Sulfur removal technologies from fuel oil for safe and sustainable environment

Fuel oil consumption has persisted as an energy source for transportation and electricity generation. The demand for fuel oil intensifies due to the rapid population growth that pushes the world toward an energy crisis. Notably, oil polluting agents render it unsafe which unfavorably increases the treatment cost and recently has become a major threat affecting the petrochemical industry. These, in due course, resulted in the emission of SOx gas which is toxic and the main cause of environmental contamination. In the mission to curb the pollution issue and mitigate the effect of the unwanted gases, developed nations have imposed restrictions and set stringent regulations on the permissible limit of sulfur in fuel oil. Owing to environmental and health concerns, the production of low-sulfur oil is vital in keeping good health and maintaining a clean and sustainable environment. In this review, various desulfurization technologies such as hydrodesulfurization, biodesulfurization, adsorptive, extractive, and oxidative or a combination of these techniques have been described. The effectiveness and multifunctional role of the techniques, the influence of structure and properties of the materials used, their multistage extraction processes, regeneration, and the recyclability are also reported. Advantages and disadvantages of the technologies for attaining a sustainable environment were elaborated. In addition, the new trend of research involving advanced materials for desulfurization applications toward obtaining green fuel oil was highlighted. In conclusion, current challenges, and future research directions in fulfilling the demand for clean fuel oil are summarized.