Abstract
The objective of the proposed work focused to provide promising solid-phase materials that combine relatively inexpensive and high removal capacity of cadmium ion from aqueous solutions. Four various zeolite minerals including natural clinoptilolite, natural chabazite, natural mordenite, and synthetic mordenite were investigated. The obtained results revealed that natural chabazite has the highest surface area and mesopore volume and appears to be the best adsorbent towards cadmium ion rather than the other investigated zeolite materials. The effective key parameters on the sorption behavior of cadmium on natural chabazite were investigated using batch equilibrium and flow through technique with respect to solution pH, contacting time, adsorbent weight, adsorption isotherm, bed depth, and flow rate. Kinetic curves rather showed a fast adsorption for cadmium, as equilibrium reached within 60 min. The affinity and adsorption capacity of natural chabazite with good fits being obtained using Dubinin-Radushkevich adsorption isotherm giving a maximum capacity of 120 mg/g. Cd+2 and adsorption found to be pH dependent over 2.5-8.5 range; this reveals that the adsorption mechanism may be controlled by chemisorption with the experimental conditions used. The results indicated the feasibility and spontaneous nature of adsorption process at high temperature. Thermodynamic parameter was determined. Column studies showed that cadmium ion removal was a strong function of initial flow rate and bed height. Natural chabazite recommended to be used as reactive barrier for hazardous heavy metals control.