Fe(2+) Alleviated the Toxicity of ZnO Nanoparticles to Pseudomonas tolaasii Y-11 by Changing Nanoparticles Behavior in Solution

The negative effect of ZnO nanoparticles (ZnO-NPs) on the biological removal of nitrate (NO(3)(−)) has received extensive attention, but the underlying mechanism is controversial. Additionally, there is no research on Fe(2+) used to alleviate the cytotoxicity of NPs. In this paper, the effects of different doses of ZnO-NPs on the growth and NO(3)(−) removal of Pseudomonas tolaasii Y-11 were studied with or without Fe(2+). The results showed that ZnO-NPs had a dose-dependent inhibition on the growth and NO(3)(−) removal of Pseudomonas tolaasii Y-11 and achieved cytotoxic effects through both the NPs themselves and the released Zn(2+). The addition of Fe(2+) changed the behavior of ZnO-NPs in an aqueous solution (inhibiting the release of toxic Zn(2+) and promoting the aggregation of ZnO-NPs), thereby alleviating the poisonous effect of ZnO-NPs on the growth and nitrogen removal of P. tolaasii Y-11. This study provides a theoretical method for exploring the mitigation of the acute toxicity of ZnO-NPs to denitrifying microorganisms.