Removal of cadmium from aqueous medium under ultrasound assistance using olive leaves as sorbent

In this work, the leaves of olive tree (Olea europaea) are proposed as a novel low-cost non-conventional sorbent for the removal of cadmium from aqueous solutions with and without the assistance of ultrasound and by associating simultaneously ultrasonic irradiation and stirring. Sorption kinetics and isotherms were investigated. The operating variables studied were initial cadmium concentration, sorbent dosage, temperature and ultrasonic power. The sorption was significantly increased in the presence of ultrasound. The amount of cadmium sorption with the assistance of ultrasound was improved with the increase of sorbate initial concentration and temperature, and with the decrease of sorbent dosage. The acoustic power was an important factor for the enhancement of the removal of cadmium. The combination of stirring and ultrasound leads to an intensification of the removal of cadmium. Sorption isothermal data could be well simulated by Freundlich model, and then Temkin and Langmuir models. Langmuir simulation showed that the monolayer sorption capacities of olive leaves were 42.19, 55.87 and 64.94 mg g−1 for the conventional method, the ultrasound-assisted method and the combined method, respectively. The kinetic data fitted very well the pseudo-second-order kinetic model.