Efficient removal of emulsified oil from water by lipase functionalized bio-catalytic graphene oxide sponges

Conventional water treatment methods struggle to tackle the oil contamination in the form of resilient emulsified droplets, measuring less than 20 μm in wastewater, due to their robust stability. The absence of economically feasible technologies capable of managing these small oil droplets leads to their prolonged existence in water, causing drastic impact on marine life, ecosystem, and public health. As such, there is an urgent need for advanced technologies capable of efficiently removing emulsified oil droplets with minimal residue. The main reason for emulsion stability is the interaction between surfactants and the oil–water interfaces. In this study, we biologically degraded surfactants to disrupt the interfacial layer between water and oil droplets, ultimately leading to destabilizing the highly stable emulsions. We combined the biocatalytic activity of lipase with the high adsorption capacity of reduced graphene oxide (rGO) to treat highly stable emulsified oil. Lipase activity was enhanced after being immobilized on the hydrophobic rGO sponges, compared to its free form, due to the enzyme structural changes. Our results demonstrate that the immobilized lipase effectively degraded the emulsion stabilizer (Tween 20), while the generated metabolites and combined oil droplets were adsorbed by the highly adsorptive rGO sponges. These synergistic mechanisms resulted in more than 96 % removal of emulsified crude oil.