Abstract
Nanoscale zerovalent iron (nZVI) has shown great promise for water treatment and soil remediation. However, the rapid aggregation of nZVIs significantly affects their mobility and reactivity, which considerably limits the practical applications. Montmorillonite- (Mt-) supported nZVI (Mt-nZVI) has received increasing attention for the past decade because it can prevent the aggregation of nZVI and incorporate the advantages of both nZVI and Mt in soil and water treatment. This work thus had a comprehensive review on the use of Mt-nZVI for soil and water treatment. We first summarized existing methods used to prepare Mt-nZVI, indicating the advantages of using Mt to support nZVI (e.g., increase of the dispersion and mobility of nZVI, reduction of the size and oxidation tendency of nZVI). We then presented the reaction mechanisms of Mt-nZVI for contaminant removal and evaluated the critical factors that influence the removal (e.g., pH, temperature, and dosage of the adsorbent). We further presented examples of applications of Mt-nZVI for the removal of typical contaminants such as heavy metals and organic compounds in soil and water. We finally discussed the limitations of the use of Mt-nZVI for water treatment and soil remediation and presented future directions for the application of nZVI technology for soil and water treatment.
Highlights
Water and soil contaminations are becoming more and more severe during the past few decades, which seriously damage the natural ecological balance and threaten human health [1]
We show in detail the reaction mechanisms of Mt-nanoscale zerovalent iron (nZVI) for contaminant removal and the main influencing factors on the removal using the Mt-supported nZVI (Mt-nZVI)
We demonstrate the limitations of Mt-nZVI composites and show future research directions
Summary
Water and soil contaminations are becoming more and more severe during the past few decades, which seriously damage the natural ecological balance and threaten human health [1]. An effective approach to overcome the aforementioned problems is to load nZVI particles onto templates such as biochar [12], zeolite [13], and polymers [14]. Montmorillonite (Mt) is a typical 2 : 1 layered silicate clay mineral with low cost, high cation exchange, and adsorption capacity (Figure 1) [17]. The Mt layers have permanent negative charges, which can be exchanged by other cations residing at and/or near the Mt surfaces [18] This structure creates an ideal template to support nZVI particles (Figure 2) [19]. The Mt-nZVI composites have shown great potential for application in water and soil treatment. Our work has important implications to improve the Mt-nZVI composites for application in water treatment and soil remediation
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