Demulsification of Crude Oil-in-Water Emulsions Driven by Graphene Oxide Nanosheets

Abstract

Seeking highly-efficient, rapid, universal and low-cost demulsification materials to break up the crude/heavy oil-in-water emulsion and emulsified oily wastewater at ambient condition has been the goal of petroleum industry. In this work, an amphiphilic material, graphene oxide nanosheets (GO), was introduced as a versatile demulsifier to break up the oil-in-water emulsion at room temperature. It was encouraging to find that the small oil droplets in the emulsion quickly coalesced to form the oil phase and separated with the water within a few minutes. The demulsification tests indicated that the residual oil in separated water samples were as low as ∼30 mg/L corresponding to a demulsification efficiency over 99.9% at an optimum GO dosage. More importantly, GO is not only useful for ordinary crude oil emulsion, but also can be used to break up the extra heavy oil emulsion. Effect of the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 emulsion pH on the demulsification was also investigated. It was interesting to find that the distribution of GO either in oil or in water phase after demulsification was dependent on the pH value of the solution, which was attributed to the pH-dependent amphiphilicity of GO. The prominent demulsification ability of GO was attributed to the strong adsorption between the GO nanosheets and molecules of asphaltenes/resins driven by π-π interaction and/or n-π interaction. The findings in this work indicate that the GO nanosheets is a simple, high-efficient and universal demulsifier to separate the oil from the crude/heavy oil-in-water emulsions at ambient condition, which shows a good application prospect in oil industry.

Recyclable magnetic graphene oxide for rapid and efficient demulsification of crude oil-in-water emulsion

“…As the M-GO dosage increased to 0.25 wt%, the residual oil concentration was reduced to $10 mg/L corresponding to a demulsification efficiency of as high as 99.98%. Such an excellent demulsification performance of the M-GO is much better than that of the GO reported in a previous study [18], which attribute to the fact that the very small oil floccules combined with M-GO suspending in the separated water after demulsification can be eliminated by external magnetic field.…”

“…In our previous study, the mechanism on demulsification of the oil-in-water emulsion by GO was discussed [18]. However, how GO interacts with the asphlatenes and/or resins consisting of the cortical protective film at the oil/water interface is still not very clear.…”

“…(synthetic powder, <20 lm, Sigma-Aldrich), The physiochemical properties of the oil sample were reported in our previous work [18]. The iron carbonyl (Fe(CO) 5 ) (Zhongke Haorong New Material Research Co., Ltd., Changchun, China) were used to prepare magnetic ferrite.…”

“…In recent study, we develop a simple but effective demulsification method for fast separating the O/W emulsions by using grapheme oxide (GO) nanosheets as demulsifier [18]. The developed GO demulsifier demonstrates a demulsification efficiency of 99.9% and extremely low residual oil content (30 mg/L) in separated water at a lower dosage of 20-100 mg/L.…”

MPEG grafted quaternized carboxymethyl chitosan for demulsification of crude oil emulsions

“…No demulsifier can be employed to destabilize all kinds of crude oil emulsions because the demulsification mechanism is quite complicated . Furthermore, the traditional demulsifiers may be not environmentally friendly, easily causing further pollution and difficult to clear . It is imperative and significant to explore new chemicals to demulsify crude oil emulsions due to environmental requirements and to achieve the highest possible efficiency …”