Heavy metal leachability in soil amended with zeolite- or biochar-modified contaminated sediment.

In this work, reuse probability of heavy metal-contaminated sediment for land application was discussed using a 100-day column leaching assessment under the situation of simulated acid rain. For comparison, NaCl-modified zeolite and biochar were firstly studied for their adsorption capacity for Cu, Cd, and Pb in aqueous solution, and then their stabilizing effects on the three metals in sediment-soil mixture. Characteristic results indicated that NaCl-modified zeolite had properties more conducive to metal adsorption than biochar, including higher BET surface area and more negative surface charges. Adsorption capacities of NaCl-modified zeolite fitted by Langmuir isotherm model were 24.83, 35.57, and 133.16 mg g-1 for Cu, Cd, and Pb, respectively. Leaching results demonstrated that metal concentrations in the leachates of soil receiving zeolite- or biochar-modified sediment reduced significantly after 100 days compared with that of soil receiving bare sediment. Moreover, the NaCl-modified zeolite presented a better performance in stabilizing the three metals than biochar from the BCR sequential extraction result. Therefore, stabilization of the dredged contaminated sediment by modified zeolite ensures an environmentally friendly reuse of the sediment on land and makes the sediment treatment operation-able and cost-effective.