A study on volatile organic sulfide causes of odors at Philadelphia's Northeast Water Pollution Control Plant

Volatile organic sulfide (VOS) causes of odors were studied at Philadelphia's Northeast Water Pollution Control Plant between September 11 and November 25, 2003. Results showed that dimethyl sulfide (DMS) dominated the VOS pool whenever VOS concentration rose above the background level (<50 microg/L). Methanethiol was generally less than 10% of VOS and it was mainly found at sites with limited or reduced dissolved oxygen (DO). Dimethyl disulfide occupied approximately 1% of the VOS and was often not detectable. Carbon disulfide was not detected. The concentrations of DMS varied by three orders of magnitude, ranging from <5 to 1260 microg/L. High concentrations of DMS, averaging 419 and ranging from <5 to 1000 microg/L, were generally found in return activated sludge. The DMS concentration in the primary effluent ranged from <5 to 729 microg/L and averaged 245 microg/L. Concentrations of DMS in the aeration tank (AT) with high DO were from <5 to 997 microg/L with an average of 250 microg/L. However, DMS concentrations in the AT representing anaerobic conditions were as high as 1260 microg/L. The estimated average purge efficiency of DMS was about 78%, which required a DMS production rate of 108 microg/Lh(-1) to keep the analyzed concentration in the AT. While a valid but weak statistical relationship between acetone and DMS was observed, there was no strong evidence to support that the methylation of hydrogen sulfide with acetone could be the mechanism for the DMS formation. Instead, DMS production was found to be associated with the characteristics of incoming wastewater. Thus, a VOS precursor was believed to be present in the incoming wastewater, which warranted a need for further investigation.     

Aspects of the aquatic chemistry of cadmium and zinc in a heavy metal contaminated lake

Concentrations of the heavy metals cadmium (Cd) and zinc (Zn) were determined at several sites in Palestine Lake, Indiana, and in the stream (Williamson Ditch) which transports metal-bearing wastes to the lake. Average dissolved Cd and Zn concentrations in the lake were as high as 17.3 μg 1^-1 and 293 μg 1^-1, respectively, while corresponding suspended levels were 30.3 μg Cd 1^-1 and 270 μg Zn 1^-1. Average levels of both Cd and Zn in the dissolved fraction exceeded those in the suspended fraction, except at one site in the lake where suspended Cd was higher. During anaerobic conditions occurring in lake's hypolimnion, a marked decrease in the dissolved fraction and concomitant increase in the suspended fraction of both Cd and Zn were noted. A cadmium-specific ion electrode was used to determine the chemical forms of dissolved Cd present in the lake. Free Cd²⁺ was the dominant form; however, Cd-organic complexes sometimes comprised a significant portion of the total dissolved Cd.     

Rapid rotating-disk-electrode evaluation of catalyst performance and durability during transient conditions: The Pt–Hf binary system

A comprehensive set of rotating disk electrode (RDE) tests has been developed to test the suitability of fuel cell catalyst candidates for use as either anode or cathode catalysts for transient conditions. The activity for Hydrogen Oxidation reaction (HOR), Oxygen Reduction reaction (ORR) and Oxygen Evolution reaction (OER) is tested together in one protocol. A total of 5 Pine Instruments RRDE test stations have been set up with automatic gas flow switching and computer software to control all aspects of the data collection process. The user simply sets up the electrochemical cell with a gas bubbler, reference electrode, counter electrode and sample and then selects a series of tests to be run. The software then switches gas flow, rotation rates and potentiostat set up files automatically. This infrastructure allows the rapid characterization of catalyst candidate materials. The series of tests is described, along with the purpose of each test in the protocol. As an example, the data collected from a Pt_1−xHf_x composition spread is presented. The optimal composition is found to be approximately 30 at.% Hf, when the ORR performance begins to decrease at a faster rate than the HOR performance and the OER current at 1300 mV is also a maximum. However, it was determined that from an applied point of view the drop in ORR performance was insufficient to adequately protect the cathode from the effects of the transient potentials during start-up of the fuel cell.     

Effect of mesophase separation and crystallization on the elastomeric behavior of olefin multi-block copolymers

The mesophase separation and crystallization as well as the elastomeric properties of olefin multi-block copolymers (OBCs) are studied. The solid state morphologies of the OBCs are determined by the competition between mesophase separation and crystallization of hard blocks. The OBC with lower Δ_C8 (octene content difference between soft and hard blocks) displays a spherulitic superstructure, while the OBC with higher Δ_C8 exhibits mesophase separation. The two OBCs show very different elastomeric properties. Wide-angle X-ray scattering shows that the two OBCs have different deformation mechanisms. It is proposed that the cooperative deformation of crystalline phase makes an important contribution to the elastomeric properties.     

