Optimization and mechanistic research on perchlorate removal by granular activated carbon-supported nanoscale...

Perchlorate (ClO₄^-), a persistent oxyanion pollutant, poses significant threats to water systems. Despite the widespread use of granular activated carbon-supported nanoscale zero-valent iron (GAC-nZVI) for removing various contaminants (e.g., heavy metals, dyes, and antibiotics), its efficacy and mechanism for perchlorate removal remain unclear. In this study, GAC-nZVI composites with different GAC:nZVI mass ratios ([GAC/nZVI]_mass) were synthesized and their perchlorate removal performance were investigated. The results indicated that GAC-nZVI exhibited a significantly higher perchlorate removal efficiency (99.5%) than GAC (51.71%) or nZVI (63.92%). Through SEM, XRD, BET, XPS, and electrochemical analyses, it was demonstrated that GAC successfully dispersed nZVI, suppressed its agglomeration and passivation, and reduced charge-transfer resistance, thereby establishing an efficient and stable platform for oxyanion remediation in complex water matrices. The reaction pathway and key intermediates (ClO₃^-, ClO^- and Cl^-) were also identified. Furthermore, the removal performance was evaluated by varying the [GAC/nZVI]_mass, dosage, pH, temperature, dissolved oxygen, and coexisting anions. The optimized composite offers scalable potential for industrial and environmental applications.