Preparation of EDTA-modified magnetic attapulgite chitosan gel bead adsorbent for the removal of Cu(II), Pb(II), and Ni(II)

Abstract

Attapulgite (ATP) has a unique porous layered chain structure and is an excellent environment-friendly decolorizer. However, its high viscosity makes it difficult to separate. First, it was combined with magnetic Fe₃O₄ nanoparticles to obtain Fe₃O₄-ATP that is easy to recycle and reuse. Then, Fe₃O₄-ATP nanoparticles were embedded in chitosan (CS) gel beads, and glutaraldehyde was used for cross-linking and curing. Lastly, ethylenediaminetetraacetic acid (EDTA) was successfully connected to Fe₃O₄-ATP/CS gel beads through amidation reaction, which further increased the capability of the adsorbent to adsorb heavy metal ions. The prepared magnetic composite adsorbent is a sphere with a rough surface and porous structure. The maximum adsorption capacity of the prepared Fe₃O₄-ATP/EDTA/CS adsorbent for Pb(II), Cu(II), and Ni(II) is 368.32, 267.94, and 220.31 mg g^-1, respectively. After 5 times of repeated use, Fe₃O₄-ATP/EDTA/CS still showed good adsorption capacity for Cu(II), Pb(II), and Ni(II). Fe₃O₄-ATP/EDTA/CS has a large adsorption capacity for heavy metal ions, a wide pH applicability, good reuse, and rapid magnetic separation. In addition, Cu(II) loaded Fe₃O₄-ATP/EDTA/CS also showed good catalytic degradation performance for bisphenol A. This study prepared a new type of adsorbent with good adsorption performance and provided a promising method for the treatment of wastewater.

Keywords: Chitosan bead; EDTA modification; Magnetic attapulgite.