Aging of zero‐valent iron‐based nanoparticles in aqueous environment and the consequent effects on their reactivity and toxicity

Abstract

A fundamental understanding of the long-term fate of nanoscale zero-valent iron (nZVI)-based particles in aqueous environment and the corresponding impacts on their reactivity and toxicity is essential for the responsible use and management of the nanoparticles in environmental applications. This paper comprehensively reviews the physicochemical transformations of nZVI-based particles and the consequent effects on the particle's reactivity and toxicity. The corrosions of nZVI in water under both anaerobic and aerobic conditions are summarized. The transformation of contaminant-bearing nZVI is also discussed. Besides, the factors influencing the transformation of nZVI (i.e., pH, typical anions and cations, natural organic matter, surface stabilizers, bimetal decoration, and sulfidation treatment) are summarized and discussed. In addition, the effects of particle aging on its reactivity and toxicity are discussed. Generally, the aging of nZVI-based particles would have negative impact on the removal of contaminants, especially for the degradation of organic pollutants. However, the aging process of nZVI-based particles would cause a significant reduction in their toxicity. It is suggested that the nZVI-based particles would finally transform to less toxic or benign materials (i.e., iron (oxyhydr)oxides) over time. Finally, future perspectives are proposed to better quantify and predict the transformation of nZVI-based particles in aqueous environment. © 2019 Water Environment Federation • Practitioner points• The corrosion rates and products of nZVI in water varied much under anaerobic and aerobic conditions. • Typical anions and cations, natural organic matter, and iron types are critical factors influencing the physicochemical transformation of nZVI. • The aging of nZVI would have negative impact its reactivity, especially for the degradation of organic pollutants. • Although the fresh nZVI exhibits obvious toxicity, the aging process would cause a significant reduction in its toxicity.

Revealing the long-term behaviour of nZVI and biochar in metal(loid)-contaminated soil: focus on Fe transformations

“…, goethite, lepidocrocite, magnetite) Fe oxides is possible. The presence of lepidocrocite was expected based on the reported results for water 56,57 and for this soil 38 and the given conditions ( i.e. , pH around 5 and oxic conditions).…”

“…Since nZVI oxidation was not directly proportional to time in the layered samples, the coexistence of poorly crystalline (i.e., ferrihydrite) and more crystalline (i.e., goethite, lepidocrocite, magnetite) Fe oxides is possible. The presence of lepidocrocite was expected based on the reported results for water 56,57 and for this soil 38 and the given conditions (i.e., pH around 5 and oxic conditions). 58 Finally, higher adsorption of metal(loid)s could be expected when ferrihydrite is present due to its higher surface area compared to more crystalline Fe oxides.…”

Environmental Impact of Nanoparticles’ Application as an Emerging Technology: A Review

“…Understanding the NP environmental impact requires detailed comprehension of the characteristics of these systems such as identification, physicochemical properties, including how they are emitted to the environment and their toxicity in living beings [39]. The inherent potential toxicity of the NPs is fundamentally conditioned by their ability to reach and invade the different environmental compartments (earth, water, air).…”

Progress and prospects of applying carbon‐based materials (and nanomaterials) to accelerate anaerobic bioprocesses for the removal of micropollutants

“…Nanoscaled zero valent iron (nano‐Fe 0 ) was efficient on dye decolourization by a microbial culture; however when in concentrations above 4 mg l ‐1 , the microbial activity was compromised (Adebiyi et al ., 2011 ). Other studies have described nano‐Fe 0 as a toxic compound, creating oxidative stress on microorganisms, damaging their membranes and eventually leading to cells death (Lee et al ., 2008 ; Dong et al ., 2019 ). The toxic mechanisms provided by this element are related with the iron oxides (reduced iron species, Fe 2+ and/or Fe 0 ) which can enter the cells, generating reactive oxygen species (ROS), or from the disturbance of electronic and ionic transport chains of the cell, due to the strong affinity of nanoparticles to the cell membranes (Auffan et al ., 2008 ; Lee et al ., 2008 ).…”