Heavy metals adsorption by novel EDTA-modified chitosan–silica hybrid materials

Novel adsorbents were synthesized by functionalizing chitosan–silica hybrid materials with (ethylenediaminetetraacetic acid) EDTA ligands. The synthesized adsorbents were found to combine the advantages of both silica gel (high surface area, porosity, rigid structure) and chitosan (surface functionality). The Adsorption potential of hybrid materials was investigated using Co(II), Ni(II), Cd(II), and Pb(II) as target metals by varying experimental conditions such as pH, contact time, and initial metal concentration. The kinetic results revealed that the pore diffusion process played a key role in adsorption kinetics, which might be attributed to the porous structure of synthesized adsorbents. The obtained maximum adsorption capacities of the hybrid materials for the metal ions ranged from 0.25 to 0.63 mmol/g under the studied experimental conditions. The adsorbent with the highest chitosan content showed the best adsorption efficiency. Bi-Langmuir and Sips isotherm model fitting to experimental data suggested the surface heterogeneity of the prepared adsorbents. In multimetal solutions, the hybrid adsorbents showed the highest affinity toward Pb(II).

Graphical abstractNovel porous EDTA-modified chitosan–silica hybrid materials were effective adsorbents for Co(II), Ni(II), Cd(II), and Pb(II).Figure optionsDownload full-size imageDownload high-quality image (94 K)Download as PowerPoint slideHighlights► Novel hybrid adsorbents combined beneficial properties of silica gel and chitosan. ► EDTA-modified hybrid materials were effective adsorbents for heavy metals. ► Porosity of the hybrid adsorbents affected the kinetics of the metal adsorption. ► Adsorption isotherms depended on the type of metal. ► Pb(II) had the highest adsorption efficiency from the mixed metal solutions.