Batch tests were conducted to evaluate the influences of several common dissolved anions in groundwater on the reduction of para-chloronitrobenzene (p-CNB) by zero-valent iron (ZVI). The results showed that p-CNB reduction was enhanced by both Cl and SO42−. HCO3 could either improve or inhibit p-CNB reduction, depending on whether the mixing speed was intense enough to rapidly eliminate Fe–carbonate complex deposited on ZVI surface. Above a concentration of 100 mg L−1, NO3 increased the p-CNB reduction rate. The reduction rate by ClO4 decreased because the ClO4 competed with p-CNB for electrons. The p-CNB reduction was inhibited by PO43−, SiO32− and humic acid, in the order humic acid < PO43− < SiO32−, since these ions could form inner-sphere complexes on iron surface. The reaction even ceased when the ion concentrations were greater than 4, 0.5, and 30 mg L−1, respectively. The results indicated that common dissolved anions in groundwater should be taken into account when ZVI is applied for contaminated groundwater remediation.

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