Unpacking capabilities underlying design (thinking) process

Engineering graduates must know how to frame and solve non-routine problems. While design classes explicitly teach problem framing and solving, it is lacking throughout much of the rest of the engineering curriculum and is often relegated to capstone classes at the end of the students’ educational experience. This paper explores problem framing and solving through the lens of experiential learning theory. It captures core problem framing and solving approaches from critical, design and systems thinking and concludes with a table of learning outcomes that might be drawn upon in designing an engineering curriculum that more fully develops the problem framing and solving capabilities of its students

Weight‐of‐Evidence Approach for Assessing Removal of Metals from the Water Column for Chronic Environmental Hazard Classification

The United Nations and the European Union have developed guidelines for the assessment of long‐term (chronic) chemical environmental hazards. This approach recognizes that these hazards are often related to spillage of chemicals into freshwater environments. The goal of the present study was to examine the concept of metal ion removal from the water column in the context of hazard assessment and classification. We propose a weight‐of‐evidence approach that assesses several aspects of metals including the intrinsic properties of metals, the rate at which metals bind to particles in the water column and settle, the transformation of metals to nonavailable and nontoxic forms, and the potential for remobilization of metals from sediment. We developed a test method to quantify metal removal in aqueous systems: the extended transformation/dissolution protocol (T/DP‐E). The method is based on that of the Organisation for Economic Co‐operation and Development (OECD). The key element of the protocol extension is the addition of substrate particles (as found in nature), allowing the removal processes to occur. The present study focused on extending this test to support the assessment of metal removal from aqueous systems, equivalent to the concept of “degradability” for organic chemicals. Although the technical aspects of our proposed method are different from the OECD method for organics, its use for hazard classification is equivalent. Models were developed providing mechanistic insight into processes occurring during the T/DP‐E method. Some metals, such as copper, rapidly decreased (within 96 h) under the 70% threshold criterion, whereas others, such as strontium, did not. A variety of method variables were evaluated and optimized to allow for a reproducible, realistic hazard classification method that mimics reasonable worst‐case scenarios. We propose that this method be standardized for OECD hazard classification via round robin (ring) testing to ascertain its intra‐ and interlaboratory variability. Environ Toxicol Chem 2019;38:1839–1849. © 2019 SETAC.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151334/1/etc4470_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151334/2/etc4470.pd

Electro-oxidation of cyanide on active and non-active anodes: Designing the electrocatalytic response of cobalt spinels

[EN] The feasibility of the electrochemical technologies for wastewater treatment greatly relies on the design of efficient but inexpensive electrocatalysts. It is generally accepted that the so-called ¿non-active¿ anodes (like the boron-doped diamond (BDD) or SnO2-based anodes), producing highly oxidizing hydroxyl radicals, are the most promising candidates for pollutants abatement. In this work, the electrocatalytic performance of various cobalt oxides, pure and doped with Cu or Au, for CN¿ oxidation has been studied and compared with that of conventional graphite, BDD, SnO2-Sb and SnO2-Sb-Pt. The metal oxide electrodes were prepared by thermal decomposition of the salt precursors onto Ti. For the M-doped Co3O4 electrodes, the nominal M/Co ratios were Cu/ Co=0.07¿1.00; and Au/Co=0.05¿0.20. The electrodes were characterized by different techniques (XRD, SEM, EDX, XPS) and their electrocatalytic response was studied by cyclic voltammetry and galvanostatic electrolysis in a H-type cell in aqueous 0.1M NaOH. The obtained results show that the nature of the dopant plays a key role on the electrocatalytic behavior of cobalt spinels. Thus, while Cu catalyzes the CN¿ electro-oxidation, Au declines it. This is explained by the fact that, unlike Au (which segregates as Au-rich particles), Cu is effectively incorporated into the spinel structure by forming a solid solution (CuxCo3-xO4). In this solid solution, atomic scale Cu(spinel)-CN¿ specific interactions occur to catalyze the reaction, whereas in segregated Au particles the oxidation is hindered probably by a too-strong adsorption of cyanide and/or its inaccessibility to oxide active sites. Electrolysis runs have revealed that ¿active¿ over-saturated Cu-doped spinels (Cu/Co=1.00) exhibit higher current efficiencies than conventional graphite and ¿non-active¿ BDD and SnO2-based anodes. Hence, we hereby demonstrate that an inexpensive ¿active¿ electrocatalyst can show even higher efficiency than the most powerful BDD anode. These results highlight the significance of anode design in the application of the electrochemical technique for wastewater treatment.Financial support from the Spanish Ministerio de Economia y Competitividad and FEDER funds (MAT2016-76595-R, IJCI-2014-20012) is gratefully acknowledgedBerenguer, R.; Quijada, C.; La Rosa-Toro, A.; Morallón, E. (2019). Electro-oxidation of cyanide on active and non-active anodes: Designing the electrocatalytic response of cobalt spinels. Separation and Purification Technology. 208:42-50. https://doi.org/10.1016/j.seppur.2018.05.024S425020

