The Preparation and Characterization of MnFe₂O₄-Decorated Expanded Graphite for Removal of Heavy Oils from Water

• Main Authors: Hoang Doan Tuan Nguyen, Hoang Tung Nguyen, Thuong Thi Nguyen, Ai Kha Le Thi, Thanh Duy Nguyen, Quynh Thi Phuong Bui, Long Giang Bach
• Format: Article
• Language: English
• Published: MDPI AG 2019-06-01
• Series: Materials
• Subjects: expanded graphite; heavy oils; magnetic adsorbent; manganese ferrite; wastewater treatment
• Online Access: https://www.mdpi.com/1996-1944/12/12/1913

Recently, many methods have been developed to efficiently eliminate oil spills due to its long-term harmful effects on marine life and human health. Expanded graphite (EG) has been considered as an excellent platform to remove contaminated oil from aqueous solution through a facile adsorption route. As an innovative approach, the decoration of magnetic components, namely, MnFe₂O₄, into graphite layers was taken into account for facilitating phase separation under magnetic field which resulted into an easy collection of the used adsorbents in a large scale. The expanded graphite/manganese ferrite composites were prepared from Vietnamese graphite flakes via a two-stage process. Characterization was performed using Scanning Electron Microscope (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), X-Ray Powder Diffraction (XRD), Vibrating Sample Magnetometer (VSM), Energy-Dispersive X-ray (EDS), and nitrogen adsorption/desorption analysis. The adsorption behavior of EG-MnFe₂O₄ for widespread used heavy oils, including diesel oil and crude oil, was investigated under the effects of adsorption conditions, i.e., contact time, loaded oil dosage, and salinity of mixing oil and water. The obtained results showed successful incorporation of MnFe₂O₄ into graphite sheets and no considerable change on the worm-like structure of EG. The results also showed that incorporated manganese ferrites enhanced the magnetism EG up to 16 emu/g, which made the recovery of used adsorbent conveniently. The EG-MnFe₂O₄ adsorbents exhibited the strong adsorption ability toward diesel oil (32.20 <inline-formula> <math display="inline"> <semantics> <mo>&#177;</mo> </semantics> </math> </inline-formula> 0.46 g DO/g EG) and crude oil (33.07 <inline-formula> <math display="inline"> <semantics> <mo>&#177;</mo> </semantics> </math> </inline-formula> 0.33 g CO/g EG). In brief, EG-MnFe₂O₄ material provides a potential and promising platform with high performance for oil spill removal.