Permeable reactive barrier (PRB) technology is increasingly considered for in situ treatment of contaminated groundwater; however, current design formulas for PRBs are limited and do not properly account for all major physical and attenuation processes driving remediation. This study focused on developing a simple methodology to design PRBs that is easy to implement while improving accuracy and being more conservative than the available design methodologies. An empirical design equation and a simple analytical design equation were obtained to calculate the thickness of a PRB capable of degrading a contaminant from a source contaminant concentration to a maximum contaminant level at a Point of compliance . Both equations integrate the fundamental components that drive the natural attenuation process of the aquifer and the reactive capacity of the PRB.The empirical design equation was derived from a dataset of random hypothetical cases that used the solutions of the PRB conceptual model (Solution I). The analytical design equation was derived from particular solutions of the model (Solution II) which the study showed fit the complex solutions of the model well. Using the hypothetical cases, the analytical equation has shown that it gives an estimated thickness of the PRB just 15 % lower or higher than the real thickness of the PRB 95 percent of the time. To calculate the design thickness of a PRB, Natural attenuation capacity of the aquifer can be estimated from the observed contaminant concentration changes along aquifer flowpaths prior to the installation of a PRB. Bench-scale or pilot testing can provide good estimates of the required residence times ( Gavaskar et al. 2000) , which will provide the reactive capacity of the PRB needed for the calculation. The results of this study suggest also that the installation location downgradient from the source of contaminant is flexible. If a PRB is installed in two different locations, it will achieve the same remediation goals. This important finding gives engineers and scientists the choice to adjust the location of their PRBs so that the overall project can be the most feasible and cost effective. / Master of Science

The behavior during dissolution of edge and basal surfaces of the mica phlogopite were examined using in situ atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) in an attempt to characterize the reactive surface area during dissolution. Mica minerals are the ideal material for this study because they offer a high degree of structural anisotropy. Therefore surfaces with different structures are easily identified. Dissolution is shown to proceed preferentially by removal of material from {hk0} edges. Dissolution rates were calculated by measuring the volume of material removed from etch pits, and normalizing to either the "reactive" surface area of {hk0} edges exposed at pit walls, or to a total "BET-equivalent" surface area. Rates normalized to total surface area are in the range of dissolution rates reported in the literature. Edge surface normalized rates are about 100 times faster. Long-term in situ AFM observations of phlogopite dissolution reveal that exposed (001) surfaces also display a distinct reactivity, though it operates on a different time scale. The top layer is shown to expand between 39 and 63 hours in contact with pH 2 HCl solution. Subsequent LEED analysis shows that the (001) surface becomes amorphous upon reacting with pH 2 HCl. Compositional characterization of the phlogopite after reaction shows that for pitted phlogopite surfaces, dissolution is characterized by leaching of octahedral cations and polymerization of the silica-enriched residual layer. No chemical changes or polymerization are observed for freshly cleaved unpitted phlogopite after reaction with pH 2 HCl for 24 hours. This suggests a gallery access mechanism is facilitated by edge attack, and is only significant on exposed (001) surfaces after a certain amount of dissolution by edge attack. / Master of Science

Yes / Recycling of polymers is a necessity in our intensively consuming polymer world but the nature of polymers is such that they are prone to thermal degradation when re-extruded and this poses technical challenges to recycling. This article describes research that seeks to rebuild the structure of degraded PA6. We present data from controlled experiments with pristine pPA6 extruded to form a base recycle rPA6 to which we added two chain extenders, separately: one with anhydride multifunctionality (ANHY), highly reactive with amide groups and one with epoxy multifunctionality (EPOX), less reactive. We found from rheological data carried out in the linear viscoelastic region (so as to study structural changes) a striking difference in the ability of the chain extenders to rebuild structure: 306% increase in the complex viscosity of rPA6/ANHY compared to 25% in that of rPA6/EPOX of the base rPA6. Mechanical and thermal (DSC and TGA) tests confirmed the superior efficacy of the multifunctional anhydride chain extender. Beside the practical benefit that ensues from this research, it also provides a strategic platform to develop chain extenders for other degrading polymers on the basis of understanding the degradation chemical reaction and targeting the most reactive end group of the split chains.

