Magnetic dithiocarbamate functionalized reduced graphene oxide for the removal of Cu(II), Cd(II), Pb(II), and Hg(II) ions from aqueous solution: Synthesis, adsorption, and regeneration

In this study, dithiocarbamate(DTC)-modified magnetic reduce graphene oxide (rGO-PDTC/Fe3O4) was synthesized for the removal of heavy metal ions (Cu(II), Cd(II), Pb(II), and Hg(II)) in synthetic waste water. The rGO-PDTC/Fe3O4 nanocomposite was prepared via a novel synthesis route that includes GO bromination, nucleophilic substitution of polyethylenimine (PEI), the reaction with carbon disulphide (CS2) and Fe3O4 nanoparticle loading. The prepared rGO-PDTC/Fe3O4 nanocomposite was characterised by XPS, FTIR, TEM and XRD, suggesting that DTC functional groups were chemically bonded to rGO surfaces. N2 adsorption-desorption results revealed that rGO-PDTC/Fe3O4 nanocomposite exhibited high BET surface area (194.8 m2/g) and large pore volume (0.33 cm³/g) which are crucial to the function of adsorbent. Adsorption experiments showed that rGO-PDTC/Fe3O4 nanocomposite is an excellent adsorbent for heavy metal removal, which exhibits large adsorption capacities, fast kinetics and solid-liquid separation. The pseudo-second-order kinetic model and Langmuir adsorption model were used to unveil the adsorption mechanisms. The maximum adsorption capacities of the Langmuir model were 113.64, 116.28, 147.06, and 181.82 mg/g for Cu(II), Cd(II), Pb(II), and Hg(II) ions, respectively. After adsorption and desorption process, the spent rGO-PDTC/Fe3O4 nanocomposite was easily regenerated via one-step organic reaction. The regenerated rGO-PDTC/Fe3O4 composite exhibited good adsorption capacities for different metals in five adsorption-desorption-regeneration cycles.