Investigation of the Equilibrium and Kinetics of Strontium Ion Adsorption from Aqueous Solutions Using Ethylenediamine-Functionalized Multi-Walled Carbon Nanotubes

Document Type : Original Article

Authors
Hossein Sid Kalal 1
Ali Mahvashian 2
Ebrahim Shirali 3
Mohammad Faryadi 1
1 Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, Tehran, Iran
2 Department of Chemical Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran
3 Department of Chemistry, Imam Ali (AS) Military University, Tehran, Iran
Abstract
In this study, multi-walled carbon nanotubes (MWCNTs) were functionalized with amine groups and employed as adsorbents for the removal of strontium ions from aqueous solutions. The adsorption behavior of the modified nanotubes was systematically investigated across a pH range of 3 to 9 using a solid-phase extraction approach. The influence of key operational parameters—including initial ion concentration, contact time, and the presence of competing ions—was examined to determine the optimal conditions for maximum adsorption efficiency. Furthermore, the performance of the synthesized adsorbent was evaluated in real environmental samples, yielding promising results. The negative value of the standard Gibbs free energy change (ΔG° < 0) confirmed the spontaneous and feasible nature of the adsorption process. Additionally, the negative values of both ΔH° and ΔS° indicated an exothermic process accompanied by a decrease in entropy upon reaching equilibrium. Finally, the experimental data were fitted to Langmuir, Freundlich, and Redlich–Peterson isotherm models, demonstrating a good agreement and providing insight into the adsorption mechanism of Sr(II) ions onto the functionalized MWCNTs.

Highlights

 

Keywords
Strontium
MWCNTs
Ethylenediamine
Adsorption
Langmuir