Fig. 6. RAC values of Pb (a), Zn (b), Cu (c), Cd (d), Cr (e), and Ni (f) in the residual solids before and after pH leaching experiments with end-point pH distributed in natural pH(12.24–13.57), medium pH (6.59–7.12), and low pH (1.39–1.93) for the two types of FA samples.