Low-Temperature Water–Gas Shift: Doping Ceria Improves Reducibility and Mobility of O-Bound Species and Catalyst Activity

Abstract  

A series of platinum loaded catalysts supported on cation (Me)-doped cerium dioxide (Me = Ba, La, Y, Hf and Zn) was prepared by co-precipitation of the Me-nitrates and impregnation of a Pt precursor. Low temperature water–gas shift activity depends on the nature of dopant employed, varying in the order of Ba > Y > Hf > La > undoped ceria > Zn. TPR-XANES measurements with flowing hydrogen reveal that adding dopants to ceria facilitate ceria reduction and increases the extents of both surface shell and bulk reduction of ceria. Experimental results confirm past theoretical models that dopants enhance both O-mobility and reducibility of ceria. DRIFTS measurements of the transient decomposition of formates in steam suggest that formate half-life follows the trend Zn > undoped ceria > La > Hf > Y > Ba, indicating that the formate decomposition rate is enhanced by the addition of most of the dopants tested. Taken together, the results suggest that dopant addition improves the WGS rate by increasing the O-mobility of O-bound associated intermediates. Therefore, less Pt and Ce, which are expensive, is required to achieve comparable levels of activity.     

Bimodal nanocrystallization of NiTi shape memory alloy by laser shock peening and post-deformation annealing

In this paper, surface nanocrystallization of NiTi intermetallic alloy by a novel method is reported. The NiTi alloy is processed by laser shock peening (LSP) and controlled annealing. The microstructure of the NiTi alloy after processing is characterized by transmission electron microscopy. At the top surface of the material, a nanostructure with bimodal grains is obtained. The mechanism of the formation of the bimodal microstructure is discussed. At the material subsurface, deformation twins are generated by LSP and retained after controlled annealing. Tensile test results showed that both strength and ductility are significantly improved through LSP and controlled annealing.     

Electrochemistry and safety of Li4Ti5O12 and graphite anodes paired with LiMn2O4 for hybrid electric vehicle Li-ion battery applications

A promising anode material for hybrid electric vehicles (HEVs) is Li₄Ti₅O₁₂ (LTO). LTO intercalates lithium at a voltage of ∼1.5 V relative to lithium metal, and thus this material has a lower energy compared to a graphite anode for a given cathode material. However, LTO has promising safety and cycle life characteristics relative to graphite anodes. Herein, we describe electrochemical and safety characterizations of LTO and graphite anodes paired with LiMn₂O₄ cathodes in pouch cells. The LTO anode outperformed graphite with regards to capacity retention on extended cycling, pulsing impedance, and calendar life and was found to be more stable to thermal abuse from analysis of gases generated at elevated temperatures and calorimetric data. The safety, calendar life, and pulsing performance of LTO make it an attractive alternative to graphite for high power automotive applications, in particular when paired with LiMn₂O₄ cathode materials.     

Co-planar bi-metallic interdigitated electrode substrate for spin-coated organic solar cells

A bulk heterojunction organic solar cell with co-planar interdigitated electrodes was fabricated and tested. The co-planar electrodes had a separation distance of 1-3 μm and were fabricated from aluminum and nickel on a heavily oxidized silicon wafer using photolithography. The device was prepared by spin-coating MEH-PPV:PCBB in a 1:3 wt ratio with a total donor:acceptor solution concentration of 2.44%. The device demonstrated a strong photovoltaic response under AM1.5 illumination of 80 mW/cm² with an open circuit voltage of 0.704 V. The co-planar electrode design offers advantages in terms of electrode material selection and reliability as well as simplified device fabrication.     

Determination of temperatures of polyamide 66 directly from near‐infrared spectra

The commercial importance of polyamides (PAs) motivates the development of chemical analysis tools for use in characterizing their structure and properties. Near‐infrared (IR) spectroscopy offers advantages in this regard because of its simplicity of sample preparation and compatibility with sample thicknesses on the order of millimeters. For applications in which the measurement of sample temperature is difficult with a conventional probe, the work presented here demonstrates the ability to determine the temperature of PA 66 directly from its near‐IR spectrum. Temperature‐induced changes in spectral shape in the 4000–5000 cm^?1 region are extracted through application of the discrete wavelet transform, and the resulting preprocessed spectra are submitted to partial least‐squares regression to construct predictive models for temperature. These models are tested across different samples of PA 66 and over a time span of 7 weeks. Errors in predicted temperatures averaged 1.50°C over the range of 21–105°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40476.