Simultaneous removal of phenanthrene and Pb using novel PPG-CNTs-nZVI beads

PPG-CNTs-nZVI bead was synthesized by polyvinyl alcohol, pumice, carbon nanotube, and guar gum-nanoscale zero-valent iron to be applied on simultaneously removal of polycyclic aromatic hydrocarbons (PAHs; phenanthrene) and heavy metals (Pb²⁺) via adsorption. The individual and simultaneous removal efficiency of phenanthrene and Pb²⁺ using the PPG-CNTs-nZVI beads was evaluated with a range of initial concentrations of these two pollutants. The kinetics and isotherms of phenanthrene and Pb²⁺ adsorption by the PPG-CNTs-nZVI beads were also determined. The PPG-CNTs-nZVI beads show reasonably high phenanthrene adsorption capacities (up to 0.16 mg/g), and they absorbed 85% of the phenanthrene (initial concentration 0.5 mg/L) in 30 min. High Pb²⁺ adsorption capabilities were also demonstrated by the PPG-CNTs-nZVI beads (up to 11.6 mg/g). The adsorption fits the Langmuir model better than the Freundlich model. The adsorption still remained stable with various ionic strength circumstances and a wide pH range (2-5). Additionally, the co-adsorption of phenanthrene and Pb²⁺ by the PPG-CNTs-nZVI beads resulted in synergistic effects. Particularly, phenanthrene-Pb²⁺ complex formation via π-cation interactions demonstrated a greater affinity than phenanthrene or Pb²⁺ alone. The present findings suggest that PPG-CNTs-nZVI beads may be effective sorbents for the simultaneous removal of PAHs and heavy metals from contaminated waters.