The activity of pyrite (FeS2) and microsized zero-valent iron (mZVI) is greatly limited by the passivating layer. This study indicated that hexavalent chromium (Cr­(VI)) could be effectively sequestered by mechanochemically activated mZVI/FeS2 composite (MA-mZVI/FeS2), which was obtained from the mZVI/FeS2 mixture by mechanochemical technology. Compared with MA-mZVI and MA-FeS2, the Cr­(VI) removal performance of MA-mZVI/FeS2 was significantly improved at a mZVI/FeS2 molar ratio of 1:9. The effects of initial concentration, coexisting anions, reaction time, and initial pH on Cr­(VI) sequestration by MA-mZVI/FeS2 were investigated. During the removal process, the concentrations of different valence states of chromium and iron were measured to explore the Cr­(VI) removal mechanism. Based on the experiments and characterizations, surface sorption accounted for 41.38% and reduction accounted for 58.62% at the Cr­(VI) adsorption equilibrium of MA-mZVI/FeS2. The ball milling destroyed the passivating layer of MA-mZVI/FeS2, resulting in a rough surface. The corrosion of mZVI can be significantly accelerated by FeS2 due to the strong interaction between mZVI and FeS2 in MA-mZVI/FeS2, which led to the enhanced Cr­(VI) sequestration. The practical application indicated that MA-mZVI/FeS2 had good Cr­(VI) removal performance in real water samples. This study revealed that MA-mZVI/FeS2 can be a hopeful adsorbent for effective Cr­(VI) sequestration in aqueous solution.

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