Novel Sustainable Adsorbents Prepared by Banana/Pomegranate Peels via EDTA Grafting for Effective Removal of Cd(II), Co(II), Mn(II), and Ni(II) from Sewage System

Biosorbents prepared by agricultural waste for eliminating heavy metal ions from sewage systems have gained widespread attention due to the high efficiency, cost-effectiveness, and sustainability. In this study, ethylenediaminetetraacetic acid (EDTA) was grafted onto banana/pomegranate peels to generate two adsorbents, EDTA@BP and EDTA@PP. They were charactered with excellent adsorption capabilities of 46.30 mg/g, 31.85 mg/g, 27.25 mg/g, and 55.25 mg/g for EDTA@BP when removing Cd(II), Co(II), Mn(II), and Ni(II) from aqueous solution, and 86.96 mg/g, 53.19 mg/g, 40.98 mg/g, 68.49 mg/g for EDTA@PP, respectively. The adsorption process was completed within 5 min and could be well described by Langmuir isotherm model and pseudo-second-order kinetic model. Surface characterization of adsorbents using scanning electron microscopy-energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy revealed that EDTA improved metal ion binding performance by introducing more surface oxygen-containing groups, and the adsorption process was dominated by ion exchange and complexation. This study showed the feasibility of EDTA grafting for converting peel biomass into adsorbents with excellent performance to deal with aqueous heavy metal pollutants.