<p>Surfactants self-assemble into diverse aggregate structures like micelles and bilayers. These aggregates play a vital role in applications ranging from wastewater treatment to soil remediation to carbon utilization. Therefore, an understanding of aggregate morphologies in solutions and at interfaces allows us to tailor surfactants for specific applications. To that end, we have used molecular dynamics (MD) simulations to glean atomic-level insights into surfactant aggregation.</p><p>First, we focus on the self-assembly of Aerosol-OT (AOT), a double-tailed anionic surfactant in aqueous media. Through extensive classical MD simulations, AOT morphologies are generated that are consistent with experimental phase diagrams. Aggregates range from spherical micelles at low concentrations (1 wt.%) to bilayers at higher concentrations (20 wt.%). A transitional biphasic regime is identified at an intermediate concentration (7.2 wt.%); this regime comprises prolate spheroidal and long rod-like micelles. Metrics of micelle shape and size are computed from the moments of inertia tensor. The polydispersity in these metrics are also quantified. The bilayer thickness and area per AOT head group agree with experimental measurements. The simulations also reveal atomic-level mechanistic insights into the early stages of surfactant aggregation. Taken together, these simulations elucidate the structural diversity of AOT aggregates as a function of concentration and temperature thus being complementary to mean-field experiments.</p><p>Second, we attempt to understand the role of AOT in the valorization of carbon dioxide to calcium carbon ultrafine particles. Through an enhanced sampling MD technique called umbrella sampling, the interactions between a single molecule of AOT and the (10m14) crystal plane of CaCO₃ are investigated. These simulations are complemented by a first principles Density Functional Theory (DFT) analysis which is performed through collaboration. DFT identifies the most stable adsorption configurations for AOT-like surrogate molecules and unravels the nature of chemical bonds between these molecules and the (10m14) crystal plane.</p><p>Finally, preliminary experimental studies pertaining to the synthesis of CaCO₃ particles using CO₂ and surfactants is discussed. The CaCO₃ particles are characterized using X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The influence of the nature of the surfactant; anionic AOT, or cationic cetyl trimethylammonium bromide (CTAB), on the morphology of CaCO₃ particles is discussed.</p>

The indiscriminate emission of CO2 is drastically aggravating climate change. Carbon Capture and Utilization (CCU) was born as a complementary solution to this issue. This thesis studies the consumption of carbon dioxide in industrial processes, starting from synthesis gas, and using this building block in subsequent syntheses; ultimately integrating CO2 utilization with previously non-CO2 consuming processes.

Carbon dioxide from biogas production is currently considered to be without value and isbecause of this released into the atmosphere in the biogas upgrading process. The residualgas is a potential carbon source and can create value in the biogas manufacturing process.By finding a suitable value-creating process that utilizes carbon dioxide, it can be possibleto provide both economic and environmental incentives for companies to develop theiroperations. This project explored the possibility to create value from this CO2. Through anevaluation of the technical maturity of CCU technologies, a recommendation could be givenat the end of the project. An analysis of technical barriers, such as pollutants in the gas, aswell as barriers in the form of competence and corporate culture were examined in orderto provide a reasoned recommendation. The project mapped which value-creating systemswould be suitable for biogas producers in a Swedish context. This included established methaneand carbon dioxide upgrading techniques currently in use and suitable CCU techniquesthat can interact with the selected upgrading processes and serve as value creators. Based onthis survey, it was then possible to identify common, critical variables for these systems. Thereafter,a recommendation of an appropriate CCU technology could be given depending onthe CO2 composition produced. One conclusion from the study was that carbon dioxide concentrationsfrom the residual gas was often high (approx. 