Iron adsorption from water using natural zeolite-kaolin aggregates: model kinetics

An experiment was carried out on 500 mL deionized water with initial iron concentrations of 2, 4 and 6 ppm to test iron adsorption in water using pre-washed natural zeolite-kaolin aggregates brought from the Kalabsha district at Aswan, Egypt. The removal efficiency of iron increased to 80% after 1 h using natural zeolite at an adsorbent dose of 100 g per 500 mL solution with a 1:10 combination of kaolin to zeolite at a pH value in solution of 5. Moreover, pseudo-first- and second-order, Elovich and intra-particle diffusion models were presented to analyze the kinetics of iron adsorption. Langmuir, Freundlich and Temkin adsorption isotherms were studied at equilibrium for different iron concentrations. Model non-linearity showed average pseudo constants of 0.021 min−1 and 1.75 g/mg/min with a maximum adsorption capacity of 0.0624 mg/g. The results also indicated a cost–benefit ratio of about 0.4 $ per % of iron removal after a 2-hr contact time.