HUANG Xiao-ming1,2, PAN Min1, CHEN Tian-hu2, ZHU Mu-lan1, XIE Jing-jing2
(1. School of Environmental Science and Engineering, Xiamen University of Technology, Xiamen 361024, China;
2. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China)
Abstract: This study investigated adsorption of ammonium from aqueous solution by natural clinoptilolite. The natural zeolite was characterized by X-ray diffraction (XRD) and X-ray fluorescence (XRF) for analysis of mineral phase and chemical composition. A series of experiments was conducted to examine the effects of pH, initial concentration of ammonium, and temperature on the removal of ammonium. To investigate the mechanism of the adsorption of ammonium by natural clinoptilolite, adsorption isotherms, kinetics and thermodynamics were studied. The results demonstrate that natural clinoptilolite shows good performance on ammonium adsorption under the condition of solution pH=8. Results show that ammonium adsorption on natural clinoptilolite is better to fit by Freundlich isotherm compared with Langmuir isotherm, and the adsorption process is favorable. Thermodynamic parameters such as Gibbs free energy change (ΔG0), enthalpy change (ΔH0), and entropy change (ΔS0) were calculated. Negative value of ΔG0 and positive value of ΔH0 confirm that ammonium adsorption on clinoptilolite is a spontaneous and endothermic process. Positive value of entropy change indicates that randomness increase during ammonium adsorption from aqueous solution onto zeolite surface. Kinetic studies show that the adsorption follows a pseudo-second-order reaction. The adsorption process is less favorable with increasing initial ammonium concentration. The fitting results indicate that the adsorption process could be divided into two stages, surface adsorption at initial 30 minutes and following inter-particle diffusion.
Keywords: clinoptilolite; adsorption; ammonium; thermodynamics; kinetics
E-mail：chentianhu168@vip.sina.com
ACTA MINERALOGICA SINICA Vol. 36, No. 3, 2016, Page 371-376
