Effects of nano-scale zero valent iron fresh and aged particles on environmental microbes

Abstract

Currently, nano-scale zero valent iron particles (nZVI) are being increasingly used in many types of environmental remediation. Due to their usage, nZVI can be left in the environment and may cause toxic effects to living beings, especially surrounding microorganisms. Environmental bacteria in soil and water are some of the main factors affecting plant productivity and other microorganisms in ecosystems. This study evaluated the toxicological effects of nZVI and aged nZVI on bacteria commonly found in the environment. Bacterial, namely E. coli, P. aeruginosa, S. aureus, B. subtilis, and Rhodococcus sp., were treated with different concentrations of nZVI at different times of exposure in in vitro conditions, and bacterial cell viability was determined in order to analyze the toxic effects of nZVI over the course of treatments. The data revealed that at the highest nZVI concentration (1,000 mg/L), B. subtilis and Rhodococcus sp. had the highest resistance to nZVI (49.35% and 48.31% viability) and less resistance in P. aeruginosa (2.26%) and E. coli (0.50%) was observed. The growth of microorganisms significantly increased after exposure with seven and 14-day aged nZVI particles. Therefore, the toxicity of aged nZVI to microbial organisms was reduced. Hence, this study demonstrated the toxic effects of nZVI and aged nZVI particles on several species of bacteria in vitro. Less toxicity to bacteria was observed in aged nZVI. These findings provide more understanding in the toxic effect of nZVI to microorganisms.