Synthesis of Chemically Modified Acid-Functionalized Multiwall Carbon Nanotubes with Benzimidazole for Removal of Lead and Cadmium Ions from Wastewater.

In this work, acid-functionalized multiwalled carbon (MWCNTs-COH) nanotube was successfully functionalized with a heterocyclic scaffold, namely benzimidazole, to give novel functionalized multiwalled carbon nanotubes (BI@MWCNTs). Then, FTIR, XRD, TEM, EDX, Raman spectroscopy, DLS, and BET analyses were used to characterize the synthesized BI@MWCNTs. The effectiveness of the adsorption of two heavy metal ions, Cd and Pb, in single metal and mixed metal solutions on the prepared material was investigated. Influencing parameters for the adsorption method, for example duration, pH, starting metal concentration, and BI@MWCNT dosage, were examined for both metal ions. Moreover, adsorption equilibrium isotherms fit with the Langmuir and Freundlich models perfectly, while the intra-particle diffusion models provide pseudo-second order adsorption kinetics. The adsorption of Cd and Pb ions onto BI@MWCNTs revealed an endothermic and a spontaneous method with great affinity as a result of the negative values of Gibbs free energy (ΔG) and the positive values of enthalpy (ΔH) and entropy (ΔS). Both Pb and Cd ions were completely eliminated from aqueous solution (100 and 98%, respectively) using the prepared material. Additionally, BI@MWCNTs have a high adsorption capacity and were regenerated in a simple way and reused for six cycles, which make them a cost-effective and efficient absorbent for the removal of such heavy metal ions from wastewater.