Immobilization of mercury in sediment using stabilized iron sulfide nanoparticles

Mercury (Hg) immobilization using stabilized iron sulfide (FeS) nanoparticles was investigated through a series of batch and column experiments. The nanoparticles were prepared using a low-cost, food-grade cellulose (sodium carboxymethyl cellulose, CMC) as the stabilizer. The hydrodynamic diameter of fresh FeS-CMC nanoparticles was measured to be 38.5 +/- 5.4 nm. Batch tests showed that the nanoparticles can effectively immobilize Hg in a clay loam sediment. The Hg distribution coefficient for the nanoparticles was determined to be 8930 +/- 1480 L/g, which is >4 orders of magnitude greater than for the sediment. When the Hg-laden sediment was treated at an FeS-to-Hg molar ratio of 26.5, the Hg concentration leached into water was reduced by 97% and the TCLP (toxicity characteristic leaching procedure) leachability of Hg was reduced by 99%. Column tests showed that water-leachable mercury from the sediment containing 3120 mg/L Hg was reduced by 67% and the TCLP leachability by >77% when the sediment was treated with 67 pore volumes (PVs) of a 0.5 g/L FeS nanoparticle suspension. Column tests proved that the stabilized nanoparticles were highly mobile in the sediment and full breakthrough of the nanoparticles occurred at similar to 18 PVs. (C) 2009 Elsevier Ltd. All rights reserved.