Simultaneous Removal of Cu(II) And Pb(Ii) From Stormwater Runoff by Y-Type-Zeolite-Modified Bioretention System

In this study, Y-type zeolite (ZMA: zeolite mineral adsorbent) was synthesized using illite and employed for a series of batch adsorption experiments for removal of heavy metal ions (i.e., Pb(II), Cu(II), Cd(II), Zn(II)). Water pH, adsorption time and adsorbent dosage were varied to observe their influence on the adsorption efficiency. The adsorption capacity of ZMA was in the order of Pb(II) > Cu(II) > Cd(II) > Zn(II), which was attributed to the hydrate radius, electronegativity, hydrolysis constant and charges of the adsorbates. The ZMA was then added to the bioretention unit as a soil amendment to remove Pb and Cu from stormwater runoff. It was proved that the bioretention system with ZMA could effectively remove the heavy metals in stormwater runoff; the average effluent concentrations of Pb and Cu were 26.65 μg L⁻¹ and 42.22 μg L⁻¹. The removal efficiencies of the system for Pb and Cu were 44.4% and 44.9%, respectively, all of which were higher than those of the system without ZMA. It was also found that ZMA could increase the retention capacity of the bioretention system for the heavy metals in the upper 10 cm of the soil layer, thus retard the migration of heavy metals in the soil to some degree. In summary, ZMA synthesized in this study could effectively improve the ability of the bioretention system to retain and immobilize heavy metals and prevent their environmental impacts.