Enhanced effect and mechanism of nano Fe-Ca bimetallic oxide modified substrate on Cu(II) and Ni(II) removal in constructed wetland

In this study, Fe2O3 nanoparticles (Fe2O3 NPs) and CaO NPs were loaded on the zeolite sphere carrier to create nano Fe-Ca bimetallic oxide (Fe-Ca-NBMO) modified substrate, which was introduced into constructed wetland (CW) to remove Cu(II) and Ni(II) via constructing substrate-microorganism system. Adsorption experiments showed that the equilibrium adsorption capacities of Fe-Ca-NBMO modified substrate for Cu(II) and Ni(II) were respectively 706.48 and 410.59 mg/kg at an initial concentration of 20 mg/L, 2.45 and 2.39 times of gravel. The Cu(II) and Ni(II) removal efficiencies in CW with Fe-Ca-NBMO modified substrate respectively reached 99.7% and 99.9% at an influent concentration of 100 mg/L, significantly higher than those in gravel-based CW (47.0% and 34.3%). Fe-Ca-NBMO modified substrate could promote Cu(II) and Ni(II) removal by increasing electrostatic adsorption, chemical precipitation, as well as the abundances of resistant microorganisms (Geobacter, Desulfur-omonas, Zoogloea, Dechloromonas, and Desulfobacter) and functional genes (copA, cusABC, ABC.CD.P, gshB, and exbB). This study provided an effective method to enhance Cu(II) and Ni(II) removal of electroplating wastewater by CW with Fe-Ca-NBMO modified substrate.

Automated summary

In this study, Fe2O3 nanoparticles and CaO nanoparticles were loaded on a zeolite sphere carrier to create a nano Fe-Ca bimetallic oxide modified substrate. This substrate was introduced into a constructed wetland to remove Cu(II) and Ni(II). The modified substrate showed significantly higher adsorption capacities and removal efficiencies for Cu(II) and Ni(II) compared to the gravel-based wetland. The enhanced removal was attributed to increased electrostatic adsorption, chemical precipitation, and the presence of resistant microorganisms and functional genes.