Facile Surface Treatment and Decoration of Graphene-based 3D Polymeric Sponges for High Performance Separation of Heavy Oil-in-water Emulsions

Published: 2021
Journal of Environmental Chemical Engineering, Volume 9, Issue 2, April 2021, 105087

Highlights

• Superhydrophobic graphene-based sponge (rGO@MF) was engineered through facile surface treatment and hydrothermal steps.
• rGO@MF sponge was developed and utilized for separating various heavy oil-in-water emulsions as well as oil/water mixtures.
• The rGO@MF sponge maintained its high separation performance over ten consecutive adsorption cycles using heavy oil-in-water emulsions.
• General adsorption mechanisms for oil separation using 3D graphene-based sponges were introduced.

Abstract

The separation of oil-in-water emulsions has become an extremely important for both environmentally and industrial related applications. Herein, a graphene-based sponge (rGO@MF) was developed and utilized for separating various heavy oil-in-water emulsions as well as oil/water mixtures. The superhydrophobic sponge was engineered through facile surface-treatment and hydrothermal steps. The surface and structural properties of the rGO@MF sponge and the nanoemulsions were thoroughly characterized by advanced techniques. The high-resolution SEM and EDX mapping confirmed the homogeneous distribution of rGO sheets surrounding the fibers. The developed rGO@MF sponge showed excellent chemical stability and durability. The correlation between the oil type, droplet size and concentration of oil/water mixtures and emulsions, and the rGO@MF adsorption capacity and removal efficiency, were extensively investigated. The developed superhydrophobic rGO@MF sponge showed water contact angle of ~164º and exhibited superior adsorption capacity and removal efficiency of up to 5647 mg/g and 95 ± 3% respectively, for crude oil-in-water emulsions of 30 g/l. In addition, the rGO@MF sponge maintained its high separation performance over ten consecutive adsorption cycles. The adsorption capacity of the rGO@MF sponge maintained up to 92% of its initial values after ten cycles. The calculated activated adsorption energy for crude oil-in-water emulsion on rGO@MF sponge was 16.59 kJ mol−1 indicating a physical adsorption process. The adsorption kinetics and interactions were carefully explored and a general mechanism of separation for both oil-in-water nanoemulsions and oil/water mixtures was introduced.