Performance and Mechanism of Contaminants Removal by Carbon Materials-Modified Zerovalent Iron

Nanoscale zero-valent iron (nZVI) is always considered to be a promising technology for water and soil remediation, due to its high reactivity and good adsorption ability. However, given the high surface energy and intrinsic magnetic interactions, unstabilized nZVI tends to aggregate and thus causes poor mobility and lower reactivity, which limits its further development and application. To address these issues, prior and ongoing research efforts have provided several promising strategies that can potentially improve the performance of nZVI. Among of them, carbon based materials such as surfactants, polymers and porous carbon materials are commonly used to modify the surface properties of nZVI, considering carbon based materials always have superior adsorption ability, stability, electron conductivity, etc. Accordingly, this review comprehensively summarizes the modification methods with different carbon materials. Moreover, the influence of surface modification on the mobility, reactivity and especially the selectivity (electron efficiency) of nZVI is discussed in detail. It can be concluded that, for the successful application of nZVI, the mobility and selectivity of nZVI are still the bottleneck factors, although they can be enhanced by the modification with carboxymethyl cellulose, starch, activated carbon and also other carbon based materials. Therefore, future research may attempt to explore some more effective modification methods, such as with the combination of different carbon materials, to improve the mobility and selectivity of nZVI.