Multi wall carbon nanotubes application for treatment of Cr(VI)-contaminated groundwater; Modeling of batch & column experiments

Multi wall carbon nanotubes (MWCNTs) are carbonaceous nanomaterials with novel adsorption properties. In this study MWCNTs were used as adsorbents for hexavalent chromium, Cr(VI), and the influence of operating parameters, on adsorption process, such as pH, MWCNTs and Cr(VI) concentration, and contact time have been investigated. Batch and column experiments were carried out in order to investigate the removal efficiency of MWCNTs for different Cr(VI) concentrations related to groundwater polluted by either anthropogenic activities or by geogenic processes. The experimental results showed that pH was the most crucial factor for adsorption efficiency. Cr(VI) adsorption was inversely proportional with pH value and more specifically adsorption was significantly decreased for pH values higher than 7. The effect of adsorbent's concentration showed the high adsorption capacity of MWCNTs. The adsorption process was very fast since was almost completed within 1 h. Different isotherm models have been adopted to interpret the experimental equilibrium data, as well as two mass-transfer based model were used to describe the dynamic behavior of Cr(VI) sorption phenomenon in column experiments.