Effective removal of copper ions from aqueous solution by iminodiacetic acid-functionalized Paeonia ostii seed coats

Abstract

A novel and efficient adsorbent, iminodiacetic acid-functionalized Paeonia ostii seed coats (IDA-PSC), was prepared for the removal of copper ions from aqueous solution. Structural and morphological characterizations were performed using BET, SEM, FT-IR and XPS analyses. The influence of solution pH and ionic strength, adsorption kinetics, isotherms and desorption studies were investigated. The results revealed that the IDA-PSC adsorbent presented high adsorption capacity for Cu(II) even at pH values as low as 2, or in the presence of Na⁺ and Ca²⁺. Langmuir isotherm and Pseudo-second-order models described the experimental data well. Maximum monolayer adsorption capability was 36.6 mg g⁻¹ at 25 °C. Thermodynamic studies confirmed the spontaneous and endothermic nature of adsorption process. FT-IR and XPS analysis indicated that the N/O-containing functional groups on the surface of IDA-PSC played important roles in the adsorption process of Cu(II). Besides, intraparticle diffusion, electrostatic attraction and ion-exchange could greatly contribute to the Cu(II) adsorption. Lastly, reusability study suggested that the efficiency did not change much even after six consecutive cycles, which further confirmed that the IDA-PSC could be a promising adsorbent for the efficient removal of copper ions from aqueous solution.

Graphical Abstract

Keywords:

• Iminodiacetic acid-functionalized Paeonia ostii seed coats
• adsorption
• copper ions

Additional information

Funding

This work was financially supported by the National Key R&D Program of China (Grant No.: 2017YFC0212404).