Optimization and evaluation of reduced graphene oxide hydrogel composite as a demulsifier for heavy crude oil-in-water emulsion

The rising production of produced water from oilfields had been proven to bring detrimental environmental effects. In this study, an efficient, recyclable, and environmental-friendly reduced graphene oxide immobilized kappa-Carrageenan hydrogel composite (kappa CaGO) was fabricated as an alternative sorbent for crude oil-in-water demulsification. Polyethyleneimine (PEI) was employed to form a stable hydrogel composite. The conditions for the immobilization of graphene oxide (GO) on PEI-modified kappa-Carrageenan (kappa C) beads were optimized appropriately. An immobilization yield of 77% was attained at 2% PEI, 2 h immobilization activation time, and pH 6.5. Moreover, the synthesized kappa CaGO is capable of demulsification with an average demulsification efficiency of 70%. It was found that the demulsification efficiency increases with salinity and kappa CaGO dosage, and it deteriorates under alkaline condition. These phenomena can be attributed to the interfacial interactions between kappa CaGO and the emulsion. Furthermore, the kappa CaGO can be recycled to use for up to six cycles without significant leaching and degradation. As such, the synthesized kappa CaGO could be further developed as a potential sorbent substitute for the separation of crude oil from produced water. (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co.. Ltd. All rights reserved.

Automated summary

In this study, an efficient, recyclable, and environmental-friendly reduced graphene oxide immobilized kappa-Carrageenan hydrogel composite (kappa CaGO) was synthesized for demulsification of crude oil-in-water. The synthesized kappa CaGO exhibited high demulsification efficiency, good adaptability to salinity and dosage, but deteriorated under alkaline condition. Moreover, the kappa CaGO could be recycled for up to six cycles without significant leaching and degradation, showing its potential as a sorbent substitute for crude oil separation from produced water.