Facile preparation of amino-functionalized polymeric microcapsules as efficient adsorbent for heavy metal ions removal

Herein, amino-functionalized monodisperse polymeric microcapsules were prepared via Schiff-base reaction between polyethyleneimine (PEI) and glutaraldehyde (GA) using a microfluidic approach. The GA encapsulated in the microcapsules leaked through thermal-induced microcracks at the shell of the microcapsules, and then the leaked GA caused crosslinking of the PEI molecules onto the shell without any further treatments. The success of amino-functionalization and the surface morphology of the microcapsules were demonstrated by Fourier transform infrared spectroscopy, scanning electron microscopy, and optical microscopy. Due to the presence of abundant amine groups in the PEI molecules on the shell, the amino-functionalized microcapsules serve as an effective adsorbent for heavy metal ions (HMI). The as-prepared microcapsules were evaluated as adsorbents to remove Cu2+, Cd2+, and Zn2+ ions from the aqueous solution under varying process parameters such as pH, contact time, and metal ion concentration. The adsorption capacity of the microcapsules for Cu2+, Cd2+, and Zn2+ was measured and fitted using the Sips isotherm model. After completion of HMI adsorption, the microcapsules were readily separated from the aqueous suspension by an external magnetic field. In addition, the cyclic adsorption-desorption efficiency of the amino-functionalized microcapsules was almost maintained for five times.

Automated summary

In this study, amino-functionalized monodisperse polymeric microcapsules were prepared using a microfluidic approach for efficient adsorption of heavy metal ions from aqueous solution. The presence of abundant amine groups on the shell of the microcapsules played a key role in the successful adsorption of Cu2+, Cd2+, and Zn2+ ions. The cyclic adsorption-desorption efficiency of the amino-functionalized microcapsules remained stable for five cycles, demonstrating their potential for practical applications in heavy metal ion removal.