Article

Kinetics and thermodynamics of cadmium ion removal by adsorption onto nano zerovalent iron particles

Department of Civil and Environmental Engineering, Faculty of Engineering, The University of Western Ontario, 1151 Richmond St. N, London, Ontario N6A 5B9, Canada
Journal of Hazardous Materials DOI:10.1016/j.jhazmat.2010.11.029 pp.458-465

ABSTRACT Nano zerovalent iron (nZVI) is an effective adsorbent for removing various organic and inorganic contaminants. In this study, nZVI particles were used to investigate the removal of Cd2+ in the concentration range of 25–450 mg L−1. The effect of temperature on kinetics and equilibrium of cadmium sorption on nZVI particles was thoroughly examined. Consistent with an endothermic reaction, an increase in the temperature resulted in increasing cadmium adsorption rate. The adsorption kinetics well fitted using a pseudo second-order kinetic model. The calculated activation energy for adsorption was 54.8 kJ mol−1, indicating the adsorption process to be chemisorption. The intraparticle diffusion model described that the intraparticle diffusion was not the only rate-limiting step. The adsorption isotherm data could be well described by the Langmuir as well as Temkin equations. The maximum adsorption capacity of nZVI for Cd2+ was found to be 769.2 mg g−1 at 297 K. Thermodynamic parameters (i.e., change in the free energy (ΔGo), the enthalpy (ΔHo), and the entropy (ΔSo)) were also evaluated. The overall adsorption process was endothermic and spontaneous in nature. EDX analysis indicated the presence of cadmium ions on the nZVI surface. These results suggest that nZVI could be employed as an efficient adsorbent for the removal of cadmium from contaminated water sources.

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Keywords

297 K. Thermodynamic parameters
 
adsorption isotherm data
 
adsorption kinetics
 
adsorption process
 
cadmium adsorption rate
 
cadmium ions
 
calculated activation energy
 
concentration range
 
effective adsorbent
 
endothermic reaction
 
intraparticle diffusion
 
intraparticle diffusion model
 
maximum adsorption capacity
 
Nano zerovalent iron
 
nZVI particles
 
pseudo second-order kinetic model
 
rate-limiting step
 
Temkin equations
 
various organic
 
water sources