Lead sorption onto ferrihydrite. 3. Multistage contacting

Few studies have demonstrated the practical application of surface complexation models, calibrated with fundamental macroscopic and spectroscopic metal sorption data, in helping to solve industrial trace metal emissions problems. In this work, multistage ferrihydrite sorption systems are evaluated for their effectiveness in reducing single-solute lead(II) [Pb(II)] concentrations in contaminated water streams to very low levels. Experimental data and modeling results indicate that a multistage sorption system can significantly reduce Pb(II) effluent concentrations for the same total amount of sorbent or, alternatively, dramatically lower total sorbent consumption for the same effluent Pb(II) concentration. Model predictions were generated using a steady-state, multistage, equilibrium adsorber model that was specifically developed for and integrated into 0LI Systems' Environmental Simulation Program. The modified triple-layer model was used to simulate Pb(II) surface-liquid equilibria within the adsorber model. Engineering screening evaluations indicate that a 2-3-stage sorption process can provide significant economic savings when compared to a 1-stage process operating with the same target effluent Pb(II) concentration. Additional equilibrium stages beyond 2 or 3 provide diminishing economic returns. The major economic driver for multiple contacting stages is reduced capital investment and operating costs for sludge handling, dewatering, and disposal.     

Arsenite oxidation by a poorly crystalline manganese-oxide. 2. Results from X-ray absorption spectroscopy and X-ray diffraction

Arsenite (As(III)) oxidation by manganese oxides (Mn-oxides) serves to detoxify and, under many conditions, immobilize arsenic (As) by forming arsenate (As(V)). As(III) oxidation by Mn(IV)-oxides can be quite complex, involving many simultaneous forward reactions and subsequent back reactions. During As(III) oxidation by Mn-oxides, a reduction in oxidation rate is often observed, which is attributed to Mn-oxide surface passivation. X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) data show that Mn(II) sorption on a poorly crystalline hexagonal birnessite (δ-MnO?) is important in passivation early during reaction with As(III). Also, it appears that Mn(III) in the δ-MnO? structure is formed by conproportionation of sorbed Mn(II) and Mn(IV) in the mineral structure. The content of Mn(III) within the δ-MnO? structure appears to increase as the reaction proceeds. Binding of As(V) to δ-MnO? also changes as Mn(III) becomes more prominent in the δ-MnO ? structure. The data presented indicate that As(III) oxidation and As(V) sorption by poorly crystalline δ-MnO? is greatly affected by Mn oxidation state in the δ-MnO? structure.     

Effect of temperature and growth media on the attachment of Listeria monocytogenes to stainless steel

Listeria monocytogenes ATCC 19111 cultivated in nutrient-rich medium (brain heart infusion, BHI) or starved in minimal medium (10% filter sterilized pond water and 90% sterilized distilled water) were investigated for their initial attachment to austenitic stainless steel No. 4 with satin finish at 4 °C, 20 °C, 30 °C, 37 °C, or 42 °C. A droplet (10 μl) containing  10⁷ CFU/ml of L. monocytogenes suspended in BHI or minimal medium was placed on the stainless steel surface. After holding in saturated humidity for 3 h at the desired temperature the surface was washed and prepared for scanning electron microscopy (SEM). Using SEM, attachment of L. monocytogenes was determined by counting cells remaining on the surface. When L. monocytogenes cultivated in BHI were used, with the exception of the number of attached cells being lower at 42 °C than at 37 °C and 30 °C, the number of attached cells increased with increasing temperature (P < 0.05). When L. monocytogenes starved in minimal medium were used, the number of attached cells also increased with increasing attachment temperature (P < 0.05), but the number of attached cells at 42 °C was lower than that at the other temperatures. The attachment of L. monocytogenes to stainless steel surface was greater when cultivated in rich medium of BHI vs starved in the minimal medium.     

Microstructure-Based Estimation of Strength and Ductility Distributions for $$\alpha +\beta $$ Titanium Alloys

Titanium alloys are processed to develop a wide range of microstructure configurations and therefore material properties. While these properties are typically measured experimentally, a framework for property prediction could greatly enhance alloy design and manufacturing. Here a microstructure-sensitive framework is presented for the prediction of strength and ductility as well as estimates of the bounds in variability for these properties. The framework explicitly considers distributions of microstructure via new approaches for instantiation of structure in synthetic samples. The parametric evaluation strategy, including the finite element simulation package FEpX, is used to create and test virtual polycrystalline samples to evaluate the variability bounds of mechanical properties in Ti-6Al-4V. Critical parameters for the property evaluation framework are provided by measurements of single crystal properties and advanced characterization of microstructure and slip system strengths in 2D and 3D. Property distributions for yield strength and ductility are presented, along with the validation and verification steps undertaken. Comparisons between strain localization and slip activity in virtual samples and in experimental grain-scale strain measurements are also discussed.

