Electronic Theses and Dissertations

Date of Award

1-1-2020

Document Type

Dissertation

Degree Name

Ph.D. in Engineering Science

First Advisor

Esteban E Urena Benavides

Second Advisor

Davita Watkins

Third Advisor

Brenda H Prager

School

University of Mississippi

Relational Format

dissertation/thesis

Abstract

Cellulose nanocrystals and their interactions with different surfactants in high ionic strength brine were studied to produce stable liquid-liquid interface (emulsions) and gas-liquid (foams) for potential application in underground CO2 storage, enhanced oil recovery, and biodegradation of crude oil at marine oil-spill sites. Three different but related studies were carried out to complete these objectives. Interfacial and surface properties of cellulose nanocrystals (CNC) and surfactants were studied in high ionic strength (I) brines and correlated to the stability of Pickering emulsions and foams in the presence of three different surfactants viz: Bis-(2-hydroxyethyl) cocoalkylamine (CAA), dodecyltrimethylammonium bromide (DTAB) and Octyl-β-D-glucopyranoside (OGP). Emulsion stability studies revealed that ionic strength, wettability, adsorption energy, and oil content strongly affect emulsion stability, more so than surfactant adsorption. DTAB increased the stability of dodecane in SSW emulsions. Emulsions stable for over 21 months were prepared with an oil volume fraction of o=0.75. Adsorption of CAA onto CNC limits the migration of both CNC and CAA to the dodecane/brine interface, while DTAB adsorption has the opposite effect. The extent of biodegradation of C15-C20 aliphatic hydrocarbons in crude oil by Serratia marcescens after 5 days of incubation was improved from 1-12% to 6-19% by emulsifying crude oil using cellulose nanocrystals (CNC) and no added surfactant. Stability studies showed a greater extent of droplet coalescence at CNC concentrations higher than 0.8 wt % for emulsions prepared in API. Coalescence was more significant in high ionic strength solutions and the presence of divalent ions compared to monovalent ions at the same ionic strength. Stable scCO2 emulsions and foams with the CO2 volume fraction of 0.75 were prepared at 25oC and 70oC respectively using CNC suspensions in API brine in the presence and absence of DTAB. The results showed that CNC suspension can stabilize scCO2 foams at 70oC and 3000psig that were resistant to creaming and macroscopic coalescence over 24 hours. DTAB containing emulsions as foams showed creaming at 25oC and creaming and macroscopic bubble coarsening at 70oC.

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