Utilization of natural chabazite and mordenite as a reactive barrier for immobilization of hazardous heavy metals

Understanding the sorption process in natural geomedia is necessary for effective utilization of these materials as low-cost adsorbents and consequently as controlled release hazardous elements. This research was oriented to investigate the affinity of two natural zeolite minerals towards cobalt, zinc, and nickel mixture as an important industrial and radioactive waste. The uptake of metal ions as a function of different parameters has been studied using a batch equilibrium technique. The results revealed that the affinity and adsorption capacity of chabazite and mordenite follow the order: Zn(2+) > Co(2+) > Ni(2+), with good fits being obtained using Langmuir and Freundlich adsorption isotherms. The metal uptake was found to be concentration-dependent and independent of the pH over 3.0 to 8.0 range; this reveals that the adsorption mechanism is controlled mainly by a pure ion-exchange reaction at the experimental conditions used. Kinetic curves showed a rather fast exchange reaction for three cations, as equilibrium was mostly reached within 20 min. These materials especially chabazite are recommended to be used as a reactive barrier for hazardous heavy metals control.