A Review on the Adsorptive Performance of Bentonite on Sulfur Compounds

When sulfur is left in fuel, it has a tendency to be oxidized during combustion and cause problems to engines and harm when released into the atmosphere. One way to reduce sulfur content is by adsorptive desulfurization, which makes use of solid materials as adsorbents to adsorb sulfur from fuel selectively. This process is gaining interest from researchers as it can produce a high sulfur yield at mild temperatures and pressure, and the use of effective and regenerative adsorbents can lower the cost of the process. Clay adsorbents, like kaolinite, bentonite, and montmorillonite, are being studied as their availability and low cost make them good candidates. The objective of this paper is to review studies making use of bentonite as a desulfurization adsorbent and determine future research topics in this scope. It also aims to gain insight into the performance of bentonite and its mechanism in adsorbing different sulfur compounds. Several studies have made use of bentonite as an adsorbent for different compounds, specifically dibenzothiophene, dibenzothiophene sulfone, benzothiophene sulfone, dimethyl sulfide, propyl-mercaptan, and thiophene. Though these studies showed the wide range of effectiveness of bentonite to adsorb sulfur, modification to the adsorbent generally increases its effectiveness as it encourages chemisorption between the adsorbent and target molecule. It also aids in improving the physical properties of the adsorbent, like the surface area available for adsorption. The review showed that modifications to bentonite improved its performance in adsorbing sulfur, presenting the potential for industrial use with further research. For future studies, other modifications of bentonite can be investigated, such as activation and impregnation of other ions for adsorption of other sulfur compounds.