A Comparative Study of the Removal of Heavy Metal Ions from Water Using a Silica−Polyamine Composite and a Polystyrene Chelator Resin

The maximum Cu(II), Ni(II), and Co(II) ion capacities of a silica−poly(ethyleneimine) composite (WP-1) are compared with those of the commercially available iminodiacetic acid chelator resin Amberlite IRC-718. Under batch (static) conditions, IRC-718 exhibits better capacities for these metals than WP-1. Dynamic studies, however, revealed that WP-1 possessed a much higher capacity for all three divalent metals than IRC-718, with relative metal capacities in the order Cu(II) > Co(II) ≈ Ni(II). In the presence of the competing chelator ethylenediaminetetraacetic acid, the Cu(II) capacities of WP-1 and IRC-718 lost 48% and 45%, respectively, of their original adsorption values. Even with this decrease, however, WP-1 maintained a higher Cu(II) capacity than IRC-718. Repeated cycle testing, using Cu(II) solutions at both room temperature and 97 °C, was conducted to compare the long-term stability of each material. WP-1 maintained 94% of its original Cu(II) capacity and maintained structural integrity after 3000 cycles using room temperature copper solutions, while IRC-718 compressed and dropped to 64% of its original capacity. When boiling copper solutions were used, the capacity of WP-1 increased slightly over 1500 cycles, while IRC-718 lost 13% of its original copper capacity and again became compressed, indicating degradation of the polystyrene beads.