Recent efforts to understand and predict the onset and maintenance of aggression have considered the heterogeneity of this behavior. Dodge (1980) and others, have suggested a distinction in aggression based on two primary subtypes: reactive and proactive aggression. The form, severity and persistence of these aggressive subtypes may depend on an on-going interaction between individual characteristics and environmental characteristics that elicit varying antecedents and consequences (Frick, 1998; Lahey et al., 1999). In particular, there exists some empirical support for the existence of relations among social likeability, attributional style, and particular subtypes of aggression symptomology. However, the exact nature of this relation is unclear. The current study examined two competing models, the mediator and moderator models, to assess the nature of the relations among social likeability, attributional style, and aggression subtypes in a sample of 419 youth in a non-clinical community setting. Results suggest that the external, stable, global attributional style serves to mediate the relation between social likeability and reactive, but not proactive aggression. Implications for assessment and treatment of aggression in adolescents are discussed. / Master of Science

Aggression is a heterogeneous behavior that has been conceptualized by two distinct but inter-related functions: proactive and reactive aggression (Dodge, 1991). Proactive aggression has been linked to externalizing behaviors and reactive aggression to internalizing behaviors (Vitaro, Gendreau, Tremblay, & Oligny, 1998). There has been some evidence to suggest that family environment may influence the relationship between the aggressive functions and the related forms of psychopathology (Dodge, 1991). However, given the limited research pertaining to the relationships among aggression, family environment, and subsequent psychopathology, the current study explored the nature of the relationships among these variables in more detail. The present study hypothesized that proactive aggression would be related to externalizing symptoms (delinquency, hyperactivity), and these relationships would be moderated by family conflict. In addition, it was predicted that reactive aggression would be related to internalizing symptoms and inattention, and these relationships would be moderated by family conflict, cohesion, and control. The study included a sample of 135 children and their parents who completed several self-report measures. Overall, the findings did not support the hypotheses, though there was mixed support for the relationship between the aggressive functions and internalizing and externalizing symptoms. / Master of Science

Natural attenuation and biotransformation are processes that can potentially control the transport and enhance the remediation of contaminants in groundwater. It is necessary to develop computer simulations that not only model the physical transport (advection and dispersion) of contaminants, but that can also accurately depict chemical reactions and some of these more complex processes, in order to determine the type and extent of contaminant plumes and to analyze potential remediation strategies. Modeling these systems effectively is becoming possible with a growing understanding of the chemical and biological processes that occur in groundwater. However, more accurate and more involved models come with much higher memory and computational requirements. Parallel processing provides the computational resources needed to employ reactive transport simulations effectively and more efficiently. N2D-H2 is a FORTRAN code that simulates two-dimensional reactive solute transport in groundwater. More specifically, it simulates the biotransformation of nitrate into the end products of denitrification. A parallel version of the N2D-H2 code is developed using the Message-Passing Interface (MPI), a library of sequences and routines that can be called from FORTRAN programs. Using MPI to develop the parallel version of the code involves decomposing the computational domain among processors, defining the computational roles of each processor, and implementing the required communication between processors by using the message-passing procedures that allow the processors to exchange data. Several test problems are developed to analyze the performance of the parallel code. The test problems are used in the benchmarking procedure to demonstrate that the parallel code returns results identical to the sequential code. The CPU time required and the speedup achieved by running the simulation on parallel processors is presented for multiple test problems with varying physical processes and computational grid sizes. For a two-dimensional plume simulation of five solutes, with a finite difference grid of 490 nodes x 99 nodes, the total CPU time is decreased from 410 seconds on one processor to 220 seconds on two processors, and 75 seconds on ten processors. The speedup achieved gets closer to the ideal speedup as the problem size increases. Although the speedup observed with the parallel version of N2D-H2 is not 100% of the ideal speedup because of communication requirements, the parallel simulation demonstrates the benefits of parallel processing and the possibility of expansion that it provides for modeling reactive transport in groundwater. / Master of Science

