Adsorption Kinetics and Thermodynamics of Perchlorate on Carbon Nanotubes in Water.

This study investigates the removal of perchlorate in solution using single-walled carbon nanotubes (SWCNTs) as sorbents. The perchlorate adsorption capacity, kinetics, and thermodynamics of the SWCNTs were assessed. The influences of pH, solution ionic strength, time, and temperature on the adsorption were examined. Adsorption equilibrium was achieved in approximately 8 h. The adsorption data were fitted with three models: modified Freundlich, pseudo-first-order, and pseudo-second-order. The modified Freundlich model produced the best fit to describe the kinetic adsorption processes. The adsorption capacity increased as the concentration of perchlorate increased and as the ionic strength of the solution decreased. Maximum perchlorate adsorption capacities of were attained within a temperature range of 5-45°C. The thermodynamic parameters were also calculated: equilibrium rate constant, standard free energy change, standard enthalpy change, and standard entropy change. In summary, the adsorption isotherm studies demonstrate that low solution pH values, low solution ionic strength, and low temperature conditions facilitate the adsorption of perchlorate on the SWCNTs, indicating that SWCNTs are a potential adsorbent for water purification. [ABSTRACT FROM AUTHOR]