Geochemical detection of carbon dioxide in dilute aquifers

<p>Abstract</p> <p>Background</p> <p>Carbon storage in deep saline reservoirs has the potential to lower the amount of CO₂emitted to the atmosphere and to mitigate global warming. Leakage back to the atmosphere through abandoned wells and along faults would reduce the efficiency of carbon storage, possibly leading to health and ecological hazards at the ground surface, and possibly impacting water quality of near-surface dilute aquifers. We use static equilibrium and reactive transport simulations to test the hypothesis that perturbations in water chemistry associated with a CO₂gas leak into dilute groundwater are important measures for the potential release of CO₂to the atmosphere. Simulation parameters are constrained by groundwater chemistry, flow, and lithology from the High Plains aquifer. The High Plains aquifer is used to represent a typical sedimentary aquifer overlying a deep CO₂storage reservoir. Specifically, we address the relationships between CO₂flux, groundwater flow, detection time and distance. The CO₂flux ranges from 10³to 2 × 10⁶t/yr (0.63 to 1250 t/m²/yr) to assess chemical perturbations resulting from relatively small leaks that may compromise long-term storage, water quality, and surface ecology, and larger leaks characteristic of short-term well failure.</p> <p>Results</p> <p>For the scenarios we studied, our simulations show pH and carbonate chemistry are good indicators for leakage of stored CO₂into an overlying aquifer because elevated CO₂yields a more acid pH than the ambient groundwater. CO₂leakage into a dilute groundwater creates a slightly acid plume that can be detected at some distance from the leak source due to groundwater flow and CO₂buoyancy. pH breakthrough curves demonstrate that CO₂leaks can be easily detected for CO₂flux ≥ 10⁴t/yr within a 15-month time period at a monitoring well screened within a permeable layer 500 m downstream from the vertical gas trace. At lower flux rates, the CO₂dissolves in the aqueous phase in the lower most permeable unit and does not reach the monitoring well. Sustained pumping in a developed aquifer mixes the CO₂-affected water with the ambient water and enhances pH signal for small leaks (10³t/yr) and reduces pH signal for larger leaks (≥ 10⁴t/yr).</p> <p>Conclusion</p> <p>The ability to detect CO₂leakage from a storage reservoir to overlying dilute groundwater is dependent on CO₂solubility, leak flux, CO₂buoyancy, and groundwater flow. Our simulations show that the most likely places to detect CO₂are at the base of the confining layer near the water table where CO₂gas accumulates and is transported laterally in all directions, and downstream of the vertical gas trace where groundwater flow is great enough to transport dissolved CO₂laterally. Our simulations show that CO₂may not rise high enough in the aquifer to be detected because aqueous solubility and lateral groundwater transport within the lower aquifer unit exceeds gas pressure build-up and buoyancy needed to drive the CO₂gas upwards.</p

Mineralogical attenuation for metallic remediation in a passive system for mine water treatment

Passive systems with constructed wetlands have been consistently used to treat mine water from abandoned mines. Long-term and cost-effective remediation is a crucial expectation for these water treatment facilities. To achieve that, a complex chain of physical, chemical, biological, and mineralogical mechanisms for pollutants removal must be designed to simulate natural attenuation processes. This paper aims to present geochemical and mineralogical data obtained in a recently constructed passive system (from an abandoned mine, Jales, Northern Portugal). It shows the role of different solid materials in the retention of metals and arsenic, observed during the start-up period of the treatment plant. The mineralogical study focused on two types of materials: (1) the ochre-precipitates, formed as waste products from the neutralization process, and (2) the fine-grained minerals contained in the soil of the wetlands. The ochre-precipitates demonstrated to be poorly ordered iron-rich material, which gave rise to hematite upon artificial heating. The heating experiments also provided mineralogical evidence for the presence of an associated amorphous arsenic-rich compound. Chemical analysis on the freshly ochre-precipitates revealed high concentrations of arsenic (51,867 ppm) and metals, such as zinc (1,213 ppm) and manganese (821 ppm), indicating strong enrichment factors relative to the water from which they precipitate. Mineralogical data obtained in the soil of the wetlands indicate that chlorite, illite, chlorite–vermiculite and mica–vermiculite mixedlayers, vermiculite, kaolinite and goethite are concentrated in the fine-grained fractions (<20 and <2 μm). The chemical analyses show that high levels of arsenic (up to 3%) and metals are also retained in these fractions, which may be enhanced by the low degree of order of the clay minerals as suggested by an XRD study. The obtained results suggest that, although the treatment plant has been receiving water only since 2006, future performance will be strongly dependent on these identified mineralogical pollutant hosts.Fundação para a Ciência e a Tecnologia (FCT

Metal release from contaminated estuarine sediment under pH changes in the marine environment

The contaminant release from estuarine sediment due to pH changes was investigated using a modified CEN/TS 14429 pH-dependence leaching test. The test is performed in the range of pH values of 0-14 using deionised water and seawater as leaching solutions. The experimental conditions mimic different circumstances of the marine environment due to the global acidification, carbon dioxide (CO2) leakages from carbon capture and sequestration technologies, and accidental chemical spills in seawater. Leaching test results using seawater as leaching solution show a better neutralisation capacity giving slightly lower metal leaching concentrations than when using deionised water. The contaminated sediment shows a low base-neutralisation capacity (BNCpH 12 = -0.44 eq/kg for deionised water and BNCpH 12 = -1.38 eq/kg for seawater) but a high acid-neutralisation capacity when using deionised water (ANCpH 4 = 3.58 eq/ kg) and seawater (ANCpH 4 = 3.97 eq/kg). Experimental results are modelled with the Visual MINTEQ geochemical software to predict metal release from sediment using both leaching liquids. Surface adsorption to iron- and aluminium- (hydr)oxides was applied for all studied elements. The consideration of the metal-organic matter binding through the NICA-Donnan model and Stockholm Humic Model for lead and copper, respectively, improves the former metal release prediction. Modelled curves can be useful for the environmental impact assessment of seawater acidification due to its match with the experimental values.This work was supported by the Spanish Ministry of Economy and Competitiveness, Project No. CTM 2011-28437-C02-01, ERDF included. M. C. Martı´n-Torre was funded by the Spanish Ministry of Economy and Competitiveness by means of FPI. Fellowship No. BES-2012-053816