Adsorption of Ammonium Ion by Multi-walled Carbon Nanotube: Kinetics and Thermodynamic Studies

This study was an attempt to examine the feasibility of removing ammonium ions from aqueous solutions by using multi-walled carbon nanotube (MWCNT). The adsorption behavior of ammonium ions (NH4+) from aqueous solution onto MWCNTs was investigated as a function of several parameters such as contact time, initial ammonium ion concentration and temperature. The adsorption of ammonium ions on carbon nanotube was studied at different temperatures ranging from 288 K to 328 K. Enthalpy (Delta H-0) and entropy (Delta S-0) of the procedure were -2.74 KJ/mol and -0.0083 KJ/mol K, respectively. The negative value of Delta H-0 indicates that the adsorption of ammonium ions onto CNTs is exothermic and that the negative value of Delta G(0) represents the fact that the process of adsorption of ammonium ions onto CNTs is spontaneous. Kinetic analysis showed that the adsorption of ammonium ions on MWCNT followed the pseudo-second-order model.