Cr6 + removal in serpentine sediment is due to both adsorption and reduction. Reduction is mostly due to the sediment magnetic fraction (mostly magnetite). In the pH range 3–7 reduction contributed almost 50% of the total removal. Adsorption is constant in the pH range 3–7 and decreases sharply in the range 7–8.5. Sediment adsorption behavior is dominated by the extra fine fraction (d < 0.075 mm).