Kinetic and Isotherm Studies of Cd(II) Removal from Aqueous Solution by Zeolite-Iron Fly Ash Composite

One of the most important environmental problems has become heavy metal pollution. Cadmium (II) has known as a toxic element and can cause a major problem to human health. Zeolites are known as a good adsorbent for removal of heavy metals. Solid waste of steel industry such as fly ashes of the furnaces can be used as a low-cost and available co-adsorbent.In this study the composite of zeolite-iron fly ash was synthetized to remove Cd (II) from aqueous solution. The effect of operation conditions including adsorbents dosage, contact time, pH and concentration were studied in batch system. The optimum adsorbents dosage was 40% iron dusts – 60% zeolite and 40 min was the best contact time with 73/4 mg/g Cd2 capacity of adsorption. pH =5.5 was selected as an optimum pH. The results of the experiments were evaluated by kinetic models (Pseudo-first order, Pseudo-second order, intraparticle diffusion) and isotherm models (3 and 2 parameters).The kinetic data of Cd ions were well described with Pseudo-second order and equilibrium data were obeyed Langmuire isotherm model, by R2=0/999.the maximum monolayer sorption capacities of Cd were estimated to be 78/12 mg/g. E=12/9 kJ was achieved by D-R model that indicated the chemical sorption.