     

Catalytic combustion for industrial gas turbines

This brief review provides a general account of work directed at the use of catalytic combustion in gas turbine engines. A major potential advantage of using catalytic combustion is that the fuel can be burnt efficiently at temperatures low enough (< 1500°C) to avoid significant oxidation of atmospheric nitrogen. This advantage was less important when catalytic combustion was demonstrated in the 1970s than it is today and received relatively little attention until the following decade. After discussion of the principles involved in the design of a combustor that must meet the mixing, size, performance and durability goals of a based gas turbine application, the review turns to accounts of experiments conducted on a laboratory scale with simple configurations. These established basic operating parameters for satisfactory combustion performance and led to larger scale work and to prototype design concepts for industrial gas turbines in the late 70s and early 80s. Test results were encouraging but were not pursued definitively in the U.S.A. Activity continued at several centres in Japan, with exploration of a number of different catalyst arrangements, geometries, and control systems, again with encouraging results. At the same time, there has been renewed interests in the U.S.A. and in Europe, spurred largely by the emphasis on reducing emissions of nitrogen oxides (NOx). The paper concludes with suggestions for further development of catalytically stabilized combustion systems for gas turbines. These systems must ensure adequate pre-catalyst temperature, with evenly premixed fuel and air, and sufficient temperature rise across the catalyst to ensure effective completion of reaction in a homogeneous reaction mode. The outstanding problems are largely concerned with questions of catalyst integrity and longevity in practical configurations and realistic engine operating conditions.     

Development and evaluation of surface treatments to enhance the fiber-matrix adhesion in PAN-based carbon fiber/liquid crystal polymer composites. Part I: Coupling agent and amine surface treatments

Several surface treatments, using both commercially available coupling agents and reagents containing multiple amines, were applied to commingled continuous as-received AS4 carbon reinforcing fiber/liquid crystal polymer (LCP) matrix fibers. Unidirectional composites (normally 60 vol% carbon fiber) were prepared from as-received and treated commingled fibers and characterized. To estimate the effect the effect of the treatments on fiber-matrix adhesion, short beam shear (SBS) tests were conducted, the failure surfaces were examined, and spectroscopic studies wee performed. The mean SBS strength of the as-received unidirectional AS4 carbon fiber/LCP matrix composite system was 49 MPa. The best coupling agent and amine treatments yielded increases in composite shear strength of ∼ 10 to 20%, relative to the as-received AS4/LCP system. For the amine treatments, ESCA and FTIR analyses suggested of both the carbon and LCP fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers (both with coupling agents and amines) showed that strong fiber-matrix adhesion was present. That is, failure occurred in the LCP matrix material.     

Energy Cost Savings Through Direct Purchase and Transportation

An end user can outperform its traditional supplier if the sum of (a) the price of gas paid to a producer or a marketer, (b) the rate paid for pipeline transportation, (c) the rate paid for distributor transportation (or in the alternative, the cost of bypassing the distributor), and (d) any other costs associated with the transaction, is less than the cost of gas currently paid to a distributor or a pipeline supplier. While an end user traditionally has relied on others to purchase, transport and deliver gas and to guarantee against interruption of supply, an end user in a direct purchase arrangement is sometimes responsible for assembling its own chain of supply and for protecting itself against interruption of supply. If an end user can reduce its purchased gas costs and if the risks inherent in arranging for its own supply are acceptable or can be mitigated suitably, a direct purchase arrangement is worth undertaking.     

Design of reflectors which will distribute sunlight in a specified manner

A differential equation is obtained for the shape of a reflecting surface which will distribute axially symmetric light intensity into a specified irradiance over a receiver surface which is symmetric about the direction of the incident light. Results are applied to the design of rotationally symmetric solar reflectors and also to a 2-dimensional geometry, that is one in which the reflector is a cylinder with its axis perpendicular to the incident beam. The procedure is used to numerically calculate the shape of reflectors which will uniformly concentrate collimated light and also light from a point source over a flat receiver surface. Results are also applied to determine the shape of a reflector which will distribute collimated light uniformly over the surface of a cylinder and also over a sphere.