Impact of Bare and CMC-coated Fe Oxide Nanoparticles on Microbial Activity and Immobilising Zinc, Lead, and Cadmium in a Contaminated Soil

The potential of bare and carboxymethyl cellulose (CMC)-coated iron oxide nanoparticles (FeONPs), including goethite, hematite, and magnetite, for stabilisation of lead (Pb), zinc (Zn), and cadmium (Cd) in contaminated soil was investigated in a greenhouse experiment. The results showed that FeONPs application decreased the availability of potentially toxic elements in soil, and CMC-coated NPs were more effective than bare NPs. CMC-coated goethite proved to be the most effective treatment in reducing the Zn and Cd availability. Its application decreased the diethylenetriaminepentaacetic acid (DTPA) extractable Zn and Cd concentrations by 49% and 56%, respectively. CMC-coated magnetite was the most effective treatment for the stabilisation of Pb. Its application decreased the DTPA-extractable Pb by 56%. Carbon dioxide (CO2) emission and microbial biomass carbon (MBC) were higher in samples treated with CMC-coated FeONPs than bare FeONPs-treated samples, indicating that CMC coating NPs enhanced microbial activity. CO2 emission and MBC were approximately three and five times higher, respectively, in samples treated with CMC-coated goethite than the control. This study suggests that coating of bare FeONPs with CMC improves the adsorption capacity of NPs, making them more chemically reactive, and is a possible technique to reduce the likely antibacterial effects of bare FeONPs.