Isotherms and kinetics of lead and cadmium uptake from the waste leachate by natural and modified clinoptilolite

Aims: The purpose of this study is to investigate the feasibility of the absorption of lead and cadmium from the leachate, by natural zeolite clinoptilolite and improving the zeolite ability by a modified surface. Materials and Methods: To examine the absorption ability of these two metals (lead and cadmium), the variables, such as, type of sorbent, sorbent concentration, and contact time were studied. Zeolite samples were analyzed by X-ray florescence, the spectrum of X-ray diffraction, and Brunauer-Emmett-Teller (BET). Results: The absorption efficiency of the modified zeolites were increased from 4.2 and 5.3 percent to 71.6 and 75.2 percent for lead and cadmium, respectively. With increasing the surfactant concentration from 2 to 20 mmol/L, the absorption efficiency of modified zeolite for lead and cadmium was increased to 71 and 74%, respectively. The best isotherm model for lead adsorption was Freundlich model, with a determination coefficient equal to 0.99, and for cadmium it was Langmuir model with a determination coefficient equal to 0.99. Conclusions: The modified zeolite with surfactant can be used as an appropriate adsorbent for the separation of heavy metals from waste Leachate. Lead and cadmium were absorbed in a single layer on the surface of the modified zeolite with surfactant, comparing different isoterm models, indicated that the capacity of the modified zeolite for lead adsorption was more than cadmium adsorption, but cadmium was absorbed with higher energy.