ADSORPTION OF NICKEL IONS ON NANOMODIFIED MATERIALS: AN ISOTHERM STUDY

The present paper describes and compares the adsorption of heavy metal ions (Ni2+) on Conventional and nanomodified AG-5 and NWC coconut shell-based activated carbons from aqueous solutions. The nanomodification of the materials was performed using "Taunit"-series carbon nanotubes (CNTs) obtained via chemical vapor deposition onto MgO-A1203 catalysts. The Ni2+ concentration in the solutions was determined spectrophotometrically. The efficiency of the Ni2+ adsorption was tested for all the materials. The adsorption mechanism was elucidated by adjusting the experimental data to the dual-site Langmuir-Freundlich (Sips) isotherm, which allowed confirming the existence of inner-sphere (higher-energy) and outer-sphere (lower-energy) sites on the adsorbent surface. For all the samples, the Ni2+ adsorption process was controlled mostly by the higher -energy sites. The results revealed that the nanomodification causes a 20 % increase in the adsorption capacity of the activated carbons at low initial and equilibrium Ni2+ concentrations, and a slight increase at higher concentrations. Thus, the CNTs-modified activated carbons can be used in water and wastewater treatment processes for efficiently removing heavy metal ions from aqueous media.