Comparison of Novel and Patented Silica-Polyamine Composite Materials as Aqueous Heavy Metal Ion Recovery Materials

A novel silica–polyamine composite material, WP-1, was synthesized according to a new patented procedure for aqueous heavy metal ion removal. The effects of pH and initial concentration of metal ions on adsorption were investigated. Results showed that WP-1 has metal ion capacities in the order Cu(II) > Ni(II) > Fe(II) and generally works best in the 2–4 pH range. Kinetic studies showed the Cu(II) adsorption reaction occurs in a second-order fashion with a rate constant of 4.4 × 10−4 s−1. Two similar silica–polyamine materials, prepared by different procedures cited in the literature, were compared with WP-1 for Cu(II) ion capacity and mechanical durability. These tests showed that capacities were more than twice as high when the new patented procedure was used, indicating much better coverage of the silica gel. During repeated metal loading and unloading tests, WP-1 maintained up to 94% of its initial Cu(II) capacity and its mechanical integrity for 3000 cycles, whereas testing of the other materials had to be stopped prematurely due to degradation of the materials.