Passive Treatment of Circumneutral Mine Drainage from the St. Louis Mine Tunnel,Rico, CO: Part 1—Case Study: Characteristics of the Mine Drainage

This publication is a case study of the seasonal variability of mine water drainage from the Saint Louis Tunnel (SLT) at the inactive Rico-Argentine mine site located in southwestern Colorado. It is an introductory paper for the two passive water treatment system technology evaluations contained in this issue. Mine water chemistry changes from baseflow to a snowmelt runoff event (SMRE) where snowmelt runoff follows preferential migration pathways to flush acidic weathering products from the upper mine workings to the SLT. Baseflow mine drainage is characterized as circumneutral, with Zn, Cd, Mn, and Ni concentrations primarily in the dissolved form. Dissolved Zn, Mn, Fe, and potentially Cd illustrate equilibrium with carbonate minerals. Total concentrations of Fe, Cu, Pb, and As are primarily in the suspended form and suggest sorption to Fe oxides. Mine water chemistry during the SMRE reflects mixing of circumneutral baseflow waters with more acidic waters flushing the upper mine workings. Geothermal activity provides for a consistently warm mine water discharge from the SLT. The two seasons that provide the most challenge to passive water treatment of SLT mine drainage are the SMRE period and the low flow stage of the Dolores River. Mine water flow and chemistry during SMRE are highly correlated with Dolores River flow and this site conceptual model was and will be used to assist in pilot project evaluation, water treatment system design, monitoring system design, a seasonal compliance approach, and water management.

     

Designing for Counterpressure Foam Molding

The counterpressure structural foam process, although not new, is generating increasing interest in the structural foam community. Initial development work began as far back as the mid-1950s in Europe. The driving impetus for its development has been the surface enhancement that it provides. While this improvement is important and beneficial, it is not the only benefit of the process. The purpose of this paper is to discuss the effect of the counterpressure process on the mechanical properties and behavior of counterpressure-processed engineering structural foam.     

Ethylene Oligomerizations by Diazene Bridged Ni(II) Catalysts Derived from Pyrazole-Scaffold-Based Binucleating Ligands with Alkyl and Aryl Pendant Arms

Abstract  

The coordination and organometallic chemistry of a series of diazene (N₂)-bridged Ni(II) catalysts derived from pyrazole-scaffold-based ligands bearing alkyl and aryl pendent arms was investigated. Binucleating ligands were obtained as products of the condensation reaction between 3,5-dichloroformyl-1H-pyrazole and aliphatic/aromatic primary/secondary amines under anhydrous conditions. The Ni(II) catalysts were activated with ethyl aluminum sesquichloride (EASC) to oligomerize the ethylene mainly into C4, C6, C8, and C10 fractions with activities up to 1.2 and 0.5 × 10⁶ g (mol-Ni)⁻¹ bar⁻¹ h⁻¹ at 30 and 50 °C, respectively. All catalysts were found to be electrochemically active in the working potential range of −2 to +2 V. A change in the potential of Ni(II) was provoked by the N₄ donor bridging ligands, increasing the ethylene oligomerization activity.     

New infrared laser transitions in Ag II

We have observed seven infrared laser transitions when exciting a He discharge in a silver hollow cathode. To our knowledge, five of the seven laser transitions have not been reported previously in the literature.     

Artificial in-plane ordering of textured YBa2Cu3O7?x films deposited on polycrystalline yttria-stabilized zirconia substrates

Anisotropie surface texturing of the polycrystalline yttria-stabilized zirconia substrates, prior to YBa₂Cu₃O_7–x film deposition, is shown to promote in-plane (basal plane) ordering of the film growth in addition to thec-axis texturing. TheJ _c 's of the films in the weak-link-dominated low-field regime are enhanced considerably, and this result is attributed to the reduction of weak links resulting from a reduction in the number of in-plane large-angle grain boundaries.The authors acknowledge the support and encouragement of V. G. Keramidas and P. L. Key. This work was supported by the Electric Power Research Institute (Contract No. RP 7911-13).     

