Facile surface treatment and decoration of graphene-based 3D polymeric sponges for high performance separation of heavy oil-in-water emulsions

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 similar to 164 degrees 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.

Automated summary

A graphene-based sponge (rGO@MF) was developed for efficient separation of oil-in-water emulsions and oil/water mixtures, showing excellent separation performance and adsorption capacity. Various factors were investigated, and a general separation mechanism was introduced.