Preparation of thiol modified olive stone-based biochar for the removal of Hg (II)from aqueous solutions

Abstract

Mercury is a heavy metal whose toxicity poses significant environmental and health risks. Utilizing biochar prepared from biomass waste is a straightforward and effective method for removing mercury from water. This research centered on producing a thiol-functionalized biochar derived from olive stone waste for the removal of Hg (II) from aqueous solutions. Characterization analyses confirmed the successful functionalization. The biochar, despite having a limited specific surface area (4.14 m2/g) due to raw material nature and pyrolysis conditions, exhibited a notable ability for Hg (II) adsorption, primarily attributed to the thiol-modified surface. Adsorption was assessed using a 2^3 factorial design, with the variables being the adsorption time, biochar dose, and initial Hg (II) concentration in the solution. The biochar dose emerged as the most influential factor, followed by the adsorption time and, lastly the initial Hg (II) concentration. The peak removal efficiency of the model stood at 98.19 %. Kinetics aligned with the pseudo-first-order and intra-particle diffusion models, suggesting a surface adsorption mechanism coupled with pore diffusion. This work accentuates the potential of olive-derived biochar, when thiol-enhanced, in treating aqueous systems contaminated with Hg (II).