A comparative study on two extraction procedures in speciation of iron in municipal solid waste

Two extraction reagents, hydrochloric acid (HCl) and acid ammonium oxalate solution (Tamm's reagent), were used to evaluate the redox state of iron in municipal solid waste (MSW) with different deposit ages. Orthogonal experiments were conducted to optimize the extraction conditions for extractable iron speciation (ferric and ferrous) in MSW. The optimal extraction conditions for HCl were determined as follows: the liquid-to-solid ratio was set at 100, and then the samples were extracted at the shaking speed of 200 rpm at 35 degrees C for 60 min by 1.00 M HCl. For Tamm's reagent, the optimal extraction conditions were extracted at the shaking speed of 175 rpm at 30 degrees C for 12 h with the same liquid-to-solid ratio. However, Tamm's reagent extraction is much more laborious and time-consuming. Thus the HC1 extraction might be a better choice for the evaluation of the redox state of iron in MSW. The results also showed that the yield of extractable iron increased with deposited age. About 60-83% of extractable iron was presented as ferrous in the MSW deposited for 1-8 years. This study supplied a tool for investigating the role of iron on the fate of pollutants in the landfill.