Fig. 1.

Fraction of selected (a) major and (b) trace elements leached from different classes of coal utilization by-products samples by the combined sequential extractions of H2O + acetic acid + hydrochloric acid leaching solutions. FBC, fluidized-bed combustion.

 


Fig. 2.

Variations in the strontium isotope composition of whole coal utilization by-products (CUB) samples (solid circles) and sequential CUB leaches (open symbols), sorted by class. BA, bottom ash; FBC, fluidized bed combustion; FGD, flue gas desulfurization product; STD, National Institute of Standards and Technology fly ash standard SRM 1633b. Error bars are much smaller than the size of the symbols, with measurement uncertainty generally <0.2 ε units (<0.000014 in the 87Sr/86Sr ratio).

 


Fig. 3.

Variation in leachate concentrations for selected (a) major and (b) trace elements in the sequential (water → acetic acid → hydrochloric acid) coal utilization by-products (CUB) leachates. Concentrations are reported as fraction extracted, which represents the total amount of element extracted by each leaching solution divided by the total amount of element in the starting (preleach or whole-CUB) sample. FBC, fluidized-bed combustion.

 


Fig. 4.

Whole-coal utilization by-products (CUB) values plotted against K/Sr ratios. The strong correlation suggests that one or more high-K (thus high-Rb) phases contain Sr with more radiogenic (high-) isotopic compositions. Such phases would likely be detrital silicate minerals inherited from the coal precursor, while authigenic minerals formed during coalification are more likely to have low values. FBC, fluidized-bed combustion.

 


Fig. 5.

Strontium isotope variations (expressed both as and 87Sr/86Sr) in coal utilization by-products (CUB) leachates plotted as function of the sequential amount of Sr extracted by H2O + HOAc + HCl. The points plotted at 100% extracted represent the calculated isotopic composition of the undissolved residue, based on the leachate and whole-CUB concentrations and isotopic compositions. Dashed lines on the right indicate the total range of isotopic compositions for each CUB class, including leachates, whole-CUB, and calculated residues. FBC, fluidized-bed combustion; FGD, flue gas desulfurization product.

 


Fig. 6.

Variation in values with the concentrations of (a) Si and (b) As in the leachates of class C (closed symbol) and class F (open symbol) coal utilization by-products (CUB). Linear best-fit curves are calculated for each CUB sample, with correlation coefficients (R2) as indicated. Most samples show a strong positive correlation, with the CRC 9 samples being the major exception.