This study focuses on the particle tracking of reactive transport with groundwater in a tailing dam, specifically at the Malmberget mine in Northern Sweden. Understanding the geochemical behaviour of major elements and trace metals in the subsurface environment with a focus on the tailings sand and moraine layers. The mobility and interactions of pollutants through a period of time were simulated using advanced modelling programmes such as FASTREACT, PHREEQC, and MIKE SHE.  The results reveal that major elements such as calcium (Ca), sodium (Na), and sulphate (SO₄) remain stable, indicating minimal geochemical reactions within the tailings sand layer. A decline in pH, primarily due to pyrite oxidation, highlights key geochemical changes. Trace metals, including cobalt (Co), copper (Cu), nickel (Ni), strontium (Sr), uranium (U), and zinc (Zn), maintain constant concentrations, attributed to the uniformity of processed water both as the infiltrating and existing solution in the tailings sand. In the moraine layer, the incoming water supersedes the existing water, achieving the concentration of the incoming water after subsurface mixing. Consequently, it is essential to assess the concentration reaching the lake to determine safety levels.  In the closure scenario, rainwater replaces the processed water as the infiltrating solution, resulting in gradual dilution and displacement of the original process water chemistry within the tailings sand. This natural attenuation process enhances subsurface water quality by reducing contaminant levels initially introduced by mining operations. In moraine, the incoming concentration from the sand supersedes that of the existing groundwater, leading to an increase in the concentration of the moraine layer. The study also examines travel times, indicating rapid particle movement through the sand layer and more variable travel times through the moraine layer, reflecting geological heterogeneities.  The study emphasises the importance to combine geochemical and hydrological models when evaluating tailings dam effects on the ecosystem in order to decrease the negative consequences of mining operations. The study recommends that future work should add dynamic situations and precise geochemical interactions to improve the knowledge of contaminant behaviour, while accepting limitations such as the assumption of steady-state flow and simplified geochemical processes.  Overall, this study contributes to the development of sustainable mining practices and the protection of surrounding water resources by providing a comprehensive analysis of a simple subsurface geochemical and hydrological processes and their impacts. / Denna studie fokuserar på partikelspårning av reaktiv transport med grundvatten i en avfallsdamm, specifikt vid Malmbergets gruva i norra Sverige. Förstå det geokemiska beteendet hos viktiga grundämnen och spårmetaller i den underjordiska miljön med fokus på avfallssand och moränlager. Föroreningarnas rörlighet och interaktioner under en tidsperiod simulerades med hjälp av avancerade modelleringsprogram som FASTREACT, PHREEQC och MIKE SHE.  Resultaten visar att huvudämnen som kalcium (Ca), natrium (Na) och sulfat (SO4) förblir stabila, vilket indikerar minimala geokemiska reaktioner i avfallssandskiktet. En minskning av pH, främst på grund av pyritoxidation, belyser viktiga geokemiska förändringar. Spårmetaller, inklusive kobolt (Co), koppar (Cu), nickel (Ni), strontium (Sr), uran (U) och zink (Zn), upprätthåller konstanta koncentrationer, vilket tillskrivs enhetligheten hos bearbetat vatten både som infiltrerande och befintlig lösning i avfallssanden. I moränskiktet ersätter det inkommande vattnet det befintliga vattnet och uppnår koncentrationen av det inkommande vattnet efter blandning under ytan. Följaktligen är det viktigt att bedöma koncentrationen som når sjön för att fastställa säkerhetsnivåer.  I stängningsscenariot ersätter regnvatten det processade vattnet som den infiltrerande lösningen, vilket resulterar i gradvis utspädning och förskjutning av den ursprungliga processvattenkemin i avfallssanden. Denna naturliga dämpningsprocess förbättrar vattenkvaliteten under ytan genom att minska föroreningsnivåerna som initialt introducerades av gruvdrift. I morän ersätter den inkommande koncentrationen från sanden den i det befintliga grundvattnet, vilket leder till en ökning av koncentrationen av moränlagret. Studien undersöker också restider, vilket indikerar snabb partikelrörelse genom sandlagret och mer varierande restider genom moränlagret, vilket återspeglar geologiska heterogeniteter.  Studien understryker vikten av att kombinera geokemiska och hydrologiska modeller vid utvärdering av avfallsdammseffekter på ekosystemet för att minska de negativa konsekvenserna av gruvdrift. Studien rekommenderar att framtida arbete bör lägga till dynamiska situationer och exakta geokemiska interaktioner för att förbättra kunskapen om föroreningars beteende, samtidigt som begränsningar som antagandet om steady-state flöde och förenklade geokemiska processer accepteras.  Sammantaget bidrar denna studie till utvecklingen av hållbara gruvdriftsmetoder och skyddet av omgivande vattenresurser genom att tillhandahålla en omfattande analys av en enkel underjordisk geokemiska och hydrologiska processer och deras effekter.

abstract: Reactive inkjet printing (RIJP) is a direct-write deposition technique that synthesizes and patterns functional materials simultaneously. It is a route to cheap fabrication of highly conductive features on a versatile range of substrates. Silver reactive inks have become a staple of conductive inkjet printing for application in printed and flexible electronics, photovoltaic metallization, and more. However, the high cost of silver makes these less effective for disposable and low-cost applications. This work aimed to develop a particle-free formulation for a nickel reactive ink capable of metallizing highly pure nickel at temperatures under 100 °C to facilitate printing on substrates like paper or plastic. Nickel offers a significantly cheaper alternative to silver at slightly reduced bulk conductivity. To meet these aims, three archetypes of inks were formulated. First were a set of glycerol-based inks temperature ink containing nickel acetate, hydrazine, and ammonia in a mixture of water and glycerol. This ink reduced between 115 – 200 °C to produce slightly oxidized deposits of nickel with carbon content around 10 wt %. The high temperature was addressed in a second series, which replaced glycerol with lower boiling glycols and added sodium hydroxide as a strong base to enhance thermodynamics and kinetics of reduction. These inks reduced between 60 and 100 °C but sodium salts contaminated the final deposits. In a third set of inks, sodium hydroxide was replaced with tetramethylammonium hydroxide (TMAH), a strong organic base, to address contamination. These inks also reduced between 60 and 100 °C. Pipetting or printing onto gold coated substrates produce metallic flakes coated in a clear, thick residue. EDS measured carbon and oxygen content up to 70 wt % of deposits. The residue was hypothesized to be a non-volatile byproduct of TMAH and acetate. Recommendations are provided to address the residue. Ultimately the formulated reactive inks did not meet design targets. However, this thesis sets the framework to design an optimal nickel reactive ink in future work. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2019

