Nonmetallic modified zero-valent iron for remediating halogenated organic compounds and heavy metals: A comprehensive review

Zero Valent Iron (ZVI), an ideal reductant treating persistent pollutants, is hampered by issues like corrosion, passivation, and suboptimal utilization. Recent advancements in nonmetallic modified ZVI (NM-ZVI) show promising potential in circumventing these challenges by modifying ZVI's surface and internal physicochemical properties. Despite its promise, a thorough synthesis of research advancements in this domain remains elusive. Here we review the innovative methodologies, regulatory principles, and reduction-centric mechanisms underpinning NM-ZVI's effectiveness against two prevalent persistent pollutants: halogenated organic compounds and heavy metals. We start by evaluating different nonmetallic modification techniques, such as liquid-phase reduction, mechanical ball milling, and pyrolysis, and their respective advantages. The discussion progresses towards a critical analysis of current strategies and mechanisms used for NM-ZVI to enhance its reactivity, electron selectivity, and electron utilization efficiency. This is achieved by optimizing the elemental compositions, content ratios, lattice constants, hydrophobicity, and conductivity. Furthermore, we propose novel approaches for augmenting NM-ZVI's capability to address complex pollution challenges. This review highlights NM-ZVI's potential as an alternative to remediate water environments contaminated with halogenated organic compounds or heavy metals, contributing to the broader discourse on green remediation technologies.