Magnetically recoverable magnetite-reduced graphene oxide as a demulsifier for surfactant stabilized crude oil-in-water emulsion.

Xin Hui Yau,Mohamed Shuaib Mohamed Saheed,Kok Yeow You,Chin Wei Lai,Cheng Seong Khe,Wai Kian Tan,P Davide Cozzoli

doi:10.1371/journal.pone.0232490

Abstract

Oily wastewater, especially water-oil emulsion has become serious environmental issue and received global attention. Chemical demulsifiers are widely used to treat oil-water emulsion, but the toxicity, non-recyclable and non-environmental friendly characteristic of chemical demulsifiers had limited their practical application in oil-water separation. Therefore, it is imperative to develop an efficient, simple, eco-friendly and recyclable demulsifiers for breaking up the emulsions from the oily wastewater. In this study, a magnetic demulsifier, magnetite-reduced graphene oxide (M-rGO) nanocomposites were proposed as a recyclable demulsifier to break up the surfactant stabilized crude oil-in-water (O/W) emulsion. M-rGO nanocomposites were prepared via in situ chemical synthesis by using only one type Fe salt and GO solid as precursor at room temperature. The prepared composites were fully characterized by various techniques. The effect of demulsifier dosage and pH of emulsion on demulsification efficiency (ED) has been studied in detailed. The demulsification mechanism was also proposed in this study. Results showed that M-rGO nanocomposites were able to demulsify crude O/W emulsion. The ED reaches 99.48% when 0.050 wt.% of M-rGO nanocomposites were added to crude O/W emulsion (pH = 4). Besides, M-rGO nanocomposites can be recycled up to 7 cycles without showing a significant change in terms of ED. Thus, M-rGO nanocomposite is a promising demulsifier for surfactant stabilized crude O/W emulsion.

Highlights

Nowadays, oil pollution has become a serious environmental issue and received global attention
It was found that Graphene oxide (GO) sheets revealed a rough and irregular wrinkled structure, which might have resulted from the introduction of oxygen-containing functional groups, including epoxy, hydroxyl, carbonyl, and carboxyl groups, during the oxidation of graphite by the improved Hummers method. (Fig 1B–1F) present the field emission scanning electron microscopy (FESEM) images and particle size histograms of the magnetite-reduced graphene oxide (M-reduced graphene oxide (rGO)) nanocomposites synthesized with various stirring durations
The FESEM images of M-rGO in (Fig 1B–1F) displayed plenty of nanoparticles spread on the surface of rGO sheets

Summary

Introduction

Oil pollution has become a serious environmental issue and received global attention. This result suggested that M-rGO nanocomposites with 3 h of stirring duration saturated the magnetite nanoparticles on the surface of rGO sheets. The broadness of the characteristic peaks (D and G bands) and the higher intensity of the D band than that of G band in the Raman spectra of the M-rGO nanocomposites suggested that more defects were generated in the synthesis process, thereby confirming the effective reduction of GO and the successful attachment of magnetite on the rGO sheets.

Objectives

Results

Conclusion