At many sites it has become apparent that most chemicals of concern (COCs) in groundwater are persistent and not effectively treated by conventional remediation methods. In recent years, the permeable reactive barrier (PRB) technology has proven to be more cost-efficient in the long-run and capable of rapidly reducing COC concentrations by up to several orders of magnitude. In its simplest form, the PRB is a vertically emplaced rectangular porous medium in which impacted groundwater passively enters a narrow treatment zone. In the treatment zone dissolved COCs are rapidly degraded as they come in contact with the reactive material. As a result, the effluent groundwater contains significantly lower solute concentrations as it re-enters the aquifer and flows towards the plane of compliance (POC). Effective implementation of the PRB relies on accurate site characterization to identify the existing COCs, their interactions, and their required residence time in the PRB and aquifer. Ensuring adequate residence time in the PRB-aquifer system allows COCs to react longer, hence improving the probability that regulatory concentrations are achieved at the POC. In this study, the Park and Zhan solution technique is used to derive steady-state analytical and transient semi-analytical solutions to multispecies reactive transport in a permeable reactive barrier-aquifer (dual domain) system. The advantage of the dual domain model is that it can account for the potential existence of natural degradation in the aquifer, when designing the required PRB thickness. Also, like the single-species Park and Zhan solution, the solutions presented here were derived using the total mass flux (third-type) boundary condition in PRB-aquifer system. The study focuses primarily on the steady-state analytical solutions of the tetrachloroethylene (PCE) serial degradation pathway and secondly on the analytical solutions of the parallel degradation pathway. Lastly, the solutions in this study are not restricted solely to the PRB-aquifer model. They can also be applied to other types of dual domain systems with distinct flow and transport properties, and up to four other species reacting in serial or parallel degradation pathways. Although the solutions are long, the results of this study are novel in that the solutions provide improved modeling flexibility. For example: 1) every species can have unique first-order reaction rates and unique retardation factors, 2) higher order daughter species can be modeled solely as byproducts by neglecting their input concentrations, 3) entire segments of the parallel degradation pathway can be neglected depending on the desired degradation pathway model, and 4) converging multi-parent reactions can be modeled. As part of the study, separate Excel spreadsheet programs were created to facilitate prompt application of the steady-state analytical solutions, for both the serial and parallel degradation pathways. The spreadsheet programs are included as supplementary material.

Polymers films and membranes with immobile and irreversible reactive sites can provide significant barrier properties for packaging materials. There is a need to develop mathematical models to understand the behavior of these reactive materials and to confidently extrapolate experimental data. Due to mechanical and optical requirements, barrier films may consist of composites, such as polymer blends and multilayer films with alternating reactive and inert layers. The reactive term that consumes the mobile species in the governing transport equations for such materials is a function of both the mobile species and the immobilized reactive sites, leading to non-linear partial differential equations that typically have to be solved numerically. Composite structures add to the complexity of the model. For the polymer blend, a multiscale model was developed, incorporating the reactive details within the particle into the bulk transport equation. For the multilayer film, initial conditions and diffusion coefficients were assigned independently for reactive or inert layers. The models developed for the three configurations were solved numerically over a wide parameter space. Three regimes were identified, namely early times characterized by an initial flux plateau, and intermediate regime, and long times, characterized by the time lag. Asymptotic analysis of the homogeneous model was used to develop analytical predictions for the three regimes, obviating the need to numerically solve the model’s non-linear equations. These predictions were generalized to polymer blends. For multilayer films, predictions for early and long times were developed. Results for polymer blends and multilayer composites were compared and discussions of the most suitable configuration for different scenarios were presented. The reactive barrier configurations studied require the knowledge of parameters such as reaction rates and coefficients of diffusion and solubility of the reactive polymer. Model and predictive equations have been developed to describe the transient mass uptake in reactive homogeneous films, enabling the extraction of these parameters from sorption experiments. / text