Comparative study on the removal of toxic metal ions by advanced carbon allotropes and g-C3N4 adsorbents: a case study from Sarcheshmeh copper mine

The sorption properties of graphene oxide nanosheets (GO), functionalized multi-walled carbon nanotubes (f-MWCNTs) and exfoliated graphite like C 3 N 4 (g-C 3 N 4 ) have been studied to evaluate their potential in treating acid mine drainage (AMD). Few-layered GO nanosheets and exfoliated g-C 3 N 4 were simply fabricated via modified Hummers’ and thermal decomposition methods, respectively. MWCNTs were functionalized in the mixture of both sulfuric and nitric acids. Fabricated nanoadsorbents were characterized by various techniques and then used for metal ion removal of prepared solutions and real AMD samples from Sarcheshmeh copper mine. To investigate the sorption activity, batch adsorption experiments were applied. GO exhibited much higher adsorption capacity toward metal ions than other adsorbents. Besides high surface area, specific groups existing on the GO surface are likely to suggest supplemental parameters, which highly improve the loading capacity in comparison to the f-MWCNTs and exfoliated g-C 3 N 4 adsorbents. Langmuir and Freundlich kinetic models have been implemented to depict and understand the adsorption reaction of metal ions. The results showed that the sorption analysis for all metal ions obeyed the second-order kinetics, and the sorption isotherms were in agreement with Langmuir and Freundlich isotherms. Additionally, cost assessment was done. Fast adsorption kinetics, large adsorption capacity, excellent reusability and the low cost create potentials for GO and g-C 3 N 4 nanoadsorbents to be effective at removing metal ions from aqueous solutions.