Kinetics and thermodynamics of mercury adsorption onto thiolated graphene oxide nanoparticles

Abstract

Mercury among heavy metals has significant worldwide importance due to major ecological effects. Numerous methods have been used to remove this metal from polluted wastewaters which adsorption by functionalized adsorbents is one of the most common methods. In the present study, graphene oxide nanoparticles were functionalized, magnetized and used for removing Hg(II) ions. In addition, FT-IR, TEM, SEM, EDS and VSM analyses were carried out to characterize the chemical, physical and surficial properties of thiol functionalized graphene oxide nanoparticles. Mercury removal experiments were done and confirmed the efficiency of the thiol-functionalized adsorbent. Additionally, adsorption trend was obtained in order to evaluate the fitness of experimental data by isothermal Langmuir, Freundlich and Dubinin-Radushkevich models in batch system. Furthermore, thermodynamic and kinetic calculations were carried out comprehensively. Results showed that Langmuir model (R2 = 0.995) and Freundlich model (R2 = 0.982) logically described the adsorption trend. Also, Dubinin-Radushkevich model offered a proper correlation (R2 = 0.997). The maximum adsorbing capacity of thiol-functionalized graphene oxide was estimated to be 129.7 mg.g−1 by Langmuir model. Thermodynamic calculations showed that Hg(II) adsorption reaction on GO/Fe3O4-Si-Pr-SH was spontaneous. Kinetic calculations confirmed that Hg(II) ion adsorption followed more accurately by pseudo-second order model than the pseudo-first order model. Generally, it was approved that thiol-functionalized graphene oxide nanoparticles can be effectively used to adsorb heavy metals and then separated easily from the liquid phase by magnetic field.