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 (E D) 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 E D 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 E D. Thus, M-rGO nanocomposite is a promising demulsifier for surfactant stabilized crude O/W emulsion.

Magnetite reduced graphene oxide were synthesized for separation of crude oil in water emulsion.

This study investigates the effects of stirring duration on the synthesis of graphene oxide (GO) using an improved Hummers' method. Various samples are examined under different stirring durations (20, 40, 60, 72, and 80 h). The synthesized GO samples are evaluated through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The GO sample with 72 h stirring duration (GO72) has the highest dspacing in the XRD results, highest atomic percentage of oxygen in EDX (49.57%), highest intensity of oxygen functional group in FTIR spectra, and highest intensity ratio in Raman analysis (I D /I G = 0.756). Results show that GO72 with continuous stirring has the highest degree of oxidation among other samples. Electrochemical impedance spectroscopy analysis shows that GO72-titanium dioxide (TiO 2) exhibits smaller charge transfer resistance and higher electron lifetime compared with the TiO 2-based photoanode. The GO72 sample incorporating TiO 2 nanocomposites achieves 6.25% photoconversion efficiency, indicating an increase of more than twice than that of the mesoporous TiO 2 sample. This condition is fully attributed to the efficient absorption rate of nanocomposites and the reduction of the recombination rate of TiO 2 by GO in dye-sensitized solar cells.

Graphene is a promising material due to its fascinating properties, such as mechanical, electronic and thermal properties. Graphene based hybrids materials also have been widely studied due to its wide applications, such as sensors, energy storage and conversion, electronic device and others. The current study presents the synthesis of magnetite-reduced graphene oxide (M-rGO) nanocomposites through in situ chemical synthesis at different stirring durations. This synthesis process involves the redox reaction between the iron(II) salts and graphene oxide (GO) sheets. Various techniques were employed to characterize the synthesized M-rGO nanocomposites. From X-ray diffraction (XRD) results, the crystal structure of M-rGO was found to be independent on the stirring duration. Three magnetite vibrations, D band and G band were observed in Raman spectrum of M-rGO with 24 hours stirring duration. From Fourier transform infrared (FTIR) analysis, M-rGO with 24 hours stirring duration showed the strong intensity of Fe-O vibration. Thus, this indicated that a large amount of magnetite nanoparticles were covered on the surface of rGO sheets. This result is further supported by the morphology of nanocomposites from scanning electron microscopy (SEM) and the elemental analysis (EDX). A monolayer of rGO sheet (C= 33.79 atomic %) with full coverage of magnetite nanoparticles (Fe= 30.20 atomic %) was found for the M-rGO with 24 hours stirring duration. Overall, M-rGO require 24 hours of continuous stirring to ensure full coverage of magnetite nanoparticles on the surface of rGO sheets.

Background: Owing to their remarkable chemical, physical and biological properties, silver nanoparticles have been widely used in water purification, electronics, bio-sensing, clothing, food industry, paint and medical devices. Various approaches, such as using harsh reducing and stabilising agents for reverse micelle and thermal decomposition, were proposed for silver nanoparticle production. However, these methods are not eco-friendly. Thus, the aim of this paper is to synthesise silver nanoparticles through a cost-effective and environmentally friendly approach. Materials and Methods: A green approach was presented for the synthesis of silver nanoparticles. This approach involved the treatment of silver nitrate and hibiscus leaf extract, which acts as reducing and capping agent. The synthesis was performed at room temperature. The resulting silver nanoparticles were characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and Fourier transform infrared (FTIR) spectroscopy. Results: Spherical, rod-like, hexagonal and triangular silver nanoparticles were obtained through the proposed synthesis method. The crystalline nature of each nanoparticle was revealed by XRD and selected area electron diffraction (SAED). The average spherical size of the silver nanoparticles produced in this route was 44.3 nm. The obtained FTIR band at 1622 cm-1 corresponded to the C=O stretch in the amine I group, which is commonly found in protein. Thus, the protein was believed to serve as capping agent that was responsible for the stabilisation of silver nanoparticles. Conclusion: In conclusion, silver nanoparticles had been successfully synthesised using hibiscus leaf extract and a plausible formation mechanism of silver nanoparticles was proposed.