The removal of zinc ions by natural and conditioned clinoptilolites

The aim of this study is to investigate the effects of conditioning with NaCl and HCl solutions on removal of Zn2+ ions from aqueous solutions using natural clinoptilolite collected from Manisa-Gördes region of Turkey. The clinoptilolite sample was used in the four different forms, which consist of one unconditioned (NC) and three conditioned (CC1, CC2 and CC3). The optimum conditions for adsorption/ion exchange by using a batch method were evaluated by changing various parameters such as chemical conditioning, adsorbent amount, initial pH of the solution, mixing temperature and initial metal ions. The results clearly showed that the conditioning improved both the exchange capacity and the removal efficiency. The influence of the temperature on the ion-exchange/adsorption process was also examined. It was found that the highest removal efficiency was obtained with CC2 sample. These values for 10, 20, 40 60, 70 and 90°C mixing temperature were found to be as 90.7, 91.2, 98.6, 99.3, 99.4 and 99.7%, respectively. The Langmuir and Freundlich adsorption isotherm equations were derived form the basic empirical equations, and used for calculation of ion exchange parameters. Adsorption isotherms of Zn2+ ions could be best modeled by the Langmuir equation. The maximum sorption capacities for zinc ions shown by NC, CC1, CC2 and CC3 samples are 21.2 mg/g, 20.8 mg/g, 22.2 mg/g and 17.9 mg/g, respectively. Results indicate a significant potential for the natural and conditioned clinoptilolites as an adsorbent/ion-exchange material for heavy metal removal.