Intensification of Co(II) adsorption from aqueous solution onto Fe3O4/bentonite nanocomposite by high-frequency ultrasound waves

The effect of ultrasound on cobalt adsorption from aqueous solution onto Fe3O4/Bentonite nanocomposite is investigated. Two layouts of using shaker and sono-separator equipped with ultrasound are considered. The effect of pH on Co(II) ions removal is investigated. Co(II) removal rate increased with increasing pH from 2 to 10, and it reduced after pH=10. For the shaker, the contact time (t) of 50 min is selected as the most effective case. However, for sono-separator the maximum value of Co(II) removal rate is 78% at t=10 min, and it decreased after 10 min. The effect of the adsorbent mass (AM) is investigated and Co(II) removal increased by increasing the specific surface area of the adsorbent. The highest Co(II) removal rates are 83.3% and 86% for the shaker and the sono-separator, respectively. No significant increase for Co(II) removal is observed for increasing AM more than 3 g. The effect of the transducer locations and initial concentration of Co(II) ions (C0) at pH=10 and AM =3 g are investigated. The results showed that the activation of all transducers had the best performance. Initially, with increasing C0 from 0.05 to 0.1 g/L, Co(II) removal rate increased from 84% to 86%, respectively, but with increasing C0 from 0.1 to 0.15 and 0.2 g/L, cobalt removal has been decreased. Finally, the experimental data are adopted with Langmuir and Freundlich isotherms. The comparison of these models showed that both models are well suited to experimental data and data compatibility with the Langmuir model is greater.