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Selenium (Se) is emerging as a contaminant that must be dealt with in many areas of the world, especially those areas impacted by past or current mining activities. In this study, we evaluate the effectiveness of synthesized nano-magnetite when used as an adsorbent to remove anionic selenium species from aqueous solutions. In conjunction with studies on the effects of pH, temperature, concentration, contact time, and presence of competing anions on selenium removal efficiency, a series of batch adsorption experiments were conducted to study adsorption isotherms and adsorptive thermodynamics. Compared with either natural magnetite ( < 5 lm) or nano-iron (*10 nm), nano-magnetite (10-20 nm) was found to be a better adsorbent for selenite, while nano-iron showed better adsorption performance for selenate. From an initial selenium concentration of 100 lg-Se/L, which is comparable to those commonly found in mine water or mining impacted streams, a final concentration of < 5 lg-Se/L could be achieved, using nano-magnetite. Low pH favored selenite adsorption, and elevated temperature enhanced selenium removal. Selenite adsorption followed the Freundlich isotherm model, and the presence of common anions did not significantly affect the adsorption capacity of nano-magnetite for selenite. Selective adsorption demonstrated that nano-magnetite could be a very promising nano-sorbent to treat selenium contaminated water.

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