97-98 %) and did not contain anycorrosive or toxic components, and that this largely depends on how the digestion reactor ishandled in the production process. Thus, questions were raised about what the actual limitationsof the CCU are, as they did not seem to be technical. CCU techniques that proved to beof particular interest were pH regulation of sewage plants, CO2 as a nutrient substrate for thecultivation of microalgae, and manufacturing of dry-ice for refrigerated transports. All of thesetechnologies currently have a sufficiently high degree of technical maturity to be installedalready today. Other CCU techniques, such as "’Power to gas”, require a high CO2 concentrationand were discarded as the literature review did not suggest the economic potential forthem as they require additional CO2 upgrading steps. Instead, CCU techniques were chosenthat could be implemented directly with the existing CO2 quality. Furthermore, it was concludedthat one reason why CCU technologies have not been widely implemented is internalbarriers between distributors and manufacturers (or users) of CCU technologies. Thus, theuse of carbon dioxide from biogas production and implementation of CCU technologies canbe promoted by eliminating barriers in companies, such as a lack of both knowledge andfinancial incentives. / Koldioxid från biogasproduktion betraktas i dagsläget som utan värde och släpps ut i atmosfärenvid uppgradering av biogas. Restgasen är en potentiell kolkälla och kan vara värdeskapandeför biogasprocessen. Genom att finna en lämplig värdeskapande process som utnyttjarkoldioxid går det att ge både ekonomiska och miljömässiga incitament till företag att utvecklasin verksamhet. I detta projekt undersöktes möjligheten att skapa värde av denna CO2.Genom en utvärdering av den tekniska mognadsgraden hos CCU-tekniker kunde en rekommendationges vid projektets slut. En analys av tekniska hinder, såsom föroreningar i gassammansättningen,såväl som hinder i form av kompetens och företagskultur undersöktes för attkunna ge en motiverad rekommendation. I projektet kartlades vilka värdeskapande systemsom skulle passa för biogasproducenter i en svensk kontext. Detta inkluderade etableradeuppgraderingstekniker för metan- och koldioxid som används i dagsläget. I projektet undersöktesäven lämpliga CCU-tekniker som kan samverka med de valda uppgraderingsprocessernaoch och agera värdeskapande. Utifrån denna kartläggning kunde det sedan anges vilkagemensamma, kritiska variabler som finns för dessa system. Därefter kunde en rekommendationav lämplig CCU-teknik ges beroende på den producerade CO2 sammansättningen. Enslutsats i projektet var att koldioxid från restgasen ofta var av hög koncentration (ca. 97-98 %)och ej innehöll några korrosiva eller toxiska komponenter, och att detta till stor del beror påhur rötkammaren är hanterad i produktionsprocessen. Således väcktes frågor kring vilka defaktiska begränsningarna för CCU är, då de inte torde vara tekniska. CCU-tekniker som visadesig vara av särskilt intresse var pH-reglering av avloppsverk, CO2 som näringssubstratför odling av mikroalger, samt tillverkning av kolsyreis för kyltransporter. Samtliga dessatekniker har tillräckligt hög teknisk mognadsgrad för att kunna installeras i dagsläget. AndraCCU-tekniker, såsom ”Power to gas”, kräver en hög CO2-koncentration och avfärdades dålitteraturstudien inte talade för den ekonomiska potentialen i dessa eftersom de kräver ytterligareuppgraderingssteg för CO2. Således valdes istället CCU-tekniker som skulle gå attimplementera direkt med den befintliga CO2 kvalitén. Vidare drogs slutsatsen att en anledningtill att CCU-tekniker inte har blivit vida implementerade till stor del är interna hindermellan distributörer och tillverkare (eller utnyttjare) av CCU-tekniker. Således kan användandetav koldioxid från biogasproduktion och implementering av CCU-tekniker främjasgenom att eliminera hinder hos företag. I projektet yttrade sig detta som bristande ekonomiskaincitament och okunskap. Ett ökat användande av CCU-tekniker kan också uppnås genomatt införa lagar och regler som begränsar användandet av föråldrade tekniker som drivs avfossila bränslen, och som kan ersättas av klimatvänliga CCU-tekniker.