Surface Engineered Sponges Enable Oily Wastewater Remediation and Residual Oil Recovery

In the US, steam-¬based oil extraction processes generate over 15 billion liters of emulsified oil contaminated wastewater annually. For sustainability, these effluents need to be remediated and/or recycled. However, the complex properties (pH, dissolved salts, and high temperature) of effluents pose challenges for removal of oil microdroplets removal using current separation methods. This thesis developed a new process to selectively recover crude oil microdroplets from wastewater using inexpensive sponges. This process synergistically uses sponge surface properties and pre-existing ionic and thermal energies of the wastewater to achieve 95-99% oil removal efficacy from wastewater. First, an acid-base polymeric sponge was applied to remove crude oil microdroplets from water. In acidic or basic environments, acid-base polymers acquire surface charge due to protonation or dissociation of surface functional groups. This property is invoked to adsorb crude oil microdroplets from water using a polyester polyurethane sponge. Using the surface charge of the sponge and oil droplets, the solution pH (5.6) for 99% oil removal efficacy was predicted and verified through adsorption experiments. The droplet adsorption onto the sponge was governed by physisorption, and the driving forces were attributed to electrostatic attraction and Lifshitz-van der Waals forces. The sponge was regenerated and reused multiple times by mechanical compression. Next, to remove oil microdroplets from water at broad pH conditions, an innovative surface engineered sponge (SEnS) was designed by combining surface chemistry, surface charge, roughness, and surface energy. Under all pH conditions, the SEnS rapidly adsorbed oil microdroplets with 95-99% removal efficiency predominantly by electrostatic attraction and Lifshitz-van der Waals forces. Furthermore, at the best pH value, 92% of the oil was adsorbed within 10 min due to synergistic charge attraction. The adsorbed oil was recovered by rinsing with a diluent while the cleaned SEnS was reused multiple times for oil adsorption. Subsequently, crude oil is recovered from the diluent using distillation. Due to the process efficacy, sponge reuse, and oil recovery, this adsorptive-recovery method using sponges demonstrates great potential for the industrial oil recovery from wastewater. Furthermore, this work lays foundation for the development of new SEnS with the potential to revolutionize water treatment technologies.Ph.D.2019-10-11 00:00:0