Citation:

Park, C., D. Wang, J. Han, J. Heo, AND C. Su. Evaluation of the colloidal stability and adsorption performance of reduced graphene oxide–elemental silver/magnetite nanohybrids for selected toxic heavy metals in aqueous solutions. Applied Surface Science. Elsevier B.V., Amsterdam, Netherlands, 471:8-17, (2019). https://doi.org/10.1016/j.apsusc.2018.11.240

Impact/Purpose:

Nanohybrids (NHs) of engineered nanomaterials are being produced as adsorbents for removing contaminants such as heavy metals from water. It is unknown if different heavy metals show different removal capacities and to what extent the competitive removal takes place. In this study, Reduced graphene oxide (rGO) hybridized with magnetite and/or elemental silver (rGO/magnetite, rGO/silver, and rGO/magnetite/silver) nanoparticles were evaluated as effective adsorbents for toxic heavy metal ions (Cd(II), Ni(II), Zn(II), Co(II), Pb(II), and Cu(II)). Although the deposition of iron oxide and silver nanoparticles on the rGO nanosheet plays an inhibitory role in metal ion adsorption, the metal adsorption efficiency by the NHs was still higher than that reported for many other sorbents (e.g., activated biochar, commercial resins, and nanosized hydrated Zr(IV) oxide particles). Competitive adsorption tests showed that the adsorption affinity of metal ions on the rGO and NHs follows the order (Cu(II), Zn(II)) > Ni(II) > Co(II) > (Pb(II), Cd(II)), which is similar to the order observed for single-metal systems. These results can be explained by the destabilization abilities of the rGO and NHs, as well as the ionic radii of the metal ions. X-ray photoelectron spectroscopy analyses revealed that complexation with deprotonated adsorbents and cation exchange was an important mechanism for Cd(II) ion removal by the rGO and NHs. Our findings demonstrate the feasibility of using rGO-based NHs as highly efficient adsorbents for heavy metal removal from water. The results can be used by EPA program offices (OLEM, OCSPP), Regions, States, and industry for evaluation of the fate and interactions of nanomaterials with contaminants and potential applications of nanohybrids for water treatment and site remediation.

Description:

Reduced graphene oxide (rGO) hybridized with magnetite and/or elemental silver (rGO/magnetite, rGO/silver, and rGO/magnetite/silver) nanoparticles were evaluated as effective adsorbents for toxic heavy metal ions (Cd(II), Ni(II), Zn(II), Co(II), Pb(II), and Cu(II)). Although the deposition of iron oxide and silver nanoparticles on the rGO nanosheet plays an inhibitory role in metal ion adsorption, the metal adsorption efficiency by the nanohybrids (NHs) was still higher than that reported for many other sorbents (e.g., activated biochar, commercial resins, and nanosized hydrated Zr(IV) oxide particles). Competitive adsorption tests showed that the adsorption affinity of metal ions on the rGO and NHs follows the order (Cu(II), Zn(II)) > Ni(II) > Co(II) > (Pb(II), Cd(II)), which is similar to the order observed for single-metal systems. These results can be explained by the destabilization abilities of the rGO and NHs, as well as the ionic radii of the metal ions. X-ray photoelectron spectroscopy analyses revealed that complexation with deprotonated adsorbents and cation exchange was an important mechanism for Cd(II) ion removal by the rGO and NHs. Our findings demonstrate the feasibility of using rGO-based NHs as highly efficient adsorbents for heavy metal removal from water.

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