Investigation of solid particle number measurement: Existence and nature of sub-23 nm particles under PMP methodology

A Particle Measurement Program (PMP) compliant system, an AVL advanced particle counter (APC) and an alternative volatile particle removal system, a catalytic stripper (CS) were evaluated and compared for measuring solid particle number (PN) emissions. The evaluations and comparisons were conducted using sulfuric acid and hydrocarbon particles as model volatile particles in laboratory tests, and diluted exhaust from a diesel particle filter (DPF)-equipped heavy-duty diesel vehicle operated on a heavy-duty chassis dynamometer under steady speed conditions at two different engine loads. For the laboratory test, both the APC and CS removed more than 99% of the volatile particles in terms of PN when using aerosols composed of pure sulfuric acid or hydrocarbons. When using laboratory test aerosols consisting of mixtures of sulfuric acid and hydrocarbons more than 99% of the particles were removed by the APC but the surviving particles were no longer entirely volatile, 12–14% were solid. For the chassis dynamometer test, PN emissions between 3 and 10 nm downstream the APC were ∼2 and 7 times higher than the PN emissions of particles above 10 nm at the 74% and 26% engine load, respectively. At the 26% engine load, PN level of the 3–10 nm particles downstream the APC were significantly higher than that in the dilution tunnel, demonstrating that the APC was making 3–10 nm particles. The PN emission of 3–10 nm particles downstream the APC was related to the heating temperature of the APC evaporation tube, suggesting these particles are artifacts formed by renucleation of semivolatiles. Considerably fewer particles between 3 to 10 nm were seen downstream of the CS for both engine loads due mainly to removal of semivolatile material by the catalytic substrates, although some of this difference could be attributed to diffusion and thermophoretic losses. The findings of this study imply that improvement of the current PMP protocol would be necessary if the PMP were to be used in other applications where the PN emissions of particles below 23 nm are important.     

X-ray tomographic microscopy of fibre-reinforced materials

Aluminium composites containing Al₂O₃ fibres and precipitates of various intermetallic phases are investigated by high-resolution computerized microtomography. Individual fibres 15 μm in diameter and intermetallic phases forming a network with about 15 μm mesh size have been imaged. The capabilities of the method and its further development down 1 μm and less spatial resolution are discussed.     

Undercooling and demixing of copper-based alloys

Since the beginning of materials science research under microgravity conditions immiscible alloys have been an interesting subject. New possibilities to investigate such systems are offered by containerless processing techniques. Of particular interest is the ternary system Cu-Fe-Co, and its limiting binaries, Cu-Co and Cu-Fe. They all show a metastable miscibility gap in the regime of the undercooled melt. Within the ESA-MAP project “CoolCop”, different aspects of this alloy have been investigated; results obtained so far are reported here.     

Electrospun bioactive nanocomposite scaffolds of polycaprolactone and nanohydroxyapatite for bone tissue engineering

Nanocomposite scaffolds based on nanofibrous poly(epsilon-caprolactone) (PCL) and nanohydroxyapatite (nanoHA) with different compositions (wt%) were prepared by electrostatic co-spinning to mimic the nano-features of the natural extracellular matrix (ECM). NanoHA was found to be well dispersed in polymers up to the addition of 20 wt%, after ultrasonication. The composite scaffolds were characterized for structure and morphology using XRD, EDX, SEM, and DSC. The scaffolds have a porous nanofibrous morphology with fibers (majority) having diameters in the range of 450-650 nm, depending on composition, and interconnected pore structures. SEM, EDX, and XRD analyses have confirmed the presence of nanoHA in the fibers. As the nanoHA content in the fibers increases, the surface of fibers becomes rougher. The mechanical (tensile) property measurement of the electrospun composites reveals that as the nanoHA content increases, the ultimate strength increases from 1.68 MPa for pure PCL to 2.17, 2.65, 3.91, and 5.49 MPa for PCL/nanoHA composites with the addition of 5, 10, 15, and 20 wt% nanoHA, respectively. Similarly the tensile modulus also increases gradually from 6.12 MPa to 21.05 MPa with the increase of nanoHA content in the PCL/nanoHA fibers, revealing an increase in stiffness of the fibers due to the presence of HA. DSC analysis reveals that as nanoHA in the composite scaffolds increases, the melting point slightly increases due to the good dispersion and interface bonding between PCL and nanoHA.