A comparative adsorption kinetic modeling of fluoride adsorption by nanoparticles and its polymeric nanocomposite

Nanoparticles (NPs) of metallic oxides/hydroxides (oxyhydroxide) are highly efficient adsorbents for pollutants but tend to agglomerate readily. So, in recent years, NPs have been embedded inside the porous polymeric matrix to decontaminate pollutants more efficiently than NPs alone. But the roles of the polymeric barrier on the performance of composite adsorbent have not been explored in literature. In the present study, diffusivity co-efficients (D-e) of fluoride ions (F-) for adsorbents mixed metal oxyhydroxides and nanocomposite were estimated using a kinetic model to understand the roles of the polymeric barrier on adsorbate diffusion from the external surface to interior pores of the nanocomposite. Adsorption kinetic modeling study of both adsorbent-F- systems reveals that Fe-Al-Mn@chitosan composite is a more efficient adsorbent than mixed metal oxide nanoparticles alone. Although, the mass fraction of metal oxides/hydroxide present in the polymeric composite is less. The kinetic model reveals that only 25% of adsorption front radius was accessible for the adsorption of fluoride ions in mixed metal oxyhydroxide (Fe-Al-Mn) NPs. But, More than 80% of the total adsorption front radius was accessible for Fe-Al-Mn@chitosan. The magnitude of D-e is found to be almost in the same order for both the adsorbents, proving that polymer layers in Fe-Al-Mn@chitosan composite provide minimum resistance to the internal pore diffusion of adsorbate ions from the external surface to interior pores.

Automated summary

The study revealed that the Fe-Al-Mn@chitosan composite is a more efficient adsorbent for fluoride ions compared to mixed metal oxide nanoparticles alone, with the polymer layers in the composite providing minimal resistance to internal pore diffusion. The diffusion coefficients of fluoride ions were estimated for both types of adsorbents, showing that the composite had a significantly higher accessible adsorption front radius compared to the mixed metal oxyhydroxide NPs.