Novel magnetic FeS2/Fe3O4 composites as adsorbents for chromium(VI) removal from aqueous solution

In this study, novel magnetite composite FeS2/Fe3O4 was synthesized by a one-pot hydrothermal method. It is applied as an adsorbent for chromium(VI) removal from aqueous solution. The pyrite (FeS2) and the magnetite (Fe3O4) were also synthesized and compared. The analysis results of X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy confirmed the formation of FeS2/Fe3O4 composite. The magnetic characterization revealed that the saturation magnetization value for FeS2/Fe3O4 was 50.89 emu g(-1), which is helpful for the separation. The effects of the initial pH values, adsorbent dosage, contact time and reaction temperatures on the Cr(VI) removal by various materials were studied and contrasted in detail through experiments. It is found that the composite FeS2/Fe3O4 had high removal capacity for Cr(VI) at high pH. 86.1% of Cr(VI) removal efficiency was obtained when the pH value is at 12.0, the contact time is 3 h and the temperature is controlled at 35 degrees C. FeS2 component was inferred as the major contribution of the composite to the Cr(VI) removal. FeS2/Fe3O4 displayed a promoted Cr(VI) removal efficiency with the increasing temperature, and its absorption process is proved spontaneous.