties are analyzed. The alloy formation energy of Pd with transition metals M can be mainly determined by their electron interaction. This may be the origin of the negative alloy formation energy for Pd-M alloys. The surface segregation energy of Pd is primarily determined by the surface energy and the atomic radius of M. The metals M which have smaller atomic radius and higher surface energy would tend to favor the surface segregation of Pd in corresponding Pd-M alloys.

Description: Steel alloys corrosion is ubiquitous and is conventionally protected by anticorrosion chromate coatings. However, the process suffers from the release of carcinogenic hexavalent chromium ions that needs to be replaced by an ecofriendly alternative. In this context, the need for the development of satisfactory ecofriendly chromium-free coating with superior corrosion performance is highly desirable. In the present study, we synthesized fully dispersible nanocrystalline Beta zeolite seeds and coated on steel alloys followed by steaming. The samples were characterized by XRD, FE-SEM, and DLS analyses. The anticorrosion behavior of the synthesized nanoparticle coatings on steel alloys was investigated by electrochemical measurements (DC polarization) and electrochemical impedance spectroscopy (EIS) in NaCl and acid and alkaline media under identical experimental conditions. The present study demonstrated that the nanozeolite coating can be a potential alternative for toxic and carcinogenic chromate coating.

Description: Soil is useful as a kind of trace evidence for forensic science. Thus it is very crucial to identify sources of soil. The nanoscale soil organic matter (NSOMs) can be used to differentiate soil sources because their constituents and contents are relatively stable with time but variant by location. In this study, NSOMs from eighteen regions of Shandong Province in China were examined by middle infrared spectrum (4000–400 cm−1). The results showed that the constituents and contents of NSOMs in eighteen samples were dramatically different; a NSOM fingerprint for each sample was drawn based on these characteristics. This suggests that a national or global NSOM fingerprint database could be rapidly established by the one-step middle infrared spectrum analysis for different soil samples, which will be helpful to determine crime scenes by comparing the middle infrared spectrum of forensic soil with the NSOMs fingerprint database.

Description: Maghemite (γ-Fe2O3) nanopowders were synthesized under aeration (oxidizing) conditions by aqueous synthesis in this study. The microstructures of the prepared powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET-BJH. The XRD analysis and the chemical experiments showed that well-crystallized γ-Fe2O3 nanoparticles were successfully obtained with a mean particle size of approximately 17 nm. The prepared γ-Fe2O3 was spherical with a BET surface area of 14.357 m2/g and a total pore volume of 0.050 cm3/g. Varying the reaction conditions, such as pH, temperature, and reaction time, we obtained crystallized γ-Fe2O3 powders with different crystallization extent and different particle sizes. When the pH of the reaction suspension was increased, the reaction time was prolonged, and the reaction temperature was increased, the γ-Fe2O3 powders underwent superior crystallization and had larger particle sizes. All the obtained γ-Fe2O3 powders had significant photocatalytic activities under both UV and visible light irradiation for Orange I degradation, and the powders with better crystallization and larger particle size had relatively lower activities for Orange I photocatalytic degradation. The one-step aqueous synthesis method presented in this paper may provide an advantageous pathway to synthesize large quantities of this important iron oxide.

Description: An analysis of the stable isotopes and the major ions in the surface water and groundwater in the Leizhou Peninsula was performed to identify the sources and recharge mechanisms of the groundwater. In this study, 70 water samples were collected from rivers, a lake, and pumping wells. The surface water was considered to have a lower salinity than the groundwater in the region of study. The regression equations for δD and δ18O for the surface water and the groundwater are similar to those for precipitation, indicating meteoric origins. The δD and δ18O levels in the groundwater ranged from −60; to −25; and −8.6; to −2.5, respectively, and were lower than the stable isotope levels from the winter and spring precipitation. The groundwater in the southern area was classified as the Ca2+-Mg2+--type, whereas the groundwater in the northern area included three types (Na+-Cl−-type, Ca2+-Mg2+--type, and Ca2+-Mg2+-Cl−-type), indicating rapid and frequent water-rock exchange in the region. A reasonable conclusion is that the groundwater chemistry is dominated by rock weathering and rainwater of local origin, which are influenced by seawater carried by the Asian monsoon.

Description: The performance of ethanethiol removal in biotrickling filter was investigated by microorganisms fixed on iron oxide-based porous ceramsite (IPC) under different operating parameters conditions. Ethanethiol removal efficiency was examined as a function of inlet concentration, empty bed residence time (EBRT), and spray density of nutrient solution. The results showed that the optimized operation conditions and operation characteristics of biotrickling filter for this study were at the inlet concentration of less than 250 mgm−3, the spray density of 0.24 m3m−2 h−1, and the EBRT of 68.7 s. The variation of the EBRT of about 100 s and the spray density of about 0.24 m3m−2 h−1 did not change the ethanethiol removal efficiencies at certain ethanethiol concentrations of less than about 300 mg/m3, respectively. The main metabolic product was sulfate such as under continuous long-running regime in filter. The ethanethiol desulfurization process better meets the Michaelis-Menien model with calculated kinetic degradation parameters  mgm−3 and  gm−3 h−1.

Description: Permanganate [Mn(VII)] chemistry oxidation of fluoroquinolone (FQ) antibiotic enrofloxacin (ENR) in water is investigated with respect to the kinetics, pH effect, buffer effect, and the evaluation of residual antibacterial activity after oxidative treatment. The degradation of ENR by Mn(VII) obeyed a secondary-order kinetics. Modern high-resolution tandem mass spectrometry coupled with high performance liquid chromatography was used to analyze the structures of degradation products. Four main oxidation products were identified at different pH values. Several influencing factors, pH value, and buffer obviously affect reaction rate and products relative abundance. Autocatalysis taking place at slightly acidic pH promotes the reaction but has no effect on the product types. A plausible oxidation pathway for enrofloxacin with Mn(VII) was proposed. The oxidation took place at the piperazine ring. Structural changes to the piperazine ring include N-dealkylation, hydroxylation, and hydrolysis. Residual antibacterial activity of the oxidative reaction solutions against nonresistant Escherichia coli reference strain DH5α is evaluated by means of quantitative bioassays. It is noticed that the oxidation products exhibited negligible antibacterial activity just when the structures of the products changed.

Description: Soil and plant samples were collected from Tongliao, China, during the maize growth cycle between May and October 2010. Heavy metals, such as Cr, Pb, Ni, and Zn, were analyzed. The concentrations of Cr, Pb, Ni, and Zn in the wastewater-irrigated area were higher than those in the topsoil from the groundwater-irrigated area. The concentrations of metals in the maize increased as follows: Pb 〈 Ni 〈 Zn 〈 Cr. In addition, Cr, Pb, and Ni mainly accumulated in the maize roots, and Zn mainly accumulated in the maize fruit. The results of translocation factors (TF) and bioconcentration factors (BCF) of maize for heavy metals revealed that maize is an excluder plant and a potential accumulator plant and can serve as an ideal slope remediation plant. In addition, the increasing heavy metal contents in soils that have been polluted by wastewater irrigation must result in the accumulation of Cr, Pb, Ni, and Zn in maize. Thus, the pollution level can be decreased by harvesting and disposing of and recovering the plant material.