Batch and fixed-bed mode mercury uptake by a modified adsorbent

The current study deals with the removal of mercury ions from aqueous solutions by sulfurized and original activated carbons (ACs) in the batch and fixed bed modes. The modified sample containing sulfur groups showed higher uptake capacities and larger breakpoints. The XPS and EDS analyses confirmed the introduction of carbon-sulfur bonds onto the AC's surface after impregnation with dimethyl-disulfide. In the work, the diffusional models named, Film Pore Concentration-Dependent Surface Diffusion (FPCDSD) and Axial dispersion Film Pore Concentration-Dependent Surface Diffusion (AFPCDSD) were respectively applied to explain the batch and bed-mode kinetic data to clarify the rate-controlling mechanisms and estimate the diffusional/mass transfer properties of adsorbate-adsorbent systems. In all cases, the sulfurized AC showed greater D-s (surface diffusivity) values attributed to the higher mercury loading on this sorbent which facilitates ion hopping on the surface sites. The internal and film diffusions both played notable roles in mercury adsorption mechanism.

Automated summary

The study shows that sulfurized activated carbon exhibits higher adsorption capacity and better performance in removing mercury ions from aqueous solutions. The sulfur groups introduced by sulfurization facilitate ion hopping on the surface sites, leading to greater surface diffusivity and improved mercury adsorption. Both internal and film diffusions play significant roles in the mercury adsorption mechanism.