Supplementary Material for MCA-D-08-00070

Sequential extraction procedureand characterization of operational fractions

The five-step extraction procedure was modified from our previous reports and adopted in this experiment. The chemical fractions were divided into a water-extractable fraction(F1), an ion-exchangeable and a carbonate fraction(F2), anFe-Mn oxide fraction(F3), an organics and sulfides-binding fraction(F4), and a residual fraction(F5). The extraction processes were followed in detail.

Step one,water-extractable fraction (F1):1.0 g sample was weighed and transferred to a 50 mL glass centrifuge tube. 20 mL deionized water was added. The obtained mixture was ultrasonicated for 2 h at ambient temperature. The extract was then separated from the solid residual by centrifugation at 3000 rpm for 15 min and the supernatant was transferred by pipette. The solid residual was retained for the next step.

Step two,acid-soluble fraction (F2): To the residual from step one was added 20 ml acetateCH3COOH at pH 2.85, then the mixture was shaken for 16 h. The supernatant was transferred after centrifuging. The residue was kept for the next step.

Step three,reducible fraction (F3):The solid residue from the above step was treated with 20 ml of 0.04 mol L−1 NH2OH·HCl adjusted to pH 2 with CH3COOH. The samples were shaken for 16 h. The metals in the supernatantwere measured. The solid residual was retained forstep four.

Step four,oxidizable fraction (F4):To the obtained residual small portions of 5 mLof 30% H2O2 (adjusted to pH 2 with HNO3) were added and heated to85°C. The content in centrifuges was digested for an hour. The content was evaporated to a small volume (1–2 mL). After vaporization of the solution, 20 mL of 1.0 mol L−1 CH3COONH4 was added to the cooled residual and shaken continuously for 16 h. After centrifugation, the obtained supernatant was analyzed for elemental analysis.

Step five, residual fraction (F5):The residual was treated with a mixture of aqua regia and HF. The residue from step four was transferred to a PTFE container for microwave digestion. 3 mL HF and 5 mL aqua regia were added for total digestion. The temperature program was set to reach 160 ºC within 5 min, holding at 160 °C for 2 min, increase to 180 °C in 1 min and hold at 180 °C for 30 min. Then it was cooled down to room temperature in 30 min. The digestion solution was transferred to polyethylene bottles for measurement after filtration through 0.45 µm filters.

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Table 1SMetal contents in each fraction in PC fly ash sample (µg·g-1, n=3)

F1 / F2 / F3 / F4 / F5 / Suma / Total / Recoveryb
V / 6.09±0.31 / 2.70±0.12 / 13.4±0.81 / 11.0±0.92 / 61.1±4.6 / 94.3 / 89.5±7.1 / 105%
Cr / 2.18±0.16 / 4.46±0.25 / 0.847±0.052 / 1.38±0.063 / 56.3±6.1 / 65.2 / 62.7±5.6 / 104%
Co / ND / 0.867±0.042 / 0.0935±0.0023 / 0.166±0.015 / 7.62±0.9 / 8.74 / 8.67±0.63 / 101%
Ni / 0.120±0.01 / 3.01±0.08 / 0.353±0.04 / 0.568±0.07 / 18.4±2.1 / 22.4 / 20.8±1.7 / 108%
Cu / 0.0742±0.008 / 9.99±0.72 / 4.38±0.51 / 4.91±0.39 / 27.1±2.0 / 46.5 / 41.1±3.6 / 113%
Zn / 0.528±0.1 / 12.9±0.95 / 2.03±0.19 / 2.04±0.23 / 63.0±3.5 / 80.4 / 82.4±4.8 / 98%
Cd* / 6.30±0.4 / 117±12 / 6.0±0.5 / 8.9±0.92 / 320±16 / 458 / 407.5±15 / 112%
Sn / 0.0231±0.002 / 0.0221±0.0014 / ND / ND / 2.93±0.19 / 2.97 / 3.67±0.28 / 81%
Pb / 0.0334±0.003 / 0.260±0.019 / 0.295±0.022 / 0.157±0.018 / 42.3±5.8 / 43.0 / 51.9±4.5 / 83%

* unit was ng·g-1

aSum=F1+F2+F3+F4+F5

bRecovery=Sum/Total

Table 2SMetal contents in each fraction in CFB fly ash sample (µg·g-1, n=3)

F1 / F2 / F3 / F4 / F5 / Suma / Total / Recoveryb
V / 14.9±1.2 / 2.02±0.11 / 15.1 ±1.2 / 47.0±3.7 / 42.5±03.8 / 122 / 115±9.5 / 106%
Cr / 0.256±0.03 / 1.48 ±0.12 / 0.780±0.08 / 2.32 ±0.19 / 34.4 ±3.1 / 39.3 / 42.8±3.9 / 92%
Co / ND / 2.10±0.20 / 0.579±0.048 / 0.854 ±0.054 / 10.7 ±1.4 / 14.3 / 12.4±0.87 / 115%
Ni / 0.153±0.015 / 3.48±0.4 / 0.992±0.08 / 1.95±0.16 / 31.9 ±3.5 / 38.5 / 32.3±3.0 / 119%
Cu / 0.113±0.009 / 0.466±0.05 / 0.826±0.071 / 6.34±0.36 / 45.1 ±4.1 / 52.8 / 46.7 ±2.7 / 113%
Zn / ND / 26.5±2.8 / 4.00±0.031 / 1.22±0.09 / 37.0 ±5.1 / 68.7 / 70.1 ±3.6 / 98%
Cd* / 5.00±0.31 / 43.7±3.6 / 28.6±2.5 / 33.1±2.7 / 329 ±29 / 440 / 373±25 / 118%
Sn / 0.0115±0.002 / 0.0235 ±0.004 / ND / ND / 3.23 ±0.28 / 3.26 / 2.98 ±0.17 / 109%
Pb / 0.0214±0.0019 / 0.247±0.031 / 0.801±0.073 / 0.393±0.043 / 43.0 ±4.9 / 44.4 / 50.2 ±5.3 / 88%

* unit was ng·g-1

aSum=F1+F2+F3+F4+F5

bRecovery=Sum/Total

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